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;   
    } 

评论

1 楼 LinApex 2012-05-19  

        int status = Main.compile(cpargs);    

这句执行不了。