[Alibaba微服务技术入门]_Sentinel服务熔断_第17讲

Sentinel的 block 机制是专门处理限流规则，降级规则，热点参数规则。但是当系统内部出现异常，比如：NullPointerException，IIlegalArgumentException等，block就不能很好的处理

于是我们可以采用Sentinel服务熔断 fallback 机制来有效处理系统内部异常，或者说系统业务功能异常

Sentinel服务熔断实战案例

第一：案例需求准备

• 服务方（9001，9002）提供 5条模拟数据
• 消费方（8001）接口需要通过 ID 参数获取服务提供的数据
• 消费方（8001）处理两种异常NullPointerException、IIlegalArgumentException，并对异常进行抛出
• 抛出的异常，需要通过Sentinel进行服务熔断

第二：在服务方（9001，9002）和消费方（8001），分别创建一个实体类

package com.liuyangjava.entity;

public class User {
    private String id;
    private String name;
    private Integer age;
    private String sex;

    public User() {
    }

    public User(String id, String name, Integer age, String sex) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.sex = sex;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    @Override
    public String toString() {
        return "User{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", sex='" + sex + '\'' +
                '}';
    }
}

第三：在消费方（8001）创建统一返回的ResultData类，此类专门提供数据响应给前端

扩展知识点：

项目中我们会将响应封装成 json 返回，一般我们会将所有接口的数据格式统一， 使前端对数据的操作更一致、轻松。

一般情况下，统一返回数据格式没有固定的格式，只要能描述清楚返回的数据状态以及要返回的具体数据就可以。但是一般会包含 响应状态、 状态码、返回消息、数据 这几部分内容

例如，我们的系统要求返回的基本数据格式如下

列表数据

{
	"success": true,
	"code": 20000,
	"message"："成功",
	"data": {
		"items": [
			{
				"id":"1",
				"name"："李白",
				"intro"："李白（701年-762年），字太白，号青莲居士，又号“谪仙人”，唐代伟大的浪漫主义诗人"
			}
		]
	}
}

单条数据：

{
	"success": true,
	"code": 20000,
	"message"："成功",
	"data": {
		"id":"1",
		"name"："李白",
		"intro"："李白（701年-762年），字太白，号青莲居士，又号“谪仙人”，唐代伟大的浪漫主义诗人"
	}
}

没有返回数据：

{
	"success": true,
	"code": 20000,
	"message"："成功",
	"data": {}
}

回调错误数据：

{
	"success": false,
	"code": 20001,
	"message"："失败",
	"data": {}
}

因此，我们可以定义一个统一的数据返回结果（每个公司对返回结果定义会有些不一样，大家不要对下面的代码太较真）

{
“success": 布尔，//响应是否成功
"code": 数字，//响应码
“message": 字符串，//返回消息
"data": HashMap //返回数据，放在键值对中
}

 创建ResultCodeEnum类，记录系统异常的相关信息

package com.liuyangjava.common.enums;

public enum ResultCodeEnum {
    SUCCESS(true, 20000, "成功"),
    UNKNOWN_REASON(false,20001,"未知错误"),
    BAD_SQL_GRAMMAR(false, 21001,"sql语法错误"),
    JSON_PARSE_ERROR(false,21002,"json解析异常"),
    PARAM_ERROR(false,21003,"参数不正确");

    private Boolean success;
    private Integer code;
    private String message;

    ResultCodeEnum(Boolean success, Integer code, String message) {
        this.success = success;
        this.code = code;
        this.message = message;
    }

    public Boolean getSuccess() {
        return success;
    }

    public void setSuccess(Boolean success) {
        this.success = success;
    }

    public Integer getCode() {
        return code;
    }

    public void setCode(Integer code) {
        this.code = code;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    @Override
    public String toString() {
        return "ResultCodeEnum{" +
                "success=" + success +
                ", code=" + code +
                ", message='" + message + '\'' +
                '}';
    }
}

创建ResultData类，返回统一定义数据结果

package com.liuyangjava.common.result;

import com.liuyangjava.common.enums.ResultCodeEnum;

public class ResultData<T> {
    private Boolean success;
    private Integer code;
    private String message;
    private T data;

    private ResultData() {}

    /**
     * 返回成功
     * @return
     */
    public static ResultData ok() {
        ResultData resultData = new ResultData();
        resultData.setSuccess(ResultCodeEnum.SUCCESS.getSuccess());
        resultData.setCode(ResultCodeEnum.SUCCESS.getCode());
        resultData.setMessage(ResultCodeEnum.SUCCESS.getMessage());
        return resultData;
    }

    /**
     * 返回失败
     * @return
     */
    public static ResultData error() {
        ResultData resultData = new ResultData();
        resultData.setSuccess(ResultCodeEnum.UNKNOWN_REASON.getSuccess());
        resultData.setCode(ResultCodeEnum.UNKNOWN_REASON.getCode());
        resultData.setMessage(ResultCodeEnum.UNKNOWN_REASON.getMessage());
        return resultData;
    }

    /**
     * 重新自定义的返回数据信息
     * @param resultCodeEnum
     * @return
     */
    public static ResultData setResultData(ResultCodeEnum resultCodeEnum) {
        ResultData resultData = new ResultData();
        resultData.setSuccess(resultCodeEnum.getSuccess());
        resultData.setCode(resultCodeEnum.getCode());
        resultData.setMessage(resultCodeEnum.getMessage());
        return resultData;
    }

    public Boolean getSuccess() {
        return success;
    }

    public void setSuccess(Boolean success) {
        this.success = success;
    }

    public Integer getCode() {
        return code;
    }

    public void setCode(Integer code) {
        this.code = code;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public T getData() {
        return data;
    }

    public void setData(T data) {
        this.data = data;
    }
}

 第四：在服务方（9001，9002）创建NacosUserProviderController接口，且在此接口中提供5条User的模拟数据

package com.liuyangjava.controller;

import com.liuyangjava.entity.User;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import java.util.HashMap;
import java.util.Map;

@RestController
public class NacosUserProviderController {

    private Map<String, User> map = new HashMap<>();

    {
        map.put("1", new User("1", "李白", 28, "男"));
        map.put("2", new User("2", "杜甫", 25, "男"));
        map.put("3", new User("3", "苏轼", 23, "男"));
        map.put("5", new User("5", "辛弃疾", 22, "男"));
        map.put("6", new User("6", "范仲淹", 21, "男"));
    }

    @GetMapping("/nacos/user/provider/{id}")
    public User getUserInfo(@PathVariable String id) {
        return map.get(id);
    }

}

第五：在消费方（8001）上创建NacosUserConsumerController接口，通过Feign去调用服务方（9001， 9002）的数据

package com.liuyangjava.controller;

import com.liuyangjava.common.result.ResultData;
import com.liuyangjava.entity.User;
import com.liuyangjava.service.NacosConsumerService;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;

@RestController
public class NacosUserConsumerController {

    @Value("${service-url.nacos-provider}")
    private String serverUrl;

    @Resource
    private NacosConsumerService nacosConsumerService;

    @GetMapping("/nacos/user/consumer/{id}")
    public ResultData<User> getUserInfo(@PathVariable String id) {
        User userInfo = nacosConsumerService.getUserInfo(id);
        if(userInfo == null) {
            throw new NullPointerException();
        }
        ResultData resultData = ResultData.ok();
        resultData.setData(userInfo);
        return resultData;
    }

}

package com.liuyangjava.service;

import com.liuyangjava.entity.User;
import com.liuyangjava.service.fallback.NacosConsumerServiceFallBack;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

@FeignClient(value = "nacos-provider", fallback = NacosConsumerServiceFallBack.class)
public interface NacosConsumerService {

    @GetMapping("/nacos/provider")
    String getInfoWithFeign();

    // 通过 feign 远程调用9001 或 9002 提供的数据
    @GetMapping("/nacos/user/provider/{id}")
    User getUserInfo(@PathVariable String id);
}

第六步：我们加入Sentinel的依赖，并对消费方（8001）的配置文件 application.yml 加入 Sentinel 的配置 

<dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
</dependency>

<!--springcloud ailibaba sentinel-datasource-nacos 后续做持久化用到-->
<dependency>
    <groupId>com.alibaba.csp</groupId>
    <artifactId>sentinel-datasource-nacos</artifactId>
</dependency>

server:
  port: 8001

spring:
  cloud:
    nacos:
      discovery:
        server-addr: 127.0.0.1:8858
    sentinel:
      transport:
        port: 8719
        dashboard: 127.0.0.1:8080
  application:
    name: nacos-consumer

management:
  endpoints:
    web:
      exposure:
        include: '*'

service-url:
  nacos-provider: http://nacos-provider

第七步：修改消费方（8001）的接口，加入 @SentinelResource 注解，完成系统业务功能出现异常后的处理方法

package com.liuyangjava.controller;

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.liuyangjava.common.result.ResultData;
import com.liuyangjava.entity.User;
import com.liuyangjava.service.NacosConsumerService;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;

@RestController
public class NacosUserConsumerController {

    @Value("${service-url.nacos-provider}")
    private String serverUrl;

    @Resource
    private NacosConsumerService nacosConsumerService;

    @GetMapping("/nacos/user/consumer/{id}")
    @SentinelResource(value = "getUserInfo", fallback = "handlerFallback")
    public ResultData<User> getUserInfo(@PathVariable String id) throws IllegalAccessException {
        if("10".equals(id)) {
            throw new IllegalAccessException("查询数据有误，参数异常...");
        }
        User userInfo = nacosConsumerService.getUserInfo(id);
        if(userInfo == null) {
            throw new NullPointerException("查询数据有误, 空指针异常...");
        }
        ResultData resultData = ResultData.ok();
        resultData.setData(userInfo);
        return resultData;
    }

    public ResultData handlerFallback(@PathVariable String id, Throwable e) {
        ResultData resultData = ResultData.error();
        resultData.setMessage(e.getMessage());
        return resultData;
    }

}

通过测试，当出现空指针异常的时候，handlerFallback 方法就会对异常进行处理

 

 

"10".equals(id)