package proxy;

 public interface Movable {

     public void move();

 }

package proxy;

import java.util.Random;

public class Tank implements Movable {

    @Override

    public void move() {

        System.out.println("Tank moving.......");

        try {

            Thread.sleep(new Random().nextInt(2000));

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

    }

}

 package proxy;

 import java.io.File;

 import java.io.FileWriter;

 import java.lang.reflect.Constructor;

 import java.net.URL;

 import java.net.URLClassLoader;

 import javax.tools.JavaCompiler;

 import javax.tools.JavaCompiler.CompilationTask;

 import javax.tools.StandardJavaFileManager;

 import javax.tools.ToolProvider;

 public class Proxy {

     public static Object newProxyInstance() throws Exception {

         String rt = "\n\r";

         //动态代理文件的源码

         String str =

         "package proxy;" + rt +

         "public class TankTimeProxy implements Movable {"+rt+

             "private Movable m;" + rt +

             "public TankTimeProxy(Movable m) {" + rt +

                 "this.m = m;" + rt +

             "}" + rt +

             "@Override" + rt +

             "public void move() {" + rt +

                 "System.out.println(\"Time Proxy start...........\");" + rt +

                 "long start = System.currentTimeMillis();" + rt +

                 "m.move();" + rt +

                 "long end = System.currentTimeMillis();" + rt +

                 "System.out.println(\"花费时间：\"+(end - start));" + rt +

                 "System.out.println(\"Time Proxy end...........\");" + rt +

             "}" + rt +

         "}" ;

         //把源码写到java文件里

         File file = new File(System.getProperty("user.dir")+"/src/proxy/TankTimeProxy.java");

         FileWriter fw = new FileWriter(file);

         fw.write(str);

         fw.flush();

         fw.close();

         //编译源码，生成class,注意编译环境要换成jdk才有compiler,单纯的jre没有compiler，会空指针错误

         JavaCompiler jc = ToolProvider.getSystemJavaCompiler();

         //文件管事器

         StandardJavaFileManager fileMgr = jc.getStandardFileManager(null, null, null);

         //编译单元

         Iterable units = fileMgr.getJavaFileObjects(file);

         //编译任务

         CompilationTask t = jc.getTask(null, fileMgr, null, null, null, units);

         //编译

         t.call();

         fileMgr.close();

         //把类load到内存里

         URL[] urls = new URL[] {new URL("file:/"+System.getProperty("user.dir")+"/src/proxy/TankTimeProxy.class")};

         URLClassLoader uc = new URLClassLoader(urls);

         Class c = uc.loadClass("proxy.TankTimeProxy");

         //生成实例

         //return c.newInstance(); //c.newInstance()会调用无参数的Construtor，若类没有无参的Constructor时会出错

         Constructor ctr = c.getConstructor(Movable.class);

         return ctr.newInstance(new Tank());

     }

 }

 package proxy;

 import java.io.IOException;

 import org.junit.Test;

 public class Client {

     @Test

     public void testProxy() throws Exception{

         Movable m = (Movable)Proxy.newProxyInstance();

         m.move();

     }

 }