SpringCloud之Feign

一. 概述

原创不易，转载请注明出处       author：yww

1. 什么是Feign?

Feign是Netflix开发的声明式，模板化的HTTP客户端，其灵感来自Retrofit,JAXRS-2.0以及WebSocket.

Feign可帮助我们更加便捷，优雅的调用HTTP API。

在SpringCloud中，使用Feign非常简单——创建一个接口，并在接口上添加一些注解，代码就完成了。

Feign支持多种注解，例如Feign自带的注解或者JAX-RS注解等。

SpringCloud对Feign进行了增强，使Feign支持了SpringMVC注解，并整合了Ribbon和Eureka，从而让Feign的使用更加方便。

2. Feign搭建

创建api工程

pom依赖引入

<?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">
    <parent>
        <artifactId>springcloudstudy</artifactId>
        <groupId>com.xxqy</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>springcloud-api</artifactId>

    <dependencies>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
        </dependency>
        <!--feign负载均衡-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</artifactId>
            <version>1.4.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
    </dependencies>

</project>

创建接口

package com.byxx.springcloud.service;

import com.byxx.springcloud.entity.Dept;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;

import java.util.List;

/**
 * Fegin 接口式编程
 * @Author yww
 * @CreateTime 2021-01-22
 *
 * 配置FeignClient value 为eureka服务实例名称
 */
@FeignClient(value = "SPRINGCLOUDDEPT",fallbackFactory = DeptClientServiceFallbackFactory.class)
public interface DeptClientService {

    @GetMapping("/dept/getById/{id}")
    public Dept getById(@PathVariable("id")Integer id);

    @GetMapping("/dept/getAll")
    public List<Dept> getAll();

    @PostMapping("/dept/add")
    public boolean addDept(Dept dept);

}

创建实现类

package com.byxx.springcloud.service;

import com.byxx.springcloud.entity.Dept;
import feign.hystrix.FallbackFactory;
import org.springframework.stereotype.Component;

import java.util.List;

/**
 * @Author yww
 * @CreateTime 2021-01-23
 */
@Component
public class DeptClientServiceFallbackFactory implements FallbackFactory {

    @Override
    public DeptClientService create(Throwable throwable) {
        return new DeptClientService() {
            @Override
            public Dept getById(Integer id) {
                return new Dept().setId(id)
                        .setName("id => "+ id +"没有对应的信息,客户端提供了降级的信息,这个服务现在已经关闭")
                        .setDb_source("没有数据~");
            }

            @Override
            public List<Dept> getAll() {
                return null;
            }

            @Override
            public boolean addDept(Dept dept) {
                return false;
            }
        };
    }
}

=========================================================>>>
=Feign工程=>>>
=================================================================>>>

建立feign工程 项目结构如下

pom依赖引入

<?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">
    <parent>
        <artifactId>springcloudstudy</artifactId>
        <groupId>com.xxqy</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>springcloud-feign</artifactId>

    <dependencies>
        <!--eureka-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
            <version>1.4.6.RELEASE</version>
        </dependency>
        <!--ribbon负载均衡-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</artifactId>
            <version>1.4.6.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>com.xxqy</groupId>
            <artifactId>springcloud-api</artifactId>
            <version>1.0-SNAPSHOT</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>
</project>

application.yml配置

server:
  port: 80

# 开启降级feign.hystrix
feign:
  hystrix:
    enabled: true

#消费者eureka配置
eureka:
  client:
    register-with-eureka: false #不向eureka注册自己
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/

编写配置类

package com.byxx.springcloud.config;

import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

/**
 * @Author yww
 * @CreateTime 2021-01-16
 */
@Configuration
public class ConfigBean {

    //配置负载均衡实现RestTemplate
    @Bean
    @LoadBalanced //ribbon
    public RestTemplate getRestTemplate(){
        return new RestTemplate();
    }
}

启动类

package com.byxx.springcloud;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;

/**
 * 消费者使用eureka服务(集群),
 * 整合Ribbon 负载均衡,使用注解@LoadBalanced 可以直接调用eureka服务
 * @Author yww
 * @CreateTime 2021-01-16
 */
@SpringBootApplication(exclude = DataSourceAutoConfiguration.class)
@EnableEurekaClient
@EnableFeignClients(basePackages = {"com.byxx.springcloud"})
public class FeignSpringCloud_Consumer_80 {
    public static void main(String[] args) {
        SpringApplication.run(FeignSpringCloud_Consumer_80.class,args);
    }

}