Spring Cloud學習筆記（四）OpenFeign

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微服務之間免不了需要服務間調用。Spring Cloud框架提供了RestTemplate和FeignClient兩個方式完成服務間調用，前面我們採用的是RestTemplate來實現調用，RestTemplate調用方式比較繁瑣，本文簡要介紹如何使用OpenFeign完成服務間調用。
創建項目openfeign,導入依賴如下

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

#服務名
spring.application.name=openfeign
#端口號
server.port=8085
#注入目標，配置服務中心url，與服務端的配置保持一致
eureka.client.service-url.defaultZone=http://localhost:8081/eureka/

在啓動加上註解@EnableFeignClients啓用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);
    }

}

創建接口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();//這裏方法名隨意
}

創建類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();
    }
}

最後啓動前面的項目eureka和provider,還有本章的項目
啓動完成訪問http://localhost:8081結果如下

啓動成功，訪問當前項目的hello接口http://localhost:8085/hello結果如下

這裏一個簡單的示例就完成了
再補充一下傳參，參數要綁定參數名