Spring cloud alibaba——sentinel（三）——@SentinelResource

• Sentinel服务熔断环境搭建
• • 一、共用类commons
  • 二、服务提供者9003，90004搭建
  • 二、服务消费者8084模块搭建
• @SentinelResource注解
• • 属性
  • fallback用法
  • blockHolder和fallbackHolder的区别

为了测试熔断保护机制，首先搭建一个服务环境，服务环境如下：
springcloud的依赖版本记得选2.2.X

搭建方式跟之前差不多

服务cloudalibaba-commons，后面9003和9004会引用这个类

package com.cloud.cloudalibabacommons.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;


@Data
@AllArgsConstructor
@NoArgsConstructor
public class JsonResult {

    
    private Integer code;

    
    private T data;

}

9003和9004项目结构、代码相同，只是端口号不一样
pom依赖：

   
        com.alibaba.cloud
        spring-cloud-starter-alibaba-nacos-discovery
    

    
    
        com.cloud
        cloudalibaba-commons
        0.0.1-SNAPSHOT
    

application.yml

server:
  port: 9003


spring:
  application:
    name: nacos-provider
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848

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

启动类记得添加@EnableDiscoveryClient注解

控制器类:

package com.cloud.cloudalibabaprovider9004.controller;

import com.cloud.cloudalibabacommons.entity.JsonResult;
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.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.HashMap;


@RestController
@RequestMapping("data")
public class DataController {

    @Value("${server.port}")
    private String serverPort;

    public static HashMap dataMap = new HashMap<>();
    //模仿数据库存储数据
    static{
        dataMap.put(1L,"鼠标");
        dataMap.put(2L,"键盘");
        dataMap.put(3L,"耳机");
    }

    @GetMapping("info/{id}")
    public JsonResult info(@PathVariable("id") Long id){
        return new JsonResult(200,serverPort+":  "+dataMap.get(id));
    }
}

pom依赖

  
     
         com.alibaba.cloud
         spring-cloud-starter-alibaba-nacos-discovery
     

     
     
         com.alibaba.cloud
         spring-cloud-starter-alibaba-sentinel
     
	 
        com.cloud
        cloudalibaba-commons
        0.0.1-SNAPSHOT
    

配置文件application.yml

server:
  port: 8084

spring:
  application:
    name: naocs-customer
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848
    sentinel:
      transport:
        #默认8719端口，假如被占用会自动从8719开始依次+1扫描,直至找到未被占用的端口
        port: 8719
        #配置Sentinel dashboard地址
        dashboard: 8080

# 消费者将要去访问的微服务名称(注册成功进nacos的微服务提供者)
service-url:
  nacos-user-service: http://nacos-provider

启动类

@SpringBootApplication
@EnableDiscoveryClient
public class CloudalibabaCustomer8084Application {

    public static void main(String[] args) {
        SpringApplication.run(CloudalibabaCustomer8084Application.class, args);
    }

    @Bean
    @LoadBalanced
    public RestTemplate getRestTemplate(){
        return new RestTemplate();
    }
}

Controller类

@RestController
@RequestMapping("demo")
public class DemoController {

    @Autowired
    private RestTemplate restTemplate;

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

    @GetMapping("info/{id}")
    public JsonResult fallbackInfo(@PathVariable("id") Long id){
        JsonResult jsonResult = restTemplate.getForObject(SERVICE_URL+"/data/info/"+id,JsonResult.class);
        return jsonResult;
    }
}

@SentinelResource官方文档说明

• value 资源名称，必需项（不能为空）
• blockHandler / blockHandlerClass: blockHandler 对应处理 BlockException 的函数名称，可选项。之前有提到过blockHandler和blockHanlderClass用法
• fallback：fallback 函数名称，可选项，用于在抛出异常的时候提供 fallback 处理逻辑。fallback 函数可以针对所有类型的异常。
• exceptionsToIgnore：用于指定哪些异常被排除掉，不会计入异常统计中，也不会进入 fallback 逻辑中，而是会原样抛出。

@RestController
@RequestMapping("demo")
public class DemoController {

    @Autowired
    private RestTemplate restTemplate;

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

    @GetMapping("info/{id}")
    @SentinelResource(value = "info", fallback = "fallBackHandler", exceptionsToIgnore = {NullPointerException.class})
    
    public JsonResult fallbackInfo(@PathVariable("id") Long id){
        if(id<3){
            JsonResult jsonResult = restTemplate.getForObject(SERVICE_URL+"/data/info/"+id,JsonResult.class);
            return jsonResult;
        }else if(id>10){
            throw new RuntimeException("----------RuntimeException----------");
        }
        throw new NullPointerException("没有查询到该数据");
    }

    
    public JsonResult fallBackHandler(Long id,Throwable e){
        return new JsonResult(441,"NullPointerException");
    }
}

为了提高服用性，避免多个@SentinelResource指定方法带来重复，也可以使用fallbackClass指定一个固定的类来处理

    @GetMapping("info/{id}")
    
    @SentinelResource(value = "info",
            fallback = "exceptionHandler",
            fallbackClass = {FallbackHandler.class})
    public JsonResult fallbackInfo(@PathVariable("id") Long id){
        if(id<3){
            JsonResult jsonResult = restTemplate.getForObject(SERVICE_URL+"/data/info/"+id,JsonResult.class);
            return jsonResult;
        }
        throw new NullPointerException("没有查询到该数据");
    }

处理异常的类

package com.cloud.cloudalibabacustomer8084.hanlder;


import com.cloud.cloudalibabacommons.entity.JsonResult;
import lombok.extern.slf4j.Slf4j;

@Slf4j
public class FallbackHandler {

    
    public static JsonResult exceptionHandler(Long id,Throwable e){
        log.info("fffffff");
        return new JsonResult(446,"访问异常");
    }
}