Spring-Cloud-OpenFeign源码解析-01-OpenFeign简介

OpenFeign简介

OpenFeign是一种声明式、模板化的HTTP客户端(仅在Application Client中使用)。声明式调用是指，就像调用本地方法一样调用远程方法，无需感知操作远程http请求。

OpenFeign和Feign的区别

Feign是Spring Cloud组件中一个轻量级RESTful的HTTP服务客户端，Feign内置了Ribbon，用来做客户端负载均衡，去调用服务注册中心的服务。

OpenFeign 是 Spring Cloud 对 Feign 的二次封装，它具有 Feign 的所有功能，并在 Feign 的基础上增加了对 Spring MVC 注解的支持，例如 @RequestMapping、@GetMapping 和 @PostMapping 等。

OpenFeign使用

创建一个父项目，引入pom文件，通过dependencyManagement统一管理依赖

<?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>

    <groupId>com.parent</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <spring.boot.version>2.7.4</spring.boot.version>
        <spring-cloud.version>2021.0.3</spring-cloud.version>
        <spring-cloud-alibaba.version>2021.0.1.0</spring-cloud-alibaba.version>
    </properties>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring.boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>

            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>

            <dependency>
                <groupId>com.alibaba.cloud</groupId>
                <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                <version>${spring-cloud-alibaba.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>

        </dependencies>
    </dependencyManagement>

</project>

创建服务提供方项目模块，引入pom文件

<?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>com.parent</groupId>
        <artifactId>demo</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>

    <groupId>com</groupId>
    <artifactId>provider</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>provider</name>
    <description>Demo project for Spring Boot</description>

    <dependencies>
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-config</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-bootstrap</artifactId>
        </dependency>
    </dependencies>
</project>

bootstrap.yaml配置

server:
  port: 8081

spring:
  application:
    name: provide

  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848
        namespace: 6ce494ed-79a0-4c58-addf-cf66aa8f32b8
      config:
        server-addr: localhost:8848
        file-extension: yaml
        namespace: 6ce494ed-79a0-4c58-addf-cf66aa8f32b8

  profiles:
    active: dev

启动类

@SpringBootApplication
@EnableDiscoveryClient
public class ProvideApplication {

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

提供接口

@RestController
public class TestController {

    @Value("${version}")
    private String version;

    @GetMapping("/test")
    public String test() {
        return version;
    }
}

创建服务消费方项目模块，引入pom文件

<?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>com.parent</groupId>
        <artifactId>demo</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>

    <groupId>com</groupId>
    <artifactId>consumer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>consumer</name>
    <description>Demo project for Spring Boot</description>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-config</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-bootstrap</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-loadbalancer</artifactId>
        </dependency>
    </dependencies>
</project>

bootstrap.yaml配置

server:
  port: 8082

spring:
  application:
    name: consumer

  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848
        namespace: 6ce494ed-79a0-4c58-addf-cf66aa8f32b8
      config:
        server-addr: localhost:8848
        file-extension: yaml
        namespace: 6ce494ed-79a0-4c58-addf-cf66aa8f32b8

  profiles:
    active: dev

启动类

@SpringBootApplication
@EnableFeignClients("com.consumer.feign")
@EnableDiscoveryClient
public class ConsumerApplication {

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

声明feign接口，name/value属性，这两个的作用是一样的，指定的是调用服务的微服务名称，互为对方的别名。url属性指定调用服务的全路径，经常用于本地测试。如果同时指定name/value和url属性，则以url属性为准，name/value属性指定的值便当做客户端的名称。

@FeignClient(value = "provide")
public interface TestFeign {

    @GetMapping("/test")
    String test();
}

外部调用

@RestController
public class TestController {

    @Autowired
    private TestFeign testFeign;

    @GetMapping("/consumer/test")
    public String test() {
        return testFeign.test();
    }
}

启动本地nacos、provide、consumer服务

访问http://localhost:8082/consumer/test

OpenFeign超时时间设置

默认不生效连接超时时间10秒、读超时时间60秒，源码在feign.Request.Options#Options()这个方法中

    public Options() {
      this(10, TimeUnit.SECONDS, 60, TimeUnit.SECONDS, true);
    }

超时时间配置

feign:
  client:
    config:
      ## default设置的全局超时时间，指定服务名称可以设置单个服务的超时时间
      default:
        connectTimeout: 5000
        readTimeout: 5000S
      ## 为serviceA这个服务单独配置超时时间
      serviceA:
        connectTimeout: 10000
        readTimeout: 10000