23种设计模式之五（代理模式）
Posted 淼淼之森
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代理模式：（为一个对象提供一个替身，以控制对这个对象的访问）
被代理的对象可以是远程对象、创建开销大的对象或需要安全控制的对象；代理模式有很多变体，都是为了控制与管理对象访问。
代理模式包含如下角色：
ISubject：抽象主题角色，是一个接口。该接口是对象和它的代理共用的接口。
RealSubject：真实主题角色，是实现抽象主题接口的类。
Proxy：代理角色，内部含有对真实对象RealSubject的引用，从而可以操作真实对象。代理对象提供与真实对象相同的接口，以便在任何时刻都能代替真实对象。同时，代理对象可以在执行真实对象操作时，附加其他的操作，相当于对真实对象进行封装。
实现动态代理的关键技术是反射。
例子：（通过这个例子，从不使用代理模式，到使用代理模式）
监控糖果机：地点、糖果库存和当前状态
ISubject：
1 package com.java.mmzs.agentmode.candymachine; 2 3 import java.io.Serializable; 4 5 public interface State extends Serializable{ 6 public void insertCoin(); 7 public void returnCoin(); 8 public void turnCrank(); 9 public void dispense(); 10 public void printstate(); 11 public String getstatename(); 12 }
1 package com.java.mmzs.agentmode.candymachinermi; 2 3 import java.rmi.Remote; 4 import java.rmi.RemoteException; 5 6 import com.java.mmzs.agentmode.candymachine.State; 7 8 public interface CandyMachineRemote extends Remote{ 9 public String getLocation() throws RemoteException; 10 public int getCount() throws RemoteException; 11 public State getstate() throws RemoteException; 12 }
RealSubject：
1 package com.java.mmzs.agentmode.candymachine; 2 3 public class OnReadyState implements State { 4 private transient CandyMachine mCandyMachine; 5 public OnReadyState(CandyMachine mCandyMachine) 6 { 7 this.mCandyMachine=mCandyMachine; 8 } 9 10 @Override 11 public void insertCoin() { 12 // TODO Auto-generated method stub 13 System.out 14 .println("you have inserted a coin,next,please turn crank!"); 15 mCandyMachine.setState(mCandyMachine.mHasCoin); 16 } 17 18 @Override 19 public void returnCoin() { 20 // TODO Auto-generated method stub 21 System.out.println("you haven\'t inserted a coin yet!"); 22 23 } 24 25 @Override 26 public void turnCrank() { 27 // TODO Auto-generated method stub 28 System.out.println("you turned,but you haven\'t inserted a coin!"); 29 30 } 31 32 @Override 33 public void dispense() { 34 // TODO Auto-generated method stub 35 36 } 37 38 @Override 39 public void printstate() { 40 // TODO Auto-generated method stub 41 System.out.println("***OnReadyState***"); 42 43 } 44 @Override 45 public String getstatename() { 46 // TODO Auto-generated method stub 47 return "OnReadyState"; 48 } 49 }
1 package com.java.mmzs.agentmode.candymachine; 2 3 import java.util.Random; 4 5 public class HasCoin implements State { 6 private transient CandyMachine mCandyMachine; 7 8 public HasCoin(CandyMachine mCandyMachine) { 9 this.mCandyMachine = mCandyMachine; 10 } 11 12 @Override 13 public void insertCoin() { 14 // TODO Auto-generated method stub 15 System.out.println("you can\'t insert another coin!"); 16 17 } 18 19 @Override 20 public void returnCoin() { 21 // TODO Auto-generated method stub 22 System.out.println("coin return!"); 23 mCandyMachine.setState(mCandyMachine.mOnReadyState); 24 } 25 26 @Override 27 public void turnCrank() { 28 // TODO Auto-generated method stub 29 System.out.println("crank turn...!"); 30 Random ranwinner=new Random(); 31 int winner=ranwinner.nextInt(10); 32 if(winner==0) 33 { 34 mCandyMachine.setState(mCandyMachine.mWinnerState); 35 36 }else 37 { 38 mCandyMachine.setState(mCandyMachine.mSoldState); 39 40 } 41 42 } 43 44 @Override 45 public void dispense() { 46 } 47 48 @Override 49 public void printstate() { 50 // TODO Auto-generated method stub 51 System.out.println("***HasCoin***"); 52 53 } 54 55 @Override 56 public String getstatename() { 57 // TODO Auto-generated method stub 58 return "HasCoin State"; 59 } 60 61 }
1 package com.java.mmzs.agentmode.candymachine; 2 3 public class SoldState implements State { 4 private transient CandyMachine mCandyMachine; 5 public SoldState(CandyMachine mCandyMachine) 6 { 7 this.mCandyMachine=mCandyMachine; 8 } 9 10 @Override 11 public void insertCoin() { 12 // TODO Auto-generated method stub 13 System.out.println("please wait!we are giving you a candy!"); 14 15 } 16 17 @Override 18 public void returnCoin() { 19 // TODO Auto-generated method stub 20 System.out.println("you haven\'t inserted a coin yet!"); 21 22 } 23 24 @Override 25 public void turnCrank() { 26 // TODO Auto-generated method stub 27 System.out 28 .println("we are giving you a candy,turning another get nothing,!"); 29 30 } 31 32 @Override 33 public void dispense() { 34 // TODO Auto-generated method stub 35 36 mCandyMachine.releaseCandy(); 37 if (mCandyMachine.getCount() > 0) { 38 mCandyMachine.setState(mCandyMachine.mOnReadyState); 39 } else { 40 System.out.println("Oo,out of candies"); 41 mCandyMachine.setState(mCandyMachine.mSoldOutState); 42 } 43 44 45 46 } 47 48 @Override 49 public void printstate() { 50 // TODO Auto-generated method stub 51 System.out.println("***SoldState***"); 52 53 } 54 @Override 55 public String getstatename() { 56 // TODO Auto-generated method stub 57 return "SoldState"; 58 } 59 }
1 package com.java.mmzs.agentmode.candymachine; 2 3 public class SoldOutState implements State { 4 5 private transient CandyMachine mCandyMachine; 6 public SoldOutState(CandyMachine mCandyMachine) 7 { 8 this.mCandyMachine=mCandyMachine; 9 } 10 11 @Override 12 public void insertCoin() { 13 // TODO Auto-generated method stub 14 System.out.println("you can\'t insert coin,the machine sold out!"); 15 16 } 17 18 @Override 19 public void returnCoin() { 20 // TODO Auto-generated method stub 21 System.out 22 .println("you can\'t return,you haven\'t inserted a coin yet!"); 23 24 } 25 26 @Override 27 public void turnCrank() { 28 // TODO Auto-generated method stub 29 System.out.println("you turned,but there are no candies!"); 30 31 } 32 33 @Override 34 public void dispense() { 35 // TODO Auto-generated method stub 36 37 } 38 39 @Override 40 public void printstate() { 41 // TODO Auto-generated method stub 42 System.out.println("***SoldOutState***"); 43 44 } 45 @Override 46 public String getstatename() { 47 // TODO Auto-generated method stub 48 return "SoldOutState"; 49 } 50 }
1 package com.java.mmzs.agentmode.candymachine; 2 3 public class WinnerState implements State { 4 5 private transient CandyMachine mCandyMachine; 6 7 public WinnerState(CandyMachine mCandyMachine) { 8 this.mCandyMachine = mCandyMachine; 9 } 10 11 @Override 12 public void insertCoin() { 13 // TODO Auto-generated method stub 14 System.out.println("please wait!we are giving you a candy!"); 15 16 } 17 18 @Override 19 public void returnCoin() { 20 // TODO Auto-generated method stub 21 System.out.println("you haven\'t inserted a coin yet!"); 22 23 } 24 25 @Override 26 public void turnCrank() { 27 // TODO Auto-generated method stub 28 System.out 29 .println("we are giving you a candy,turning another get nothing,!"); 30 31 } 32 33 @Override 34 public void dispense() { 35 // TODO Auto-generated method stub 36 37 38 mCandyMachine.releaseCandy(); 39 if (mCandyMachine.getCount() == 0) { 40 mCandyMachine.setState(mCandyMachine.mSoldOutState); 41 } else { 42 System.out.println("you are a winner!you get another candy!"); 43 mCandyMachine.releaseCandy(); 44 if (mCandyMachine.getCount() > 0) { 45 mCandyMachine.setState(mCandyMachine.mOnReadyState); 46 } else { 47 System.out.println("Oo,out of candies"); 48 mCandyMachine.setState(mCandyMachine.mSoldOutState); 49 } 50 } 51 52 } 53 54 @Override 55 public void printstate() { 56 // TODO Auto-generated method stub 57 System.out.println("***WinnerState***"); 58 59 } 60 @Override 61 public String getstatename() { 62 // TODO Auto-generated method stub 63 return "WinnerState"; 64 } 65 }
1 package com.java.mmzs.agentmode.candymachine; 2 3 import java.rmi.RemoteException; 4 import java.rmi.server.UnicastRemoteObject; 5 6 import com.java.mmzs.agentmode.candymachinermi.CandyMachineRemote; 7 8 public class CandyMachine extends UnicastRemoteObject implements CandyMachineRemote{ 9 10 State mSoldOutState; 11 State mOnReadyState; 12 State mHasCoin; 13 State mSoldState; 14 State mWinnerState; 15 private String location=""; 16 private State state; 17 private int count = 0; 18 19 public CandyMachine(String location,int count) throws RemoteException{ 20 this.location=location; 21 this.count = count; 22 mSoldOutState = new SoldOutState(this); 23 mOnReadyState = new OnReadyState(this); 24 mHasCoin = new HasCoin(this); 25 mSoldState = new SoldState(this); 26 mWinnerState = new WinnerState(this); 27 if (count > 0) { 28 state = mOnReadyState; 29 } else { 30 state = mSoldOutState; 31 } 32 } 33 public String getLocation() 34 { 35 return location; 36 } 37 public void setState(State state) { 38 this.state = state; 39 } 40 41 public void insertCoin() { 42 state.insertCoin(); 43 } 44 45 public void returnCoin() { 46 state.returnCoin(); 47 } 48 49 public void turnCrank() { 50 state.turnCrank(); 51 state.dispense(); 52 } 53 54 void releaseCandy() { 55 56 // TODO Auto-generated method stub 57 if (count > 0) { 58 count = count - 1; 59 System.out.println("a candy rolling out!"); 60 } 61 62 } 63 64 public int getCount() { 65 return count; 66 } 67 68 public void printstate() { 69 state.printstate(); 70 } 71 public State getstate() { 72 return state; 73 } 74 }
不使用代理：
1 package com.java.mmzs.agentmode; 2 3 import java.util.ArrayList; 4 5 import com.java.mmzs.agentmode.candymachine.CandyMachine; 6 7 public class Monitor { 8 private ArrayList<CandyMachine> candyMachinelst; 9 10 public Monitor() { 11 candyMachinelst = new ArrayList<CandyMachine>(); 12 } 13 14 public void addMachine(CandyMachine mCandyMachine) { 15 candyMachinelst.add(mCandyMachine); 16 } 17 18 public void report() { 19 CandyMachine mCandyMachine; 20 for (int i = 0, len = candyMachinelst.size(); i < len; i++) { 21 mCandyMachine = candyMachinelst.get(i); 22 System.out.println("Machine Loc:" + mCandyMachine.getLocation()); 23 System.out.println("Machine Candy count:" 24 + mCandyMachine.getCount()); 25 System.out.println("Machine State:" 26 + mCandyMachine.getstate().getstatename()); 27 28 } 29 30 } 31 32 }
1 package com.java.mmzs.agentmode; 2 3 import java.rmi.RemoteException; 4 5 import com.java.mmzs.agentmode.candymachine.CandyMachine; 6 7 public class MainTest { 8 public static void main(String[] args) throws RemoteException { 9 Monitor mMonitor=new Monitor(); 10 CandyMachine mCandyMachine = new CandyMachine("NY",6); 11 mMonitor.addMachine(mCandyMachine); 23种设计模式（23）：代理模式