/*
* Copyright (C) 2010 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.truth.codegen;
import static java.util.Collections.singleton;
import com.google.common.annotations.GwtIncompatible;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import javax.tools.DiagnosticListener;
import javax.tools.FileObject;
import javax.tools.ForwardingJavaFileManager;
import javax.tools.JavaCompiler;
import javax.tools.JavaFileManager;
import javax.tools.JavaFileObject;
import javax.tools.SimpleJavaFileObject;
import javax.tools.ToolProvider;
// NICKED FROM JSILVER -- BUT DAVID BEAUMONT WROTE MOST OF THAT ONE TOO !
/**
* This is a Java ClassLoader that will attempt to load a class from a string of source code.
*
* <h3>Example</h3>
*
* <pre>
* String className = "com.foo.MyClass";
* String classSource =
* "package com.foo;\n" +
* "public class MyClass implements Runnable {\n" +
* " @Override public void run() {\n" +
* " log(\"Hello world\");\n" +
* " }\n" +
* "}";
*
* // Load class from source.
* ClassLoader classLoader = new CompilingClassLoader(
* parentClassLoader, className, classSource);
* Class myClass = classLoader.loadClass(className);
*
* // Use it.
* Runnable instance = (Runnable)myClass.newInstance();
* instance.run();
* </pre>
*
* Only one chunk of source can be compiled per instance of CompilingClassLoader. If you need to
* compile more, create multiple CompilingClassLoader instances.
*
* Uses Java 1.6's in built compiler API.
*
* If the class cannot be compiled, loadClass() will throw a ClassNotFoundException and log the
* compile errors to System.err. If you don't want the messages logged, or want to explicitly handle
* the messages you can provide your own {@link javax.tools.DiagnosticListener} through
* {#setDiagnosticListener()}.
*
* @see java.lang.ClassLoader
* @see javax.tools.JavaCompiler
*/
@GwtIncompatible("java.lang.reflect.*")
public class CompilingClassLoader extends ClassLoader {
/**
* Thrown when code cannot be compiled.
*/
public static class CompilerException extends Exception {
private static final long serialVersionUID = -2936958840023603270L;
public CompilerException(String message) {
super(message);
}
}
private final Map<String, ByteArrayOutputStream> byteCodeForClasses =
new HashMap<String, ByteArrayOutputStream>();
private static final URI EMPTY_URI;
static {
try {
// Needed to keep SimpleFileObject constructor happy.
EMPTY_URI = new URI("");
} catch (URISyntaxException e) {
throw new Error(e);
}
}
/**
* @param parent Parent classloader to resolve dependencies from.
* @param className Name of class to compile. eg. "com.foo.MyClass".
* @param sourceCode Java source for class. e.g. "package com.foo; class MyClass { ... }".
* @param diagnosticListener Notified of compiler errors (may be null).
*/
public CompilingClassLoader(ClassLoader parent, String className, String sourceCode,
DiagnosticListener<JavaFileObject> diagnosticListener) throws CompilerException {
super(parent);
if (!compileSourceCodeToByteCode(className, sourceCode, diagnosticListener)) {
throw new CompilerException("Could not compile " + className);
}
}
/**
* Override ClassLoader's class resolving method. Don't call this directly, instead use
* {@link ClassLoader#loadClass(String)}.
*/
@Override
public Class<?> findClass(String name) throws ClassNotFoundException {
ByteArrayOutputStream byteCode = byteCodeForClasses.get(name);
if (byteCode == null) {
throw new ClassNotFoundException(name);
}
return defineClass(name, byteCode.toByteArray(), 0, byteCode.size());
}
/**
* @return Whether compilation was successful.
*/
private boolean compileSourceCodeToByteCode(String className, String sourceCode,
DiagnosticListener<JavaFileObject> diagnosticListener) {
JavaCompiler javaCompiler = ToolProvider.getSystemJavaCompiler();
// Set up the in-memory filesystem.
InMemoryFileManager fileManager =
new InMemoryFileManager(javaCompiler.getStandardFileManager(null, null, null));
JavaFileObject javaFile = new InMemoryJavaFile(className, sourceCode);
// Javac option: remove these when the javac zip impl is fixed
// (http://b/issue?id=1822932)
System.setProperty("useJavaUtilZip", "true"); // setting value to any non-null string
List<String> options = new LinkedList<String>();
// this is ignored by javac currently but useJavaUtilZip should be
// a valid javac XD option, which is another bug
options.add("-XDuseJavaUtilZip");
// Now compile!
JavaCompiler.CompilationTask compilationTask = javaCompiler.getTask(null, // Null: log any
// unhandled errors to
// stderr.
fileManager, diagnosticListener, options, null, singleton(javaFile));
return compilationTask.call();
}
/**
* Provides an in-memory representation of JavaFileManager abstraction, so we do not need to write
* any files to disk.
*
* When files are written to, rather than putting the bytes on disk, they are appended to buffers
* in byteCodeForClasses.
*
* @see javax.tools.JavaFileManager
*/
private class InMemoryFileManager extends ForwardingJavaFileManager<JavaFileManager> {
public InMemoryFileManager(JavaFileManager fileManager) {
super(fileManager);
}
@Override
public JavaFileObject getJavaFileForOutput(Location location, final String className,
JavaFileObject.Kind kind, FileObject sibling) throws IOException {
return new SimpleJavaFileObject(EMPTY_URI, kind) {
@Override
public OutputStream openOutputStream() throws IOException {
ByteArrayOutputStream outputStream = byteCodeForClasses.get(className);
if (outputStream != null) {
throw new IllegalStateException("Cannot write more than once");
}
// Reasonable size for a simple .class.
outputStream = new ByteArrayOutputStream(256);
byteCodeForClasses.put(className, outputStream);
return outputStream;
}
};
}
}
private static class InMemoryJavaFile extends SimpleJavaFileObject {
private final String sourceCode;
public InMemoryJavaFile(String className, String sourceCode) {
super(makeUri(className), Kind.SOURCE);
this.sourceCode = sourceCode;
}
private static URI makeUri(String className) {
try {
return new URI(className.replaceAll("\\.", "/") + Kind.SOURCE.extension);
} catch (URISyntaxException e) {
throw new RuntimeException(e); // Not sure what could cause this.
}
}
@Override
public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException {
return sourceCode;
}
}
}