【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:
1 package com.tn.proxy; 2 3 public class Client { 4 public static void main(String[] args) { 5 /* Car car=new Car(); 6 car.move(); */ 7 8 //通过继承计算方法的运行时间 9 /* CarTimeByExtends ctp=new CarTimeByExtends(); 10 ctp.move(); */ 11 12 //通过聚合计算类中方法运行时间 13 /* Car car=new Car(); 14 CarTimeByAggregate ctba=new CarTimeByAggregate(car); 15 ctba.getCarRunningTime(); */ 16 } 17 }
Movable:
1 package com.tn.proxy; 2 3 public interface Movable { 4 void move(); 5 void stop(); 6 }
Car:
1 package com.tn.proxy; 2 3 import java.util.Random; 4 5 public class Car implements Movable { 6 7 @Override 8 public void move() { 9 /** 10 * 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。 11 */ 12 /* long start=System.currentTimeMillis(); 13 System.out.println("Car is start moving..."+start); */ 14 System.out.println("Car is moving..."); 15 try { 16 Thread.sleep(new Random().nextInt(1500)); 17 } catch (InterruptedException e) { 18 e.printStackTrace(); 19 } 20 /* long end=System.currentTimeMillis(); 21 System.out.println("Car is stop moving..."+end); 22 System.out.println("Car running time is "+(end-start)); */ 23 } 24 25 @Override 26 public void stop() { 27 System.out.println("Car is stopped."); 28 } 29 30 }
CarTimeByExtends:
1 package com.tn.proxy; 2 /** 3 * 通过继承计算类中方法的运行时间 4 * @author xiongjiawei 5 * 6 */ 7 public class CarTimeByExtends extends Car{ 8 @Override 9 public void move() { 10 long start=System.currentTimeMillis(); 11 super.move(); 12 long end=System.currentTimeMillis(); 13 System.out.println("Car running time is:"+(end-start)); 14 } 15 }
CarTimeByAggregate:
1 package com.tn.proxy; 2 /** 3 * 通过聚合计算方法运行时间 4 * @author xiongjiawei 5 * 6 */ 7 public class CarTimeByAggregate { 8 Car car; 9 10 public CarTimeByAggregate(Car car){ 11 this.car=car; 12 } 13 14 public void getCarRunningTime(){ 15 long start=System.currentTimeMillis(); 16 car.move(); 17 long end=System.currentTimeMillis(); 18 System.out.println("Car running time is:"+(end-start)); 19 } 20 }
通过静态代理实现以上功能：
Client:
1 package com.tn.proxy; 2 3 public class Client { 4 public static void main(String[] args) { 5 Car car=new Car(); 6 CarTimeProxy ctp=new CarTimeProxy(car); 7 CarLogProxy clp=new CarLogProxy(ctp); 8 clp.move(); 9 /* 运行结果：Car被时间包装，时间被日志包装 10 logging... 11 start time:1494730233358 12 Car is moving... 13 end time:1494730234835 14 logged. 15 */ 16 System.out.println("--------------------------------------"); 17 Movable clp2=new CarLogProxy(car); 18 Movable ctp2=new CarTimeProxy(clp2); 19 ctp2.move(); 20 /* 21 运行结果：时间包装日志，日志包装car 22 start time:1494730473747 23 logging... 24 Car is moving... 25 logged. 26 end time:1494730474995 27 */ 28 } 29 }
Movable:
1 package com.tn.proxy; 2 3 public interface Movable { 4 void move(); 5 }
Car:
1 package com.tn.proxy; 2 3 import java.util.Random; 4 5 public class Car implements Movable { 6 7 @Override 8 public void move() { 9 System.out.println("Car is moving..."); 10 try { 11 Thread.sleep(new Random().nextInt(1500)); 12 } catch (InterruptedException e) { 13 e.printStackTrace(); 14 } 15 } 16 }
CarTimeProxy:
1 package com.tn.proxy; 2 3 public class CarTimeProxy implements Movable{ 4 Movable movable; 5 public CarTimeProxy(Movable movable){ 6 this.movable=movable; 7 } 8 @Override 9 public void move() { 10 long start=System.currentTimeMillis(); 11 System.out.println("start time:"+start); 12 movable.move(); 13 long end=System.currentTimeMillis(); 14 System.out.println("end time:"+end); 15 } 16 }
CarLogProxy:
1 package com.tn.proxy; 2 3 public class CarLogProxy implements Movable { 4 Movable movable; 5 6 public CarLogProxy(Movable movable){ 7 this.movable=movable; 8 } 9 10 @Override 11 public void move() { 12 System.out.println("logging..."); 13 movable.move(); 14 System.out.println("logged."); 15 } 16 17 }
利用反射动态加载：
1 package com.tn.proxy2; 2 3 import java.io.File; 4 import java.io.FileWriter; 5 import java.io.IOException; 6 import java.lang.reflect.Constructor; 7 import java.lang.reflect.InvocationTargetException; 8 import java.net.URL; 9 import java.net.URLClassLoader; 10 11 import javax.tools.JavaCompiler; 12 import javax.tools.JavaCompiler.CompilationTask; 13 14 import com.tn.proxy.Car; 15 import com.tn.proxy.Movable; 16 17 import javax.tools.StandardJavaFileManager; 18 import javax.tools.ToolProvider; 19 20 public class Test { 21 public static void main(String[] args) throws IOException, ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException { 22 String rt="\r\t"; 23 String str= 24 "package com.tn.proxy;"+rt+ 25 26 "public class CarTimeProxy implements Movable{"+rt+ 27 " Movable movable;"+rt+ 28 " public CarTimeProxy(Movable movable){"+rt+ 29 " this.movable=movable;"+rt+ 30 " }"+rt+ 31 " @Override"+rt+ 32 " public void move() {"+rt+ 33 " long start=System.currentTimeMillis();"+rt+ 34 " System.out.println(\"start time:\"+start);"+rt+ 35 " movable.move();"+rt+ 36 " long end=System.currentTimeMillis();"+rt+ 37 " System.out.println(\"end time:\"+end);"+rt+ 38 " }"+rt+ 39 "}"; 40 41 //源代码文件生成 42 String fileName=System.getProperty("user.dir") 43 +"/src/com/tn/proxy/CarTimeProxy.java"; 44 // System.out.println(fileName); 45 File f=new File(fileName); 46 FileWriter fw=new FileWriter(f); 47 fw.write(str); 48 fw.flush(); 49 fw.close(); 50 51 //编译 52 JavaCompiler compiler=ToolProvider.getSystemJavaCompiler(); 53 // System.out.println(compiler.getClass().getName()); 54 StandardJavaFileManager fMgr=compiler.getStandardFileManager(null, null, null); 55 Iterable iterable=fMgr.getJavaFileObjects(fileName); 56 CompilationTask ct=compiler.getTask(null, fMgr, null, null, null, iterable); 57 ct.call(); 58 fMgr.close(); 59 60 //载入内存，创建类对象实例 61 URL[] urls=new URL[]{new URL("file:/"+System.getProperty("user.dir")+"/src")}; 62 URLClassLoader ul=new URLClassLoader(urls); 63 Class c=ul.loadClass("com.tn.proxy.CarTimeProxy"); 64 ul.close(); 65 // System.out.println(c); 66 67 Constructor constructor=c.getConstructor(Movable.class); 68 Movable movable=(Movable)constructor.newInstance(new Car()); 69 movable.move(); 70 } 71 }
