【java设计模式】代理模式

计算类中方法运行时间的几种方案：

Client:

package com.tn.proxy;

public class Client {
    public static void main(String[] args) {
        /* Car car=new Car();
        car.move(); */
        
        //通过继承计算方法的运行时间
        /* CarTimeByExtends ctp=new CarTimeByExtends();
        ctp.move(); */
        
        //通过聚合计算类中方法运行时间
        /* Car car=new Car();
        CarTimeByAggregate ctba=new CarTimeByAggregate(car);
        ctba.getCarRunningTime(); */
    }
}

Movable:

package com.tn.proxy;

public interface Movable {
    void move();
    void stop();
}

Car:

package com.tn.proxy;

import java.util.Random;

public class Car implements Movable {

    @Override
    public void move() {
        /**
         * 方法内的两段注释代码为给move()方法增加日志及计算方法执行时间。
         */
        /* long start=System.currentTimeMillis();
        System.out.println("Car is start moving..."+start); */
        System.out.println("Car is moving...");
        try {
            Thread.sleep(new Random().nextInt(1500));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        /* long end=System.currentTimeMillis();
        System.out.println("Car is stop moving..."+end);
        System.out.println("Car running time is "+(end-start)); */
    }

    @Override
    public void stop() {
        System.out.println("Car is stopped.");
    }

}

CarTimeByExtends:

package com.tn.proxy;
/**
 * 通过继承计算类中方法的运行时间
 * @author xiongjiawei
 *
 */
public class CarTimeByExtends extends Car{
    @Override
    public void move() {
        long start=System.currentTimeMillis();
        super.move();
        long end=System.currentTimeMillis();
        System.out.println("Car running time is:"+(end-start));
    }
}

CarTimeByAggregate:

package com.tn.proxy;
/**
 * 通过聚合计算方法运行时间
 * @author xiongjiawei
 *
 */
public class CarTimeByAggregate {
    Car car;

    public CarTimeByAggregate(Car car){
        this.car=car;
    }
    
    public void getCarRunningTime(){
        long start=System.currentTimeMillis();
        car.move();
        long end=System.currentTimeMillis();
        System.out.println("Car running time is:"+(end-start));
    }
}

---

 通过静态代理实现以上功能：

Client:

package com.tn.proxy;

public class Client {
    public static void main(String[] args) {
        Car car=new Car();
        CarTimeProxy ctp=new CarTimeProxy(car);
        CarLogProxy clp=new CarLogProxy(ctp);
        clp.move();
        /*    运行结果：Car被时间包装，时间被日志包装
             logging...
            start time:1494730233358
            Car is moving...
            end time:1494730234835
            logged.
         */
        System.out.println("--------------------------------------");
        Movable clp2=new CarLogProxy(car);
        Movable ctp2=new CarTimeProxy(clp2);
        ctp2.move();
        /*
        运行结果：时间包装日志，日志包装car
        start time:1494730473747
        logging...
        Car is moving...
        logged.
        end time:1494730474995
        */
    }
}

Movable:

package com.tn.proxy;

public interface Movable {
    void move();
}

Car:

package com.tn.proxy;

import java.util.Random;

public class Car implements Movable {

    @Override
    public void move() {
        System.out.println("Car is moving...");
        try {
            Thread.sleep(new Random().nextInt(1500));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

CarTimeProxy:

package com.tn.proxy;

public class CarTimeProxy implements Movable{
    Movable movable;
    public CarTimeProxy(Movable movable){
        this.movable=movable;
    }
    @Override
    public void move() {
        long start=System.currentTimeMillis();
        System.out.println("start time:"+start);
        movable.move();
        long end=System.currentTimeMillis();
        System.out.println("end time:"+end);
    }
}

CarLogProxy:

package com.tn.proxy;

public class CarLogProxy implements Movable {
    Movable movable;
    
    public CarLogProxy(Movable movable){
        this.movable=movable;
    }
    
    @Override
    public void move() {
        System.out.println("logging...");
        movable.move();
        System.out.println("logged.");
    }

}

---

利用反射动态加载：

package com.tn.proxy2;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.net.URL;
import java.net.URLClassLoader;

import javax.tools.JavaCompiler;
import javax.tools.JavaCompiler.CompilationTask;

import com.tn.proxy.Car;
import com.tn.proxy.Movable;

import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;

public class Test {
    public static void main(String[] args) throws IOException, ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
        String rt="
	";
        String str=
                "package com.tn.proxy;"+rt+

        "public class CarTimeProxy implements Movable{"+rt+
        "    Movable movable;"+rt+
        "    public CarTimeProxy(Movable movable){"+rt+
        "        this.movable=movable;"+rt+
        "    }"+rt+
        "    @Override"+rt+
        "    public void move() {"+rt+
        "        long start=System.currentTimeMillis();"+rt+
        "        System.out.println("start time:"+start);"+rt+
        "        movable.move();"+rt+
        "        long end=System.currentTimeMillis();"+rt+
        "        System.out.println("end time:"+end);"+rt+
        "    }"+rt+
        "}";
        
        //源代码文件生成
        String fileName=System.getProperty("user.dir")
                        +"/src/com/tn/proxy/CarTimeProxy.java";
//        System.out.println(fileName);
        File f=new File(fileName);
        FileWriter fw=new FileWriter(f);
        fw.write(str);
        fw.flush();
        fw.close();
        
        //编译
        JavaCompiler compiler=ToolProvider.getSystemJavaCompiler();
//        System.out.println(compiler.getClass().getName());
        StandardJavaFileManager fMgr=compiler.getStandardFileManager(null, null, null);
        Iterable iterable=fMgr.getJavaFileObjects(fileName);
        CompilationTask ct=compiler.getTask(null, fMgr, null, null, null, iterable);
        ct.call();
        fMgr.close();
        
        //载入内存，创建类对象实例
        URL[] urls=new URL[]{new URL("file:/"+System.getProperty("user.dir")+"/src")};
        URLClassLoader ul=new URLClassLoader(urls);
        Class c=ul.loadClass("com.tn.proxy.CarTimeProxy");
        ul.close();
//        System.out.println(c);
        
        Constructor constructor=c.getConstructor(Movable.class);
        Movable movable=(Movable)constructor.newInstance(new Car());
        movable.move();
    }
}