設計模式12--代理模式（Proxy）

代理模式的本質：控制對象訪問

模式定義：爲其他對象提供一種代理以控制對這個對象的訪問。

1 虛代理：根據需要來創建開銷很大的對象，改對象值有在需要的時候纔會被真正創建。

package com;

public interface UserModelApi {

	public String getUserId();
	public void setUserId(String userId);
	public String getName();
	public void setName(String name);
	public String getDepId();
	public void setDepId(String depId);
	public String getSex();
	public void setSex(String sex);
	public String getId();
	public void setId(String id);
}

package com.impl;

import com.UserModelApi;

public class UserModel implements UserModelApi{
	
	private String userId;
	private String name;
	private String depId;
	private String sex;
	private String id;
	
	@Override
	public String getUserId() {
		return userId;
	}
	@Override
	public void setUserId(String userId) {
		this.userId = userId;
	}
	@Override
	public String getName() {
		return name;
	}
	@Override
	public void setName(String name) {
		this.name = name;
	}
	@Override
	public String getDepId() {
		return depId;
	}
	@Override
	public void setDepId(String depId) {
		this.depId = depId;
	}
	@Override
	public String getSex() {
		return sex;
	}
	@Override
	public void setSex(String sex) {
		this.sex = sex;
	}
	@Override
	public String getId() {
		return id;
	}
	@Override
	public void setId(String id) {
		this.id = id;
		
	}	
}

package com.impl;

import com.UserModelApi;

public class Proxy implements UserModelApi {

	private UserModel realSubject = null;
	private boolean loaded = false;

	public Proxy(UserModel realSubject) {
		this.realSubject = realSubject;
	}

	@Override
	public String getUserId() {
		return realSubject.getUserId();
	}

	@Override
	public String getName() {
		return realSubject.getName();
	}

	@Override
	public String getDepId() {
		return realSubject.getDepId();
	}

	@Override
	public String getSex() {
		if (!loaded) {
			reload();
			loaded = true;
		}
		return realSubject.getSex();
	}

	@Override
	public String getId() {
		if (!loaded) {
			reload();
			loaded = true;
		}
		return realSubject.getId();
	}

	@Override
	public void setDepId(String depId) {
		realSubject.setDepId(depId);
	}

	@Override
	public void setName(String name) {
		realSubject.setName(name);

	}

	@Override
	public void setSex(String sex) {
		realSubject.setSex(sex);

	}

	@Override
	public void setUserId(String userId) {
		realSubject.setUserId(userId);

	}

	@Override
	public void setId(String id) {
		realSubject.setId(id);
	}

	private void reload() {
		// 模擬數據庫查詢過程，字段很多時更有價值
		System.out.println("reload~~~~");
		this.setSex("男");
		this.setId("210782XXXXXXXX1234");
	}

	public void showSimpleInfo() {
		System.out.println("DepId = " + this.getDepId() + ",UserId = "
				+ this.getUserId() + ",name = " + this.getName());
	}

	public void showAllInfo() {
		System.out.println("DepId = " + this.getDepId() + ",UserId = "
				+ this.getUserId() + ",Name = " + this.getName() + ",Sex = "
				+ this.getSex() + ",Id = " + this.getId());
	}
}

package com;

import java.util.ArrayList;
import java.util.List;

import com.impl.Proxy;
import com.impl.UserModel;

public class UserManager {
	public List getUsersByDepId(String depId){
		List usersList = new ArrayList();
		//模擬數據庫查詢過程，只初始化depId，userId，name
		Proxy userModel1 = new Proxy(new UserModel());
		userModel1.setDepId("0103");
		userModel1.setUserId("0103001");
		userModel1.setName("SHIXIN747");
		usersList.add(userModel1);
		Proxy userModel2 = new Proxy(new UserModel());
		userModel2.setDepId("0103");
		userModel2.setUserId("0103002");
		userModel2.setName("AXUE630");
		usersList.add(userModel2);
		Proxy userModel3 = new Proxy(new UserModel());
		userModel3.setDepId("0103");
		userModel3.setUserId("0103003");
		userModel3.setName("YUANJIA258");
		usersList.add(userModel3);
		return usersList;	
	}
}

import java.util.List;

import com.UserManager;
import com.impl.Proxy;

public class Client {
	public static void main(String[] args) {
		UserManager userManager = new UserManager();
		List<Proxy> usersList = userManager.getUsersByDepId("0103");
		
		for(Proxy userproxy : usersList){
			userproxy.showSimpleInfo();
		}
		
		for(Proxy userproxy : usersList){
			userproxy.showAllInfo();
		}
	}
}

2 保護代理：控制對原始對象的訪問，如果有需要，可以給不同的用戶提供不同的訪問權限，以控制他們對原始對象的訪問。

package com;

public interface OrderApi {

	String getProductName();
	void setProductName(String productName,String user);//此處參數不得不加了個user
	int getOrderNum();
	void setOrderNum(int orderNum,String user);//此處參數不得不加了個user
	String getOrderUser();
	void setOrderUser(String orderUser,String user);//此處參數不得不加了個user
	
}

package com.impl;

import com.OrderApi;

public class Order implements OrderApi{
	
	private String productName;
	private int orderNum;
	private String orderUser;
	
	public Order(String productName, int orderNum, String orderUser) {
		super();
		this.productName = productName;
		this.orderNum = orderNum;
		this.orderUser = orderUser;
	}

	@Override
	public String getProductName() {
		return productName;
	}
	
	@Override
	public void setProductName(String productName,String user) {
		this.productName = productName;
	}
	
	@Override
	public int getOrderNum() {
		return orderNum;
	}
	
	@Override
	public void setOrderNum(int orderNum,String user) {
		this.orderNum = orderNum;
	}
	
	@Override
	public String getOrderUser() {
		return orderUser;
	}
	
	@Override
	public void setOrderUser(String orderUser,String user) {
		this.orderUser = orderUser;
	}
}

package com.impl;

import com.OrderApi;

public class OrderProxy implements OrderApi {

	private Order order = null;

	public OrderProxy(Order order) {
		this.order = order;
	}

	public int getOrderNum() {
		return order.getOrderNum();
	}

	@Override
	public String getOrderUser() {
		return order.getOrderUser();
	}

	@Override
	public String getProductName() {
		return order.getProductName();
	}

	@Override
	public void setOrderNum(int orderNum, String user) {
		if (user.equals(order.getOrderUser())) {
			order.setOrderNum(orderNum, user);
		} else {
			System.out.println("對不起,您無權限進行此操作");
		}

	}

	@Override
	public void setOrderUser(String orderUser, String user) {
		if (user.equals(order.getOrderUser())) {
			order.setOrderUser(orderUser, user);
		} else {
			System.out.println("對不起,您無權限進行此操作");
		}

	}

	@Override
	public void setProductName(String productName, String user) {
		if (user.equals(order.getOrderUser())) {
			order.setProductName(productName, user);
		} else {
			System.out.println("對不起,您無權限進行此操作");
		}
	}

	public String toString() {
		return "productName = " + this.getProductName() + ",orderUser = "
				+ this.getOrderUser() + ",orderNum = " + this.getOrderNum();
	}

}

import com.OrderApi;
import com.impl.Order;
import com.impl.OrderProxy;

public class Client {
	public static void main(String[] args) {
		OrderApi order = new OrderProxy(new Order("寶馬",5,"SHIXIN747"));
		System.out.println(order);
		order.setOrderNum(10, "AXUE630");
		order.setOrderNum(10, "SHIXIN747");
		System.out.println(order);
	}
}

3 Java的動態代理

package com;

public interface OrderApi {

	String getProductName();
	void setProductName(String productName,String user);//此處參數不得不加了個user
	int getOrderNum();
	void setOrderNum(int orderNum,String user);//此處參數不得不加了個user
	String getOrderUser();
	void setOrderUser(String orderUser,String user);//此處參數不得不加了個user
	
}

package com.impl;

import com.OrderApi;

public class Order implements OrderApi{
	
	private String productName;
	private int orderNum;
	private String orderUser;
	
	public Order(String productName, int orderNum, String orderUser) {
		super();
		this.productName = productName;
		this.orderNum = orderNum;
		this.orderUser = orderUser;
	}

	@Override
	public String getProductName() {
		return productName;
	}
	
	@Override
	public void setProductName(String productName,String user) {
		this.productName = productName;
	}
	
	@Override
	public int getOrderNum() {
		return orderNum;
	}
	
	@Override
	public void setOrderNum(int orderNum,String user) {
		this.orderNum = orderNum;
	}
	
	@Override
	public String getOrderUser() {
		return orderUser;
	}
	
	@Override
	public void setOrderUser(String orderUser,String user) {
		this.orderUser = orderUser;
	}
	
	public String toString() {  
        return "productName = " + this.getProductName() + ",orderUser = "  
                + this.getOrderUser() + ",orderNum = " + this.getOrderNum();  
    }  

}

package com.impl;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import com.OrderApi;

public class DynamicProxy implements InvocationHandler {

	private Order order = null;

	public OrderApi getProxyInterface(Order order) {
		// 設置被代理的對象，好方便invoke裏面的操作
		this.order = order;
		// 把真正的訂單對象和動態代理關聯起來
		OrderApi orderApi = (OrderApi) Proxy.newProxyInstance(order.getClass()
				.getClassLoader(), order.getClass().getInterfaces(), this);
		return orderApi;
	}

	@Override
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {
		//如果是調用setter方法就需要檢查權限
		if(method.getName().startsWith("set")){
			if(order.getOrderUser() != null && order.getOrderUser().equals(args[1])){
				return method.invoke(order, args);
			}else{
				System.out.println("對不起，" + args[1] + ",你無權修改本訂單的數據");
			}
		}else{
			return method.invoke(order, args);
		}
		return null;
	}
}

import com.OrderApi;
import com.impl.DynamicProxy;
import com.impl.Order;

public class Client {
	public static void main(String[] args) {
		DynamicProxy DynamicProxy = new DynamicProxy();
		Order order = new Order("奔馳",20,"SHIXIN747");
		System.out.println(order);
		OrderApi orderApi = DynamicProxy.getProxyInterface(order);
		orderApi.setOrderNum(30, "AXUE630");
		orderApi.setOrderNum(30, "SHIXIN747");
		System.out.println(order);
	}
}