查看“OpenFeign 无参接口调用”的源代码

https://www.bilibili.com/video/BV1My4y1W7vy/?p=3

=== pom.xml ===
<syntaxhighlight lang="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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>io.github.jihch</groupId>
    <artifactId>feign-demo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.4.RELEASE</version>
    </parent>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <spring-cloud.version>Hoxton.SR8</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>

</project>
</syntaxhighlight>



=== application.yml ===
<syntaxhighlight lang="yaml">
spring:
  application:
    name: feign-demo
server:
  port: 8088
  
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/
</syntaxhighlight>


=== ServiceDemoFeign.java ===
<syntaxhighlight lang="java">
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;

@FeignClient("MYPROJECT")
public interface ServiceDemoFeign {

    /**
     * 方法要求：
     *      返回值：要对应
     *      方法名：随意
     *      参数：要对应
     *  方法上添加 SpringMVC 注解
     */
    @RequestMapping("/demo")
    String suiyi();

}
</syntaxhighlight>FeignClient 括号里的参数值就是要调用的目标接口在 Eureka 中注册的 application name
[[文件:Feign 通过 application name 进行接口调用.png|无|缩略图|1198x1198像素]]


=== 将 FeignClient 注解的类注入到要进行调用的类 ===

==== FeignDemoServiceImpl.java ====
<syntaxhighlight lang="java">
import io.github.jihch.feign.ServiceDemoFeign;
import io.github.jihch.service.FeignDemoService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class FeignDemoServiceImpl implements FeignDemoService {

    @Autowired
    private ServiceDemoFeign serviceDemoFeign;

    @Override
    public String demo() {
        return serviceDemoFeign.suiyi();
    }
}
</syntaxhighlight>注意：Feign 在应用程序中默认是不开启的，<code>private ServiceDemoFeign serviceDemoFeign;</code> 这行代码会编译报错，此时需要在启动类上加注解 <code>@EnableFeignClients</code> 来开启 Feign

==== FeignDemoApplication.java ====
<syntaxhighlight lang="java">
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
@EnableFeignClients
public class FeignDemoApplication {

    public static void main(String[] args) {

        SpringApplication.run(FeignDemoApplication.class, args);

    }
}
</syntaxhighlight>访问 http://localhost:8088/demo 进行测试