我正在使用javax.tools包中的JavaCompiler（JDK 1.7）来动态编译一些代码，就像这样：
compiler.run(null, null, "-cp", paths, "path/to/my/file.java");
它可以工作，但我想全部在内存中完成（例如，传递包含代码的字符串，而不是源文件，并返回字节码而不是 .class 文件）。我发现扩展 InputStream 和 OutputStream 参数没用，因为它可能与控制台中的相同。您知道如何使运行方法像这样工作吗？或者您知道使用 getTask() 方法进行此操作的确认方式吗？（扩展 FileManager 看起来很容易，但没有那么容易 :)
我在Mac OS Java 7上运行了上面的代码，没有一个能够工作。所以我写了一个https://github.com/trung/InMemoryJavaCompiler
StringBuilder source = new StringBuilder()
.append("package org.mdkt;\n")
.append("public class HelloClass {\n")
.append(" public String hello() { return \"hello\"; }")
.append("}");
Class<?> helloClass = InMemoryJavaCompiler.compile("org.mdkt.HelloClass", source.toString());
我认为这里可能会有帮助，它基本上展示了如何从内存中编译Java源代码（字符串位于类中）。
它使用PrinterWriter和StringWriter将源代码写入String/内存中，然后使用JavaCompiler类（自JDK 6以来）来编译和运行程序：
import javax.tools.Diagnostic;
import javax.tools.DiagnosticCollector;
import javax.tools.JavaCompiler;
import javax.tools.JavaCompiler.CompilationTask;
import javax.tools.JavaFileObject;
import javax.tools.SimpleJavaFileObject;
import javax.tools.ToolProvider;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.InvocationTargetException;
import java.net.URI;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Arrays;
public class CompileSourceInMemory {
public static void main(String args[]) throws IOException {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();
StringWriter writer = new StringWriter();
PrintWriter out = new PrintWriter(writer);
out.println("public class HelloWorld {");
out.println(" public static void main(String args[]) {");
out.println(" System.out.println(\"This is in another java file\");");
out.println(" }");
out.println("}");
out.close();
JavaFileObject file = new JavaSourceFromString("HelloWorld", writer.toString());
Iterable<? extends JavaFileObject> compilationUnits = Arrays.asList(file);
CompilationTask task = compiler.getTask(null, null, diagnostics, null, null, compilationUnits);
boolean success = task.call();
for (Diagnostic diagnostic : diagnostics.getDiagnostics()) {
System.out.println(diagnostic.getCode());
System.out.println(diagnostic.getKind());
System.out.println(diagnostic.getPosition());
System.out.println(diagnostic.getStartPosition());
System.out.println(diagnostic.getEndPosition());
System.out.println(diagnostic.getSource());
System.out.println(diagnostic.getMessage(null));
}
System.out.println("Success: " + success);
if (success) {
try {
URLClassLoader classLoader = URLClassLoader.newInstance(new URL[] { new File("").toURI().toURL() });
Class.forName("HelloWorld", true, classLoader).getDeclaredMethod("main", new Class[] { String[].class }).invoke(null, new Object[] { null });
} catch (ClassNotFoundException e) {
System.err.println("Class not found: " + e);
} catch (NoSuchMethodException e) {
System.err.println("No such method: " + e);
} catch (IllegalAccessException e) {
System.err.println("Illegal access: " + e);
} catch (InvocationTargetException e) {
System.err.println("Invocation target: " + e);
}
}
}
}
class JavaSourceFromString extends SimpleJavaFileObject {
final String code;
JavaSourceFromString(String name, String code) {
super(URI.create("string:///" + name.replace('.','/') + Kind.SOURCE.extension),Kind.SOURCE);
this.code = code;
}
@Override
public CharSequence getCharContent(boolean ignoreEncodingErrors) {
return code;
}
}
这是一个完全在内存中编译的类。
我几乎全部引用自Rekha Kumari（2011年6月）的博客，不过我的版本要短100多行，并且具有更多功能（但没有文档：P）。
它可以一次编译多个类，这是编译彼此依赖的类的唯一方法。如果您想知道“CompilerFeedback”类的作用，我正在为编码游戏开发一个小型Java IDE，我需要它。我包含在这里，因为我觉得你想要对这个编译器做些事情，这个简化可能会有所帮助。（我意识到CompilerFeedback类中的某些代码是完全错误的。它被回收自数年前的一次尝试。）
还有一个实用方法，虽然不需要编译，但从类的源代码（包括包名，如果提供了）中派生出完整的类名。对于调用需要此信息的编译器非常有用。
演示类：
import java.util.ArrayList;
import java.util.List;
public class Demo {
public static void main(final String[] args) {
final InMemoryCompiler.IMCSourceCode cls1source;
final InMemoryCompiler.IMCSourceCode cls2source;
final StringBuilder sb = new StringBuilder();
sb.append("package toast;\n");
sb.append("public class DynaClass {\n");
sb.append(" public static void main(final String[] args) {");
sb.append(" System.out.println(\"Based massively on the work of Rekha Kumari, http://javapracs.blogspot.de/2011/06/dynamic-in-memory-compilation-using.html\");\n");
sb.append(" System.out.println(\"This is the main method speaking.\");\n");
sb.append(" System.out.println(\"Args: \" + java.util.Arrays.toString(args));\n");
sb.append(" final Test test = new Test();\n");
sb.append(" }\n");
sb.append(" public String toString() {\n");
sb.append(" return \"Hello, I am \" + ");
sb.append("this.getClass().getSimpleName();\n");
sb.append(" }\n");
sb.append("}\n");
cls1source = new InMemoryCompiler.IMCSourceCode("toast.DynaClass", sb.toString());
sb.setLength(0);
sb.append("package toast;\n");
sb.append("public class Test {\n");
sb.append(" public Test() {\n");
sb.append(" System.out.println(\"class Test constructor reporting in.\");\n");
sb.append(" System.out.println(new DynaClass());\n");
sb.append(" }\n");
sb.append("}\n");
cls2source = new InMemoryCompiler.IMCSourceCode("toast.Test", sb.toString());
final List<InMemoryCompiler.IMCSourceCode> classSources = new ArrayList<>();
classSources.add(cls1source);
classSources.add(cls2source);
final InMemoryCompiler uCompiler = new InMemoryCompiler(classSources);
final CompilerFeedback compilerFeedback = uCompiler.compile();
System.out.println("\n\nCOMPILER FEEDBACK: " + compilerFeedback);
if (compilerFeedback != null && compilerFeedback.success) {
try {
System.out.println("\nTOSTRING DEMO:");
uCompiler.runToString(cls1source.fullClassName);
} catch (Exception e) {
e.printStackTrace();
}
try {
System.out.println("\nMAIN DEMO:");
uCompiler.runMain(cls1source.fullClassName, new String[] { "test1", "test2" });
} catch (Exception e) {
e.printStackTrace();
}
}
System.exit(0);
}
}
编译器类：
import javax.tools.*;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URI;
import java.security.SecureClassLoader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* MASSIVELY based on http://javapracs.blogspot.de/2011/06/dynamic-in-memory-compilation-using.html by Rekha Kumari
* (June 2011)
*/
final public class InMemoryCompiler {
final public static class IMCSourceCode {
final public String fullClassName;
final public String sourceCode;
/**
* @param fullClassName Full name of the class that will be compiled. If the class should be in some package,
* fullName should contain it too, for example: "testpackage.DynaClass"
* @param sourceCode the source code
*/
public IMCSourceCode(final String fullClassName, final String sourceCode) {
this.fullClassName = fullClassName;
this.sourceCode = sourceCode;
}
}
final public boolean valid;
final private List<IMCSourceCode> classSourceCodes;
final private JavaFileManager fileManager;
public InMemoryCompiler(final List<IMCSourceCode> classSourceCodes) {
this.classSourceCodes = classSourceCodes;
final JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
if (compiler == null) {
fileManager = null;
valid = false;
System.err.println("ToolProvider.getSystemJavaCompiler() returned null! This program needs to be run on a system with an installed JDK.");
return;
}
valid = true;
fileManager = new ForwardingJavaFileManager<JavaFileManager>(compiler.getStandardFileManager(null, null, null)) {
final private Map<String, ByteArrayOutputStream> byteStreams = new HashMap<>();
@Override
public ClassLoader getClassLoader(final Location location) {
return new SecureClassLoader() {
@Override
protected Class<?> findClass(final String className) throws ClassNotFoundException {
final ByteArrayOutputStream bos = byteStreams.get(className);
if (bos == null) {
return null;
}
final byte[] b = bos.toByteArray();
return super.defineClass(className, b, 0, b.length);
}
};
}
@Override
public JavaFileObject getJavaFileForOutput(final Location location, final String className, final JavaFileObject.Kind kind, final FileObject sibling) throws IOException {
return new SimpleJavaFileObject(URI.create("string:///" + className.replace('.', '/') + kind.extension), kind) {
@Override
public OutputStream openOutputStream() throws IOException {
ByteArrayOutputStream bos = byteStreams.get(className);
if (bos == null) {
bos = new ByteArrayOutputStream();
byteStreams.put(className, bos);
}
return bos;
}
};
}
};
}
public CompilerFeedback compile() {
if (!valid) {
return null;
}
final List<JavaFileObject> files = new ArrayList<>();
for (IMCSourceCode classSourceCode : classSourceCodes) {
URI uri = null;
try {
uri = URI.create("string:///" + classSourceCode.fullClassName.replace('.', '/') + JavaFileObject.Kind.SOURCE.extension);
} catch (Exception e) {
// e.printStackTrace();
}
if (uri != null) {
final SimpleJavaFileObject sjfo = new SimpleJavaFileObject(uri, JavaFileObject.Kind.SOURCE) {
@Override
public CharSequence getCharContent(final boolean ignoreEncodingErrors) {
return classSourceCode.sourceCode;
}
};
files.add(sjfo);
}
}
final DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
final JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
if (files.size() > 0) {
final JavaCompiler.CompilationTask task = compiler.getTask(null, fileManager, diagnostics, null, null, files);
return new CompilerFeedback(task.call(), diagnostics);
} else {
return null;
}
}
public void runToString(final String className) throws InstantiationException, IllegalAccessException, ClassNotFoundException {
if (!valid) {
return;
}
final Class<?> theClass = getCompiledClass(className);
final Object instance = theClass.newInstance();
System.out.println(instance);
}
public void runMain(final String className, final String[] args) throws IllegalAccessException, ClassNotFoundException, NoSuchMethodException, InvocationTargetException {
if (!valid) {
return;
}
final Class<?> theClass = getCompiledClass(className);
final Method mainMethod = theClass.getDeclaredMethod("main", String[].class);
mainMethod.invoke(null, new Object[] { args });
}
public Class<?> getCompiledClass(final String className) throws ClassNotFoundException {
if (!valid) {
throw new IllegalStateException("InMemoryCompiler instance not usable because ToolProvider.getSystemJavaCompiler() returned null: No JDK installed.");
}
final ClassLoader classLoader = fileManager.getClassLoader(null);
final Class<?> ret = classLoader.loadClass(className);
if (ret == null) {
throw new ClassNotFoundException("Class returned by ClassLoader was null!");
}
return ret;
}
}
编译器反馈类：
import javax.tools.Diagnostic;
import javax.tools.DiagnosticCollector;
import javax.tools.JavaFileObject;
import javax.tools.SimpleJavaFileObject;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
final public class CompilerFeedback {
final public boolean success;
final public List<CompilerMessage> messages = new ArrayList<>();
public CompilerFeedback(final Boolean success, final DiagnosticCollector<JavaFileObject> diagnostics) {
this.success = success != null && success;
for (Diagnostic<? extends JavaFileObject> diagnostic : diagnostics.getDiagnostics()) {
messages.add(new CompilerMessage(diagnostic));
}
}
public String toString() {
final StringBuilder sb = new StringBuilder();
sb.append("SUCCESS: ").append(success).append('\n');
final int iTop = messages.size();
for (int i = 0; i < iTop; i++) {
sb.append("\n[MESSAGE ").append(i + 1).append(" OF ").append(iTop).append("]\n\n");
// sb.append(messages.get(i).toString()).append("\n");
// sb.append(messages.get(i).toStringForList()).append("\n");
sb.append(messages.get(i).toStringForDebugging()).append("\n");
}
return sb.toString();
}
final public static class CompilerMessage {
final public Diagnostic<? extends JavaFileObject> compilerInfo;
final public String typeOfProblem;
final public String typeOfProblem_forDebugging;
final public String multiLineMessage;
final public int lineNumber;
final public int columnNumber;
final public int textHighlightPos_lineStart;
final public int textHighlightPos_problemStart;
final public int textHighlightPos_problemEnd;
final public String sourceCode;
final public String codeOfConcern;
final public String codeOfConcernLong;
CompilerMessage(final Diagnostic<? extends JavaFileObject> diagnostic) {
final JavaFileObject sourceFileObject = diagnostic.getSource();
String sourceCodePreliminary = null;
if (sourceFileObject instanceof SimpleJavaFileObject) {
final SimpleJavaFileObject simpleSourceFileObject = (SimpleJavaFileObject) sourceFileObject;
try {
final CharSequence charSequence = simpleSourceFileObject.getCharContent(false);
sourceCodePreliminary = charSequence.toString();
} catch (IOException e) {
e.printStackTrace();
}
}
if (sourceCodePreliminary == null) {
sourceCode = "[SOURCE CODE UNAVAILABLE]";
} else {
sourceCode = sourceCodePreliminary;
}
compilerInfo = diagnostic;
typeOfProblem = diagnostic.getKind().name();
typeOfProblem_forDebugging = "toString() = " + diagnostic.getKind().toString() + "; name() = " + typeOfProblem;
lineNumber = (int) compilerInfo.getLineNumber();
columnNumber = (int) compilerInfo.getColumnNumber();
final int sourceLen = sourceCode.length();
textHighlightPos_lineStart = (int) Math.min(Math.max(0, diagnostic.getStartPosition()), sourceLen);
textHighlightPos_problemStart = (int) Math.min(Math.max(0, diagnostic.getPosition()), sourceLen);
textHighlightPos_problemEnd = (int) Math.min(Math.max(0, diagnostic.getEndPosition()), sourceLen);
final StringBuilder reformattedMessage = new StringBuilder();
final String message = diagnostic.getMessage(Locale.US);
final int messageCutOffPosition = message.indexOf("location:");
final String[] messageParts;
if (messageCutOffPosition >= 0) {
messageParts = message.substring(0, messageCutOffPosition).split("\n");
} else {
messageParts = message.split("\n");
}
for (String s : messageParts) {
String s2 = s.trim();
if (s2.length() > 0) {
boolean lengthChanged;
do {
final int lBeforeReplace = s2.length();
s2 = s2.replace(" ", " ");
lengthChanged = (s2.length() != lBeforeReplace);
} while (lengthChanged);
reformattedMessage.append(s2).append("\n");
}
}
codeOfConcern = sourceCode.substring(textHighlightPos_problemStart, textHighlightPos_problemEnd);
codeOfConcernLong = sourceCode.substring(textHighlightPos_lineStart, textHighlightPos_problemEnd);
if (!codeOfConcern.isEmpty()) {
reformattedMessage.append("Code of concern: \"").append(codeOfConcern).append('\"');
}
multiLineMessage = reformattedMessage.toString();
}
public String toStringForList() {
if (compilerInfo == null) {
return "No compiler!";
} else {
return compilerInfo.getCode();
}
}
public String toStringForDebugging() {
final StringBuilder ret = new StringBuilder();
ret.append("Type of problem: ").append(typeOfProblem_forDebugging).append("\n\n");
ret.append("Message:\n").append(multiLineMessage).append("\n\n");
ret.append(compilerInfo.getCode()).append("\n\n");
ret.append("line number: ").append(lineNumber).append("\n");
ret.append("column number: ").append(columnNumber).append("\n");
ret.append("textHighlightPos_lineStart: ").append(textHighlightPos_lineStart).append("\n");
ret.append("textHighlightPos_problemStart: ").append(textHighlightPos_problemStart).append("\n");
ret.append("textHighlightPos_problemEnd: ").append(textHighlightPos_problemEnd).append("\n");
return ret.toString();
}
@Override
public String toString() {
// return compilerInfo.getMessage(Locale.US);
return typeOfProblem + ": " + multiLineMessage + "\n";
}
}
}
实用方法（三个上述类不需要）：
final public static String PREFIX_CLASSNAME = "class ";
final public static String PREFIX_PACKAGENAME = "package ";
final public static String CHARSET_JAVAKEYWORDENDERS = " \n[](){}<>;,\"\\/*+-=%!&?@:";
/**
* @return e.g. "com.dreamspacepresident.TestClass" if the source's first root level "class" (I'm talking about {}
* hierarchy.) is named "TestClass", and if the "package" name is "com.dreamspacepresident". Null is returned if
* sourceCode is null or does not provide a class name. (Mind that the parsing is done in a quite crappy way.)
*/
public static String deriveFullClassNameFromSource(final String sourceCode) {
if (sourceCode == null) {
return null;
}
final int firstBr = sourceCode.indexOf('{');
if (firstBr >= 0) {
// DETERMINE CLASS NAME
final int firstClass = sourceCode.indexOf(PREFIX_CLASSNAME);
if (firstClass < firstBr) {
String className = sourceCode.substring(firstClass + PREFIX_CLASSNAME.length(), firstBr).trim();
final int classNameEnd = indexOfAnyOfThese(className, CHARSET_JAVAKEYWORDENDERS);
if (classNameEnd >= 0) {
className = className.substring(0, classNameEnd);
}
if (!className.isEmpty()) {
// DETERMINE PACKAGE NAME
String packageName = null;
final int firstPackage = sourceCode.indexOf(PREFIX_PACKAGENAME);
if (firstPackage >= 0 && firstPackage < firstBr && firstPackage < firstClass) {
packageName = sourceCode.substring(firstPackage + PREFIX_PACKAGENAME.length(), firstBr).trim();
final int packageNameEnd = indexOfAnyOfThese(packageName, CHARSET_JAVAKEYWORDENDERS);
if (packageNameEnd >= 0) {
packageName = packageName.substring(0, packageNameEnd);
}
}
return (packageName != null && !packageName.isEmpty() ? packageName + "." : "") + className;
}
}
}
return null;
}
/**
* Looks for the first occurrence of ANY of the given characters, which is easier than using a bunch of
* String.indexOf() calls.
*
* @return -1 if not found, otherwise the String index of the first hit
*/
public static int indexOfAnyOfThese(final String text, final String characters) {
if (text != null && !text.isEmpty() && characters != null && !characters.isEmpty()) {
final int lenT = text.length();
final int lenC = characters.length();
for (int i = 0; i < lenT; i++) {
final char c = text.charAt(i);
for (int ii = 0; ii < lenC; ii++) {
if (c == characters.charAt(ii)) {
return i;
}
}
}
}
return -1;
}
erolagnab的示例，可以这么做。
http://vanillajava.blogspot.co.uk/2010_11_01_archive.html
StringBuilder sourceCode = new StringBuilder();
sourceCode.append("package org.mdkt;\n")
.append("public class HelloClass {\n")
.append(" public String hello() { return \"hello\"; }")
.append("}");
Class<?> helloClass = CACHED_COMPILER.compile("org.mdkt.HelloClass",
sourceCode.toString());
更新，源代码可以在这里找到 https://github.com/OpenHFT/Java-Runtime-Compiler
您可以通过maven获取最新版本的构建 http://search.maven.org/#browse%7C842970587
以下是一个更长的例子。
// this writes the file to disk only when debugging is enabled.
CachedCompiler cc = CompilerUtils.DEBUGGING ?
new CachedCompiler(new File(parent, "src/test/java"), new File(parent, "target/compiled")) :
CompilerUtils.CACHED_COMPILER;
String text = "generated test " + new Date();
Class fooBarTeeClass = cc.loadFromJava("eg.FooBarTee", "package eg;\n" +
'\n' +
"import eg.components.BarImpl;\n" +
"import eg.components.TeeImpl;\n" +
"import eg.components.Foo;\n" +
'\n' +
"public class FooBarTee{\n" +
" public final String name;\n" +
" public final TeeImpl tee;\n" +
" public final BarImpl bar;\n" +
" public final BarImpl copy;\n" +
" public final Foo foo;\n" +
'\n' +
" public FooBarTee(String name) {\n" +
" // when viewing this file, ensure it is synchronised with the copy on disk.\n" +
" System.out.println(\"" + text + "\");\n" +
" this.name = name;\n" +
'\n' +
" tee = new TeeImpl(\"test\");\n" +
'\n' +
" bar = new BarImpl(tee, 55);\n" +
'\n' +
" copy = new BarImpl(tee, 555);\n" +
'\n' +
" // you should see the current date here after synchronisation.\n" +
" foo = new Foo(bar, copy, \"" + text + "\", 5);\n" +
" }\n" +
'\n' +
" public void start() {\n" +
" }\n" +
'\n' +
" public void stop() {\n" +
" }\n" +
'\n' +
" public void close() {\n" +
" stop();\n" +
'\n' +
" }\n" +
"}\n");
// add a debug break point here and step into this method.
FooBarTee fooBarTee = new FooBarTee("test foo bar tee");
Foo foo = fooBarTee.foo;
assertNotNull(foo);
assertEquals(text, foo.s);
您可以在此处先尝试：http://ideone.com/cu1GhE#view_edit_box
以下代码基于Rekha Kumari的代码：
Main.java
package com.mycompany.java;
//import org.slf4j.Logger;
//import org.slf4j.LoggerFactory;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class Main {
//private static final Logger logger = LoggerFactory.getLogger(Main.class);
public static void main(String[] args) {
try {
StringWriter writer = new StringWriter();
PrintWriter out = new PrintWriter(writer);
out.println("package com.mycompany.script;");
out.println("");
out.println("public class HelloWorld {");
out.println(" public static void main(String args[]) {");
out.println(" System.out.println(\"This is in another java file\");");
out.println(" }");
out.println("}");
out.close();
String fullName = "com.mycompany.script.HelloWorld";
String src = writer.toString();
DynamicCompiler uCompiler = new DynamicCompiler(fullName, src);
uCompiler.compile();
uCompiler.run();
} catch (Exception e) {
//logger.error("Exception:", e);
System.out.print("Exception");
}
}
}
DynamicCompiler.java
package com.mycompany.java;
//import org.slf4j.Logger;
//import org.slf4j.LoggerFactory;
import javax.tools.*;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.reflect.InvocationTargetException;
import java.net.URI;
import java.security.SecureClassLoader;
import java.util.ArrayList;
import java.util.List;
// Based on: http://javapracs.blogspot.cz/2011/06/dynamic-in-memory-compilation-using.html
public class DynamicCompiler {
//private static final Logger logger = LoggerFactory.getLogger(DynamicCompiler.class);
private JavaFileManager fileManager;
private String fullName;
private String sourceCode;
public DynamicCompiler(String fullName, String srcCode) {
this.fullName = fullName;
this.sourceCode = srcCode;
this.fileManager = initFileManager();
}
public JavaFileManager initFileManager() {
if (fileManager != null)
return fileManager;
else {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
fileManager = new
ClassFileManager(compiler
.getStandardFileManager(null, null, null));
return fileManager;
}
}
public void compile() {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
List<JavaFileObject> files = new ArrayList<>();
files.add(new CharSequenceJavaFileObject(fullName, sourceCode));
compiler.getTask(
null,
fileManager,
null,
null,
null,
files
).call();
}
public void run() throws InstantiationException, IllegalAccessException, ClassNotFoundException {
try {
fileManager
.getClassLoader(null)
.loadClass(fullName)
.getDeclaredMethod("main", new Class[]{String[].class})
.invoke(null, new Object[]{null});
} catch (InvocationTargetException e) {
System.out.print("InvocationTargetException");
//logger.error("InvocationTargetException:", e);
} catch (NoSuchMethodException e) {
System.out.print("NoSuchMethodException ");
//logger.error("NoSuchMethodException:", e);
}
}
public class CharSequenceJavaFileObject extends SimpleJavaFileObject {
/**
* CharSequence representing the source code to be compiled
*/
private CharSequence content;
public CharSequenceJavaFileObject(String className, CharSequence content) {
super(URI.create("string:///" + className.replace('.', '/') + Kind.SOURCE.extension), Kind.SOURCE);
this.content = content;
}
public CharSequence getCharContent(boolean ignoreEncodingErrors) {
return content;
}
}
public class ClassFileManager extends ForwardingJavaFileManager {
private JavaClassObject javaClassObject;
public ClassFileManager(StandardJavaFileManager standardManager) {
super(standardManager);
}
@Override
public ClassLoader getClassLoader(Location location) {
return new SecureClassLoader() {
@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {
byte[] b = javaClassObject.getBytes();
return super.defineClass(name, javaClassObject.getBytes(), 0, b.length);
}
};
}
public JavaFileObject getJavaFileForOutput(Location location, String className, JavaFileObject.Kind kind, FileObject sibling) throws IOException {
this.javaClassObject = new JavaClassObject(className, kind);
return this.javaClassObject;
}
}
public class JavaClassObject extends SimpleJavaFileObject {
protected final ByteArrayOutputStream bos =
new ByteArrayOutputStream();
public JavaClassObject(String name, Kind kind) {
super(URI.create("string:///" + name.replace('.', '/')
+ kind.extension), kind);
}
public byte[] getBytes() {
return bos.toByteArray();
}
@Override
public OutputStream openOutputStream() throws IOException {
return bos;
}
}
}
Object instance = fileManager.getClassLoader(null).loadClass(name).newInstance();
而在运行时，我想将该“instance”变量用作调用方法调用的第一个参数，但这不起作用，因为调用期望一个声明类的实例，而不是对象。有没有办法让这个工作？ - SinghDynamicCompiler类中。然后，你创建对象实例并将它传递给.invoke(null, new Object[]{null})调用作为一个参数。没有细节信息，我们无法提供更多帮助。也许你应该将它发布为一个新问题。 :-) - MartyIX[interface] instance = fileManager.getClassLoader(null).loadClass(name).asSubclass([interface].class).newInstance（）;instance.[methodName]()。MemoryJavaCompiler.java
package me.soulmachine.compiler;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Writer;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import javax.tools.*;
/**
* Simple interface to Java compiler using JSR 199 Compiler API.
*/
public class MemoryJavaCompiler {
private javax.tools.JavaCompiler tool;
private StandardJavaFileManager stdManager;
public MemoryJavaCompiler() {
tool = ToolProvider.getSystemJavaCompiler();
if (tool == null) {
throw new RuntimeException("Could not get Java compiler. Please, ensure that JDK is used instead of JRE.");
}
stdManager = tool.getStandardFileManager(null, null, null);
}
/**
* Compile a single static method.
*/
public Method compileStaticMethod(final String methodName, final String className,
final String source)
throws ClassNotFoundException {
final Map<String, byte[]> classBytes = compile(className + ".java", source);
final MemoryClassLoader classLoader = new MemoryClassLoader(classBytes);
final Class clazz = classLoader.loadClass(className);
final Method[] methods = clazz.getDeclaredMethods();
for (final Method method : methods) {
if (method.getName().equals(methodName)) {
if (!method.isAccessible()) method.setAccessible(true);
return method;
}
}
throw new NoSuchMethodError(methodName);
}
public Map<String, byte[]> compile(String fileName, String source) {
return compile(fileName, source, new PrintWriter(System.err), null, null);
}
/**
* compile given String source and return bytecodes as a Map.
*
* @param fileName source fileName to be used for error messages etc.
* @param source Java source as String
* @param err error writer where diagnostic messages are written
* @param sourcePath location of additional .java source files
* @param classPath location of additional .class files
*/
private Map<String, byte[]> compile(String fileName, String source,
Writer err, String sourcePath, String classPath) {
// to collect errors, warnings etc.
DiagnosticCollector<JavaFileObject> diagnostics =
new DiagnosticCollector<JavaFileObject>();
// create a new memory JavaFileManager
MemoryJavaFileManager fileManager = new MemoryJavaFileManager(stdManager);
// prepare the compilation unit
List<JavaFileObject> compUnits = new ArrayList<JavaFileObject>(1);
compUnits.add(fileManager.makeStringSource(fileName, source));
return compile(compUnits, fileManager, err, sourcePath, classPath);
}
private Map<String, byte[]> compile(final List<JavaFileObject> compUnits,
final MemoryJavaFileManager fileManager,
Writer err, String sourcePath, String classPath) {
// to collect errors, warnings etc.
DiagnosticCollector<JavaFileObject> diagnostics =
new DiagnosticCollector<JavaFileObject>();
// javac options
List<String> options = new ArrayList<String>();
options.add("-Xlint:all");
// options.add("-g:none");
options.add("-deprecation");
if (sourcePath != null) {
options.add("-sourcepath");
options.add(sourcePath);
}
if (classPath != null) {
options.add("-classpath");
options.add(classPath);
}
// create a compilation task
javax.tools.JavaCompiler.CompilationTask task =
tool.getTask(err, fileManager, diagnostics,
options, null, compUnits);
if (task.call() == false) {
PrintWriter perr = new PrintWriter(err);
for (Diagnostic diagnostic : diagnostics.getDiagnostics()) {
perr.println(diagnostic);
}
perr.flush();
return null;
}
Map<String, byte[]> classBytes = fileManager.getClassBytes();
try {
fileManager.close();
} catch (IOException exp) {
}
return classBytes;
}
}
MemoryJavaFileManager.java
package me.soulmachine.compiler;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URI;
import java.nio.CharBuffer;
import java.util.HashMap;
import java.util.Map;
import javax.tools.FileObject;
import javax.tools.ForwardingJavaFileManager;
import javax.tools.JavaFileManager;
import javax.tools.JavaFileObject;
import javax.tools.JavaFileObject.Kind;
import javax.tools.SimpleJavaFileObject;
/**
* JavaFileManager that keeps compiled .class bytes in memory.
*/
@SuppressWarnings("unchecked")
final class MemoryJavaFileManager extends ForwardingJavaFileManager {
/** Java source file extension. */
private final static String EXT = ".java";
private Map<String, byte[]> classBytes;
public MemoryJavaFileManager(JavaFileManager fileManager) {
super(fileManager);
classBytes = new HashMap<>();
}
public Map<String, byte[]> getClassBytes() {
return classBytes;
}
public void close() throws IOException {
classBytes = null;
}
public void flush() throws IOException {
}
/**
* A file object used to represent Java source coming from a string.
*/
private static class StringInputBuffer extends SimpleJavaFileObject {
final String code;
StringInputBuffer(String fileName, String code) {
super(toURI(fileName), Kind.SOURCE);
this.code = code;
}
public CharBuffer getCharContent(boolean ignoreEncodingErrors) {
return CharBuffer.wrap(code);
}
}
/**
* A file object that stores Java bytecode into the classBytes map.
*/
private class ClassOutputBuffer extends SimpleJavaFileObject {
private String name;
ClassOutputBuffer(String name) {
super(toURI(name), Kind.CLASS);
this.name = name;
}
public OutputStream openOutputStream() {
return new FilterOutputStream(new ByteArrayOutputStream()) {
public void close() throws IOException {
out.close();
ByteArrayOutputStream bos = (ByteArrayOutputStream)out;
classBytes.put(name, bos.toByteArray());
}
};
}
}
public JavaFileObject getJavaFileForOutput(JavaFileManager.Location location,
String className,
Kind kind,
FileObject sibling) throws IOException {
if (kind == Kind.CLASS) {
return new ClassOutputBuffer(className);
} else {
return super.getJavaFileForOutput(location, className, kind, sibling);
}
}
static JavaFileObject makeStringSource(String fileName, String code) {
return new StringInputBuffer(fileName, code);
}
static URI toURI(String name) {
File file = new File(name);
if (file.exists()) {
return file.toURI();
} else {
try {
final StringBuilder newUri = new StringBuilder();
newUri.append("mfm:///");
newUri.append(name.replace('.', '/'));
if(name.endsWith(EXT)) newUri.replace(newUri.length() - EXT.length(), newUri.length(), EXT);
return URI.create(newUri.toString());
} catch (Exception exp) {
return URI.create("mfm:///com/sun/script/java/java_source");
}
}
}
}
MemoryClassLoader.java
package me.soulmachine.compiler;
import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.StringTokenizer;
/**
* ClassLoader that loads .class bytes from memory.
*/
final class MemoryClassLoader extends URLClassLoader {
private Map<String, byte[]> classBytes;
public MemoryClassLoader(Map<String, byte[]> classBytes,
String classPath, ClassLoader parent) {
super(toURLs(classPath), parent);
this.classBytes = classBytes;
}
public MemoryClassLoader(Map<String, byte[]> classBytes, String classPath) {
this(classBytes, classPath, ClassLoader.getSystemClassLoader());
}
public MemoryClassLoader(Map<String, byte[]> classBytes) {
this(classBytes, null, ClassLoader.getSystemClassLoader());
}
public Class load(String className) throws ClassNotFoundException {
return loadClass(className);
}
public Iterable<Class> loadAll() throws ClassNotFoundException {
List<Class> classes = new ArrayList<Class>(classBytes.size());
for (String name : classBytes.keySet()) {
classes.add(loadClass(name));
}
return classes;
}
protected Class findClass(String className) throws ClassNotFoundException {
byte[] buf = classBytes.get(className);
if (buf != null) {
// clear the bytes in map -- we don't need it anymore
classBytes.put(className, null);
return defineClass(className, buf, 0, buf.length);
} else {
return super.findClass(className);
}
}
private static URL[] toURLs(String classPath) {
if (classPath == null) {
return new URL[0];
}
List<URL> list = new ArrayList<URL>();
StringTokenizer st = new StringTokenizer(classPath, File.pathSeparator);
while (st.hasMoreTokens()) {
String token = st.nextToken();
File file = new File(token);
if (file.exists()) {
try {
list.add(file.toURI().toURL());
} catch (MalformedURLException mue) {}
} else {
try {
list.add(new URL(token));
} catch (MalformedURLException mue) {}
}
}
URL[] res = new URL[list.size()];
list.toArray(res);
return res;
}
}
解释:
MemoryJavaFileManager.java中定义了一个StringInputBuffer类。.class文件保存在内存中，我实现了一个MemoryJavaFileManager类。主要思路是重写getJavaFileForOutput()函数，将字节码存储到一个映射表中。MemoryClassLoader，它从映射表中读取字节码并将其转换为类。以下是单元测试。
package me.soulmachine.compiler;
import org.junit.Test;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import static org.junit.Assert.assertEquals;
public class MemoryJavaCompilerTest {
private final static MemoryJavaCompiler compiler = new MemoryJavaCompiler();
@Test public void compileStaticMethodTest()
throws ClassNotFoundException, InvocationTargetException, IllegalAccessException {
final String source = "public final class Solution {\n"
+ "public static String greeting(String name) {\n"
+ "\treturn \"Hello \" + name;\n" + "}\n}\n";
final Method greeting = compiler.compileStaticMethod("greeting", "Solution", source);
final Object result = greeting.invoke(null, "soulmachine");
assertEquals("Hello soulmachine", result.toString());
}
}
String fileToCompile = ;
JavaCompile compiler = ToolProvider.getSystemJavaCompiler();
if(
compiler.run(null, null, null, "PACKAGE_NAME" + java.io.File.separator +"CLASS_NAME.java") == 0
)
System.out.println("Compilation is successful");
else
System.out.println("Compilation Failed");