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SpringCloudAlibaba — — OpenFeign的简单应用
SpringCloudAlibaba — — OpenFeign的概念及应用
1 什么是OpenFeign
OpenFeign是一种声明式、模板化的HTTP客户端。在Spring Cloud中使用OpenFeign，可以做到使用HTTP请求访问远程服务，就像调用本地方法一样的，开发者完全感知不到这是在调用远程方法，更感知不到在访问HTTP请求，用法其实就是编写一个接口，在接口上添加注解即可。
可以简单理解它是借鉴Ribbon的基础之上，封装的一套服务接口+注解的方式的远程调用器。1.1 OpenFeign作用
它的宗旨是编写Java Http客户端接口的时候变得更加容易，其底层也整合了Ribbon，所以也可以支持负载均衡。
之前我们在使用Ribbon的时候，利用的是RestTemplate对Http请求进行封装处理，但是在实际开发过程中，对服务依赖的调用不可能就一处，往往一个接口会被多处调用，所以通常都会针对每个微服务自行封装一些客户端类来包装这些依赖服务的调用。所以OpenFeign在此基础上做了进一步的封装，由它帮我们定义和实现依赖服务接口的定义，我们只需要创建一个接口并使用使用的方式配置它，即可完成对微服务提供方的接口绑定，简化Ribbon的操作。
1.2 OpenFeign的使用
使用OpenFeign其实就是在消费端去远程调用，就必须要是FeignClient注解，来标注要调用的服务提供者名称，然后再通过一个接口来定义要调用的方法
2 Ribbon、Feign、OpenFeign联系
①Ribbon
- Ribbon是Netflix开源的基于HTTP与TCP等协议的负载均衡组件
②Feign
- SpringCloud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，去调用注册中心（Nacos等）的服务
- Feign的使用方式：使用Feign自己的注解定义接口，然后调用这个接口就可以调用注册中心的服务
- Feign本身不支持Spring MVC注解，它有一套自己的注解
③OpenFeign
- OpenFeign是SpringCloud在Feign的基础上支持了SpringMVC的注解，如：@RequestMapping等
- OpenFeign的@FeignClient可以解析SpringMVC的@RequestMapping注解下的接口【通过动态代理的方式产生实现类，实现类中做负载均衡并调用其他服务】
- 注意：@RequestMapping不能在类名上与@FeignClient同时使用
3 OpenFeign实战小案例
3.1 创建一个模块cloudalibaba-provider-9003，作为消费者注册到本地Nacos上
模块结构如下：
创建好maven模块，继承父模块，并导入相关jar包：包括nacos、mybatis、mysql等
①pom.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>com.zi</groupId> <artifactId>SpringCloudAlibabaAll</artifactId> <version>0.0.1-SNAPSHOT</version> <relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.zi</groupId> <artifactId>cloudalibaba-provider-9003</artifactId> <version>0.0.1-SNAPSHOT</version> <name>cloudalibaba-provider-9003</name> <description>cloudalibaba-provider-9003</description> <properties> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>com.alibaba.cloud</groupId> <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid-spring-boot-starter</artifactId> <version>1.2.6</version> </dependency> <dependency> <groupId>org.mybatis.spring.boot</groupId> <artifactId>mybatis-spring-boot-starter</artifactId> <version>2.2.2</version> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>- 1
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②父模块的pom如下：
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> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.8.1</version> <configuration> <source>8</source> <target>8</target> </configuration> </plugin> </plugins> </build> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.2.13.RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.zi</groupId> <artifactId>SpringCloudAlibabaAll</artifactId> <version>0.0.1-SNAPSHOT</version> <name>SpringCloudAlibabaAll</name> <packaging>pom</packaging> <description>SpringCloudAlibabaAll</description> <properties> <java.version>1.8</java.version> <spring-cloud-alibaba-version>2.2.5.RELEASE</spring-cloud-alibaba-version> <openfeign-version>2.2.7.RELEASE</openfeign-version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> <scope>provided</scope> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-openfeign</artifactId> <version>${openfeign-version}</version> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> </dependency> </dependencies> <dependencyManagement> <dependencies> <dependency> <groupId>com.alibaba.cloud</groupId> <artifactId>spring-cloud-alibaba-dependencies</artifactId> <version>${spring-cloud-alibaba-version}</version> <type>pom</type> <scope>import</scope> </dependency> </dependencies> </dependencyManagement> <modules> <module>cloudAlibaba-Nacos-9001</module> <module>cloudalibaba-nacos-9002</module> <module>cloudalibaba-consumer-8083</module> <module>cloudalibaba-config-3377</module> <module>cloudalibaba-openFeign-consumer-8888</module> <module>cloudalibaba-provider-9003</module> </modules> </project>- 1
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3.1.1 创建pojo、service、mapper、controller层
①User.java
@Data @AllArgsConstructor @NoArgsConstructor public class User implements Serializable { private Integer uid; private String uname; private Integer upwd; }- 1
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②UserMapper.java
@Mapper public interface UserMapper { public User getUserById(Integer uid); }- 1
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③UserMapper.xml
DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.zi.mapper.UserMapper"> <select id="getUserById" resultType="user"> select * from user where uid = #{uid} select> mapper>- 1
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④UserService.java
public interface UserService { public User getUserById(Integer uid); }- 1
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⑤UserServiceImpl.java
@Service public class UserServiceImpl implements UserService { @Autowired private UserMapper userMapper; @Override public User getUserById(Integer uid) { return userMapper.getUserById(uid); } }- 1
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⑥UserController.java
@Controller @RequestMapping("/zi") public class UserController { @Autowired private UserService userService; @RequestMapping("/{id}") @ResponseBody public User getUser(@PathVariable("id") Integer uid){ User user = userService.getUserById(uid); return user; } @GetMapping @ResponseBody public String test(){ return "this is test"; } }- 1
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⑦启动类【加上@EnableDiscoveryClient注册到nacos上】
@SpringBootApplication @EnableDiscoveryClient public class CloudalibabaProvider9003Application { public static void main(String[] args) { SpringApplication.run(CloudalibabaProvider9003Application.class, args); } }- 1
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3.1.2 配置application.yml
server: # 服务端口 port: 9003 spring: application: #服务名称 name: feign-provider cloud: discovery: #nacos地址 server-addr: 127.0.0.1:8848 #配置数据源 datasource: driver-class-name: com.mysql.cj.jdbc.Driver url: jdbc:mysql://localhost:3306/mp?serverTimezone=UTC username: root password: 200151 type: com.alibaba.druid.pool.DruidDataSource management: endpoint: web: exposure: include: '*' #配置mybatis mybatis: mapper-locations: classpath:*.xml type-aliases-package: com.zi.pojo # 日志的方式打印sql logging: level: com.seamax.bdsearch.dao: DEBUG- 1
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3.3 访问本地nacos
访问之前需要启动本地nacos【进入到nacosbin目录下执行 startup.cmd -m standalone】
结果如下：
3.2 创建另外一个模块，来远程调用cloudalibaba-provider-9003模块上的服务
3.2.1 创建好对应包结构，导好对应jar包
该模块也继承于父工程
pom.xml
<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>4.0.0modelVersion> <parent> <groupId>com.zigroupId> <artifactId>SpringCloudAlibabaAllartifactId> <version>0.0.1-SNAPSHOTversion> <relativePath/> parent> <groupId>com.zigroupId> <artifactId>cloudalibaba-openFeign-consumer-8888artifactId> <version>0.0.1-SNAPSHOTversion> <name>cloudalibaba-openFeign-consumer-8888name> <description>cloudalibaba-openFeign-consumer-8888description> <properties> <java.version>1.8java.version> properties> <dependencies> <dependency> <groupId>org.springframework.bootgroupId> <artifactId>spring-boot-starterartifactId> dependency> <dependency> <groupId>org.springframework.bootgroupId> <artifactId>spring-boot-starter-testartifactId> <scope>testscope> dependency> <dependency> <groupId>com.alibaba.cloudgroupId> <artifactId>spring-cloud-starter-alibaba-nacos-discoveryartifactId> dependency> dependencies> <build> <plugins> <plugin> <groupId>org.springframework.bootgroupId> <artifactId>spring-boot-maven-pluginartifactId> plugin> plugins> build> project>- 1
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整体模块结构：
User.java
【后期也可以将所有pojo类放在同一个模块下】@Data @AllArgsConstructor @NoArgsConstructor public class User implements Serializable { private Integer uid; private String uname; private Integer upwd; }- 1
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OpenFeignService.java
需要添加@FeignClient注解并配置远程调用的服务名称
/** * 此接口就是配合使用OpenFeign的接口， * 在此接口中添加@FeignClient接口同时标注 * 要调用的服务端名称，同时使用与服务提供者 * 方法签名一致的抽象方法来表示远程调用的 * 具体内容 */ @Service @FeignClient("feign-provider")//远程调用的服务名称 public interface OpenFeignService { /** * 该方法表示远程调用zi/{id}接口 * @param uid * @return */ @GetMapping("zi/{id}") public User getUserById(@PathVariable("id") Integer uid); }- 1
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OpenFeignController.java
@RestController public class OpenFeignController { @Autowired private OpenFeignService openFeignService; @GetMapping("getInfo/{id}") public User getInfo(@PathVariable("id") Integer uid){ return openFeignService.getUserById(uid); } }- 1
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启动类：
需要加上@EnableFeignClients注解及@EnableDiscoveryClient
@SpringBootApplication @EnableDiscoveryClient//让nacos找到 @EnableFeignClients public class CloudalibabaOpenFeignConsumer8888Application { public static void main(String[] args) { SpringApplication.run(CloudalibabaOpenFeignConsumer8888Application.class, args); } }- 1
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配置文件application.yml
server: port: 8888 spring: application: name: nacos-consumer-openFeign cloud: nacos: discovery: server-addr: localhost:8848 management: endpoints: web: exposure: include: '*'- 1
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- 原文地址：https://blog.csdn.net/weixin_45565886/article/details/126192687
