在上一篇java动态编译 （java在线执行代码后端实现原理（一））文章中实现了 字符串编译成字节码，然后通过反射来运行代码的demo。这一篇文章提供一个如何防止死循环的代码占用cpu的问题。
思路：由于CustomStringJavaCompiler中重定向了System.out的输出位置，肯定不能有多线程并发的情况，否则会照成System.out输出内容错乱，所以我用了 Executors.newFixedThreadPool(1)， 通过Future模式来获取结果，我自定义了一个CustomCallable来处理核心逻辑，在call方法中重新new 了一个Thread来编译并执行代码，然后通过join等待N秒之后强制stop掉正在运行的线程。这样就能及时的kill掉动态运行的代码。
CustomStringJavaCompiler 编译核心类
package compiler.mydemo;
import javax.tools.Diagnostic;
import javax.tools.DiagnosticCollector;
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.StandardJavaFileManager;
import javax.tools.ToolProvider;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URI;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* Create by andy on 2018-12-06 21:25
*/
public class CustomStringJavaCompiler {
//类全名
private String fullClassName;
private String sourceCode;
//存放编译之后的字节码(key:类全名,value:编译之后输出的字节码)
private Map<String, ByteJavaFileObject> javaFileObjectMap = new ConcurrentHashMap<>();
//获取java的编译器
private JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
//存放编译过程中输出的信息
private DiagnosticCollector<JavaFileObject> diagnosticsCollector = new DiagnosticCollector<>();
//执行结果（控制台输出的内容）
private String runResult;
//编译耗时(单位ms)
private long compilerTakeTime;
//运行耗时(单位ms)
private long runTakeTime;
public CustomStringJavaCompiler(String sourceCode) {
this.sourceCode = sourceCode;
this.fullClassName = getFullClassName(sourceCode);
}
/**
* 编译字符串源代码,编译失败在 diagnosticsCollector 中获取提示信息
*
* @return true:编译成功 false:编译失败
*/
public boolean compiler() {
long startTime = System.currentTimeMillis();
//标准的内容管理器,更换成自己的实现，覆盖部分方法
StandardJavaFileManager standardFileManager = compiler.getStandardFileManager(diagnosticsCollector, null, null);
JavaFileManager javaFileManager = new StringJavaFileManage(standardFileManager);
//构造源代码对象
JavaFileObject javaFileObject = new StringJavaFileObject(fullClassName, sourceCode);
//获取一个编译任务
JavaCompiler.CompilationTask task = compiler.getTask(null, javaFileManager, diagnosticsCollector, null, null, Arrays.asList(javaFileObject));
//设置编译耗时
compilerTakeTime = System.currentTimeMillis() - startTime;
return task.call();
}
/**
* 执行main方法，重定向System.out.print
*/
public void runMainMethod() throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, IllegalAccessException, UnsupportedEncodingException {
PrintStream out = System.out;
try {
long startTime = System.currentTimeMillis();
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
PrintStream printStream = new PrintStream(outputStream);
//PrintStream PrintStream = new PrintStream("/Users/andy/Desktop/tem.sql"); //输出到文件
System.setOut(printStream); //测试kill线程暂时屏蔽
StringClassLoader scl = new StringClassLoader();
Class<?> aClass = scl.findClass(fullClassName);
Method main = aClass.getMethod("main", String[].class);
Object[] pars = new Object[]{1};
pars[0] = new String[]{};
main.invoke(null, pars); //调用main方法
//设置运行耗时
runTakeTime = System.currentTimeMillis() - startTime;
//设置打印输出的内容
runResult = new String(outputStream.toByteArray(), "utf-8");
} finally {
//还原默认打印的对象
System.setOut(out);
}
}
/**
* @return 编译信息(错误 警告)
*/
public String getCompilerMessage() {
StringBuilder sb = new StringBuilder();
List<Diagnostic<? extends JavaFileObject>> diagnostics = diagnosticsCollector.getDiagnostics();
for (Diagnostic diagnostic : diagnostics) {
sb.append(diagnostic.toString()).append("
");
}
return sb.toString();
}
/**
* @return 控制台打印的信息
*/
public String getRunResult() {
return runResult;
}
public long getCompilerTakeTime() {
return compilerTakeTime;
}
public long getRunTakeTime() {
return runTakeTime;
}
/**
* 获取类的全名称
*
* @param sourceCode 源码
* @return 类的全名称
*/
public static String getFullClassName(String sourceCode) {
String className = "";
Pattern pattern = Pattern.compile("package\s+\S+\s*;");
Matcher matcher = pattern.matcher(sourceCode);
if (matcher.find()) {
className = matcher.group().replaceFirst("package", "").replace(";", "").trim() + ".";
}
pattern = Pattern.compile("class\s+\S+\s+\{");
matcher = pattern.matcher(sourceCode);
if (matcher.find()) {
className += matcher.group().replaceFirst("class", "").replace("{", "").trim();
}
return className;
}
/**
* 自定义一个字符串的源码对象
*/
private class StringJavaFileObject extends SimpleJavaFileObject {
//等待编译的源码字段
private String contents;
//java源代码 => StringJavaFileObject对象 的时候使用
public StringJavaFileObject(String className, String contents) {
super(URI.create("string:///" + className.replaceAll("\.", "/") + Kind.SOURCE.extension), Kind.SOURCE);
this.contents = contents;
}
//字符串源码会调用该方法
@Override
public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException {
return contents;
}
}
/**
* 自定义一个编译之后的字节码对象
*/
private class ByteJavaFileObject extends SimpleJavaFileObject {
//存放编译后的字节码
private ByteArrayOutputStream outPutStream;
public ByteJavaFileObject(String className, Kind kind) {
super(URI.create("string:///" + className.replaceAll("\.", "/") + Kind.SOURCE.extension), kind);
}
//StringJavaFileManage 编译之后的字节码输出会调用该方法（把字节码输出到outputStream）
@Override
public OutputStream openOutputStream() {
outPutStream = new ByteArrayOutputStream();
return outPutStream;
}
//在类加载器加载的时候需要用到
public byte[] getCompiledBytes() {
return outPutStream.toByteArray();
}
}
/**
* 自定义一个JavaFileManage来控制编译之后字节码的输出位置
*/
private class StringJavaFileManage extends ForwardingJavaFileManager {
StringJavaFileManage(JavaFileManager fileManager) {
super(fileManager);
}
//获取输出的文件对象，它表示给定位置处指定类型的指定类。
@Override
public JavaFileObject getJavaFileForOutput(Location location, String className, JavaFileObject.Kind kind, FileObject sibling) throws IOException {
ByteJavaFileObject javaFileObject = new ByteJavaFileObject(className, kind);
javaFileObjectMap.put(className, javaFileObject);
return javaFileObject;
}
}
/**
* 自定义类加载器, 用来加载动态的字节码
*/
private class StringClassLoader extends ClassLoader {
@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {
ByteJavaFileObject fileObject = javaFileObjectMap.get(name);
if (fileObject != null) {
byte[] bytes = fileObject.getCompiledBytes();
return defineClass(name, bytes, 0, bytes.length);
}
try {
return ClassLoader.getSystemClassLoader().loadClass(name);
} catch (Exception e) {
return super.findClass(name);
}
}
}
}
CustomCallable 调用编译并运行，设置超时时间
package compiler.mydemo;
import java.lang.reflect.InvocationTargetException;
import java.util.concurrent.Callable;
/**
* Create by andy on 2018-12-07 13:10
*/
public class CustomCallable implements Callable<RunInfo> {
private String sourceCode;
public CustomCallable(String sourceCode) {
this.sourceCode = sourceCode;
}
//方案1
//@Override
//public RunInfo call() throws Exception {
// System.out.println("开始执行call" + LocalTime.now());
// RunInfo runInfo = new RunInfo();
// CustomStringJavaCompiler compiler = new CustomStringJavaCompiler(sourceCode);
// if (compiler.compiler()) {
// runInfo.setCompilerSuccess(true);
// try {
// compiler.runMainMethod();
// runInfo.setRunSuccess(true);
// runInfo.setRunTakeTime(compiler.getRunTakeTime());
// runInfo.setRunMessage(compiler.getRunResult()); //获取运行的时候输出内容
// } catch (Exception e) {
// e.printStackTrace();
// runInfo.setRunSuccess(false);
// runInfo.setRunMessage(e.getMessage());
// }
// } else {
// //编译失败
// runInfo.setCompilerSuccess(false);
// }
// runInfo.setCompilerTakeTime(compiler.getCompilerTakeTime());
// runInfo.setCompilerMessage(compiler.getCompilerMessage());
// System.out.println("call over" + LocalTime.now());
// return runInfo;
//}
//方案2
@Override
public RunInfo call() throws Exception {
RunInfo runInfo = new RunInfo();
Thread t1 = new Thread(() -> realCall(runInfo));
t1.start();
try {
t1.join(3000); //等待3秒
} catch (InterruptedException e) {
e.printStackTrace();
}
//不管有没有正常执行完成，强制停止t1
t1.stop();
return runInfo;
}
private void realCall(RunInfo runInfo) {
CustomStringJavaCompiler compiler = new CustomStringJavaCompiler(sourceCode);
if (compiler.compiler()) {
runInfo.setCompilerSuccess(true);
try {
compiler.runMainMethod();
runInfo.setRunSuccess(true);
runInfo.setRunTakeTime(compiler.getRunTakeTime());
runInfo.setRunMessage(compiler.getRunResult()); //获取运行的时候输出内容
} catch (InvocationTargetException e) {
//反射调用异常了,是因为超时的线程被强制stop了
if ("java.lang.ThreadDeath".equalsIgnoreCase(e.getCause().toString())) {
return;
}
} catch (Exception e) {
e.printStackTrace();
runInfo.setRunSuccess(false);
runInfo.setRunMessage(e.getMessage());
}
} else {
//编译失败
runInfo.setCompilerSuccess(false);
}
runInfo.setCompilerTakeTime(compiler.getCompilerTakeTime());
runInfo.setCompilerMessage(compiler.getCompilerMessage());
runInfo.setTimeOut(false); //走到这一步代表没有超时
}
}
RunInfo 动态编译、运行信息的bean
public class RunInfo {
//true:代表超时
private Boolean timeOut;
private Long compilerTakeTime;
private String compilerMessage;
private Boolean compilerSuccess;
private Long runTakeTime;
private String runMessage;
private Boolean runSuccess;
//省略get和set方法
}
CompilerUtil 把一整套流程封装了一个工具类
package compiler.mydemo;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
/**
* Create by andy on 2018-12-07 16:32
*/
public class CompilerUtil {
//这里用一个线程是因为防止System.out输出内容错乱
private static ExecutorService pool = Executors.newFixedThreadPool(1);
public static RunInfo getRunInfo(String javaSourceCode) {
RunInfo runInfo;
CustomCallable compilerAndRun = new CustomCallable(javaSourceCode);
Future<RunInfo> future = pool.submit(compilerAndRun);
//方案1
try {
runInfo = future.get();
} catch (Exception e) {
e.printStackTrace();
//代码编译或者运行超时
runInfo = new RunInfo();
runInfo.setTimeOut(true);
}
//方案2：不可行的原因：future.get超时会有问题，由于线程池只有1个线程，同时提交10个任务， 当前面几个任务执行时间很长，后面调用get就会立马失败，也就是说get的超时时间是从调用get开始算的，并不是线程真正执行时间开始计算的
//try {
// runInfo = future.get(5, TimeUnit.SECONDS);
// return runInfo;
//} catch (InterruptedException e) {
// System.out.println("future在睡着时被打断");
// e.printStackTrace();
//} catch (ExecutionException e) {
// System.out.println("future在尝试取得任务结果时出错");
// e.printStackTrace();
//} catch (TimeoutException e) {
// System.out.println("future时间超时");
// e.printStackTrace();
// future.cancel(true);
//}
//runInfo = new RunInfo();
//runInfo.setTimeOut(true);
return runInfo;
}
}
测试类：
package compiler.mydemo;
/**
* Create by andy on 2018-12-10 10:43
*/
public class Test3 {
public static void main(String[] args) throws InterruptedException {
String loop = "public class HelloWorld {
" +
" public static void main(String[] args) {
" +
" while(true){
" +
//" System.out.println("Hello World!");
" +
" }
" +
"
" +
" }
" +
"}";
String sleep_loop = "public class HelloWorld {
" +
" public static void main(String[] args) {
" +
" try {
" +
" Thread.sleep(6000);
" +
" } catch (InterruptedException e) {
" +
" e.printStackTrace();
" +
" }
" +
" System.out.println("Hello World!");
" +
" while(true){
" +
//" System.out.println("Hello World!");
" +
" }
" +
" }
" +
"}";
String ok = "public class HelloWorld {
" +
" public static void main(String[] args) {
" +
" System.out.println("Hello World!");
" +
" }
" +
"}";
TestRun t = new TestRun(ok, "thread:ok");
t.start();
TestRun t1 = new TestRun(loop, "thread:loop:");
t1.start();
//
TestRun t2 = new TestRun(sleep_loop, "thread:sleep_loop:");
t2.start();
}
}
class TestRun extends Thread {
String code;
TestRun(String code, String name) {
this.code = code;
super.setName(name);
}
@Override
public void run() {
System.out.println(CompilerUtil.getRunInfo(code));
}
}