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。
转载于:https://www.cnblogs.com/forlina/archive/2011/06/21/2085831.html
