Java设计模式之职责链模式

• 1. 职责链模式概述
• • 1.1 职责链简介
  • 1.2 职责链类图
  • 1.3 职责链注意事项
• 2. 职责链模式实现
• • 2.1 项目说明
  • 2.2 项目实现

1.职责链模式(Chain of Responsibility Pattern), 又叫 责任链模式,为请求创建了一个接收者对象的链(简单示意 图).这种模式对请求的发送者和接收者进行解耦。
2.职责链模式通常每个接收者都包含对另一个接收者的引用.如果一个对象不能处理该请求,那么它会把相同的 请求传给下一个接收者,依此类推。
3.这种类型的设计模式属于行为型模式

1.将请求和处理分开,实现解耦,提高系统的灵活性。
2.简化了对象,使对象不需要知道链的结构。
3.性能会受到影响,特别是在链比较长的时候,因此需控制链中最大节点数量,一般通过在 Handler 中设置一个 最大节点数量,在 setNext()方法中判断是否已经超过阀值,超过则不允许该链建立,避免出现超长链无意识地 破坏系统性能。
4.调试不方便.采用了类似递归的方式,调试时逻辑可能比较复杂 5) 最佳应用场景：有多个对象可以处理同一个请求时,比如：多级请求,请假/加薪等审批流程,Java Web 中 Tomcat 对 Encoding 的处理,拦截器。

Approver：审批人抽象类
DepartmentApprover：部门审批
CollegeApprover：院长审批
ViceSchoolMasterApprover：副校长审批
SchoolMasterApprover：校长审批

PurchaseRequest：购买请求类

Client：职责链模式测试类

Approver：审批人抽象类

package com.zrj.design.responsibility;


public abstract class Approver {
    Approver approver;  //下一个处理者
    String name; // 名字

    public Approver(String name) {
        this.name = name;
    }

    //下一个处理者
    public void setApprover(Approver approver) {
        this.approver = approver;
    }

    //处理审批请求的方法，得到一个请求, 处理是子类完成，因此该方法做成抽象
    public abstract void processRequest(PurchaseRequest purchaseRequest);
}

DepartmentApprover：部门审批

package com.zrj.design.responsibility;


public class DepartmentApprover extends Approver {
    public DepartmentApprover(String name) {
        super(name);
    }

    @Override
    public void processRequest(PurchaseRequest purchaseRequest) {
        if (purchaseRequest.getPrice() <= 5000) {
            System.out.println("请求编号id=" + purchaseRequest.getId() + "，" + this.name + "已处理！");
        } else {
            approver.processRequest(purchaseRequest);
        }
    }

}

CollegeApprover：院长审批

package com.zrj.design.responsibility;


public class CollegeApprover extends Approver {

    public CollegeApprover(String name) {
        super(name);
    }

    @Override
    public void processRequest(PurchaseRequest purchaseRequest) {
        if (purchaseRequest.getPrice() > 5000 && purchaseRequest.getPrice() <= 10000) {
            System.out.println("请求编号id=" + purchaseRequest.getId() + "，" + this.name + "已处理！");
        } else {
            approver.processRequest(purchaseRequest);
        }
    }
}

ViceSchoolMasterApprover：副校长审批

package com.zrj.design.responsibility;


public class ViceSchoolMasterApprover extends Approver {
    public ViceSchoolMasterApprover(String name) {
        super(name);
    }

    @Override
    public void processRequest(PurchaseRequest purchaseRequest) {
        if (purchaseRequest.getPrice() < 10000 && purchaseRequest.getPrice() <= 30000) {
            System.out.println("请求编号id=" + purchaseRequest.getId() + "，" + this.name + "已处理！");
        } else {
            approver.processRequest(purchaseRequest);
        }
    }
}

SchoolMasterApprover：校长审批

package com.zrj.design.responsibility;


public class SchoolMasterApprover extends Approver {
    public SchoolMasterApprover(String name) {
        super(name);
    }

    @Override
    public void processRequest(PurchaseRequest purchaseRequest) {
        if (purchaseRequest.getPrice() > 30000) {
            System.out.println("请求编号id=" + purchaseRequest.getId() + "，" + this.name + "已处理！");
        } else {
            approver.processRequest(purchaseRequest);
        }
    }
}

PurchaseRequest：购买请求类

package com.zrj.design.responsibility;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;


@Data
@NoArgsConstructor
@AllArgsConstructor
public class PurchaseRequest {
    //编号
    private int id = 0;
    //请求类型
    private int type = 0;
    //请求金额
    private float price = 0.0f;
}

Client：职责链模式测试类

package com.zrj.design.responsibility;


public class Client {
    public static void main(String[] args) {
        //创建一个请求
        PurchaseRequest purchaseRequest = new PurchaseRequest(1, 1, 31000);

        //创建相关的审批人
        DepartmentApprover departmentApprover = new DepartmentApprover("张主任");
        CollegeApprover collegeApprover = new CollegeApprover("李院长");
        ViceSchoolMasterApprover viceSchoolMasterApprover = new ViceSchoolMasterApprover("刘副校");
        SchoolMasterApprover schoolMasterApprover = new SchoolMasterApprover("王校长");

        //需要将各个审批级别的下一个设置好 (处理人构成环形: )
        departmentApprover.setApprover(collegeApprover);
        collegeApprover.setApprover(viceSchoolMasterApprover);
        viceSchoolMasterApprover.setApprover(schoolMasterApprover);
        schoolMasterApprover.setApprover(departmentApprover);

        departmentApprover.processRequest(purchaseRequest);
        //viceSchoolMasterApprover.processRequest(purchaseRequest);
    }

}