Feign入门实例

此案例为替换原有的消费者，注册中心和消息提供者延用之前的

注册中心的案例   https://www.cnblogs.com/songlove/p/14793575.html

消息提供者：https://www.cnblogs.com/songlove/p/14794021.html

先创建一个工程，引用maven控制 ，比着之前的消费者的项目增加了一个feign的依赖

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

第一步补全pom文件，完整的pom文件内容为

<?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>2.5.0</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.ssc</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>2020.0.3-SNAPSHOT</spring-cloud.version>
    </properties>
    <dependencies>
        <dependency>
            <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-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </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-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/snapshot</url>
            <releases>
                <enabled>false</enabled>
            </releases>
        </repository>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>

</project>

第二步、在启动类上增加@EnableFeignClients和@EnableEurekaClient 注解，@EnableFeignClients注解是启用了feign客户端，如果Feign接口与启动类不是在同一个包下，需要增加包的扫描，@EnableFeignClients（basePackages=“com.ssc.demo”）

package com.ssc.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
@EnableEurekaClient
@SpringBootApplication
@EnableFeignClients
public class DemoApplication {

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

}

第三步，创建Feign接口

package com.ssc.demo;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
//@FeignClient注解，这个注解标识当前是一个 Feign 的客户端，value 属性是对应的服务名称，也就是你需要调用哪个服务中的接口。
@FeignClient(value = "eureka-user-provide")
public interface UserRemoteClient {
//这个位置的请求路径就是，在这个提供者实例下提供具体服务的路径
    @RequestMapping(value = "/user/hello",method = RequestMethod.GET)
    String hello();
}

第四步，写消费者调用类

package com.ssc.demo;

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

@RestController
public class CallHello {

    @Autowired
    private UserRemoteClient userRemoteClient;
    @GetMapping(value = "/callHello")
    public String calloHello(){
//此时的调用相当于 http://eureka-user-provide/user/hello
        String result=userRemoteClient.hello();
        System.out.println("调用结果："+result);
        return result;
    }
}

第五步，书写yml配置文件

server:
  port: 8099
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka
  instance:
    instance-id: ${spring.application.name}:${spring.cloud.client.ip-address}:${server.port}
spring:
  application:
    name: feign-user-consumer

第六步启动应用，调用接口。先查看eureka注册中心

输入请求路径，查看http://127.0.0.1:8099/callHello，成功调用

项目的gitee地址：Feign_demo: 创建一个feign案例 (gitee.com)

参考：http://c.biancheng.net/view/5357.html