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: 8081spring:application:name: providecloud:nacos:discovery:server-addr: localhost:8848namespace: 6ce494ed-79a0-4c58-addf-cf66aa8f32b8config:server-addr: localhost:8848file-extension: yamlnamespace: 6ce494ed-79a0-4c58-addf-cf66aa8f32b8profiles: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: 8082spring:application:name: consumercloud:nacos:discovery:server-addr: localhost:8848namespace: 6ce494ed-79a0-4c58-addf-cf66aa8f32b8config:server-addr: localhost:8848file-extension: yamlnamespace: 6ce494ed-79a0-4c58-addf-cf66aa8f32b8profiles: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 {@Autowiredprivate 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

在这里插入图片描述

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: 5000readTimeout: 5000S## 为serviceA这个服务单独配置超时时间serviceA:connectTimeout: 10000readTimeout: 10000