springCloud alibabanacos openFeign服务之间调用（二）

上一篇文章介绍了order-service  调用 user-service

 @Autowired

      private RestTemplate restTemplate;              @Bean       //负载均衡       @LoadBalanced

      public RestTemplate getRestTemplate(){

          return new     RestTemplate();

      }              @GetMapping("/order")

      public String test1() {           //此处服务名称   http://user-service           return restTemplate.getForObject("http://user-service/hello",String.class);

      }

 

RestTemplate还需要写上服务及IP这些信息，本章介绍openFeign  

openFeign是基于REST的服务调用上提供更高级别的抽象。Spring Cloud openFeign在声明性原则上工作。使用openFeign时，我们在客户端编写声明式REST服务接口，并使用这些接口来编写客户端程序。开发人员不用担心这个接口的实现。这将在运行时由Spring动态配置。通过这种声明性的方法，开发人员不需要深入了解由HTTP提供的HTTP级别API的细节的RestTemplate。

 

一，编写接口，user-service-api  提供一组基于rest风格的api,新建子模块user-service-api

此时项目结构为

1,加入依赖pom 

<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">   <modelVersion>4.0.0</modelVersion>   <parent>     <groupId>com.liu.dianmall</groupId>     <artifactId>mall-parent</artifactId>     <version>0.0.1-SNAPSHOT</version>   </parent>   <artifactId>user-service-api</artifactId>       <properties>         <java.version>1.8</java.version>     </properties>

    <dependencies>         <dependency>             <groupId>com.alibaba.cloud</groupId>             <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>         </dependency>         <dependency>             <groupId>org.springframework.cloud</groupId>             <artifactId>spring-cloud-starter-openfeign</artifactId>         </dependency>     </dependencies>

    <build>         <plugins>             <plugin>                 <groupId>org.springframework.boot</groupId>                 <artifactId>spring-boot-maven-plugin</artifactId>             </plugin>         </plugins>     </build> </project>

2，添加配置文件application.yml

server:   port: 9002

spring:   application:     name: user-service-api   cloud:     nacos:       discovery:         server-addr: 127.0.0.1:8848 3,添加接口userClient

package com.liu.nacos;

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

import com.liu.nacos.impl.UserClientHystrix;

//user-service  服务名 fallback  阻断后调用的服务

@FeignClient(name = "user-service",fallback = UserClientHystrix.class) public interface UserClient {

     @GetMapping("/hello")      String helloNacos(); }

添加实现类

package com.liu.nacos.impl;

import com.liu.nacos.UserClient;

public class UserClientHystrix implements UserClient{

    public String helloNacos() {         return "请求超时!";     } }  

添加启动类，测试

package com.liu.nacos;

import org.springframework.beans.factory.annotation.Autowired; 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.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication @RestController @EnableDiscoveryClient @EnableFeignClients public class UserServiceApiApplication {

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

    @Autowired     private UserClient userClient;

    @GetMapping("/api/user")     public String test() {         return userClient.helloNacos();     } }

四，修改 order-service项目，修改为feign调用

1，加入api依赖

      <dependency>             <groupId>com.liu.dianmall</groupId>             <artifactId>user-service-api</artifactId>             <version>0.0.1-SNAPSHOT</version>         </dependency>

2，修改，

package com.liu.nacos;

import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.client.discovery.EnableDiscoveryClient; import org.springframework.cloud.client.loadbalancer.LoadBalanced; import org.springframework.context.annotation.Bean; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController; import org.springframework.web.client.RestTemplate;

@SpringBootApplication @EnableDiscoveryClient @RestController public class OrderServiceApplication {

    public static void main(String[] args) {         SpringApplication.run(OrderServiceApplication.class, args);     }                 @Autowired UserClient userClient;                         /*          * @Autowired private RestTemplate restTemplate;          *           * @Bean          *           * @LoadBalanced public RestTemplate getRestTemplate(){ return new          * RestTemplate(); }          *           * @GetMapping("/order") public String test1() {          *           * return restTemplate.getForObject("http://user-service/hello",String.class); }          */                       @GetMapping("/order")        public String test1() {                       return userClient.helloNacos();              }       }