大话设计模式二十四：职责链模式（加薪非要老总批?）

职责连模式：

使多个对象都有机会处理请求，从而避免请求的发送者和接受者之间的耦合关系，将多个对象连成一条链，并沿着这条链传递请求，直到有一个对象处理它为止。

// 管理者
public abstract class Manager {
	
	// 当前管理者的上级
	private Manager superior;

	public Manager getSuperior() {
		return superior;
	}

	public void setSuperior(Manager superior) {
		this.superior = superior;
	}
	
	// 处理员工请求
	public abstract void handleRequest(Request req);
}

// 经理
public class CommonMannager extends Manager {

	@Override
	public void handleRequest(Request req) {
		if (req.getType().equals("leave") && req.getNum() <= 2) {
			System.out.println("CommonManager: I agree the leave request");
		} else {
			System.out.println("CommonManager: I has no right to handle it, Pls ask help from Majordemo!");
			
			// 申请转到上级处理
			this.getSuperior().handleRequest(req);
		}
	}
}

// 总监
public class Majordemo extends Manager {

	@Override
	public void handleRequest(Request req) {
		if (req.getType().equals("leave") && req.getNum() <= 5) {
			System.out.println("Majordemo: I agree the leave request");
		} else {
			System.out.println("Majordemo: I has no right to handle it, Pls ask help from GereralManager!");
			
			// 申请转到上级处理
			this.getSuperior().handleRequest(req);
		}
	}

}

// 总经理
public class GeneralManager extends Manager {

	@Override
	public void handleRequest(Request req) {
		if (req.getType().equals("leave")) {
			System.out.println("GereralManager: I agree the leave request");
		} else if (req.getType().equals("increase salary") && req.getNum() <= 1000) {
			System.out.println("GereralManager: I agree the salary increase request");
		} else {
			System.out.println("GereralManager: pls request next time");
		}
	}

}

// 申请者
public class Request {
	
	// 申请类别
	private String type;
	
	// 申请内容
	private String content;
	
	// 申请数量
	private int num;

	public Request(String type, int num) {
		this.type = type;
		this.num = num;
	}

	public String getType() {
		return type;
	}

	public void setType(String type) {
		this.type = type;
	}

	public String getContent() {
		return content;
	}

	public void setContent(String content) {
		this.content = content;
	}

	public int getNum() {
		return num;
	}

	public void setNum(int num) {
		this.num = num;
	}
}

// 客户端
public class ChainOfResponsibilityMain {

	public static void main(String[] args) {
		Manager commonManager = new CommonMannager();
		Manager majordemo = new Majordemo();
		Manager generalManager = new GeneralManager();

		// 设置自己的上级
		commonManager.setSuperior(majordemo);
		majordemo.setSuperior(generalManager);
		
		// 设置员工请求内容
		Request req1 = new Request("leave", 3);
		Request req2 = new Request("increase salary", 2000);
		
		// 经理接受请求
		commonManager.handleRequest(req1);
		commonManager.handleRequest(req2);
	}

}

职责链的好处：

1. 职责链可以简化对象的相互连接，它们仅需保持一个指向其后继者的引用，而不需要保持它所有候选接受者的引用。

2. 由于是客户端来定义链的结构，我们可以随时地增加或修改处理一个请求的结构，增加了给对象指派职责的灵活性。