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JAVA 6 引入了动态编译机制。Java 动态编译是指在运行时将Java源代码编译成可执行的字节码。这通常使用Java的内置编译器API javax.tools.JavaCompiler 来实现。
动态编译的应用场景
可以做一个浏览器编写java代码#xff0c;上传服务器编译和运行的在线测评系统服…动态编译
JAVA 6 引入了动态编译机制。Java 动态编译是指在运行时将Java源代码编译成可执行的字节码。这通常使用Java的内置编译器API javax.tools.JavaCompiler 来实现。
动态编译的应用场景
可以做一个浏览器编写java代码上传服务器编译和运行的在线测评系统服务器动态加载某些类文件进行编译
动态编译的两种实现方式 JAVA6之前可以通过Runtime调用javac启动新的进程去操作 Runtime run Runtime.getRuntime();
Process process run.exec(javac D:/myjava/demo/HelloWorld.java);JAVA6之后可以使用JavaCompiler实现 public static in compileFile(String sourceFile){JavaCompiler compiler ToolProvider.getSystemJavaCompiler();int result compiler.run(null,null,null,sourceFile);System.out.println(result 0 ? 编译通过 : 编译失败)return result;}compiler.run(null,null,null,sourceFile)参数说明 第一个参数为java编译器提供参数 第二个参数得到Java编译器的输出信息 第三个参数接受编译器的错误信息 第四个参数可变参数是一个String[]数组能传入一个或多个Java源文件 返回值0 表示编译成 非0 表示编译失败 使用runtime.exec方法编译
package demo2;import java.io.*;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;/*** 使用Runtime编译,通过反射调用main方法** author Anna.* date 2024/4/4 11:13*/
public class DyanmaicDemo {public static void main(String[] args) throws Exception {String path DyanmaicDemo.class.getResource().getPath();String javaName Hello;// 创建文件File tempFile createFile(path, javaName);// 使用Runtime 编译compilation(tempFile);// 反射执行文件extracted(path, javaName);}/*** 创建文件** param path* param javaName* return java.io.File* author Anna.* date 2024/4/4 13:05*/private static File createFile(String path, String javaName) throws IOException {// 创建编译内容StringBuffer sb new StringBuffer();sb.append(public class ).append(javaName).append({).append(public static void main(String[] args){).append(System.out.println(\hello world !!!\);).append(}).append(});// 写入临时文件File tempFile new File(path javaName .java);FileWriter fileWriter new FileWriter(tempFile);fileWriter.write(sb.toString());fileWriter.close();return tempFile;}/*** 编译** param tempFile* return void* author Anna.* date 2024/4/4 13:05*/private static void compilation(File tempFile) throws IOException, InterruptedException {String replace tempFile.getAbsolutePath().replace(tempFile.getName(), );replace replace.substring(0, replace.length() - 1);String str javac tempFile.getAbsolutePath();Runtime runtime Runtime.getRuntime();Process process runtime.exec(str);// 读取命令的标准输出BufferedReader reader new BufferedReader(new InputStreamReader(process.getInputStream()));String line;while ((line reader.readLine()) ! null) {System.out.println(line);}// 读取命令的错误输出BufferedReader errorReader new BufferedReader(new InputStreamReader(process.getErrorStream()));while ((line errorReader.readLine()) ! null) {System.err.println(line);}// 等待进程结束并获取退出值int exitValue process.waitFor();if (exitValue 0) {System.out.println(Compilation is successful);} else {System.out.println(Compilation Failed);}}/*** 反射执行main方法** param path* param javaName* return void* author Anna.* date 2024/4/4 13:05*/private static void extracted(String path, String javaName) throws MalformedURLException, ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException {URLClassLoader urlClassLoader new URLClassLoader(new URL[]{new URL(file:/ path)});Class? clazz urlClassLoader.loadClass(javaName);Method mainMethod clazz.getMethod(main, String[].class);// 注意由于可变参数是JDK5之后才有的下面代码如果new String[]{1,2}强制在转换才Object则会被编译成 mainMethod.invoke(null,1,2)从而导致找不到方法。// 因此如果传参则徐亚加上(Object)避免这个问题mainMethod.invoke(null, (Object) new String[]{1, 2});}}执行结果 使用JavaCompiler实现
package demo1;import javax.tools.*;
import java.io.File;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Arrays;
import java.util.Collections;/*** 使用JavaCompiler编译,通过反射调用main方法** author Anna.* date 2024/4/4 10:55*/
public class DyanmicDemo1 {public static void main(String[] args) throws Exception {// 创建编译内容String javaName Hello;// 获取JavaFileObjectJavaFileObject source getJavaFileObject(javaName);// 编译compiler(source);// 执行extracted(javaName);}/*** 获取JavaFileObject** param javaName* return javax.tools.JavaFileObject* author Anna.* date 2024/4/4 13:56*/private static JavaFileObject getJavaFileObject(String javaName) {StringBuffer sb new StringBuffer();sb.append(public class ).append(javaName).append({).append(public static void main(String[] args){).append(System.out.println(\hello world !!!\);).append(}).append(});// 创建一个Java源代码文件 string:///是一个特殊的URI协议用于表示源代码内容直接来自一个字符串而不是来自文件系统中的一个文件。 好处是你可以完全在内存中处理源代码无需涉及文件系统的I/O操作。JavaFileObject source new SimpleJavaFileObject(URI.create(string:/// javaName .java), JavaFileObject.Kind.SOURCE) {Overridepublic CharSequence getCharContent(boolean ignoreEncodingErrors) {return sb.toString();}};return source;}/*** 编译** param source* return void* author Anna.* date 2024/4/4 13:49*/private static void compiler(JavaFileObject source) {// 获取系统Java编译器JavaCompiler systemJavaCompiler ToolProvider.getSystemJavaCompiler();// 创建诊断收集器DiagnosticCollectorJavaFileObject diagnostics new DiagnosticCollector();// 创建编译任务StandardJavaFileManager fileManager systemJavaCompiler.getStandardFileManager(diagnostics, null, null);// 设置输出目录Iterable? extends File locations fileManager.getLocation(StandardLocation.CLASS_OUTPUT);try {fileManager.setLocation(StandardLocation.CLASS_OUTPUT, Collections.singleton(new File(DyanmicDemo1.class.getClassLoader().getResource().getPath())));} catch (IOException e) {e.printStackTrace();return;}Iterable? extends JavaFileObject compilationUnits Arrays.asList(source);JavaCompiler.CompilationTask task systemJavaCompiler.getTask(null, fileManager, diagnostics, null, null, compilationUnits);// 执行编译任务boolean success task.call();// 关闭文件管理器try {fileManager.close();} catch (IOException e) {e.printStackTrace();}// 处理编译诊断信息for (Diagnostic? diagnostic : diagnostics.getDiagnostics()) {System.out.println(diagnostic);System.out.println(diagnostic.getKind() : diagnostic.getMessage(null));}System.out.println(success ? 编译通过 : 编译失败);}/*** 反射执行** param javaName* return void* author Anna.* date 2024/4/4 13:50*/private static void extracted(String javaName) throws MalformedURLException, ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException {URLClassLoader urlClassLoader new URLClassLoader(new URL[]{new URL(file:/ DyanmicDemo1.class.getClassLoader().getResource().getPath())});Class? clazz urlClassLoader.loadClass(javaName);Method mainMethod clazz.getMethod(main, String[].class);// 注意由于可变参数是JDK5之后才有的下面代码如果new String[]{1,2}强制在转换才Object则会被编译成 mainMethod.invoke(null,1,2)从而导致找不到方法。// 因此如果传参则徐亚加上(Object)避免这个问题mainMethod.invoke(null, (Object) new String[]{1, 2});}}执行结果 注意 Runtime不仅仅是可以用于执行javac当然可以用来执行其他命令这里就不进一步说明了 CommandUtil调用系统命令工具类
import org.apache.commons.exec.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;/*** 调用系统命令工具类** author Anna.* date 2021/9/8 16:05*/
public class CommandUtil {private static Logger logger LoggerFactory.getLogger(CommandUtil.class);private static final String DEFAULT_CHARSET UTF-8;private static final Long TIMEOUT 10000L;/*** 执行指定命令** param command 命令* return 命令执行完成返回结果* throws RuntimeException 失败时抛出异常由调用者捕获处理*/public synchronized static String exeCommand(String command) throws RuntimeException {try (ByteArrayOutputStream out new ByteArrayOutputStream()) {int exitCode exeCommand(command, out);if (exitCode 0) {logger.info(命令运行成功: System.currentTimeMillis());} else {logger.info(命令运行失败: System.currentTimeMillis());}return out.toString(DEFAULT_CHARSET);} catch (Exception e) {logger.info(e.getMessage());throw new RuntimeException(e.getMessage());}}/*** 执行指定命令输出结果到指定输出流中** param command 命令* param out 执行结果输出流* return 执行结果状态码执行成功返回0* throws ExecuteException 失败时抛出异常由调用者捕获处理* throws IOException 失败时抛出异常由调用者捕获处理*/public synchronized static int exeCommand(String command, OutputStream out) throws ExecuteException, IOException {CommandLine commandLine CommandLine.parse(command);PumpStreamHandler pumpStreamHandler null;if (null out) {pumpStreamHandler new PumpStreamHandler();} else {pumpStreamHandler new PumpStreamHandler(out);}// 设置超时时间为10秒ExecuteWatchdog watchdog new ExecuteWatchdog(TIMEOUT);DefaultExecutor executor new DefaultExecutor();executor.setStreamHandler(pumpStreamHandler);executor.setWatchdog(watchdog);return executor.execute(commandLine);}public static void main(String[] args) {String out null;try {
// out CommandUtil.exeCommand(ipconfig);out CommandUtil.exeCommand(D:\\SoftWare\\ffmpeg\\bin\\ffmpeg.exe -y -i D:/test/1631090617181_191979483992900.mp3 -acodec pcm_s16le -f s16le -ac 1 -ar 16000 D:/test/PCM1631090617181_191979483992900.mp3.pcm);} catch (Exception e) {e.printStackTrace();}System.out.println(out);//CommandUtil.executeCommand(kill -9 3104);}}gitee源码 git clone https://gitee.com/dchh/JavaStudyWorkSpaces.git
