类定义：
1、被代理接口和实现类：Tank类实现了Moveable接口，能够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、代理加工接口和实现类：TimeHandler类实现了InvocationHandler接口，能够invoke（Object object，Method m）在object的m方法前后加上自己记录时间的逻辑，并不是代理类，只是提供了对被代理类的加工逻辑；
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、生成动态代理类的Proxy静态类：代理产生器，根据传进来的参数Class Intface和InvocationHandler h，产生动态代理类；从而使intface中的所有方法都加上了h中invoke方法的自定义逻辑；为了便于代理类的组合和扩展，代理类也会实现Intface接口，最终返回一个代理类对象；
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、测试类
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、学习心得：
（1）为了增强代理类的可扩展性，代理类和被代理类实现的是同一个接口，这样代理类可以作为被代理类再次被代理，可以实现不同功能代理的组合，本例中为Moveable；
（2）InvocationHandler接口定义了对特定对象的方法的代理加工方法，Proxy为代理生成器，newInstance（Class intface,InvocationHandler h）方法表示对intface接口的所有方法进行加工，加工的逻辑由h的invoke方法定义；
（3）代理生成器最后返回一个intface类型的引用，指向已经生成的动态代理类；
（4）对于使用者来说，不必关心动态代理类的名称，只需要指定要代理的接口类型和处理类就可以了。