類定義：

1、被代理介面和實現類：Tank類實現了Moveable介面，能夠move()

package com.zec.disignmode;
public interface Moveable {
    public void move();
}

package com.zec.disignmode;
import java.util.Random;
public class Tank implements Moveable{
    @Override
    public void move() {
        System.out.println("Tank moving....");
        try {
            Thread.sleep(new Random().nextInt(10000));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

2、代理加工介面和實現類：TimeHandler類實現了InvocationHandler介面，能夠invoke（Object object，Method m）在object的m方法前後加上自己記錄時間的邏輯，並不是代理類，只是提供了對被代理類的加工邏輯；

package com.zec.disignmode;
import java.lang.reflect.Method;
public interface InvocationHandler {
    public void invoke(Object o,Method m);
}

package com.zec.disignmode;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class TimeHandler implements InvocationHandler{
    @Override
    public void invoke(Object object, Method m) {
        System.out.println("Time Before "+m.getName());
        try {
            m.invoke(object);
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println("Time After  "+m.getName());
    }

}

3、生成動態代理類的Proxy靜態類：代理產生器，根據傳進來的引數Class Intface和InvocationHandler h，產生動態代理類；從而使intface中的所有方法都加上了h中invoke方法的自定義邏輯；為了便於代理類的組合和擴充套件，代理類也會實現Intface介面，最終返回一個代理類物件；

package com.zec.disignmode;
import java.io.File;
import java.io.FileWriter;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLClassLoader;
import javax.tools.JavaCompiler;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;
import javax.tools.JavaCompiler.CompilationTask;
public class Proxy {
    public static Object newInstance(Class intface,InvocationHandler h) throws Exception {
        /*Generate the source code*/
        String rt = "\r\n";
        String methodStr = "";
        for (Method method:intface.getMethods()) {
            methodStr +=
            "    @Override"+rt+
            "    public void "+ method.getName() +"() {"+rt+
            "        try{"+rt+
            "            Method m = "+ intface.getName()+".class.getMethod(\""+ method.getName() +"\");" + rt+
            "            h.invoke(tank,m);"+rt+
            "        }catch(Exception e){e.printStackTrace();}"+rt+
            "    }"+rt
            ;
        }
        String src =
            "package com.zec.disignmode;"+rt+
            "import java.util.Random;"+rt+
            "import java.lang.reflect.*;"+rt+
            "public class TankTimeProxy implements "+ intface.getName() +"{"+rt+
            "    "+ intface.getName() +" tank;"+rt+
            "    com.zec.disignmode.InvocationHandler h;"+rt+
            "    public TankTimeProxy("+ intface.getName() +" t,com.zec.disignmode.InvocationHandler h) {"+rt+
            "        tank = t;"+rt+
            "        this.h = h;"+rt+
            "    }"+rt+
            methodStr+
            "}";
        /*Generate the java file*/
        String fileName = System.getProperty("user.dir")+"/src/com/zec/disignmode/TankTimeProxy.java";
        File f = new File(fileName);
        FileWriter fw = new FileWriter(f);
        fw.write(src);
        fw.flush();
        fw.close();
        /*Generate the class file*/
        JavaCompiler jc = ToolProvider.getSystemJavaCompiler();
        StandardJavaFileManager jfMgr = jc.getStandardFileManager(null, null, null);
        Iterable units = jfMgr.getJavaFileObjects(fileName);
        CompilationTask ct =  jc.getTask(null, jfMgr, null, null, null, units);
        ct.call();
        jfMgr.close();
        /*Load the class into the memory*/
        URL[] urls = new URL[]{new URL("file:/"+System.getProperty("user.dir")+"/src")};
        URLClassLoader urlLoader = new URLClassLoader(urls);
        Class c = urlLoader.loadClass("com.zec.disignmode.TankTimeProxy");
        /*Generate the object*/
        Constructor constructor = c.getConstructor(Moveable.class,InvocationHandler.class);
        Object moveable = constructor.newInstance(new Tank(),h);
        return moveable;
    }
}

4、測試類

package com.zec.disignmode;
public class Client {
    public static void main(String[] args) {
        Moveable m = new Tank();
        LogHandler h = new LogHandler();
        try {
            Moveable moveable = (Moveable) Proxy.newInstance(Moveable.class, h);
            moveable.move();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

5、學習心得：

（1）為了增強代理類的可擴充套件性，代理類和被代理類實現的是同一個介面，這樣代理類可以作為被代理類再次被代理，可以實現不同功能代理的組合，本例中為Moveable；

（2）InvocationHandler介面定義了對特定物件的方法的代理加工方法，Proxy為代理生成器，newInstance（Class intface,InvocationHandler h）方法表示對intface介面的所有方法進行加工，加工的邏輯由h的invoke方法定義；

（3）代理生成器最後返回一個intface型別的引用，指向已經生成的動態代理類；

（4）對於使用者來說，不必關心動態代理類的名稱，只需要指定要代理的介面型別和處理類就可以了。