Feign和openFeign

Feign

Fegin使java Http客户端更加方便简洁，

Feign集成了Ribbon、RestTemplate实现了负载均衡的执行Http调用，只不过对原有的方式（Ribbon+RestTemplate）进行了封装，开发者不必手动使用RestTemplate调服务，而是定义一个接口，在这个接口中标注一个注解即可完成服务调用，这样更加符合面向接口编程的宗旨，简化了开发

openFeign

底层使用的是java的URL connection作为默认http客户端，不支持连接池，建议使用HttpClient，支持连接池

openFeign是springcloud在Feign的基础上支持了SpringMVC的注解，如@RequestMapping等等。OpenFeign的@FeignClient可以解析SpringMVC的@RequestMapping注解下的接口，并通过动态代理的方式产生实现类，并交给spring容器管理，实现类中做负载均衡并调用其他服务，调用的时候非常简单便捷，只需要注入Bean即可，这里的动态代理指的是jdk动态代理，因为是基于接口的http代理调用

环境搭建

这里注册中心使用nacos作为注册中心

建立被调用服务并注册nacos

配置文件

spring:
  application:
    name: cloud-test-service
  cloud:
    nacos:
      discovery:
        server-addr: 127.0.0.1:8848

controller

package com.slbuildenv.cloud.controller;

import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

@RestController
@RequestMapping("/find")
@RefreshScope
public class TestFeign {


    @GetMapping("/date")
    public String getDate(){
        return LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd"));
    }
}

建立调用服务并注册nacos

添加依赖

openFeign有条件注解判断是否引入Httpclient，如果引入此依赖，则使用Httpclient,默认无需配置，默认值就是开启

<dependencies>
        <!--nacos客户端依赖-->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
         <!--feign-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <!--  feign性能优化 apache httpclient包 支持连接池 默认使用jdk urlConnection 不支持连接池-->
        <dependency>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-httpclient</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
 </dependencies>

配置文件

spring:
  application:
    name: cloud-feign-client
  cloud:
    nacos:
      discovery:
        server-addr: 127.0.0.1:8848
server:
  port: 9300
feign:
  httpclient:
    connection-timeout: 5000

client接口

package com.slbuildenv.cloud.client;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;

@FeignClient("cloud-test-service")
public interface TestFeign {

    @GetMapping("/find/date")
    String findDate();
}

contoller调用

package com.slbuildenv.cloud.controller;

import com.slbuildenv.cloud.client.TestFeign;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

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

    @Autowired
    private TestFeign testFeign;

    @GetMapping("/date")
    public String getRemoteDate(){
       return  testFeign.findDate();
    }
}

启动类加开启feign的客户端注解

package com.slbuildenv.cloud;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.ComponentScan;

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class FeignMainApplication {
    public static void main(String[] args) {
        SpringApplication.run(FeignMainApplication.class,args);
    }
}

项目结构