什么是責(zé)任鏈？

什么是責(zé)任鏈？

責(zé)任鏈模式是行為模式的一種，它將需要觸發(fā)的Handler組成一條鏈，發(fā)送者將請(qǐng)求發(fā)給鏈的第一個(gè)接收者，并且沿著這條鏈傳遞，直到有一個(gè)Handler來處理它或者直到最后也沒有對(duì)象處理而留在鏈末尾端；責(zé)任連模式的重點(diǎn)是在鏈上，由一條鏈去處理相似的請(qǐng)求，在鏈中決定誰來處理這個(gè)請(qǐng)求

責(zé)任鏈分為純責(zé)任鏈與不純責(zé)任鏈（一般實(shí)戰(zhàn)應(yīng)用較多）

**純職責(zé)鏈 **

1.每個(gè)處理者接收到請(qǐng)求后，要么單純轉(zhuǎn)發(fā)請(qǐng)求，要么單純處理請(qǐng)求。不允許既處理請(qǐng)求，又轉(zhuǎn)發(fā)請(qǐng)求的情況。

2.請(qǐng)求必須被責(zé)任鏈上的某個(gè)處理者處理。不允許出現(xiàn)請(qǐng)求未被處理的情況。

**不純職責(zé)鏈 **

1.每個(gè)處理者接收到請(qǐng)求后，除了單純轉(zhuǎn)發(fā)請(qǐng)求，或者單純處理請(qǐng)求，還可以部分處理請(qǐng)求后，轉(zhuǎn)發(fā)。

2.請(qǐng)求可以不被責(zé)任鏈上的任何處理者處理。

責(zé)任鏈優(yōu)點(diǎn)

1.解耦請(qǐng)求者和處理者。

2.非常靈活，可以任意組裝

3.各個(gè)節(jié)點(diǎn)的責(zé)任明確

缺點(diǎn)

1.每次都是從鏈頭開始。

2. 可能造成死循環(huán)。責(zé)任鏈如果是環(huán)狀的，可能會(huì)導(dǎo)致循環(huán)調(diào)用，造成死循環(huán)。

純責(zé)任鏈的代碼Demo:

/**
     * 在公司OA系統(tǒng)請(qǐng)假審批流程
如果請(qǐng)假小于3天只需要項(xiàng)目經(jīng)理批復(fù)就行；
如果請(qǐng)假大于等于3天，小于7天需要人事經(jīng)理批復(fù)了；
如果請(qǐng)假大于等于7天，小于15天需要總經(jīng)理批復(fù)了；
如果申請(qǐng)請(qǐng)假大于等于15天，決絕批復(fù)......
     * @param args
     */
 public static void main(String[] args) {
        Leader manager = new Manager("張三");
        Leader hrManager = new HrManager("李四");
        Leader generalManager = new GeneralManager("王麻子");


        //組織責(zé)任鏈對(duì)象的關(guān)系
        manager.setNextLeader(hrManager);
        hrManager.setNextLeader(generalManager);
        //請(qǐng)假
        LeaveRequest request = new LeaveRequest("parry", 10, "回家相親！");
        manager.dealLeaveRequest(request);
  }

public abstract class Leader {
    // 領(lǐng)導(dǎo)姓名
    protected String name;
    // 責(zé)任鏈上的后繼對(duì)象
    protected Leader nextLeader;
    public Leader(String name) {
        super();
        this.name = name;
    }


    public void setNextLeader(Leader nextLeader) {
        this.nextLeader = nextLeader;
    }

    public abstract void dealLeaveRequest(LeaveRequest request);
}

  public class HrManager extends Leader{
      public HrManager(String name) {
          super(name);
      }


      @Override
      public void dealLeaveRequest(LeaveRequest request) {
        if (3 <= request.getLeaveDay() && request.getLeaveDay() < 7) {
            System.out.println("人事經(jīng)理：" + name + " 審批了 " + request.getEmployee() + "請(qǐng)假" + request.getLeaveDay()
                    + "天的請(qǐng)求,請(qǐng)假原因：" + request.getReason());
        } else {
            if (this.nextLeader != null) {
                this.nextLeader.dealLeaveRequest(request);
            }
        }
    }
}


public class GeneralManager extends Leader {
    public GeneralManager(String name) {
        super(name);
    }


    @Override
    public void dealLeaveRequest(LeaveRequest request) {
        if (7 <= request.getLeaveDay() && request.getLeaveDay() <= 15) {
            System.out.println("總經(jīng)理：" + name + " 審批了 " + request.getEmployee() + "請(qǐng)假" + request.getLeaveDay()
                    + "天的請(qǐng)求,請(qǐng)假原因：" + request.getReason());
        } else {
            System.out.println(
                    "總經(jīng)理：" + name + " 拒絕了 " + request.getEmployee() + "請(qǐng)假" + request.getLeaveDay() + "天的請(qǐng)求,請(qǐng)假不能超過15天");
        }
    }
}


public class Manager extends Leader{
    public Manager(String name) {
        super(name);
    }


    @Override
    public void dealLeaveRequest(LeaveRequest request) {
        if (request.getLeaveDay() < 3) {
            System.out.println("經(jīng)理：" + name + " 審批了 " + request.getEmployee() + "請(qǐng)假" + request.getLeaveDay()
                    + "天的請(qǐng)求,請(qǐng)假原因：" + request.getReason());
        } else {
            if (this.nextLeader != null) {
                this.nextLeader.dealLeaveRequest(request);
            }
        }
    }
}


@Data
public class LeaveRequest {
   //姓名
    private String name;
   //請(qǐng)假天數(shù)
    private int leaveDay;
    //請(qǐng)假原因
    private String reason;


    public LeaveRequest(String name, int leaveDay, String reason) {
        this.name=name;
        this.leaveDay=leaveDay;
        this.reason=reason;
    }  
}

電商售后使用責(zé)任鏈（不純責(zé)任鏈）

售后業(yè)務(wù)梳理

電商售后常見三種模式：

僅退款、退款退貨、退款換貨

售后業(yè)務(wù)可分為

僅退款： 采購(gòu)商申請(qǐng)——>商家審核——>完成

退款退貨：采購(gòu)商申請(qǐng)——>商家審核——>采購(gòu)商發(fā)貨——>商家確認(rèn)收貨——>完成

退款換貨：采購(gòu)商申請(qǐng)——>商家審核——>采購(gòu)商發(fā)貨——>商家確認(rèn)收貨——>商家發(fā)出新品——>采購(gòu)商確認(rèn)收貨——>完成

僅退款的實(shí)際退款等操作在商家審核時(shí)，而退款退貨和退款換貨則在確認(rèn)收貨時(shí)。

以下為售后責(zé)任鏈流程：

售后->校驗(yàn)退款單狀態(tài)->原路退款(以下單支付方式為準(zhǔn))->退積分或其它優(yōu)惠->更新訂單及對(duì)應(yīng)商品退款信息->保存結(jié)算->保存財(cái)務(wù)流水->保存/更新退款日志->發(fā)送退款成功異步消息

三種售后的核心退款業(yè)務(wù)流程基本是一致的，少個(gè)別節(jié)點(diǎn)業(yè)務(wù)邏輯有所區(qū)別，將核心業(yè)務(wù)抽成責(zé)任鏈的各個(gè)節(jié)點(diǎn)，這對(duì)售后來說，代碼的復(fù)用性提高了很多，同時(shí)業(yè)務(wù)處理更加清晰，犯錯(cuò)率大大降低。

以下為售后中代碼使用Demo

定義一個(gè)節(jié)點(diǎn)的基類接口

public interface BaseRefundHandler {
    void handle(PipelineContext context); 
}

售后責(zé)任鏈組裝，以下以僅退款為例

public class RefundPipeBean {
/**
 * 僅退款,責(zé)任鏈初始化節(jié)點(diǎn)
 */
public List<String> refundPipe = new ArrayList<>();


  public List<String> getRefundPipe() {
      refundPipe.add("checkRefundStatus"); //校驗(yàn)退款單狀態(tài)
      refundPipe.add("refundMoney");  //原路退款（獲取訂單支付方式）
      refundPipe.add("returnScore");  //退積分或其它優(yōu)惠券類
       ......
      return refundPipe;
  }


  @Bean
  @Scope("prototype")
  public CheckRefundStatus checkRefundStatus() {return new CheckRefundStatus();}

  @Bean
  @Scope("prototype")
  public RefundMoney refundMoney() {return new RefundMoney();}
  ......
}

** 注： 這個(gè)配置就等同于之前在xml里的配置**

"checkRefundStatus" class="com.xx.CheckRefundStatus"/>

創(chuàng)建一個(gè)啟動(dòng)監(jiān)聽器

@Component
public class RefundPipeListener extends ApplicationObjectSupport implements InitializingBean {
    private static Map<String, List> handlersMap = new HashMap<>();
     
   public static Map<String, List> getHandlersMap() {
        return handlersMap;
    }

    //最好定義成全局的，此處因演示 才在類中寫 。 責(zé)任鏈的名稱
   public static String ONLY_REFUND="ONLY_REFUND";
  @Override
  public void afterPropertiesSet() throws Exception {
    RefundPipeBean refundPipeBean=new RefundPipeBean();
     //裝載退款業(yè)務(wù)鏈.....
    List normalHandlers=new ArrayList<>();

    for (String s : refundPipeBean.getRefundPipe()) {
        BaseRefundHandler normalHandler = (BaseRefundHandler) getApplicationContext().getBean(s);
        normalHandlers.add(normalHandler);
        handlersMap.put(ONLY_REFUND, normalHandlers);
    } 
  }
}

創(chuàng)建節(jié)點(diǎn)傳遞對(duì)象所用POJO類

@Data
public class PipelineContext<K, V> extends ConcurrentHashMap<K, V> {
    protected boolean success = false;
    //責(zé)任鏈結(jié)束標(biāo)識(shí)
    protected boolean isEnd = false;
    protected String resultCode;
    private  Object data;


    public boolean isSuccess() {
        return success;
    }
    public void setSuccess(boolean success) {
        this.success = success;
    }


    public boolean isEnd() {
        return isEnd;
    }


    public void setEnd(boolean end) {
        isEnd = end;
    }
}


public class RefundPipelineContext<K, V> extends PipelineContext<K, V> {
    /**
     * 封裝退款單信息
    */
    private RefundInfoPipeVo refundInfoPipeVo;


    public RefundInfoPipeVo getRefundInfoPipeVo() {
        return refundInfoPipeVo;
    }


    public void setRefundInfoPipeVo(RefundInfoPipeVo refundInfoPipeVo) {
        this.refundInfoPipeVo = refundInfoPipeVo;
    }
}

創(chuàng)建節(jié)點(diǎn)

public class CheckRefundStatus implements BaseRefundHandler {
  @Override
  public void handle(PipelineContext<String, RefundInfoPipeVo> context) {
     //業(yè)務(wù)邏輯 todo
     ......
   //表示該節(jié)點(diǎn)運(yùn)行正常，可以繼續(xù)向下走
   context.setSuccess(true);
  }
}

業(yè)務(wù)調(diào)用層

@RestController
public class RefundInfoController {
  @Autowired
  RefundInfoService refundInfoService;

  @ApiOperation("僅退款")
  @RequestMapping(value = "/auditRefund", method = {RequestMethod.GET, RequestMethod.POST}, produces = "application/json;charset=UTF-8")
  public RespData<Boolean> auditRefund(xxx) {
      refundInfoService.auditRefund(xxx);
      return RespData.success("審核成功",true);
  }
}


public interface RefundInfoService {
  void auditRefund(xxx);
}


@Service("refundInfoService")
public class RefundInfoServiceImpl implements RefundInfoService {


    @Override
    public void auditRefund(xxx) {
        //業(yè)務(wù)邏輯 todo 
        RefundInfoResultVo refundInfoResultVo = refundInfoMapper.queryById(platformId, refundId);
        ......
        PipelineContext<String, RefundInfoPipeVo> refund = new RefundPipelineContext<>();
        //在責(zé)任鏈中傳遞參數(shù)對(duì)象
        refund.put("refund", refundInfoResultVo);
        Map<String, List> map = RefundPipelineChangeListener.getHandlersMap();
        //通過責(zé)任鏈的名稱獲取對(duì)應(yīng)鏈 。 此處key值應(yīng)為一個(gè)全局的常量，與上面監(jiān)聽器中的鏈條名一致
        List baseRefundHandlers = map .get(ONLY_REFUND); 
        for (BaseRefundHandler handler : baseRefundHandlers) {
            handler.handle(refund);
            if (refund.isEnd()) {
                System.out.println("責(zé)任鏈執(zhí)行結(jié)束...");
                break;
            }
            if (!refund.isSuccess()) {
                        System.out.println("責(zé)任鏈執(zhí)行失敗...");
                break;
            }
        }
    }
}

整體總結(jié)

以上是責(zé)任鏈在業(yè)務(wù)中創(chuàng)建及使用的流程。

同時(shí)以上流程也還存在一些可優(yōu)化點(diǎn)：

1. 責(zé)任鏈節(jié)點(diǎn)硬編碼問題
2. 添加同步事務(wù)控制