前言

接触springboot有三四年的时间，调用接口一直用restTemplate. postForObject等这样方法，也知道有feign这样的调用方法，但一直没有实践过，今天抽空试了一下，没有应用到开发中，但目前感觉还是比较方便的。

筹备

需要三个项目：
1、feign-client 客户端
2、feign-consumer 消费端
3、eureka-server 不再多说

开始1、

新建springboot项目，命名为feign-client，引入feign和eureka

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

main文件顺代开启两个配置

@SpringBootApplication
@EnableFeignClients //启用feign客户端
@EnableEurekaClient //启用eureka客户端
public class FeignClientApplication {

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

配置文件如下

server.port=9002
spring.application.name=feign-client

eureka.client.service-url.defaultZone=http://localhost:9000/eureka/

新建Hello测试文件,最最原生，没有多余的代码

package com.zsh.api;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloApi {
    @RequestMapping("/hello")
    public String sayHello() {
        return "hello feign";
    }
}

开始2 ，

新建springboot的feign-consumer项目，同样引用和开启feign和eureka
和feign-client项目相同，这里不再累赘

新建feignClient引用文件

package com.zsh.FeignClient;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;

@FeignClient("feign-client")
//注意，这里的feign-client 是feign-client项目的spring.application.name 不要写错
public interface HelloFeignClient{

    @GetMapping("/hello")
    public String sayHello();
}

新建测试文件

package com.zsh.api;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloApi {

    @RequestMapping("/hello")
    public String sayHello() {
        return "hello feign";
    }
}

至此全部完成

@auth 填过坑1

HelloFeignClient 一开始没有加注解@FeignClient("feign-client")
一直在提示

***************************
APPLICATION FAILED TO START
***************************

Description:

Field helloFeignClient in com.zsh.controller.HelloController required a bean of type 'com.zsh.FeignClient.HelloFeignClient' that could not be found.

Action:

Consider defining a bean of type 'com.zsh.FeignClient.HelloFeignClient' in your configuration.

@auth 填过坑1

public String sayHello();
没有加注解 @GetMapping("/hello")
提示

org.springframework.beans.factory.UnsatisfiedDependencyException: 
Error creating bean with name 'helloController': 
Unsatisfied dependency expressed through field 'helloFeignClient'; 
nested exception is org.springframework.beans.factory.BeanCreationException: 
Error creating bean with name 'com.zsh.FeignClient.HelloFeignClient': 
FactoryBean threw exception on object creation; 
nested exception is java.lang.IllegalStateException: Method sayHello not annotated with HTTP method type (ex. GET, POST)