设计模式责任链模式

Z时代
2024-01-10
分类：综合

设计模式-责任链模式

定义

使多个对象都有机会处理请求，避免请求发送者和接受者之间的耦合关系，将接收者对象组成一条链，并沿着这条链处理请求，直到处理请求中的某个接受者返回（也包含无下一个接受者的情况）

UML

假设有一个根据不同等级的会员发送卡券包的需求

优点

将请求和处理分开，请求无须知道处理的细节，处理不用知道请求的全貌，两者解耦，提高功能或系统的灵活性

能够动态的变更（增加、删除、改变顺序）接受者，易扩展

缺点

接受者的链路过长导致性能问题以及调试问题

实现

定义了会员以及会员等级的枚举


public class Member {
	public Member(String name, MemberLevel memberLevel) {
		this.name = name;
		this.memberLevel = memberLevel;
	}
	private String name;
	private MemberLevel memberLevel;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public MemberLevel getMemberLevel() {
		return memberLevel;
	}
	public void setMemberLevel(MemberLevel memberLevel) {
		this.memberLevel = memberLevel;
	}
	@Override
	public String toString() {
		return "Member{" +
				"name="" + name + """ +
				", memberLevel=" + memberLevel +
				"}";
	}
}

public enum MemberLevel {
	/**
	 * 钻石
	 */
	DIAMOND(100),
	/**
	 * 黄金
	 */
	GOLD(90),
	/**
	 * 白银
	 */
	SILVER(80),
	/**
	 * 青铜
	 */
	BRONZE(70);
	private Integer level;
	 MemberLevel(int level){
		 this.level = level;
	}
	public int getLevelValue(){
		return this.level;
	}
}

抽象卡券助手java

public abstract class AbstractCouponAssistant {
	protected Integer memberLevel;
	protected AbstractCouponAssistant nextCouponAssistant;
	protected void setNext(AbstractCouponAssistant couponAssistant) {
		this.nextCouponAssistant = couponAssistant;
	}
	public  void sendCoupon(Member member){
		if(member.getMemberLevel().getLevelValue() >= memberLevel){
			 this.addCouponToPackage(member);
		}
		if(nextCouponAssistant != null){
			nextCouponAssistant.sendCoupon(member);
		}
	}
	/**
	 *  增加卡券到卡包
	 * @param member
	 */
	protected  abstract void addCouponToPackage(Member member) ;
}

具体的卡券助手


public class DiamondCouponAssistant extends AbstractCouponAssistant {
	public DiamondCouponAssistant(Integer memberLevel) {
		this.memberLevel = memberLevel;
	}
	@Override
	protected void addCouponToPackage(Member member) {
		System.out.println("为会员 {" + member.toString() + "}增加 钻石卡券");
	}
}

public class GoldCouponAssistant extends AbstractCouponAssistant {
	public GoldCouponAssistant(Integer memberLevel){
		this.memberLevel = memberLevel;
	}
	@Override
	protected void addCouponToPackage(Member member) {
		System.out.println("为会员 {" + member.toString() + "}增加 黄金卡券");
	}
}

public class SilverCouponAssistant extends AbstractCouponAssistant {
	public SilverCouponAssistant(Integer memberLevel) {
		this.memberLevel = memberLevel;
	}
	@Override
	protected void addCouponToPackage(Member member) {
		System.out.println("为会员 {" + member.toString() + "}增加 白银卡券");
	}
}

public class BronzeCouponAssistant extends AbstractCouponAssistant {
	public BronzeCouponAssistant(Integer memberLevel) {
		this.memberLevel = memberLevel;
	}
	@Override
	protected void addCouponToPackage(Member member) {
		System.out.println("为会员 {" + member.toString() + "}增加 青铜卡券");
	}
}

调用client

public class ChainPatternDenoClient {
	public static void main(String[] args) {
		AbstractCouponAssistant couponAssistant = getCouponAssistantChain();
		Member diamondMember = new Member("钻石王", MemberLevel.DIAMOND);
		Member goldMember = new Member("黄金张", MemberLevel.GOLD);
		Member silverMember = new Member("白银黄", MemberLevel.SILVER);
		Member bronzeMember = new Member("青铜吴", MemberLevel.BRONZE);
		System.out.println("开始发送卡券");
		couponAssistant.sendCoupon(diamondMember);
		System.out.println("=====发送下一个====");
		couponAssistant.sendCoupon(goldMember);
		System.out.println("=====发送下一个====");
		couponAssistant.sendCoupon(silverMember);
		System.out.println("=====发送下一个====");
		couponAssistant.sendCoupon(bronzeMember);
	}
	private static AbstractCouponAssistant getCouponAssistantChain() {
		DiamondCouponAssistant diamondCouponAssistant = new DiamondCouponAssistant(MemberLevel.DIAMOND.getLevelValue());
		GoldCouponAssistant goldCouponAssistant = new GoldCouponAssistant(MemberLevel.GOLD.getLevelValue());
		SilverCouponAssistant silverCouponAssistant = new SilverCouponAssistant(MemberLevel.SILVER.getLevelValue());
		BronzeCouponAssistant bronzeCouponAssistant = new BronzeCouponAssistant(MemberLevel.BRONZE.getLevelValue());
		diamondCouponAssistant.setNext(goldCouponAssistant);
		goldCouponAssistant.setNext(silverCouponAssistant);
		silverCouponAssistant.setNext(bronzeCouponAssistant);
		return diamondCouponAssistant;
	}
}