设计模式之动态代理

动态代理的具体实现实现代码
代理方法类的接口InvocationHandler;

package com.proxy;
import java.lang.reflect.Method;

import com.proxy.InvocationHandler;
/**
 * 时间代理类
 * @author Administrator
 *
 */
public class TimeHandler implements InvocationHandler{
	/**
	 * 要被代理的对象
	 */
	private Object target;

	public TimeHandler(Object target) {
		super();
		this.target = target;
	}

	/**
	 * 在方法的前后可以添加自己的逻辑
	 */
	@Override
	public void invoke(Method method) {
		System.out.println("start"+System.currentTimeMillis());
		try {
			method.invoke(target);
		} catch (Exception e) {
			e.printStackTrace();
		}
		System.out.println("end"+System.currentTimeMillis());
		
	}
	
}

Moveable接口

package com.proxy;

public interface Moveable {
       public void move();
}
	

具体实体类Tank.java

package com.proxy;
/**
 * 坦克类
 * @author Administrator
 *
 */
public class Tank implements Moveable{

	@Override
	public void move() {
		System.out.println("坦克开起来...");
	}

  public static void main(String[] args) throws Exception
 {
	  Tank k=new Tank();
	  Moveable m=(Moveable) Proxy.newProxyInstance(Moveable.class , new TimeHandler(k));
      m.move();
 }

}

动态生成代理类 Proxy.java

package com.proxy;

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;
/**
 * 动态代理类
 * @author Administrator
 *
 */
public class Proxy {
 /**
  * 
  * @param infce 要代理interface
  * @param h     需要代理的方法
  * @return
  * @throws Exception
  */
	public static Object newProxyInstance(Class infce, InvocationHandler h) throws Exception { //JDK6 Complier API, CGLib, ASM
		String methodStr = "";
		String rt = "\r\n";
		
		Method[] methods = infce.getMethods();
	
		/**
		 * 得到该类的所有方法，都进行代理
		 */
		for(Method m : methods) {
			methodStr += "@Override" + rt + 
						 "public void " + m.getName() + "() {" + rt +
						 "    try {" + rt +
						 "    Method md = " + infce.getName() + ".class.getMethod(\"" + 
						       m.getName() + "\");" + rt +
						 "    h.invoke( md);" + rt +
						 "    }catch(Exception e) {e.printStackTrace();}" + rt +
						
						 "}";
		}
		
		String src = 
			"package com.proxy;" +  rt +
			"import java.lang.reflect.Method;" + rt +
			"public class $Proxy1 implements " + infce.getName() + "{" + rt +
			"    public $Proxy1(InvocationHandler h) {" + rt +
			"        this.h = h;" + rt +
			"    }" + rt +
			
			
			"    com.proxy.InvocationHandler h;" + rt +
							
			methodStr +
			"}";
		
		String fileName = 
			"D:/EclipseWorkplace/JavaProject/DesignPattern/src/com/proxy/$Proxy1.java";
		File f = new File(fileName);
		FileWriter fw = new FileWriter(f);
		fw.write(src);
		fw.flush();
		fw.close();
		
		/**
		 * 编译目标类
		 */
		JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
		StandardJavaFileManager fileMgr = compiler.getStandardFileManager(null, null, null);
		Iterable units = fileMgr.getJavaFileObjects(fileName);
		CompilationTask t = compiler.getTask(null, fileMgr, null, null, null, units);
		t.call();
		fileMgr.close();
		
		/**
		 * 把目标类加入内存并且创建一个实例
		 */
		URL[] urls = new URL[] {new URL("file:/" + "D:/EclipseWorkplace/JavaProject/DesignPattern/src/")};
		URLClassLoader ul = new URLClassLoader(urls);
		Class c = ul.loadClass("com.proxy.$Proxy1");
		Constructor ctr = c.getConstructor(InvocationHandler.class);
		Object m = ctr.newInstance(h);
		return m;
	}
}