spring cloud feign组件简单使用

springcloud是使用rest协议(RestTemplate)进行信息传递,同时在netfix的项目中实现了一个feign组件来简化编写代码的麻烦,并且有自动负载均衡


调用的原理:

通过动态代理,产生了一个代理类交给了spring容器。然后通过反射获取接口的注解以及里面的配置,获取路径,获取参数名,参数值,获取返回的类型。然后封装到RestTemolate中,然后模拟浏览器请求。


简单使用:

1,加入起步依赖,在调用者模块中加入

<dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>

2,启动类添加@EnableFeignClients注解

@SpringBootApplication
@EnableEurekaClient
@EnableCircuitBreaker//开启熔断机制
@EnableFeignClients//
public class UserConsumerApplication {
    public static void main(String[] args) {
        SpringApplication.run(UserConsumerApplication.class,args);
    }

   /* @Bean
    @LoadBalanced //启动负载均衡
    public RestTemplate restTemplate(){
        return new RestTemplate();
    }*/
}

3,创建一个接口,接口里面的方法名,参数名,以及返回值要和controller类一致

package org.example.feign;

import org.example.pojo.User;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
//声明feign组件,name是指定服务名,
//@FeignClient(name = "${feign.name}", url = "${feign.url}")
@FeignClient(name = "user-provider")
public interface UserFeign {
    @GetMapping("/user/{id}")
    public User findById(@PathVariable(name = "id") Integer id);
}

4,controller类,直接注入接口,然后调用接口的方法即可

package org.example.controller;

import org.example.feign.UserFeign;
import org.example.pojo.User;
import org.springframework.beans.factory.annotation.Autowired;
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;

@RestController
@RequestMapping("/feign")
public class TestFeignController {

    @Autowired
    private UserFeign userFeign;

    @GetMapping("/{id}")
    public User findByid(@PathVariable(name = "id") Integer id){
        //接受浏览器请求
        //调用feign
        User user = userFeign.findById(id);
        return user;
    }
}

负载均衡配置

1,通过Ribbon来配置

# 修改服务地址轮询策略,默认是轮询,配置之后变随机
# WeightedResponseTimeRule 根据服务响应时间权重值策略
# RoundRobinRule 轮询策略
# RandomRule 随机策略
# Zone Avoidance Rule 区域避免规则。
# 配置负载均衡
user-provider:
  ribbon:
    NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule #默认是轮询,配置为随机
    ConnectTimeout: 1000 # 连接超时时间
    ReadTimeout: 2000 # 数据读取超时时间,连接之后,数据传输过程
    MaxAutoRetries: 0 # 最大重试次数(第一个服务)
    MaxAutoRetriesNextServer: 0 # 最大重试下一个服务次数(集群的情况才会用到)
    OkToRetryOnAllOperations: false # 是否对所有的请求都重试

2,或者通过fegin来配置

feign:
  client:
    config:
      feignName:
        connectTimeout: 5000
        readTimeout: 5000
        loggerLevel: full
        errorDecoder: com.example.SimpleErrorDecoder
        retryer: com.example.SimpleRetryer
       defaultQueryParameters:
          query: queryValue
        defaultRequestHeaders:
          header: headerValue
        requestInterceptors:
          - com.example.FooRequestInterceptor
          - com.example.BarRequestInterceptor
        decode404: false
        encoder: com.example.SimpleEncoder
        decoder: com.example.SimpleDecoder
        contract: com.example.SimpleContract

熔断器支持(默认没有开启)

# To disable Hystrix in Feign
feign:
  hystrix:
    enabled: true

使用:

创建一个对应的Feign类的实现类

package org.example.feign.impl;

import org.example.feign.UserFeign;
import org.example.pojo.User;
@Component
public class UserFeignImpl implements UserFeign {

    //降级方法
    @Override
    public User findById(Integer id) {
        User user = new User();
        user.setId(0);
        user.setUsername("默认名称");
        return user;
    }
}

然后在@FeignClient注解加上一个参数fallback

package org.example.feign;

import org.example.feign.impl.UserFeignImpl;
import org.example.pojo.User;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
//声明feign组件,name是指定服务名,
//@FeignClient(name = "${feign.name}", url = "${feign.url}")
@FeignClient(name = "user-provider",fallback = UserFeignImpl.class)
public interface UserFeign {
    @GetMapping("/user/{id}")
    public User findById(@PathVariable(name = "id") Integer id);
}

注意项:

如果你需要使用Hystrix那么就不要把@RequestMapping注解写到类上,因为实现类实现了接口,而@RequestMapping加在接口上,那么实现类也会生成两个动态代理类和一个同样的路径,导致url路径不唯一,所以会报错

解决方法:

1,直接不在类上加@RequestMapping注解

2,或者在@FeignClient加入一个参数:path即可

package org.example.feign;

import org.example.feign.impl.UserFeignImpl;
import org.example.pojo.User;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
//声明feign组件,name是指定服务名,
//@FeignClient(name = "${feign.name}", url = "${feign.url}")
@FeignClient(name = "user-provider",fallback = UserFeignImpl.class,path="/user")
public interface UserFeign {
    @GetMapping("/{id}")
    public User findById(@PathVariable(name = "id") Integer id);
}

另外还可以了解一下请求压缩,和日志级别配置

(15条消息) SpringCloud Feign 优化_xjune的专栏-****博客

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