责任链模式

责任链模式(chain of responsibility):

• 将能够处理同一类请求的对象连成一条链，所提交的请求沿着链传递，链上的对象逐个判断是否有能力处理该请求，如果能则处理，如果不能则传递给链上的下一个对象

角色:

• 抽象处理者(Handler)

• 具体处理者(ConcreteHandler)

• 客户端（Client）

下面模拟请假来实现责任链模式

package designmode.chainofresponsibility;
public class LeaveRequest {
    private String empName;
    private int leaveDays;
    private String reason; //请假原因
    public String getEmpName() {
        return empName;
    }
    public void setEmpName(String empName) {
        this.empName = empName;
    }
    public int getLeaveDays() {
        return leaveDays;
    }
    public void setLeaveDays(int leaveDays) {
        this.leaveDays = leaveDays;
    }
    public String getReason() {
        return reason;
    }
    public void setReason(String reason) {
        this.reason = reason;
    }
    public LeaveRequest(String empName, int leaveDays, String reason) {
        super();
        this.empName = empName;
        this.leaveDays = leaveDays;
        this.reason = reason;
    }

}

package designmode.chainofresponsibility;
public abstract class Leader {


    protected String name;
    protected Leader nextLeader; //责任链上的后维对象
    public Leader(String name) {
        super();
        this.name = name;
    }
    public void setNextLeader(Leader nextLeader) {
        this.nextLeader = nextLeader;
    }
    public abstract void handleRequest(LeaveRequest request);
}

package designmode.chainofresponsibility;
/**
 * 经理
 * @author baiyi
 *
 */
public class Manager extends Leader{
    public Manager(String name) {
        super(name);
    }
    @Override
    public void handleRequest(LeaveRequest request) {
        if(request.getLeaveDays()<10) {
            System.out.println("经理审批通过！！");
        }else {
            if(this.nextLeader !=null) {
                System.out.println("权限不够！需要总经理审批！！");
                this.nextLeader.handleRequest(request);
            }
        }

    }
}

package designmode.chainofresponsibility;
/**
 * 总经理
 * @author baiyi
 *
 */
public class GeneralManager extends Leader{
    public GeneralManager(String name) {
        super(name);
    }
    @Override
    public void handleRequest(LeaveRequest request) {
        if(request.getLeaveDays()<30) {
            System.out.println("审批通过！！");
        }else {
            System.out.println("审批不予通过");
        }

    }

}

package designmode.chainofresponsibility;
/**
 * 主任
 * @author baiyi
 *
 */
public class Director extends Leader{
    public Director(String name) {
        super(name);

    }
    public void handleRequest(LeaveRequest request) {
        if (request.getLeaveDays()<3) {
            System.out.println("主任审批通过");
        }else {
            if(this.nextLeader != null) {
                System.out.println("权限不够，需要经理审批！！");
                this.nextLeader.handleRequest(request);
            }
        }
    }
}

package designmode.chainofresponsibility;
public class Client {
    public static void main(String [] args) {
        Leader a = new Director("张三");
        Leader b = new Manager("李四");
        Leader c = new GeneralManager("王五");

        //组织责任链对象的关系
        a.setNextLeader(b);
        b.setNextLeader(c);

        LeaveRequest req = new LeaveRequest("TOM",20,"go to English");
        a.handleRequest(req);
    }
}

非链表方式实现职责链

• 通过集合，数组生成职责链更加实用，实际上，很多项目中每个具体的Handler并不是由开发团队定义的，而是项目上线后由外部单位追加的，所以使用链表方式定义COR链就很困难

• java中的Filter过滤器就是使用数组的方式。

来自为知笔记(Wiz)