SpringCloud Feign实现微服务之间相互请求问题

2022-11-13 11:11:30 微服请求相互

?Feign简介

GitHub：Https://github.com/OpenFeign/feign

Feign是Netflix开发的声明式、模板化的HTTP客户端， Feign可以帮助我们更快捷、优雅地实现微服务之间的调用。
1.Feign可帮助我们更加便捷，优雅的调用HTTP api。
2.在SpringCloud中，使用Feign非常简单——创建一个接口，并在接口上添加一些注解，代码就完成了。
3.Feign支持多种注解，例如Feign自带的注解或者JAX-RS注解等。
4.springCloud对Feign进行了增强，使Feign支持了springMVC注解，并整合了Ribbon和Eureka，从而让Feign的使用更加方便。

?Spring Cloud 组件依赖版本

官网文档

本文参考使用组件依赖如下

?Feign实现服务之间访问

创建微服务项目，结构如下图所示

root 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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.ber</groupId>
    <artifactId>SprinGCloud-Feign</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>pom</packaging>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.12.RELEASE</version>
        <relativePath/>
    </parent>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <java.version>1.8</java.version>
        <spring-boot.version>2.3.12.RELEASE</spring-boot.version>
        <spring-cloud-alibaba.version>2.2.8.RELEASE</spring-cloud-alibaba.version>
        <spring-cloud.version>Hoxton.SR12</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-bootstrap</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-WEB</artifactId>
        </dependency>
    </dependencies>

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

    <modules>
        <!-- 注册中心 -->
        <module>ber-nacos</module>
    </modules>

</project>

ber-nacos 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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>SpringCloud-Feign</artifactId>
        <groupId>com.ber</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>ber-nacos</artifactId>
    <packaging>pom</packaging>

    <modules>
        <module>nacos-consumer</module>
        <module>nacos-provider</module>
        <module>nacos-consumer-feign</module>
    </modules>
</project>

☘创建nacos-consumer-feign微服务

nacos-consumer-feign 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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>ber-nacos</artifactId>
        <groupId>com.ber</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>nacos-consumer-feign</artifactId>


    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
        <!-- 负载均衡 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-loadbalancer</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <!-- feign -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
    </dependencies>

</project>

application.properties

spring.application.name=nacos-consumer-feign

spring.cloud.nacos.discovery.server-addr=127.0.0.1:8848

server.port=8895

feign.hystrix.enabled=true

启动类，注意添加注解@EnableFeignClients、@EnableDiscoveryClient

package com.ber.nacos.feign;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;


@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class FeignApplication {
    public static void main(String[] args) {
        SpringApplication.run(FeignApplication.class, args);
    }
}

controller接口，通过/queryMsg/{msgStr}访问provider微服务接口

package com.ber.nacos.feign.controller;

import com.ber.nacos.feign.service.MsgService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;


@RestController
public class MsgController {

    @Autowired
    MsgService msgService;

    
    @GetMapping("/queryMsg/{msgStr}")
    public String getMsg(@PathVariable(value = "msgStr") String msgStr) {
        return msgService.getMsg(msgStr);
    }
}

创建feign client

FeignClient 默认集成了 Ribbon，使用@FeignClient注解将MsgService 接口作为 FeignClient ，其属性名称与服务名称nacos-provider对应

package com.ber.nacos.feign.service;

import com.ber.nacos.feign.service.fallback.MsgServiceFallback;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;


@Component
@FeignClient(name = "nacos-provider", fallback = MsgServiceFallback.class)
public interface MsgService {

    @GetMapping("/getMsg/{msgStr}")
    String getMsg(@PathVariable("msgStr") String msgStr);
}

Feign的Fallback机制，在网络请求时，可能会出现异常请求，如果还想再异常情况下使系统可用，那么就需要容错处理，执行设置的容错业务代码。
当接口请求不成功时，就会调用MsgServiceFallback类这里的实现

package com.ber.nacos.feign.service.fallback;

import com.ber.nacos.feign.service.MsgService;
import org.springframework.stereotype.Component;


@Component
public class MsgServiceFallback implements MsgService {
    @Override
    public String getMsg(String msgStr) {
        return "请求失败";
    }
}

☘nacos-provider微服务

代码参考上篇文章《RestTemplate实现微服务之间访问》

?Feign微服务之间访问测试

启动nacos-consumer-feign和nacos-provider，访问http://localhost:8848/nacos，使用 nacos/nacos 登陆后，可以发现服务列表中，两个微服务已经注册，如下图所示。

访问http://localhost:8895/queryMsg/hello，即consumer-feign的接口，可以得到如下图所示的界面

☘Feign容错机制

修改feign client代码如下所示
改为@GetMapping("/getMsg-error/{msgStr}")，即原本的queryMsg会被请求到getMsg-error，而provider并没有提供getMsg-error，此时feign会进入容错机制。

package com.ber.nacos.feign.service;

import com.ber.nacos.feign.service.fallback.MsgServiceFallback;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;


@Component
@FeignClient(name = "nacos-provider", fallback = MsgServiceFallback.class)
public interface MsgService {

    @GetMapping("/getMsg-error/{msgStr}")
    String getMsg(@PathVariable("msgStr") String msgStr);
}

再次访问http://localhost:8895/queryMsg/hello，即consumer-feign的接口，可以得到如下图所示的界面

到此这篇关于SpringCloud Feign实现微服务之间相互请求的文章就介绍到这了,更多相关SpringCloud Feign微服务请求内容请搜索以前的文章或继续浏览下面的相关文章希望大家以后多多支持！

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