尚硅谷设计模式学习(24)---[职责链模式(Chain of Responsibility Pattern)]

Posted 2021-10-28 小智RE0

尚硅谷传送门==>B站尚硅谷Java设计模式

❤❤❤感谢尚硅谷❤❤❤

最近开始计划学习一下设计模式了,加油!!!

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ml

• • 情景引入
  • 职责链模式

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情景引入

首先看一个案例

学校OA系统的采购审批项目：需求是

• 1 采购员采购教学器材
• 2 如果金额 小于等于5000, 由教学主任审批 （0<=x<=5000）
• 3 如果金额 小于等于10000, 由院长审批 (5000<x<=10000)
• 4 如果金额 小于等于30000, 由副校长审批 (10000<x<=30000)
• 5 如果金额 超过30000以上，有校长审批 ( 30000<x)

要是按照传统的方式解决的话.

每次都要进行判断,然后决定具体去找对应的审批检验人,要是到时候判断的条件改了,这个对应关系的依赖也要改动.
采购请求进行处理 和 审批人产生强耦合关系，不利于代码的扩展和维护

那么,来看看职责链模式

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职责链模式

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,形成一个链条.
(就像过滤器一样)

需要注意的是;要控制链中最大节点数量,节点过多可能会影响性能，一般通过在Handler中设置一个最大节点数量.

原理图

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OK,继续回到之前的材料审批问题

需要处理的请求类SchoolRequest

//学校的购买请求;
public class SchoolRequest {
    //请求的类型;
    private String type = null;
    //请求的大概金额;
    private float price=0.0f;
    //Id;
    private int  id=0;

    //初始化;
    public SchoolRequest(String type, float price, int id) {
        this.type = type;
        this.price = price;
        this.id = id;
    }

    public String getType() {
        return type;
    }

    public float getPrice() {
        return price;
    }

    public int getId() {
        return id;
    }
}

审批者Approver

/**
 * @author by CSDN@小智RE0
 */

//审批者
public abstract class Approver {
    //聚合,下一个处理的审批者;
    Approver approver;
    //当前审批者的部门名;
    String name;

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

    //设置下一个审批者到底是谁;
    public void setApprover(Approver approver) {
        this.approver = approver;
    }

    //处理请求的办法;
    public  abstract void  HandlingTheRequest(SchoolRequest schoolRequest);
}

教导主任审批DirectorApprover

/**
 * @author by CSDN@小智RE0
 */

//教导主任审批;
public class DirectorApprover extends Approver{
    //初始化;
    public DirectorApprover(String name) {
        super(name);
    }

    public void HandlingTheRequest(SchoolRequest schoolRequest) {
        if(schoolRequest.getPrice()<=5000){
            System.out.println(this.name+"表示能处理这个项目-->"+schoolRequest.getType());
            System.out.println("项目Id为==>"+schoolRequest.getId());
        }
        else {
            System.out.println(this.name+"表示不行,你去找院长-->");
            approver.HandlingTheRequest(schoolRequest);
        }
    }
}

院长审批DeanApprover

/**
 * @author by CSDN@小智RE0
 */
//院长审批;
public class DeanApprover extends Approver{
    //初始化;
    public DeanApprover(String name) {
        super(name);
    }

    public void HandlingTheRequest(SchoolRequest schoolRequest) {
        if(schoolRequest.getPrice()>5000 && schoolRequest.getPrice()<=10000){
            System.out.println(this.name+"表示能处理这个项目-->"+schoolRequest.getType());
            System.out.println("项目Id为==>"+schoolRequest.getId());
        }else {
            System.out.println(this.name+"表示不行,你去找副校长吧");
            approver.HandlingTheRequest(schoolRequest);
        }
    }
}

副校长审批VicePresidentApprover

/**
 * @author by CSDN@小智RE0
 */

//副校长审批;
public class VicePresidentApprover extends Approver {
    //初始化;
    public VicePresidentApprover(String name) {
        super(name);
    }

    public void HandlingTheRequest(SchoolRequest schoolRequest) {
        if( schoolRequest.getPrice()>10000 && schoolRequest.getPrice()<=30000){
            System.out.println(this.name+"表示能处理这个项目-->"+schoolRequest.getType());
            System.out.println("项目Id为==>"+schoolRequest.getId());
        }else {
            System.out.println(this.name+"表示不行,你去找校长吧");
            approver.HandlingTheRequest(schoolRequest);
        }
    }
}

校长审批PresidentApprover

/**
 * @author by CSDN@小智RE0
 */
//校长审批;
public class PresidentApprover extends Approver{
    //初始化;
    public PresidentApprover(String name) {
        super(name);
    }

    public void HandlingTheRequest(SchoolRequest schoolRequest) {
        if(schoolRequest.getPrice()>30000){
            System.out.println(this.name+"表示能处理这个项目-->"+schoolRequest.getType());
            System.out.println("项目Id为==>"+schoolRequest.getId());
        }else {
            approver.HandlingTheRequest(schoolRequest);
        }
    }
}

模拟客户端

/**
 * @author by CSDN@小智RE0
 */

//模拟客户端;
public class Client {
    public static void main(String[] args) {
        //提出请求;
        SchoolRequest schoolRequest = new SchoolRequest("采购教学用品",60000,0);

        Approver directorApprover = new DirectorApprover("教导主任");
        Approver deanApprover = new DeanApprover("院长");
        Approver vicePresidentApprover = new VicePresidentApprover("副校长");
        Approver presidentApprover = new PresidentApprover("校长");

        //设置好下一个处理的人;
        directorApprover.setApprover(deanApprover);
        deanApprover.setApprover(vicePresidentApprover);
        vicePresidentApprover.setApprover(presidentApprover);
        presidentApprover.setApprover(directorApprover);

        //教导主任收到请求时;
        directorApprover.HandlingTheRequest(schoolRequest);

    }
}

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