动态运行Java代码
有些情况下，我们不得不动态运行Java代码，以便提供更加灵活的方式，以下代码可参考（在JDK 1.5+平台上运行通过）：
public static void main(String[] args) {//PrintWriter out;//PrintStream myOut = new PrintStream(out);//System.setOut(myOut);//System.setErr(myOut);int i = 10;String code = "System.out.println("Hello World!"+(13+2*5/3));";code += "for(int i=0;i<" + i + ";i++){";code += " System.out.println(Math.pow(i,2));";code += "}";try {run(code);} catch (Exception e) {e.printStackTrace();}}private synchronized static File compile(String code) throws Exception {File file = File.createTempFile("JavaRuntime", ".java", new File(System.getProperty("user.dir")));file.deleteOnExit();//获得类名 String classname = getBaseFileName(file);//将代码输出到文件 PrintWriter out = new PrintWriter(new FileOutputStream(file));out.println(getClassCode(code, classname));out.close();//编译生成的java文件 String[] cpargs = new String[] { "-d",System.getProperty("user.dir") + "\\WebRoot\\WEB-INF\\classes",file.getName() };int status = Main.compile(cpargs);if (status != 0) {throw new Exception("语法错误！");}return file;}private static synchronized void run(String code) throws Exception {String classname = getBaseFileName(compile(code));new File(System.getProperty("user.dir")+ "\\WebRoot\\WEB-INF\\classes\" + classname + ".class").deleteOnExit();try {Class cls = Class.forName(classname);Method main = cls.getMethod("method", null);main.invoke(cls, null);} catch (Exception se) {se.printStackTrace();}}private static String getClassCode(String code, String className) {StringBuffer text = new StringBuffer();text.append("public class " + className + "{\n");text.append(" public static void method(){\n");text.append(" " + code + "\n");text.append(" }\n");text.append("}");return text.toString();}private static String getBaseFileName(File file) {String fileName = file.getName();int index = fileName.indexOf(".");String result = "";if (index != -1) {result = fileName.substring(0, index);} else {result = fileName;}return result;}? int status = Main.compile(cpargs); if (status != 0) { throw new Exception("语法错误！"); } 5 楼 bloodrate 2008-12-16 Main.compile