前言:設(shè)計(jì)模式源于生活

責(zé)任鏈基本概念

客戶端發(fā)出一個(gè)請(qǐng)求，鏈上的對(duì)象都有機(jī)會(huì)來(lái)處理這一請(qǐng)求，而客戶端不需要知道誰(shuí)是具體的處理對(duì)象。
這樣就實(shí)現(xiàn)了請(qǐng)求者和接受者之間的解耦，并且在客戶端可以實(shí)現(xiàn)動(dòng)態(tài)的組合職責(zé)鏈。使編程更有靈活性。

責(zé)任鏈定義

使多個(gè)對(duì)象都有機(jī)會(huì)處理請(qǐng)求，從而避免了請(qǐng)求的發(fā)送者和接受者之間的耦合關(guān)系。將這些對(duì)象連成一條鏈，并沿著這條鏈傳遞該請(qǐng)求，直到有對(duì)象處理它為止。其過(guò)程實(shí)際上是一個(gè)遞歸調(diào)用。

要點(diǎn):

1.有多個(gè)對(duì)象共同對(duì)一個(gè)任務(wù)進(jìn)行處理。
2.這些對(duì)象使用鏈?zhǔn)酱鎯?chǔ)結(jié)構(gòu)，形成一個(gè)鏈，每個(gè)對(duì)象知道自己的下一個(gè)對(duì)象。
3.一個(gè)對(duì)象對(duì)任務(wù)進(jìn)行處理，可以添加一些操作后將對(duì)象傳遞個(gè)下一個(gè)任務(wù)。也可以在此對(duì)象上結(jié)束任務(wù)的處理，并結(jié)束任務(wù)。
4.客戶端負(fù)責(zé)組裝鏈?zhǔn)浇Y(jié)構(gòu)，但是客戶端不需要關(guān)心最終是誰(shuí)來(lái)處理了任務(wù)。

責(zé)任鏈優(yōu)缺點(diǎn)

優(yōu)點(diǎn):

職責(zé)鏈模式的最主要功能就是：動(dòng)態(tài)組合，請(qǐng)求者和接受者解耦。
請(qǐng)求者和接受者松散耦合：請(qǐng)求者不需要知道接受者，也不需要知道如何處理。每個(gè)職責(zé)對(duì)象只負(fù)責(zé)自己的職責(zé)范圍，其他的交給后繼者。各個(gè)組件間完全解耦。
動(dòng)態(tài)組合職責(zé)：職責(zé)鏈模式會(huì)把功能分散到單獨(dú)的職責(zé)對(duì)象中，然后在使用時(shí)動(dòng)態(tài)的組合形成鏈，從而可以靈活的分配職責(zé)對(duì)象，也可以靈活的添加改變對(duì)象職責(zé)。

缺點(diǎn):

產(chǎn)生很多細(xì)粒度的對(duì)象：因?yàn)楣δ芴幚矶挤稚⒌搅藛为?dú)的職責(zé)對(duì)象中，每個(gè)對(duì)象功能單一，要把整個(gè)流程處理完，需要很多的職責(zé)對(duì)象，會(huì)產(chǎn)生大量的細(xì)粒度職責(zé)對(duì)象。
不一定能處理：每個(gè)職責(zé)對(duì)象都只負(fù)責(zé)自己的部分，這樣就可以出現(xiàn)某個(gè)請(qǐng)求，即使把整個(gè)鏈走完，都沒(méi)有職責(zé)對(duì)象處理它。這就需要提供默認(rèn)處理，并且注意構(gòu)造鏈的有效性。

責(zé)任鏈應(yīng)用場(chǎng)景

1.java過(guò)濾器的底層實(shí)現(xiàn)filter（例如:請(qǐng)求進(jìn)來(lái)到服務(wù)端,filter會(huì)經(jīng)過(guò)參數(shù)過(guò)濾、session過(guò)濾、表單過(guò)濾、請(qǐng)求頭過(guò)濾等等）
2.erp審批流程（例如:項(xiàng)目組長(zhǎng)->項(xiàng)目經(jīng)理->項(xiàng)目總監(jiān)->人事經(jīng)理）
3.多重if判斷問(wèn)題

責(zé)任鏈模式環(huán)境流程圖

1.抽象處理者(Handler)角色：定義出一個(gè)處理請(qǐng)求的接口。如果需要，接口可以定義 出一個(gè)方法以設(shè)定和返回對(duì)下家的引用。這個(gè)角色通常由一個(gè)Java抽象類或者Java接口實(shí)現(xiàn)。上圖中Handler類的聚合關(guān)系給出了具體子類對(duì)下家的引用，抽象方法handleRequest()規(guī)范了子類處理請(qǐng)求的操作。
2.具體處理者(ConcreteHandler)角色：具體處理者接到請(qǐng)求后，可以選擇將請(qǐng)求處理掉，或者將請(qǐng)求傳給下家。由于具體處理者持有對(duì)下家的引用，因此，如果需要，具體處理者可以訪問(wèn)下家

接下來(lái)將通過(guò)兩種基于責(zé)任鏈設(shè)計(jì)模式實(shí)現(xiàn)網(wǎng)關(guān)權(quán)限方式

兩種方式POM都通用

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>responsiit_model</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.1.RELEASE</version>
    </parent>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>29.0-jre</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.12</version>
            <!--            <scope>provided</scope>-->
        </dependency>

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.3.2</version>
        </dependency>
        <!-- mysql 依賴 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>

        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.11</version>
        </dependency>


    </dependencies>
</project>

第一種:基于內(nèi)存,模板模式+工廠模式+責(zé)任鏈模式實(shí)現(xiàn)網(wǎng)關(guān)權(quán)限框架

抽象handler

/**
 * @Author: klm
 * @Description: 抽象網(wǎng)關(guān)
 */
public abstract class GatewayHandler {

    abstract public void service();

    protected GatewayHandler nextGatewayHandler;

    public void setNextGatewayHandler(GatewayHandler gatewayHandler) {
        this.nextGatewayHandler = gatewayHandler;
    }

    protected void nextService() {
        if (nextGatewayHandler != null) {
            nextGatewayHandler.service();
        }
    }
}

具體API限流handler

/**
 * @Author: klm
 * @Description: API接口限流Handler
 */
@Slf4j
public class CurrentLimitHandler extends GatewayHandler {

    @Override
    public void service() {
        log.info("第一關(guān):API接口限流");
        nextService();
    }
}

具體黑名單限流Handler

/**
 * @Author: klm
 * @Description: 黑名單限流Handler
 */
@Slf4j
public class BlacklistHandler extends GatewayHandler {

    @Override
    public void service() {
        log.info("第二關(guān):黑名單限流");
        nextService();
    }
}

具體攔截用戶信息Handler

/**
 * @Author: klm
 * @Description: 攔截用戶信息Handler
 */
@Slf4j
public class ConversationHandler extends GatewayHandler {

    @Override
    public void service() {
        log.info("第三關(guān):攔截用戶信息");
    }
}

工廠:初始化對(duì)象并設(shè)置引用執(zhí)行順序

/**
 * @Author: klm
 * @Description: 工廠
 */
public class FactoryHandler {

    public static GatewayHandler getCurrentLimitHandler() {
        //初始化對(duì)象
        GatewayHandler currentLimitHandler = new CurrentLimitHandler();
        GatewayHandler blacklistHandler = new BlacklistHandler();
        GatewayHandler conversationHandler = new ConversationHandler();

        //設(shè)置引用,執(zhí)行順序設(shè)置
        currentLimitHandler.setNextGatewayHandler(blacklistHandler);
        blacklistHandler.setNextGatewayHandler(conversationHandler);
        return currentLimitHandler;
    }
}

測(cè)試類,執(zhí)行一波,看看效果

public class test {
    public static void main(String[] args) {
        GatewayHandler currentLimitHandler = FactoryHandler.getCurrentLimitHandler();
        currentLimitHandler.service();
    }
}

代碼還有需要改進(jìn)的地方

改進(jìn)點(diǎn):在每個(gè)handler處理器里面,都會(huì)要執(zhí)行一次nextService()方法,執(zhí)行下一個(gè)Handler,但是這種行為比較冗余,low所以我們改造一波
抽象Handler改造點(diǎn)

抽象Handler改造點(diǎn)

/**
 * @Author: klm
 * @Description: 抽象網(wǎng)關(guān)
 */
public abstract class GatewayHandler {

    //改造點(diǎn)1:將訪問(wèn)修飾符改為只有子類才能使用,不再進(jìn)行公開(kāi)使用
    protected abstract void service();

    protected GatewayHandler nextGatewayHandler;

    public void setNextGatewayHandler(GatewayHandler gatewayHandler) {
        this.nextGatewayHandler = gatewayHandler;
    }

    //改造點(diǎn)3:將執(zhí)行下一次操作的行為,改為我們的入口操作
    protected void nextService() {
        if (nextGatewayHandler != null) {
//            nextGatewayHandler.service();
            nextGatewayHandler.execute();
        }
    }

    //改造點(diǎn)2:抽出一個(gè)模板:用于外部調(diào)用的入口
    public void execute() {
        service();

        nextService();
    }
}

具體執(zhí)行的handler,其他的handler也需要去掉冗余,我這里就不顯示

/**
 * @Author: klm
 * @Description: 黑名單限流Handler
 */
@Slf4j
public class BlacklistHandler extends GatewayHandler {

    @Override
    public void service() {
        log.info("第二關(guān):黑名單限流");
        //改造點(diǎn)4:注釋掉,去掉冗余操作
//        nextService();
    }
}

測(cè)試類

/**
 * @Author: klm
 * @Description:
 */
public class test {
    public static void main(String[] args) {
        GatewayHandler currentLimitHandler = FactoryHandler.getCurrentLimitHandler();
//        currentLimitHandler.service();
        currentLimitHandler.execute();
    }
}

第二種:基于Mysql,模板模式+責(zé)任鏈模式實(shí)現(xiàn)網(wǎng)關(guān)權(quán)限框架

db sql文件

CREATE TABLE `gateway_handler` (
  `ID` int(11) NOT NULL AUTO_INCREMENT COMMENT '主鍵ID',
  `handler_name` varchar(32) DEFAULT NULL COMMENT 'handler名稱',
  `handler_id` varchar(32) DEFAULT NULL COMMENT 'handler主鍵id',
  `prev_handler_id` varchar(32) DEFAULT NULL,
  `next_handler_id` varchar(32) DEFAULT NULL COMMENT '下一個(gè)handler',
  PRIMARY KEY (`ID`)
) ENGINE=InnoDB AUTO_INCREMENT=19 DEFAULT CHARSET=utf8 COMMENT='權(quán)限表';

-- ----------------------------
-- Records of gateway_handler
-- ----------------------------
INSERT INTO `gateway_handler` VALUES ('16', 'Api接口限流', 'currentLimitHandler', null, 'blacklistHandler');
INSERT INTO `gateway_handler` VALUES ('17', '黑名單攔截', 'blacklistHandler', 'currentLimitHandler', 'conversationHandler');
INSERT INTO `gateway_handler` VALUES ('18', '會(huì)話驗(yàn)證', 'conversationHandler', 'blacklistHandler', null);


-- 查詢第一個(gè)
SELECT id as id ,handler_name as handlerName,handler_id as handlerId,prev_handler_id as prevHandlerId,next_handler_id as nextHandlerId FROM gateway_handler gh where gh.prev_handler_id is null;

SELECT id as id ,handler_name as handlerName,handler_id as handlerId,prev_handler_id as prevHandlerId,next_handler_id as nextHandlerId FROM gateway_handler gh where gh.handler_id = 'blacklistHandler';

entity類

/**
 * @Author: klm
 * @Description:
 */
@Data
public class GatewayHandlerEntity implements Serializable, Cloneable {
    /**
     * 主鍵ID
     */
    private Integer id;
    /**
     * handler名稱
     */
    private String handlerName;
    /**
     * handler主鍵id
     */
    private String handlerId;
    /**
     * 下一個(gè)handler
     */
    private String nextHandlerId;

}

mapper類

/**
 * @Author: klm
 * @Description:
 */
@Repository
public interface GatewayHandlerMapper {

    /**
     * 獲取第一個(gè)執(zhí)行的handler
     *
     * @return
     */
    @Select("SELECT id as id ,handler_name as handlerName,handler_id as handlerId,prev_handler_id as prevHandlerId," +
            "next_handler_id as nextHandlerId FROM gateway_handler gh " +
            "where gh.prev_handler_id is null;")
    GatewayHandlerEntity getFirstGatewayHandler();

    /**
     * 獲取下一個(gè)執(zhí)行的handler
     *
     * @param handlerId
     * @return
     */
    @Select("SELECT id as id ,handler_name as handlerName,handler_id as handlerId,prev_handler_id as prevHandlerId," +
            "next_handler_id as nextHandlerId FROM gateway_handler gh " +
            "where gh.handler_id = #{handlerId};")
    GatewayHandlerEntity getNextGatewayHandler(@Param("handlerId") String handlerId);
}

service類

/**
 * @Author: klm
 * @Description:
 */
public interface GatewayHandlerService {

    /**
     * db責(zé)任鏈模式
     *
     * @return
     */
    GatewayHandler getGatewayHandler();
}

service實(shí)現(xiàn)類

/**
 * @Author: klm
 * @Description:
 */
@Service
@Slf4j
public class GatewayHandlerServiceImpl implements GatewayHandlerService {

    @Autowired
    private GatewayHandlerMapper gatewayHandlerMapper;

    @Override
    public GatewayHandler getGatewayHandler() {

        //獲取頭節(jié)點(diǎn)
        GatewayHandlerEntity firstGatewayHandler = gatewayHandlerMapper.getFirstGatewayHandler();
        if (Objects.isNull(firstGatewayHandler)) {
            log.info("未配置頭節(jié)點(diǎn),請(qǐng)注意");
            return null;
        }

        String handlerId = firstGatewayHandler.getHandlerId();
        if (StringUtils.isEmpty(handlerId)) {
            log.info("未配置頭節(jié)點(diǎn),請(qǐng)注意");
            return null;
        }

        //從容器中獲取bean對(duì)象
        GatewayHandler bean = SpringUtils.getBean(handlerId, GatewayHandler.class);
        if (Objects.isNull(bean)) {
            log.info("容器中未找到");
            return null;
        }

        //下一節(jié)點(diǎn)名稱
        String nextHandlerId = firstGatewayHandler.getNextHandlerId();

        //記錄當(dāng)前對(duì)象
        GatewayHandler currentBean = bean;
        while (!StringUtils.isEmpty(nextHandlerId)) {

            //從容器獲取下一個(gè)執(zhí)行handler
            GatewayHandler nextBean = SpringUtils.getBean(nextHandlerId, GatewayHandler.class);
            if (Objects.isNull(nextBean)) {
                break;
            }

            //查詢db獲取下一個(gè)handlerid
            GatewayHandlerEntity nextGatewayHandler = gatewayHandlerMapper.getNextGatewayHandler(nextHandlerId);
            if (Objects.isNull(nextGatewayHandler)) {
                break;
            }
            nextHandlerId = nextGatewayHandler.getNextHandlerId();


            currentBean.setNextGatewayHandler(nextBean);
            currentBean = nextBean;
        }

        return bean;
    }
}

抽象handler

/**
 * @Author: klm
 * @Date: 2020/8/5 09:41
 * @Description:
 */
public abstract class GatewayHandler {

    protected abstract void doService();

    protected GatewayHandler nextGatewayHandler;

    public void setNextGatewayHandler(GatewayHandler gatewayHandler) {
        this.nextGatewayHandler = gatewayHandler;
    }

    protected void nextService() {
        if (nextGatewayHandler != null) {
//            nextGatewayHandler.doService();
            nextGatewayHandler.execute();
        }
    }

    public void execute() {
        doService();

        nextService();
    }
}

具體API接口限流Handler

/**
 * @Author: klm
 * @Description:
 */
@Component
@Slf4j
public class CurrentLimitHandler extends GatewayHandler {

    @Override
    public void doService() {
        log.info("第一關(guān):API接口限流");
//        nextService();
    }
}

具體黑名單限流Handler

/**
 * @Author: klm
 * @Description:
 */
@Component
@Slf4j
public class BlacklistHandler extends GatewayHandler {

    @Override
    public void doService() {
        log.info("第二關(guān):黑名單限流");
//        nextService();
    }
}

具體攔截用戶信息Handler

/**
 * @Author: klm
 * @Description:
 */
@Component
@Slf4j
public class ConversationHandler extends GatewayHandler {

    @Override
    public void doService() {
        log.info("第三關(guān):攔截用戶信息");
    }
}

SpringUtils類

/**
 * @Author: klm
 * @Description:
 */
@Component
public class SpringUtils implements ApplicationContextAware {

    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }

    //獲取applicationContext
    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    //通過(guò)name獲取 Bean.
    public static Object getBean(String name){
        return getApplicationContext().getBean(name);
    }

    //通過(guò)class獲取Bean.
    public static <T> T getBean(Class<T> clazz){
        return getApplicationContext().getBean(clazz);
    }

    //通過(guò)name,以及Clazz返回指定的Bean
    public static <T> T getBean(String name,Class<T> clazz){
        return getApplicationContext().getBean(name, clazz);
    }

}

controller類

/**
 * @Author: klm
 * @Description:
 */
@RestController
public class GatewayHandlerController {

    @Autowired
    private GatewayHandlerService gatewayHandlerService;

    @GetMapping("/test")
    public void test() {
        GatewayHandler gatewayHandler = gatewayHandlerService.getGatewayHandler();
        gatewayHandler.execute();
    }
}

application.yml文件

###服務(wù)啟動(dòng)端口號(hào)
server:
  port: 8080

spring:
  datasource:
    url: jdbc:mysql://127.0.0.1:3306/responsibility?useUnicode=true&characterEncoding=UTF-8&useSSL=true&serverTimezone=UTC
    username: root
    password: root
    driver-class-name: com.mysql.cj.jdbc.Driver


####打印MyBatias日志
logging:
  level:
    ### 開(kāi)發(fā)環(huán)境使用DEBUG 生產(chǎn)環(huán)境info或者error
    com.xuyu.mapper: DEBUG

訪問(wèn)網(wǎng)頁(yè):執(zhí)行l(wèi)ocalhost:8080/test
執(zhí)行效果圖