diff --git a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/NodeSet.java b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/NodeSet.java
index aa8eeb170d3..d8dc27c0651 100644
--- a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/NodeSet.java
+++ b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/NodeSet.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2022, Oracle and/or its affiliates. All rights reserved.
  */
 /*
  * Licensed to the Apache Software Foundation (ASF) under one or more
@@ -55,7 +55,7 @@ import org.w3c.dom.traversal.NodeIterator;
  * to the same calls; the disadvantage is that some of them may return
  * less-than-enlightening results when you do so.</p>
  * @xsl.usage advanced
- * @LastModified: Nov 2017
+ * @LastModified: May 2022
  */
 public class NodeSet
         implements NodeList, NodeIterator, Cloneable, ContextNodeList
@@ -379,11 +379,7 @@ public class NodeSet
    */
   public void addNode(Node n)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
-    this.addElement(n);
+    addElement(n);
   }
 
   /**
@@ -397,10 +393,6 @@ public class NodeSet
    */
   public void insertNode(Node n, int pos)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
     insertElementAt(n, pos);
   }
 
@@ -413,11 +405,7 @@ public class NodeSet
    */
   public void removeNode(Node n)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
-    this.removeElement(n);
+    removeElement(n);
   }
 
   /**
@@ -431,10 +419,6 @@ public class NodeSet
    */
   public void addNodes(NodeList nodelist)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
     if (null != nodelist)  // defensive to fix a bug that Sanjiva reported.
     {
       int nChildren = nodelist.getLength();
@@ -471,10 +455,6 @@ public class NodeSet
    */
   public void addNodes(NodeSet ns)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
     addNodes((NodeIterator) ns);
   }
 
@@ -488,10 +468,6 @@ public class NodeSet
    */
   public void addNodes(NodeIterator iterator)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
     if (null != iterator)  // defensive to fix a bug that Sanjiva reported.
     {
       Node obj;
@@ -516,10 +492,6 @@ public class NodeSet
    */
   public void addNodesInDocOrder(NodeList nodelist, XPathContext support)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
     int nChildren = nodelist.getLength();
 
     for (int i = 0; i < nChildren; i++)
@@ -544,10 +516,6 @@ public class NodeSet
    */
   public void addNodesInDocOrder(NodeIterator iterator, XPathContext support)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
     Node node;
 
     while (null != (node = iterator.nextNode()))
@@ -572,10 +540,6 @@ public class NodeSet
   private boolean addNodesInDocOrder(int start, int end, int testIndex,
                                      NodeList nodelist, XPathContext support)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
     boolean foundit = false;
     int i;
     Node node = nodelist.item(testIndex);
@@ -632,10 +596,6 @@ public class NodeSet
    */
   public int addNodeInDocOrder(Node node, boolean test, XPathContext support)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
     int insertIndex = -1;
 
     if (test)
@@ -706,10 +666,6 @@ public class NodeSet
    */
   public int addNodeInDocOrder(Node node, XPathContext support)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
     return addNodeInDocOrder(node, true, support);
   }  // end addNodeInDocOrder(Vector v, Object obj)
 
@@ -767,9 +723,6 @@ public class NodeSet
     return n;
   }
 
-  /** True if this list can be mutated.  */
-  transient protected boolean m_mutable = true;
-
   /** True if this list is cached.
    *  @serial  */
   transient protected boolean m_cacheNodes = true;
@@ -804,7 +757,6 @@ public class NodeSet
         XSLMessages.createXPATHMessage(XPATHErrorResources.ER_CANNOT_CALL_SETSHOULDCACHENODE, null)); //"Can not call setShouldCacheNodes after nextNode has been called!");
 
     m_cacheNodes = b;
-    m_mutable = true;
   }
 
 
@@ -875,9 +827,6 @@ public class NodeSet
    */
   public void addElement(Node value)
   {
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
     if ((m_firstFree + 1) >= m_mapSize)
     {
       if (null == m_map)
@@ -1102,9 +1051,6 @@ public class NodeSet
    */
   public void insertElementAt(Node value, int at)
   {
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
     if (null == m_map)
     {
       m_map = new Node[m_blocksize];
@@ -1195,9 +1141,6 @@ public class NodeSet
    */
   public boolean removeElement(Node s)
   {
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
     if (null == m_map)
       return false;
 
@@ -1258,9 +1201,6 @@ public class NodeSet
    */
   public void setElementAt(Node node, int index)
   {
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
-
     if (null == m_map)
     {
       m_map = new Node[m_blocksize];
diff --git a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/NodeSetDTM.java b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/NodeSetDTM.java
index 6b0c1bde1b5..ae0e196f0bb 100644
--- a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/NodeSetDTM.java
+++ b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/NodeSetDTM.java
@@ -1,6 +1,5 @@
 /*
- * reserved comment block
- * DO NOT REMOVE OR ALTER!
+ * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
  */
 /*
  * Licensed to the Apache Software Foundation (ASF) under one or more
@@ -57,6 +56,7 @@ import org.w3c.dom.traversal.NodeIterator;
  * to the same calls; the disadvantage is that some of them may return
  * less-than-enlightening results when you do so.</p>
  * @xsl.usage advanced
+ * @LastModified: May 2022
  */
 public class NodeSetDTM extends NodeVector
         implements /* NodeList, NodeIterator, */ DTMIterator,
@@ -536,11 +536,7 @@ public class NodeSetDTM extends NodeVector
    */
   public void addNode(int n)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
-    this.addElement(n);
+    addElement(n);
   }
 
   /**
@@ -554,10 +550,6 @@ public class NodeSetDTM extends NodeVector
    */
   public void insertNode(int n, int pos)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
     insertElementAt(n, pos);
   }
 
@@ -570,10 +562,6 @@ public class NodeSetDTM extends NodeVector
    */
   public void removeNode(int n)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
     this.removeElement(n);
   }
 
@@ -647,10 +635,6 @@ public class NodeSetDTM extends NodeVector
    */
   public void addNodes(DTMIterator iterator)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
     if (null != iterator)  // defensive to fix a bug that Sanjiva reported.
     {
       int obj;
@@ -704,10 +688,6 @@ public class NodeSetDTM extends NodeVector
    */
   public void addNodesInDocOrder(DTMIterator iterator, XPathContext support)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
     int node;
 
     while (DTM.NULL != (node = iterator.nextNode()))
@@ -793,10 +773,6 @@ public class NodeSetDTM extends NodeVector
    */
   public int addNodeInDocOrder(int node, boolean test, XPathContext support)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
     int insertIndex = -1;
 
     if (test)
@@ -868,10 +844,6 @@ public class NodeSetDTM extends NodeVector
    */
   public int addNodeInDocOrder(int node, XPathContext support)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
     return addNodeInDocOrder(node, true, support);
   }  // end addNodeInDocOrder(Vector v, Object obj)
 
@@ -894,10 +866,6 @@ public class NodeSetDTM extends NodeVector
    */
   public void addElement(int value)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
     super.addElement(value);
   }
 
@@ -914,10 +882,6 @@ public class NodeSetDTM extends NodeVector
    */
   public void insertElementAt(int value, int at)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
     super.insertElementAt(value, at);
   }
 
@@ -930,10 +894,6 @@ public class NodeSetDTM extends NodeVector
    */
   public void appendNodes(NodeVector nodes)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
     super.appendNodes(nodes);
   }
 
@@ -947,10 +907,6 @@ public class NodeSetDTM extends NodeVector
    */
   public void removeAllElements()
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
     super.removeAllElements();
   }
 
@@ -969,10 +925,6 @@ public class NodeSetDTM extends NodeVector
    */
   public boolean removeElement(int s)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
     return super.removeElement(s);
   }
 
@@ -988,10 +940,6 @@ public class NodeSetDTM extends NodeVector
    */
   public void removeElementAt(int i)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
     super.removeElementAt(i);
   }
 
@@ -1009,10 +957,6 @@ public class NodeSetDTM extends NodeVector
    */
   public void setElementAt(int node, int index)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
     super.setElementAt(node, index);
   }
 
@@ -1026,10 +970,6 @@ public class NodeSetDTM extends NodeVector
    */
   public void setItem(int node, int index)
   {
-
-    if (!m_mutable)
-      throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_NOT_MUTABLE, null)); //"This NodeSetDTM is not mutable!");
-
     super.setElementAt(node, index);
   }
 
@@ -1157,9 +1097,6 @@ public class NodeSetDTM extends NodeVector
     return n;
   }
 
-  /** True if this list can be mutated.  */
-  transient protected boolean m_mutable = true;
-
   /** True if this list is cached.
    *  @serial  */
   transient protected boolean m_cacheNodes = true;
@@ -1197,7 +1134,6 @@ public class NodeSetDTM extends NodeVector
         XSLMessages.createXPATHMessage(XPATHErrorResources.ER_CANNOT_CALL_SETSHOULDCACHENODE, null)); //"Can not call setShouldCacheNodes after nextNode has been called!");
 
     m_cacheNodes = b;
-    m_mutable = true;
   }
 
   /**
@@ -1208,7 +1144,7 @@ public class NodeSetDTM extends NodeVector
    */
   public boolean isMutable()
   {
-    return m_mutable;
+    return true;
   }
 
   transient private int m_last = 0;
diff --git a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/XPath.java b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/XPath.java
index 18632eab6ab..bd2d5a093a0 100644
--- a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/XPath.java
+++ b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/XPath.java
@@ -42,7 +42,7 @@ import jdk.xml.internal.XMLSecurityManager;
  * The XPath class wraps an expression object and provides general services
  * for execution of that expression.
  * @xsl.usage advanced
- * @LastModified: Jan 2022
+ * @LastModified: May 2022
  */
 public class XPath implements Serializable, ExpressionOwner
 {
@@ -208,22 +208,16 @@ public class XPath implements Serializable, ExpressionOwner
     else if (MATCH == type)
       parser.initMatchPattern(compiler, exprString, prefixResolver);
     else
-      throw new RuntimeException(XSLMessages.createXPATHMessage(
+      throw new TransformerException(XSLMessages.createXPATHMessage(
             XPATHErrorResources.ER_CANNOT_DEAL_XPATH_TYPE,
             new Object[]{Integer.toString(type)}));
-            //"Can not deal with XPath type: " + type);
 
-    // System.out.println("----------------");
-    Expression expr = compiler.compileExpression(0);
-
-    // System.out.println("expr: "+expr);
-    this.setExpression(expr);
+    m_mainExp = compiler.compileExpression(0);
 
     if((null != locator) && locator instanceof ExpressionNode)
     {
-        expr.exprSetParent((ExpressionNode)locator);
+        m_mainExp.exprSetParent((ExpressionNode)locator);
     }
-
   }
 
   /**
@@ -274,7 +268,7 @@ public class XPath implements Serializable, ExpressionOwner
    */
   public XPath(Expression expr)
   {
-    this.setExpression(expr);
+    m_mainExp = expr;
     initFunctionTable();
   }
 
diff --git a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/axes/PredicatedNodeTest.java b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/axes/PredicatedNodeTest.java
index 6e52dc80393..b4ecbee15a0 100644
--- a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/axes/PredicatedNodeTest.java
+++ b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/axes/PredicatedNodeTest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2022, Oracle and/or its affiliates. All rights reserved.
  */
 /*
  * Licensed to the Apache Software Foundation (ASF) under one or more
@@ -24,6 +24,7 @@ import com.sun.org.apache.xml.internal.dtm.DTM;
 import com.sun.org.apache.xml.internal.dtm.DTMIterator;
 import com.sun.org.apache.xml.internal.utils.PrefixResolver;
 import com.sun.org.apache.xml.internal.utils.QName;
+import com.sun.org.apache.xml.internal.utils.WrappedRuntimeException;
 import com.sun.org.apache.xpath.internal.Expression;
 import com.sun.org.apache.xpath.internal.ExpressionOwner;
 import com.sun.org.apache.xpath.internal.XPathContext;
@@ -34,7 +35,7 @@ import com.sun.org.apache.xpath.internal.patterns.NodeTest;
 import java.util.List;
 
 /**
- * @LastModified: May 2020
+ * @LastModified: May 2022
  */
 public abstract class PredicatedNodeTest extends NodeTest implements SubContextList
 {
@@ -491,9 +492,8 @@ public abstract class PredicatedNodeTest extends NodeTest implements SubContextL
     }
     catch (javax.xml.transform.TransformerException se)
     {
-
-      // TODO: Fix this.
-      throw new RuntimeException(se.getMessage());
+      // the Xalan/XPath impl use WrappedRuntimeException to carry errors over
+      throw new WrappedRuntimeException(se);
     }
     finally
     {
diff --git a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/compiler/XPathParser.java b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/compiler/XPathParser.java
index 1efc5a32c37..e7f2f567c84 100644
--- a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/compiler/XPathParser.java
+++ b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/compiler/XPathParser.java
@@ -35,7 +35,7 @@ import jdk.xml.internal.XMLSecurityManager;
  * Tokenizes and parses XPath expressions. This should really be named
  * XPathParserImpl, and may be renamed in the future.
  * @xsl.usage general
- * @LastModified: Apr 2022
+ * @LastModified: May 2022
  */
 public class XPathParser
 {
@@ -79,6 +79,16 @@ public class XPathParser
   // XML security manager
   XMLSecurityManager m_xmlSecMgr;
 
+  // Union operands must be node-sets, e.g. //a | //b
+  // A flag indicating whether the operand is a location path
+  boolean isLocationPath = false;
+
+  // A flag indicating whether the next operand is required to be a location path
+  boolean lPathRequired = false;
+
+  // Keep track of the status of reading the next token after lPathRequired is flagged
+  boolean nextTokenRead = false;
+
   /**
    * The parser constructor.
    */
@@ -434,9 +444,19 @@ public class XPathParser
    * Retrieve the next token from the command and
    * store it in m_token string.
    */
-  private final void nextToken()
+  private final void nextToken() throws TransformerException
   {
-
+    // before reading another token, check the last one
+    if (lPathRequired) {
+        if (nextTokenRead) {
+            // check whether the operand behind the union was a Location path
+            checkNodeSet();
+            lPathRequired = false;
+            nextTokenRead = false;
+        } else {
+            nextTokenRead = true;
+        }
+    }
     if (m_queueMark < m_ops.getTokenQueueSize())
     {
       m_token = (String) m_ops.m_tokenQueue.elementAt(m_queueMark++);
@@ -497,31 +517,28 @@ public class XPathParser
   }
 
   /**
-   * Consume an expected token, throwing an exception if it
-   * isn't there.
-   *
-   * @param expected The string to be expected.
-   *
-   * @throws TransformerException
+   * Checks whether the function token represents a function that returns a
+   * nodeset.
+   * @param funcTok the function token
+   * @return true if the function token represents a function that returns a
+   * nodeset, false otherwise
    */
-  private final void consumeExpected(String expected)
-          throws TransformerException
-  {
+  private boolean isNodesetFunction(int funcTok) {
+      return (funcTok == FunctionTable.FUNC_CURRENT || funcTok == FunctionTable.FUNC_HERE
+              || funcTok == FunctionTable.FUNC_ID);
+  }
 
-    if (tokenIs(expected))
+  /**
+   * Checks whether the operand is a location path, reports error if not.
+   *
+   * @throws TransformerException if an error is found
+   */
+  private void checkNodeSet() throws TransformerException {
+    if (!isLocationPath)
     {
-      nextToken();
+      error(XPATHErrorResources.ER_UNION_MUST_BE_NODESET,
+            new Object[]{});
     }
-    else
-    {
-      error(XPATHErrorResources.ER_EXPECTED_BUT_FOUND, new Object[]{ expected,
-                                                                     m_token });  //"Expected "+expected+", but found: "+m_token);
-
-          // Patch for Christina's gripe. She wants her errorHandler to return from
-          // this error and continue trying to parse, rather than throwing an exception.
-          // Without the patch, that put us into an endless loop.
-                throw new XPathProcessorException(CONTINUE_AFTER_FATAL_ERROR);
-        }
   }
 
   /**
@@ -1209,13 +1226,17 @@ public class XPathParser
 
       if (tokenIs(Token.VBAR))
       {
+        // check whether the operand before the union is a location path
+        checkNodeSet();
+
         if (false == foundUnion)
         {
           foundUnion = true;
-
           insertOp(opPos, 2, OpCodes.OP_UNION);
         }
 
+        isLocationPath = false;
+        lPathRequired = true;
         nextToken();
       }
       else
@@ -1464,7 +1485,7 @@ public class XPathParser
       m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH + 1, m_queueMark - 1);
 
       nextToken();
-      consumeExpected(':');
+      consumeExpected(Token.COLON);
 
       m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH + 2, m_queueMark - 1);
 
@@ -1494,6 +1515,10 @@ public class XPathParser
         m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH + 1, funcTok);
       }
 
+      // XML Signature here() function returns a node-set
+      if (isNodesetFunction(funcTok)) {
+          isLocationPath = true;
+      }
       nextToken();
     }
 
@@ -1544,7 +1569,7 @@ public class XPathParser
    */
   protected void LocationPath() throws TransformerException
   {
-
+    isLocationPath = true;
     int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);
 
     // int locationPathOpPos = opPos;
@@ -1861,7 +1886,7 @@ public class XPathParser
         }
 
         nextToken();
-        consumeExpected(':');
+        consumeExpected(Token.COLON);
       }
       else
       {
@@ -1908,7 +1933,7 @@ public class XPathParser
       nextToken();
       PredicateExpr();
       countPredicate--;
-      consumeExpected(']');
+      consumeExpected(Token.RBRACK);
     }
   }
 
@@ -1950,7 +1975,7 @@ public class XPathParser
       m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);
 
       nextToken();
-      consumeExpected(':');
+      consumeExpected(Token.COLON);
     }
     else
     {
@@ -1969,7 +1994,7 @@ public class XPathParser
    * NCName ::=  (Letter | '_') (NCNameChar)
    * NCNameChar ::=  Letter | Digit | '.' | '-' | '_' | CombiningChar | Extender
    */
-  protected void NCName()
+  protected void NCName() throws TransformerException
   {
 
     m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), m_queueMark - 1);
diff --git a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/functions/FuncExtFunction.java b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/functions/FuncExtFunction.java
index ac1fd12745f..6fe57d28d2f 100644
--- a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/functions/FuncExtFunction.java
+++ b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/functions/FuncExtFunction.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2022, Oracle and/or its affiliates. All rights reserved.
  */
 /*
  * Licensed to the Apache Software Foundation (ASF) under one or more
@@ -34,13 +34,14 @@ import com.sun.org.apache.xpath.internal.res.XPATHErrorResources;
 import com.sun.org.apache.xpath.internal.res.XPATHMessages;
 import java.util.ArrayList;
 import java.util.List;
+import javax.xml.transform.TransformerException;
 
 /**
  * An object of this class represents an extension call expression.  When
  * the expression executes, it calls ExtensionsTable#extFunction, and then
  * converts the result to the appropriate XObject.
  * @xsl.usage advanced
- * @LastModified: Oct 2017
+ * @LastModified: May 2022
  */
 public class FuncExtFunction extends Function
 {
@@ -183,8 +184,7 @@ public class FuncExtFunction extends Function
    *
    * @throws javax.xml.transform.TransformerException
    */
-  public XObject execute(XPathContext xctxt)
-          throws javax.xml.transform.TransformerException
+  public XObject execute(XPathContext xctxt) throws TransformerException
   {
     if (xctxt.isSecureProcessing())
       throw new javax.xml.transform.TransformerException(
@@ -209,6 +209,12 @@ public class FuncExtFunction extends Function
     }
     //dml
     ExtensionsProvider extProvider = (ExtensionsProvider)xctxt.getOwnerObject();
+    if (extProvider == null) {
+        String fmsg = XSLMessages.createXPATHMessage(
+            XPATHErrorResources.ER_NO_XPATH_FUNCTION_PROVIDER,
+            new Object[] {argVec} );
+        throw new TransformerException ( fmsg );
+    }
     Object val = extProvider.extFunction(this, argVec);
 
     if (null != val)
diff --git a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/jaxp/JAXPVariableStack.java b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/jaxp/JAXPVariableStack.java
index 46e7996fd9a..4a75ae4f1ff 100644
--- a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/jaxp/JAXPVariableStack.java
+++ b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/jaxp/JAXPVariableStack.java
@@ -1,6 +1,5 @@
 /*
- * reserved comment block
- * DO NOT REMOVE OR ALTER!
+ * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
  */
 /*
  * Licensed to the Apache Software Foundation (ASF) under one or more
@@ -38,6 +37,7 @@ import com.sun.org.apache.xalan.internal.res.XSLMessages;
  * {@link javax.xml.xpath.XPathVariableResolver}.
  *
  * @author Ramesh Mandava
+ * @LastModified: May 2022
  */
 public class JAXPVariableStack extends VariableStack {
 
@@ -61,6 +61,13 @@ public class JAXPVariableStack extends VariableStack {
             new javax.xml.namespace.QName(
                 qname.getNamespace(),
                 qname.getLocalPart());
+
+        if (resolver == null) {
+            String fmsg = XSLMessages.createXPATHMessage(
+                XPATHErrorResources.ER_NO_XPATH_VARIABLE_RESOLVER,
+                new Object[] { name.toString()} );
+            throw new TransformerException( fmsg );
+        }
         Object varValue = resolver.resolveVariable( name );
         if ( varValue == null ) {
             String fmsg = XSLMessages.createXPATHMessage(
diff --git a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/jaxp/XPathExpressionImpl.java b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/jaxp/XPathExpressionImpl.java
index 79f6dc382bb..5ded2b99eaa 100644
--- a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/jaxp/XPathExpressionImpl.java
+++ b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/jaxp/XPathExpressionImpl.java
@@ -20,6 +20,7 @@
 
 package com.sun.org.apache.xpath.internal.jaxp;
 
+import com.sun.org.apache.xml.internal.utils.WrappedRuntimeException;
 import com.sun.org.apache.xpath.internal.objects.XObject;
 import javax.xml.namespace.QName;
 import javax.xml.transform.TransformerException;
@@ -27,6 +28,7 @@ import javax.xml.xpath.XPathConstants;
 import javax.xml.xpath.XPathEvaluationResult;
 import javax.xml.xpath.XPathExpression;
 import javax.xml.xpath.XPathExpressionException;
+import javax.xml.xpath.XPathFunctionException;
 import javax.xml.xpath.XPathFunctionResolver;
 import javax.xml.xpath.XPathVariableResolver;
 import jdk.xml.internal.JdkXmlFeatures;
@@ -37,7 +39,7 @@ import org.xml.sax.InputSource;
  * The XPathExpression interface encapsulates a (compiled) XPath expression.
  *
  * @author  Ramesh Mandava
- * @LastModified: Apr 2022
+ * @LastModified: May 2022
  */
 public class XPathExpressionImpl extends XPathImplUtil implements XPathExpression {
 
@@ -77,7 +79,7 @@ public class XPathExpressionImpl extends XPathImplUtil implements XPathExpressio
     }
 
     public Object eval(Object item, QName returnType)
-            throws javax.xml.transform.TransformerException {
+            throws TransformerException {
         XObject resultObject = eval(item, xpath);
         return getResultAsType(resultObject, returnType);
     }
@@ -88,20 +90,20 @@ public class XPathExpressionImpl extends XPathImplUtil implements XPathExpressio
         isSupported(returnType);
         try {
             return eval(item, returnType);
-        } catch (java.lang.NullPointerException npe) {
-            // If VariableResolver returns null Or if we get
-            // NullPointerException at this stage for some other reason
-            // then we have to reurn XPathException
-            throw new XPathExpressionException (npe);
-        } catch (javax.xml.transform.TransformerException te) {
+        } catch (TransformerException te) {
             Throwable nestedException = te.getException();
-            if (nestedException instanceof javax.xml.xpath.XPathFunctionException) {
-                throw (javax.xml.xpath.XPathFunctionException)nestedException;
+            if (nestedException instanceof XPathFunctionException) {
+                throw (XPathFunctionException)nestedException;
             } else {
                 // For any other exceptions we need to throw
                 // XPathExpressionException (as per spec)
                 throw new XPathExpressionException(te);
             }
+        } catch (RuntimeException re) {
+            if (re instanceof WrappedRuntimeException) {
+                throw new XPathExpressionException(((WrappedRuntimeException)re).getException());
+            }
+            throw new XPathExpressionException(re);
         }
     }
 
@@ -115,12 +117,18 @@ public class XPathExpressionImpl extends XPathImplUtil implements XPathExpressio
     @Override
     public Object evaluate(InputSource source, QName returnType)
         throws XPathExpressionException {
+        requireNonNull(source, "Source");
         isSupported (returnType);
         try {
             Document document = getDocument(source);
             return eval(document, returnType);
         } catch (TransformerException e) {
             throw new XPathExpressionException(e);
+        } catch (RuntimeException re) {
+            if (re instanceof WrappedRuntimeException) {
+                throw new XPathExpressionException(((WrappedRuntimeException)re).getException());
+            }
+            throw new XPathExpressionException(re);
         }
     }
 
@@ -143,8 +151,13 @@ public class XPathExpressionImpl extends XPathImplUtil implements XPathExpressio
                 return XPathResultImpl.getValue(resultObject, type);
             }
 
-        } catch (javax.xml.transform.TransformerException te) {
+        } catch (TransformerException te) {
             throw new XPathExpressionException(te);
+        } catch (RuntimeException re) {
+            if (re instanceof WrappedRuntimeException) {
+                throw new XPathExpressionException(((WrappedRuntimeException)re).getException());
+            }
+            throw new XPathExpressionException(re);
         }
     }
 
diff --git a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/jaxp/XPathImpl.java b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/jaxp/XPathImpl.java
index c070b2806f2..79a06eec785 100644
--- a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/jaxp/XPathImpl.java
+++ b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/jaxp/XPathImpl.java
@@ -20,6 +20,7 @@
 
 package com.sun.org.apache.xpath.internal.jaxp;
 
+import com.sun.org.apache.xml.internal.utils.WrappedRuntimeException;
 import com.sun.org.apache.xpath.internal.*;
 import com.sun.org.apache.xpath.internal.objects.XObject;
 import javax.xml.namespace.NamespaceContext;
@@ -47,7 +48,7 @@ import org.xml.sax.InputSource;
  * New methods: evaluateExpression
  * Refactored to share code with XPathExpressionImpl.
  *
- * @LastModified: Jan 2022
+ * @LastModified: May 2022
  */
 public class XPathImpl extends XPathImplUtil implements javax.xml.xpath.XPath {
 
@@ -134,11 +135,6 @@ public class XPathImpl extends XPathImplUtil implements javax.xml.xpath.XPath {
 
             XObject resultObject = eval(expression, item);
             return getResultAsType(resultObject, returnType);
-        } catch (java.lang.NullPointerException npe) {
-            // If VariableResolver returns null Or if we get
-            // NullPointerException at this stage for some other reason
-            // then we have to reurn XPathException
-            throw new XPathExpressionException (npe);
         } catch (TransformerException te) {
             Throwable nestedException = te.getException();
             if (nestedException instanceof javax.xml.xpath.XPathFunctionException) {
@@ -146,10 +142,14 @@ public class XPathImpl extends XPathImplUtil implements javax.xml.xpath.XPath {
             } else {
                 // For any other exceptions we need to throw
                 // XPathExpressionException (as per spec)
-                throw new XPathExpressionException (te);
+                throw new XPathExpressionException(te);
             }
+        } catch (RuntimeException re) {
+            if (re instanceof WrappedRuntimeException) {
+                throw new XPathExpressionException(((WrappedRuntimeException)re).getException());
+            }
+            throw new XPathExpressionException(re);
         }
-
     }
 
     //-Override-
@@ -172,26 +172,18 @@ public class XPathImpl extends XPathImplUtil implements javax.xml.xpath.XPath {
             return ximpl;
         } catch (TransformerException te) {
             throw new XPathExpressionException (te) ;
+        } catch (RuntimeException re) {
+            if (re instanceof WrappedRuntimeException) {
+                throw new XPathExpressionException(((WrappedRuntimeException)re).getException());
+            }
+            throw new XPathExpressionException(re);
         }
     }
 
     //-Override-
     public Object evaluate(String expression, InputSource source,
             QName returnType) throws XPathExpressionException {
-        isSupported(returnType);
-
-        try {
-            Document document = getDocument(source);
-            XObject resultObject = eval(expression, document);
-            return getResultAsType(resultObject, returnType);
-        } catch (TransformerException te) {
-            Throwable nestedException = te.getException();
-            if (nestedException instanceof javax.xml.xpath.XPathFunctionException) {
-                throw (javax.xml.xpath.XPathFunctionException)nestedException;
-            } else {
-                throw new XPathExpressionException (te);
-            }
-        }
+        return evaluate(expression, getDocument(source), returnType);
     }
 
     //-Override-
@@ -210,7 +202,8 @@ public class XPathImpl extends XPathImplUtil implements javax.xml.xpath.XPath {
     //-Override-
     public <T> T evaluateExpression(String expression, Object item, Class<T> type)
             throws XPathExpressionException {
-        isSupportedClassType(type);
+         requireNonNull(expression, "XPath expression");
+         isSupportedClassType(type);
         try {
             XObject resultObject = eval(expression, item);
             if (type == XPathEvaluationResult.class) {
@@ -219,7 +212,12 @@ public class XPathImpl extends XPathImplUtil implements javax.xml.xpath.XPath {
                 return XPathResultImpl.getValue(resultObject, type);
             }
         } catch (TransformerException te) {
-            throw new XPathExpressionException (te);
+            throw new XPathExpressionException(te);
+        } catch (RuntimeException re) {
+            if (re instanceof WrappedRuntimeException) {
+                throw new XPathExpressionException(((WrappedRuntimeException)re).getException());
+            }
+            throw new XPathExpressionException(re);
         }
     }
 
diff --git a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/res/XPATHErrorResources.java b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/res/XPATHErrorResources.java
index 9df76ef6632..409d06e638e 100644
--- a/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/res/XPATHErrorResources.java
+++ b/src/java.xml/share/classes/com/sun/org/apache/xpath/internal/res/XPATHErrorResources.java
@@ -31,7 +31,7 @@ import java.util.ListResourceBundle;
   * Also you need to  update the count of messages(MAX_CODE)or
  * the count of warnings(MAX_WARNING) [ Information purpose only]
  * @xsl.usage advanced
- * @LastModified: Apr 2022
+ * @LastModified: May 2022
  */
 public class XPATHErrorResources extends ListResourceBundle
 {
@@ -140,6 +140,7 @@ public class XPATHErrorResources extends ListResourceBundle
          "ER_EXPECTED_SINGLE_QUOTE";
   public static final String ER_EMPTY_EXPRESSION = "ER_EMPTY_EXPRESSION";
   public static final String ER_EXPECTED_BUT_FOUND = "ER_EXPECTED_BUT_FOUND";
+  public static final String ER_UNION_MUST_BE_NODESET = "ER_UNION_MUST_BE_NODESET";
   public static final String ER_INCORRECT_PROGRAMMER_ASSERTION =
          "ER_INCORRECT_PROGRAMMER_ASSERTION";
   public static final String ER_BOOLEAN_ARG_NO_LONGER_OPTIONAL =
@@ -203,9 +204,6 @@ public static final String ER_IGNORABLE_WHITESPACE_NOT_HANDLED =
          "ER_FUNCTION_TOKEN_NOT_FOUND";
   public static final String ER_CANNOT_DEAL_XPATH_TYPE =
          "ER_CANNOT_DEAL_XPATH_TYPE";
-  public static final String ER_NODESET_NOT_MUTABLE = "ER_NODESET_NOT_MUTABLE";
-  public static final String ER_NODESETDTM_NOT_MUTABLE =
-         "ER_NODESETDTM_NOT_MUTABLE";
    /**  Variable not resolvable:   */
   public static final String ER_VAR_NOT_RESOLVABLE = "ER_VAR_NOT_RESOLVABLE";
    /** Null error handler  */
@@ -309,6 +307,8 @@ public static final String ER_IGNORABLE_WHITESPACE_NOT_HANDLED =
   //BEGIN: Keys needed for exception messages of  JAXP 1.3 XPath API implementation
   public static final String ER_EXTENSION_FUNCTION_CANNOT_BE_INVOKED = "ER_EXTENSION_FUNCTION_CANNOT_BE_INVOKED";
   public static final String ER_RESOLVE_VARIABLE_RETURNS_NULL = "ER_RESOLVE_VARIABLE_RETURNS_NULL";
+  public static final String ER_NO_XPATH_VARIABLE_RESOLVER = "ER_NO_XPATH_VARIABLE_RESOLVER";
+  public static final String ER_NO_XPATH_FUNCTION_PROVIDER = "ER_NO_XPATH_FUNCTION_PROVIDER";
   public static final String ER_UNSUPPORTED_RETURN_TYPE = "ER_UNSUPPORTED_RETURN_TYPE";
   public static final String ER_SOURCE_RETURN_TYPE_CANNOT_BE_NULL = "ER_SOURCE_RETURN_TYPE_CANNOT_BE_NULL";
   public static final String ER_ARG_CANNOT_BE_NULL = "ER_ARG_CANNOT_BE_NULL";
@@ -460,6 +460,9 @@ public static final String ER_IGNORABLE_WHITESPACE_NOT_HANDLED =
   { ER_EXPECTED_BUT_FOUND,
      "Expected {0}, but found: {1}"},
 
+  { ER_UNION_MUST_BE_NODESET,
+     "Operands for a union must be node-sets."},
+
   { ER_INCORRECT_PROGRAMMER_ASSERTION,
       "Programmer assertion is incorrect! - {0}"},
 
@@ -574,12 +577,6 @@ public static final String ER_IGNORABLE_WHITESPACE_NOT_HANDLED =
   { ER_CANNOT_DEAL_XPATH_TYPE,
        "Can not deal with XPath type: {0}"},
 
-  { ER_NODESET_NOT_MUTABLE,
-       "This NodeSet is not mutable"},
-
-  { ER_NODESETDTM_NOT_MUTABLE,
-       "This NodeSetDTM is not mutable"},
-
   { ER_VAR_NOT_RESOLVABLE,
         "Variable not resolvable: {0}"},
 
@@ -780,6 +777,12 @@ public static final String ER_IGNORABLE_WHITESPACE_NOT_HANDLED =
   { ER_RESOLVE_VARIABLE_RETURNS_NULL,
        "resolveVariable for variable {0} returning null"},
 
+  { ER_NO_XPATH_VARIABLE_RESOLVER,
+       "Attempting to resolve variable {0}, but a variable resolver is not set."},
+
+  { ER_NO_XPATH_FUNCTION_PROVIDER,
+       "Attempting to call an extension function {0}, but an extension provider is not set."},
+
   /** Field ER_UNSUPPORTED_RETURN_TYPE                       */
 
   { ER_UNSUPPORTED_RETURN_TYPE,
diff --git a/test/jaxp/javax/xml/jaxp/unittest/xpath/XPathExceptionTest.java b/test/jaxp/javax/xml/jaxp/unittest/xpath/XPathExceptionTest.java
index 3b6a61745db..9069f0ad4ac 100644
--- a/test/jaxp/javax/xml/jaxp/unittest/xpath/XPathExceptionTest.java
+++ b/test/jaxp/javax/xml/jaxp/unittest/xpath/XPathExceptionTest.java
@@ -24,34 +24,96 @@
 package xpath;
 
 import java.io.StringReader;
+import javax.xml.namespace.QName;
 import javax.xml.parsers.DocumentBuilder;
 import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.parsers.ParserConfigurationException;
 import javax.xml.xpath.XPath;
+import static javax.xml.xpath.XPathConstants.BOOLEAN;
+import static javax.xml.xpath.XPathConstants.NODE;
+import static javax.xml.xpath.XPathConstants.NODESET;
+import static javax.xml.xpath.XPathConstants.NUMBER;
+import static javax.xml.xpath.XPathConstants.STRING;
 import javax.xml.xpath.XPathExpression;
 import javax.xml.xpath.XPathExpressionException;
 import javax.xml.xpath.XPathFactory;
+import javax.xml.xpath.XPathNodes;
 import org.testng.Assert;
 import org.testng.annotations.DataProvider;
 import org.testng.annotations.Test;
 import org.w3c.dom.Document;
 import org.w3c.dom.Node;
+import org.xml.sax.InputSource;
 
 /*
  * @test
- * @bug 8284548
+ * @bug 8284400 8284548
  * @run testng xpath.XPathExceptionTest
- * @summary This is a general test for Exception handling. Additional cases may
- * be added with a bug id in the test cases.
+ * @summary This is a general test for Exception handling in XPath. This test
+ * covers the followings:
+ * NPE: refer to DataProvider NPE for more details.
+ * IAE: covered by existing tests: Bug4991939, XPathAnyTypeTest, XPathExpAnyTypeTest
+ *      and XPathTest
+ * XPathExpressionException: all other cass other than NPE and IAE.
  */
 public class XPathExceptionTest {
+    private final String XPATH_EXPRESSION = "ext:helloWorld()";
 
     /*
-     * DataProvider: invalid XPath expressions
-     * Illegal expressions and structures that may escape the validation check.
+     * DataProvider: used for NPE test, provides the following fields:
+     *     expression, context, useSource, source, QName, class type, provided
+     * Refer to testNPEWithEvaluate.
      */
-    @DataProvider(name = "invalid")
-    public Object[][] getInvalid() throws Exception {
+    @DataProvider(name = "NPE")
+    public Object[][] getNullParameter() throws Exception {
         return new Object[][]{
+            /**
+             * Existing NPE tests:
+             *     for XPath::evaluate:
+             *     Bug4992788: expression != null, source = null
+             *     Bug4992793: expression = null, source != null
+             *     Bug4992805: source != null, QName = null
+             *
+             *     for XPath::evaluateExpression
+             *     XPathAnyTypeTest: expression = null or classType = null
+            */
+            // NPE if expression = null
+            {null, (Node)null, false, null, STRING, String.class, true},
+            {null, getDummyDoc(), false, null, STRING, String.class, true},
+            {null, (Node)null, false, null, null, null, false},
+            {null, getDummyDoc(), false, null, null, null, false},
+            // NPE if returnType = null
+            {"exp", (Node)null, false, null, null, null, true},
+            {"exp", getDummyDoc(), false, null, null, null, true},
+            // NPE if source = null
+            {"exp", (Node)null, true, null, STRING, String.class, true},
+            {"exp", getDummyDoc(), true, null, STRING, String.class, true},
+            {"exp", (Node)null, true, null, null, null, false},
+            {"exp", getDummyDoc(), true, null, null, null, false},
+        };
+    }
+
+    /*
+     * DataProvider: used for compile-time error test, provides:
+     *     invalid XPath expressions
+     */
+    @DataProvider(name = "invalidExp")
+    public Object[][] getInvalidExp() throws Exception {
+        return new Object[][]{
+            {"8|b"},
+            {"8[x=2]|b"},
+            {"8/a|b"},
+            {"a|7"},
+            {"a|7|b"},
+            {"a|7[x=2]"},
+            {"b|'literal'"},
+            {"b|\"literal\""},
+            {"a|$x:y"},
+            {"a|(x or y)"},
+            {"a|(x and y)"},
+            {"a|(x=2)"},
+            {"a|string-length(\"xy\")"},
+            {"/a/b/preceding-sibling::comment()|7"},
             // @bug JDK-8284548: expressions ending with relational operators
             // throw StringIndexOutOfBoundsException instead of XPathExpressionException
             {"/a/b/c[@d >"},
@@ -61,22 +123,476 @@ public class XPathExceptionTest {
         };
     }
 
+    /*
+     * DataProvider: expressions that cause exceptions in the given context.
+     */
+    @DataProvider(name = "expInContext1")
+    public Object[][] getExpressionAndContext1() throws Exception {
+        InputSource source = new InputSource(new StringReader("<A/>"));
+        return new Object[][]{
+
+            // expressions invalid for the null context, return type not provided
+            {"x+1", (Node)null, false, null, null, null, false},
+            {"5 mod a", (Node)null, false, null, null, null, false},
+            {"8 div ", (Node)null, false, null, null, null, false},
+            {"/bookstore/book[price>xx]", (Node)null, false, null, null, null, false},
+            // expressions invalid for the null context, return type is irrelevant
+            // for the eval, but needs to be a valid one when used
+            // Note that invalid class type was tested in XPathAnyTypeTest,
+            // and invalid QName tested in Bug4991939.
+            {"x+1", (Node)null, false, null, STRING, String.class, true},
+            {"5 mod a", (Node)null, false, null, STRING, String.class, true},
+            {"8 div ", (Node)null, false, null, STRING, String.class, true},
+            {"/bookstore/book[price>xx]", (Node)null, false, null, STRING, String.class, true},
+
+            // undefined variable, context not relevant, return type not provided
+            {"/  *     [n*$d2]/s", getDummyDoc(), false, null, null, null, false},
+            {"/  *               [n|$d1]/s", getDummyDoc(), false, null, null, null, false},
+            {"/  *     [n*$d2]/s", null, true, source, null, null, false},
+            {"/  *               [n|$d1]/s", null, true, source, null, null, false},
+            // undefined variable, context/return type not relevant for the eval
+            // but need to be valid when provided
+            {"/  *     [n*$d2]/s", getDummyDoc(), false, null, STRING, String.class, true},
+            {"/  *               [n|$d1]/s", getDummyDoc(), false, null, STRING, String.class, true},
+            {"/  *     [n*$d2]/s", null, true, source, STRING, String.class, true},
+            {"/  *               [n|$d1]/s", null, true, source, STRING, String.class, true},
+        };
+    }
+
+    /*
+     * DataProvider: provides edge cases that are valid
+     */
+    @DataProvider(name = "expInContext2")
+    public Object[][] getExpressionAndContext2() throws Exception {
+        return new Object[][]{
+            // The context can be empty
+            {"/node[x=2]", getEmptyDocument(), false, null, STRING, String.class, true},
+            {"/a/b/c", getEmptyDocument(), false, null, BOOLEAN, Boolean.class, true},
+        };
+    }
+
+    /*
+     * DataProvider: provides expressions that contain function calls.
+     */
+    @DataProvider(name = "functions")
+    public Object[][] getExpressionWithFunctions() throws Exception {
+        InputSource source = new InputSource(new StringReader("<A/>"));
+        return new Object[][]{
+            // expression with a function call
+            {XPATH_EXPRESSION, getEmptyDocument(), false, null, STRING, String.class, true},
+            {XPATH_EXPRESSION, null, true, source, BOOLEAN, Boolean.class, true},
+        };
+    }
+
     /**
-     * Verifies that the XPath processor throws XPathExpressionException upon
-     * encountering illegal XPath expressions.
+     * Verifies that NPE is thrown if the expression, source, or returnType is
+     * null.
+     * This test tests these methods:
+     *     XPath::evaluate and XPathExpression::evaluate.
+     *     XPath::evaluateExpression and XPathExpression::evaluateExpression.
+     *
+     * @param expression the expression
+     * @param item the context item, can be null (for non-context dependent expressions)
+     * @param useSource a flag indicating whether the source shall be used instead
+     *                  of the context item
+     * @param source the source
+     * @param qn the return type in the form of a QName, can be null
+     * @param cls the return type in the form of a class type, can be null
+     * @param provided a flag indicating whether the return type is provided
+     * @throws Exception if the test fails
+     */
+    @Test(dataProvider = "NPE")
+    public void testNPEWithEvaluate(String expression, Object item, boolean useSource,
+            InputSource source, QName qn, Class<?> cls, boolean provided)
+            throws Exception {
+        XPath xPath = XPathFactory.newInstance().newXPath();
+
+        // test with XPath::evaluate
+        Assert.assertThrows(NullPointerException.class, () -> xpathEvaluate(
+                xPath, expression, item, useSource, source, qn, provided));
+
+        // test with XPathExpression::evaluate
+        Assert.assertThrows(NullPointerException.class, () -> xpathExpressionEvaluate(
+                xPath, expression, item, useSource, source, qn, provided));
+
+        // test with XPath::evaluateExpression
+        Assert.assertThrows(NullPointerException.class, () -> xpathEvaluateExpression(
+                xPath, expression, item, useSource, source, cls, provided));
+
+        // test with XPathExpression::evaluateExpression
+        Assert.assertThrows(NullPointerException.class, () -> xpathExpressionEvaluateExpression(
+                xPath, expression, item, useSource, source, cls, provided));
+    }
+
+    /**
+     * Verifies that XPathExpressionException is thrown upon encountering illegal
+     * XPath expressions when XPath::compile is called.
+     *
      * @param invalidExp an illegal XPath expression
      * @throws Exception if the test fails
      */
-    @Test(dataProvider = "invalid")
-    public void testIllegalExp(String invalidExp) throws Exception {
-        DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
-        Document doc = builder.parse(new org.xml.sax.InputSource(new StringReader("<A/>")));
-        Assert.assertThrows(XPathExpressionException.class, () -> evaluate(doc, invalidExp));
+    @Test(dataProvider = "invalidExp")
+    public void testXPathCompile(String invalidExp) throws Exception {
+        Assert.assertThrows(XPathExpressionException.class, () -> xpathCompile(invalidExp));
     }
 
-    private void evaluate(Document doc, String s) throws XPathExpressionException {
+    /**
+     * Verifies that XPathExpressionException is thrown upon encountering illegal
+     * XPath expressions.
+     * This test tests these methods:
+     *     XPath::evaluate and XPathExpression::evaluate.
+     *     XPath::evaluateExpression and XPathExpression::evaluateExpression.
+
+     *
+     * @param expression an illegal XPath expression
+     * @throws Exception if the test fails
+     */
+    @Test(dataProvider = "invalidExp")
+    public void testCompileErrorWithEvaluate(String expression)
+            throws Exception {
+        XPath xPath = XPathFactory.newInstance().newXPath();
+
+        // test with XPath::evaluate
+        Assert.assertThrows(XPathExpressionException.class, () -> xpathEvaluate(
+                xPath, expression, (Node)null, false, null, null, false));
+
+        // test with XPathExpression::evaluate
+        Assert.assertThrows(XPathExpressionException.class, () -> xpathExpressionEvaluate(
+                xPath, expression, (Node)null, false, null, null, false));
+
+        // test with XPath::evaluateExpression
+        Assert.assertThrows(XPathExpressionException.class, () -> xpathEvaluateExpression(
+                xPath, expression, (Node)null, false, null, null, false));
+
+        // test with XPathExpression::evaluateExpression
+        Assert.assertThrows(XPathExpressionException.class, () -> xpathExpressionEvaluateExpression(
+                xPath, expression, (Node)null, false, null, null, false));
+    }
+
+    /**
+     * Verifies that XPathExpressionException is thrown if the expression is
+     * invalid with the given context.
+     * This test tests these methods:
+     *     XPath::evaluate and XPathExpression::evaluate.
+     *     XPath::evaluateExpression and XPathExpression::evaluateExpression.
+     *
+     * @param expression the expression
+     * @param item the context item, can be null (for non-context dependent expressions)
+     * @param useSource a flag indicating whether the source shall be used instead
+     *                  of the context item
+     * @param source the source
+     * @param qn the return type in the form of a QName, can be null
+     * @param cls the return type in the form of a class type, can be null
+     * @param provided a flag indicating whether the return type is provided
+     * @throws Exception if the test fails
+     */
+    @Test(dataProvider = "expInContext1")
+    public void testExpInContextEval1(String expression, Object item, boolean useSource,
+            InputSource source, QName qn, Class<?> cls, boolean provided)
+            throws Exception {
+        XPath xPath = XPathFactory.newInstance().newXPath();
+
+        // test with XPath::evaluate
+        Assert.assertThrows(XPathExpressionException.class, () -> xpathEvaluate(
+                xPath, expression, item, useSource, source, qn, provided));
+
+        // test with XPathExpression::evaluate
+        Assert.assertThrows(XPathExpressionException.class, () -> xpathExpressionEvaluate(
+                xPath, expression, item, useSource, source, qn, provided));
+
+        // test with XPath::evaluateExpression
+        Assert.assertThrows(XPathExpressionException.class, () -> xpathEvaluateExpression(
+                xPath, expression, item, useSource, source, cls, provided));
+
+        // test with XPathExpression::evaluateExpression
+        Assert.assertThrows(XPathExpressionException.class, () -> xpathExpressionEvaluateExpression(
+                xPath, expression, item, useSource, source, cls, provided));
+    }
+
+    /**
+     * Verifies that XPathExpressionException is thrown if the expression is
+     * invalid with the given context.
+     * This test tests these methods:
+     *     XPath::evaluate and XPathExpression::evaluate.
+     *     XPath::evaluateExpression and XPathExpression::evaluateExpression.
+     *
+     * @param expression the expression
+     * @param item the context item, can be null (for non-context dependent expressions)
+     * @param useSource a flag indicating whether the source shall be used instead
+     *                  of the context item
+     * @param source the source
+     * @param qn the return type in the form of a QName, can be null
+     * @param cls the return type in the form of a class type, can be null
+     * @param provided a flag indicating whether the return type is provided
+     * @throws Exception if the test fails
+     */
+    @Test(dataProvider = "expInContext1")
+    public void testExpInContext(String expression, Object item, boolean useSource,
+            InputSource source, QName qn, Class<?> cls, boolean provided)
+            throws Exception {
+        QName[] qns = {NUMBER, STRING, BOOLEAN, NODESET, NODE};
+        Class[] classes = {Integer.class, Boolean.class, String.class, XPathNodes.class, Node.class};
+        XPath xPath = XPathFactory.newInstance().newXPath();
+
+        for (QName qn1 : qns) {
+            // test with XPath::evaluate
+            Assert.assertThrows(XPathExpressionException.class, () -> xpathEvaluate(
+                    xPath, expression, item, useSource, source, qn1, provided));
+
+            // test with XPathExpression::evaluate
+            Assert.assertThrows(XPathExpressionException.class, () -> xpathExpressionEvaluate(
+                    xPath, expression, item, useSource, source, qn1, provided));
+        }
+
+        for (Class<?> cls1 : classes) {
+            // test with XPath::evaluateExpression
+            Assert.assertThrows(XPathExpressionException.class, () -> xpathEvaluateExpression(
+                    xPath, expression, item, useSource, source, cls1, provided));
+
+            // test with XPathExpression::evaluateExpression
+            Assert.assertThrows(XPathExpressionException.class, () -> xpathExpressionEvaluateExpression(
+                    xPath, expression, item, useSource, source, cls1, provided));
+        }
+    }
+
+    /**
+     * Verifies that the expression is valid with the given context.
+     * This test tests these methods:
+     *     XPath::evaluate and XPathExpression::evaluate.
+     *     XPath::evaluateExpression and XPathExpression::evaluateExpression.
+     *
+     * @param expression the expression
+     * @param item the context item, can be null (for non-context dependent expressions)
+     * @param useSource a flag indicating whether the source shall be used instead
+     *                  of the context item
+     * @param source the source
+     * @param qn the return type in the form of a QName, can be null
+     * @param cls the return type in the form of a class type, can be null
+     * @param provided a flag indicating whether the return type is provided
+     * @throws Exception if the test fails
+     */
+    @Test(dataProvider = "expInContext2")
+    public void testExpInContextEval2(String expression, Object item, boolean useSource,
+            InputSource source, QName qn, Class<?> cls, boolean provided)
+            throws Exception {
+        XPath xPath = XPathFactory.newInstance().newXPath();
+
+        // test with XPath::evaluate
+        xpathEvaluate(xPath, expression, item, useSource, source, qn, provided);
+
+        // test with XPathExpression::evaluate
+        xpathExpressionEvaluate(xPath, expression, item, useSource, source, qn, provided);
+
+        // test with XPath::evaluateExpression
+        xpathEvaluateExpression(xPath, expression, item, useSource, source, cls, provided);
+
+        // test with XPathExpression::evaluateExpression
+        xpathExpressionEvaluateExpression(xPath, expression, item, useSource, source, cls, provided);
+    }
+
+    /**
+     * Verifies that the XPath processor without XPathFunctionResolver throws
+     * XPathExpressionException upon processing an XPath expression that attempts
+     * to call a function.
+     *
+     * @param expression the expression
+     * @param item the context item, can be null (for non-context dependent expressions)
+     * @param useSource a flag indicating whether the source shall be used instead
+     *                  of the context item
+     * @param source the source
+     * @param qn the return type in the form of a QName, can be null
+     * @param cls the return type in the form of a class type, can be null
+     * @param provided a flag indicating whether the return type is provided
+     * @throws Exception if the test fails
+     */
+    @Test(dataProvider = "functions")
+    public void testFunction(String expression, Object item, boolean useSource,
+            InputSource source, QName qn, Class<?> cls, boolean provided)
+            throws Exception {
+        XPath xPath = XPathFactory.newInstance().newXPath();
+
+        // test with XPath::evaluate
+        Assert.assertThrows(XPathExpressionException.class, () -> xpathEvaluate(
+                xPath, expression, item, useSource, source, qn, provided));
+
+        // test with XPathExpression::evaluate
+        Assert.assertThrows(XPathExpressionException.class, () -> xpathExpressionEvaluate(
+                xPath, expression, item, useSource, source, qn, provided));
+
+        // test with XPath::evaluateExpression
+        Assert.assertThrows(XPathExpressionException.class, () -> xpathEvaluateExpression(
+                xPath, expression, item, useSource, source, cls, provided));
+
+        // test with XPathExpression::evaluateExpression
+        Assert.assertThrows(XPathExpressionException.class, () -> xpathExpressionEvaluateExpression(
+                xPath, expression, item, useSource, source, cls, provided));
+    }
+
+// ---- utility methods ----
+    /**
+     * Compiles the specified expression.
+     * @param s the expression
+     * @throws XPathExpressionException if the expression is invalid
+     */
+    private void xpathCompile(String s) throws XPathExpressionException {
         XPath xp = XPathFactory.newInstance().newXPath();
         XPathExpression xe = xp.compile(s);
-        xe.evaluateExpression(doc, Node.class);
+    }
+
+    /**
+     * Runs evaluation using the XPath::evaluate methods.
+     *
+     * @param xPath the XPath object
+     * @param expression the expression
+     * @param item the context item, can be null (for non-context dependent expressions)
+     * @param useSource a flag indicating whether the source shall be used instead
+     *                  of the context item
+     * @param source the source
+     * @param qn the return type in the form of a QName, can be null
+     * @param qnProvided a flag indicating whether the QName is provided
+     * @throws XPathExpressionException
+     */
+    private void xpathEvaluate(XPath xPath, String expression, Object item,
+            boolean useSource, InputSource source, QName qn, boolean qnProvided)
+            throws XPathExpressionException {
+        if (useSource) {
+            if (!qnProvided) {
+                xPath.evaluate(expression, source);
+            } else {
+                xPath.evaluate(expression, source, qn);
+            }
+        } else {
+            if (!qnProvided) {
+                xPath.evaluate(expression, item);
+            } else {
+                xPath.evaluate(expression, item, qn);
+            }
+        }
+    }
+
+    /**
+     * Runs evaluation using the XPathExpression::evaluate methods.
+     *
+     * @param xe the XPathExpression object
+     * @param item the context item, can be null (for non-context dependent expressions)
+     * @param useSource a flag indicating whether the source shall be used instead
+     *                  of the context item
+     * @param source the source
+     * @param qn the return type in the form of a QName, can be null
+     * @param qnProvided a flag indicating whether the QName is provided
+     * @throws XPathExpressionException
+     */
+    private void xpathExpressionEvaluate(XPath xPath, String expression, Object item,
+            boolean useSource, InputSource source, QName qn, boolean qnProvided)
+            throws XPathExpressionException {
+        XPathExpression xe = xPath.compile(expression);
+        if (useSource) {
+            if (!qnProvided) {
+                xe.evaluate(source);
+            } else {
+                xe.evaluate(source, qn);
+            }
+        } else {
+            if (!qnProvided) {
+                xe.evaluate(item);
+            } else {
+                xe.evaluate(item, qn);
+            }
+        }
+    }
+
+    /**
+     * Runs evaluation using the XPath::evaluateExpression methods.
+     *
+     * @param xPath the XPath object
+     * @param expression the expression
+     * @param item the context item, can be null (for non-context dependent expressions)
+     * @param useSource a flag indicating whether the source shall be used instead
+     *                  of the context item
+     * @param source the source
+     * @param cls the class type, can be null
+     * @param clsProvided a flag indicating whether the class type is provided
+     * @throws XPathExpressionException
+     */
+    private void xpathEvaluateExpression(XPath xPath, String expression, Object item,
+            boolean useSource, InputSource source, Class<?> cls, boolean clsProvided)
+            throws XPathExpressionException {
+        if (useSource) {
+            if (!clsProvided) {
+                xPath.evaluateExpression(expression, source);
+            } else {
+                xPath.evaluateExpression(expression, source, cls);
+            }
+        } else {
+            if (!clsProvided) {
+                xPath.evaluateExpression(expression, item);
+            } else {
+                xPath.evaluateExpression(expression, item, cls);
+            }
+        }
+    }
+
+    /**
+     * Runs evaluation using the XPathExpression::evaluateExpression methods.
+     *
+     * @param xe the XPathExpression object
+     * @param item the context item, can be null (for non-context dependent expressions)
+     * @param useSource a flag indicating whether the source shall be used instead
+     *                  of the context item
+     * @param source the source
+     * @param qn the return type in the form of a QName, can be null
+     * @param qnProvided a flag indicating whether the QName is provided
+     * @throws XPathExpressionException
+     */
+    private void xpathExpressionEvaluateExpression(XPath xPath, String expression,
+            Object item, boolean useSource, InputSource source, Class<?> cls, boolean qnProvided)
+            throws XPathExpressionException {
+        XPathExpression xe = xPath.compile(expression);
+        if (useSource) {
+            if (!qnProvided) {
+                xe.evaluateExpression(source);
+            } else {
+                xe.evaluateExpression(source, cls);
+            }
+        } else {
+            if (!qnProvided) {
+                xe.evaluateExpression(item);
+            } else {
+                xe.evaluateExpression(item, cls);
+            }
+        }
+    }
+
+    /**
+     * Returns an empty {@link org.w3c.dom.Document}.
+     * @return a DOM Document, null in case of Exception
+     */
+    private Document getEmptyDocument() {
+        try {
+            return DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
+        } catch (ParserConfigurationException e) {
+            return null;
+        }
+    }
+
+    /**
+     * Returns a DOM Document with dummy content.
+     * @return a DOM Document
+     * @throws Exception
+     */
+    private Document getDummyDoc() throws Exception {
+        DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
+        return builder.parse(new InputSource(new StringReader("<A/>")));
+    }
+
+    /**
+     * Returns a DOM Document with the specified source.
+     * @param s the source
+     * @return a DOM Document
+     * @throws Exception
+     */
+    private Document getDoc(InputSource s) throws Exception {
+        DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
+        return builder.parse(s);
     }
 }