SpringCloud学习之Feign 的使用（五）

2023-01-07 20:37:08

Feign 是一个声明式的伪RPC的REST客户端，它用了基于接口的注解方式，很方便的客户端配置，刚开始使用时还不习惯，感觉是在客户端写服务端的代码，Spring Cloud 给 Feign 添加了支持Spring MVC注解，并整合Ribbon及Eureka进行支持负载均衡。

Feign的使用很简单，有以下几步：

1、添加依赖

2、启动类添加 @EnableFeignClients 注解支持

3、建立Client接口，并在接口中定义需调用的服务方法

4、使用Client接口。

具体如下首先先添加feign需要的依赖

1、添加 spring-cloud-starter-openfeign 依赖

<dependency>

    <groupId>org.springframework.cloud</groupId>

    <artifactId>spring-cloud-starter-openfeign</artifactId>

</dependency>

完整的 pom.xml

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <parent>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>2.2.0.RELEASE</version>

        <relativePath/> <!-- lookup parent from repository -->

    </parent>

    <groupId>com.xu</groupId>

    <artifactId>service-consumer-feign</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <name>service-consumer-feign</name>

    <description>Demo project for Spring Boot</description>

    <properties>

        <java.version>1.8</java.version>

        <spring-cloud.version>Hoxton.M3</spring-cloud.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>

        </dependency>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>

        </dependency>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-starter-openfeign</artifactId>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-test</artifactId>

            <scope>test</scope>

            <exclusions>

                <exclusion>

                    <groupId>org.junit.vintage</groupId>

                    <artifactId>junit-vintage-engine</artifactId>

                </exclusion>

            </exclusions>

        </dependency>

        <dependency>

            <groupId>com.alibaba</groupId>

            <artifactId>fastjson</artifactId>

            <version>1.2.48</version>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</artifactId>

        </dependency>

    </dependencies>

    <dependencyManagement>

        <dependencies>

            <dependency>

                <groupId>org.springframework.cloud</groupId>

                <artifactId>spring-cloud-dependencies</artifactId>

                <version>${spring-cloud.version}</version>

                <type>pom</type>

                <scope>import</scope>

            </dependency>

        </dependencies>

    </dependencyManagement>

    <build>

        <plugins>

            <plugin>

                <groupId>org.springframework.boot</groupId>

                <artifactId>spring-boot-maven-plugin</artifactId>

            </plugin>

        </plugins>

    </build>

    <repositories>

        <repository>

            <id>spring-milestones</id>

            <name>Spring Milestones</name>

            <url>https://repo.spring.io/milestone</url>

        </repository>

    </repositories>

</project>

2、启动类添加 @EnableFeignClients 注解支持

package com.xu.serviceconsumer;

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.cloud.openfeign.EnableFeignClients;

import org.springframework.context.annotation.Bean;

import org.springframework.web.client.RestTemplate;

@SpringBootApplication

@EnableDiscoveryClient

@EnableFeignClients

public class ServiceConsumerFeignApplication {

    public static void main(String[] args) {

        SpringApplication.run(ServiceConsumerFeignApplication.class, args);

    }

    @Bean

    @LoadBalanced

    RestTemplate restTemplate() {

        return new RestTemplate();

    }

}

3、建立Client接口，并在接口中定义需调用的服务方法

package com.xu.serviceconsumer.service;

import org.springframework.cloud.openfeign.FeignClient;

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

import org.springframework.web.bind.annotation.RequestMethod;

import org.springframework.web.bind.annotation.RequestParam;

@FeignClient(name = "service-hello")

public interface UserFeignClient {

    @RequestMapping(value="/hi",method = RequestMethod.GET)

    String getName(@RequestParam String name);

}

说明：>> name="service-hello"，这里的"service-hello"是注册到Eureka 中的要调用的应用名

>> @GetMapping("/hi") 这里的“/hi”是要调用的应用里的相应的方法（这里需注意，如果service-hello服务下面的访问路径是 /hi/hello ，则这里也要写"/hi/hello"）。

4、使用Client接口

package com.xu.serviceconsumer.controller;

import com.alibaba.fastjson.JSONObject;

import com.fasterxml.jackson.databind.util.JSONPObject;

import com.xu.serviceconsumer.service.HelloService;

import com.xu.serviceconsumer.service.UserFeignClient;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.cloud.client.ServiceInstance;

import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;

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

import org.springframework.web.bind.annotation.RequestParam;

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

import org.springframework.web.client.RestTemplate;

import java.util.HashMap;

import java.util.Map;

@RestController

public class HelloControler {

    private static final Logger LOGGER = LoggerFactory.getLogger(HelloControler.class);

    @Autowired

    private HelloService helloService;

    @Autowired

    private LoadBalancerClient loadBalancerClient;

    @Autowired

    private UserFeignClient userFeignClient;

    @RequestMapping(value = "/hi")

    public String hi(@RequestParam String name) {

        return helloService.hiService(name);

    }

    @RequestMapping(value = "/hello")

    public String hello(@RequestParam String name) {

        return userFeignClient.getName(name);

    }

    @RequestMapping(value = "/log-instance")

    public Object logInstance() {

        ServiceInstance serviceInstance = this.loadBalancerClient.choose("SERVICE-HELLO");

        LOGGER.info("{}:{}:{}", serviceInstance.getServiceId(),

                serviceInstance.getHost(),serviceInstance.getPort());

        JSONObject object1 = new JSONObject();

        object1.put("ServiceId",serviceInstance.getServiceId());

        object1.put("Host",serviceInstance.getHost());

        object1.put("Port",serviceInstance.getPort());

        return object1.toJSONString();

    }

}

打开浏览器，访问上面Controller中的RestApi请求http://localhost:8767/hello?name=Ronnie结果如下：

看到这里显然我们的请求响应成功了，成功调用了服务提供者的服务，本节课程到此就结束了，各位如有疑问请再下方留言，我会尽快答复，谢谢观赏！

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SpringCloud学习之Feign 的使用（五）

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