Spring Cloud学习笔记（四）OpenFeign

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微服务之间免不了需要服务间调用。Spring Cloud框架提供了RestTemplate和FeignClient两个方式完成服务间调用，前面我们采用的是RestTemplate来实现调用，RestTemplate调用方式比较繁琐，本文简要介绍如何使用OpenFeign完成服务间调用。
创建项目openfeign,导入依赖如下

完整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>2.2.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>openfeign</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>openfeign</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Hoxton.SR3</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-netflix-eureka-client</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>
    </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>

</project>

配置application.properties

#服务名
spring.application.name=openfeign
#端口号
server.port=8085
#注入目标，配置服务中心url，与服务端的配置保持一致
eureka.client.service-url.defaultZone=http://localhost:8081/eureka/

在启动加上注解@EnableFeignClients启用feign

package com.example.openfeign;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
@EnableFeignClients
public class OpenfeignApplication {

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

}

创建接口HelloService

package com.example.openfeign.service;

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

@FeignClient("provider")
public interface HelloService {
    @GetMapping("/hello")
    String hello();//这里方法名随意
}

创建类HelloController

package com.example.openfeign.controller;

import com.example.openfeign.service.HelloService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {
    @Autowired
    private HelloService helloService;

    @GetMapping("/hello")
    public String hello(){
        return helloService.hello();
    }
}

最后启动前面的项目eureka和provider,还有本章的项目
启动完成访问http://localhost:8081结果如下

启动成功，访问当前项目的hello接口http://localhost:8085/hello结果如下

这里一个简单的示例就完成了
再补充一下传参，参数要绑定参数名