111 lines
3.9 KiB
Java
111 lines
3.9 KiB
Java
/*
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* Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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import java.io.DataInputStream;
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import java.io.ByteArrayOutputStream;
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import java.io.File;
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import java.io.FileInputStream;
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import java.io.FileWriter;
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import java.io.IOException;
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import java.io.PrintWriter;
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import javax.tools.JavaCompiler;
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import javax.tools.ToolProvider;
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/**
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* A factory that generates a class with many methods.
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*/
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public class ClassWithManyMethodsClassLoader extends ClassLoader {
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/**
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* Used to enable/disable keeping the class files and java sources for
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* the generated classes.
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*/
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private static boolean deleteFiles = Boolean.parseBoolean(
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System.getProperty("ClassWithManyMethodsClassLoader.deleteFiles", "true"));
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private JavaCompiler javac;
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public ClassWithManyMethodsClassLoader() {
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javac = ToolProvider.getSystemJavaCompiler();
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}
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private String generateSource(String className, String methodPrefix, int methodCount) {
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StringBuilder sb = new StringBuilder();
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sb.append("public class ")
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.append(className)
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.append("{\n");
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for (int i = 0; i < methodCount; i++) {
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sb.append("public void ")
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.append(methodPrefix)
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.append(i)
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.append("() {}\n");
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}
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sb.append("\n}");
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return sb.toString();
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}
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private byte[] generateClassBytes(String className, String methodPrefix, int methodCount) throws IOException {
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String src = generateSource(className, methodPrefix, methodCount);
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File file = new File(className + ".java");
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try (PrintWriter pw = new PrintWriter(new FileWriter(file))) {
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pw.append(src);
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pw.flush();
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}
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ByteArrayOutputStream err = new ByteArrayOutputStream();
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int exitcode = javac.run(null, null, err, file.getCanonicalPath());
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if (exitcode != 0) {
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// Print Error
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System.err.print(err);
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if (err.toString().contains("java.lang.OutOfMemoryError: Java heap space")) {
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throw new OutOfMemoryError("javac failed with resources exhausted");
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} else {
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throw new RuntimeException("javac failure when compiling: " +
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file.getCanonicalPath());
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}
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} else {
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if (deleteFiles) {
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file.delete();
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}
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}
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File classFile = new File(className + ".class");
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byte[] bytes;
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try (DataInputStream dis = new DataInputStream(new FileInputStream(classFile))) {
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bytes = new byte[dis.available()];
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dis.readFully(bytes);
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}
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if (deleteFiles) {
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classFile.delete();
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}
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return bytes;
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}
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public Class<?> create(String className, String methodPrefix, int methodCount) throws IOException {
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byte[] bytes = generateClassBytes(className, methodPrefix, methodCount);
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return defineClass(className, bytes, 0, bytes.length);
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}
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}
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