SpringCloud之OpenFeign简单使用

SpringCloud之OpenFeign简单使用

OpenFeign是springcloud在Feign的基础上支持了SpringMVC的注解，如@RequestMapping等等。OpenFeign的@FeignClient可以解析SpringMVC的@RequestMapping注解下的接口，并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。

一、远程调用功能

1. 创建提供服务的模块remote-feign-provider

• 引入依赖

<dependencies>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
        dependency>

        <dependency>
            <groupId>com.alibaba.cloudgroupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discoveryartifactId>
        dependency>

        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-bootstrapartifactId>
        dependency>
    dependencies>
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版本信息如下

<properties>
        <maven.compiler.source>8maven.compiler.source>
        <maven.compiler.target>8maven.compiler.target>
        <project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
        <spring-boot.version>2.4.2spring-boot.version>
        <spring-cloud-alibaba.version>2021.1spring-cloud-alibaba.version>
        <nacos.version>2021.1nacos.version>
        <spring-cloud.version>2020.0.1spring-cloud.version>
        <spring-cloud-bootstrap.version>3.0.3spring-cloud-bootstrap.version>
        <spring-cloud-loadbalancer.version>3.0.1spring-cloud-loadbalancer.version>
        <spring-cloud-openfeign.version>3.0.1spring-cloud-openfeign.version>
properties>
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• 创建主类

@EnableDiscoveryClient
@SpringBootApplication
public class RemoteFeignProviderApplication {

    public static void main(String[] args) {
        SpringApplication.run(RemoteFeignProviderApplication.class, args);
    }
}
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• 创建bootstrap.yml

spring:
  application:
    name: remote-feign-provider
  cloud:
    nacos:
      discovery:
        group: remote-group
        namespace: remoteinvoke
        server-addr: 192.168.56.102:8848
        weight: 5

server:
  port: 8082
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注意nacos面板中需要新建相应的命名空间

• 创建TestController，提供相应的调用服务

@RestController
public class TestController {

    @Value("${server.port}")
    private int port;

    @GetMapping("/service")
    public String test(){
        return "provicer servvice: [from port]:" + port;
    }
}
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开启8081,8082两个端口的remote-feign-provider服务集群

2. 下面开始创建调用模块，consumer模块

• 创建remote-feign-service模块
• 引入依赖

<dependencies>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-openfeignartifactId>
        dependency>

        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
        dependency>

        <dependency>
            <groupId>com.alibaba.cloudgroupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discoveryartifactId>
        dependency>

        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-bootstrapartifactId>
        dependency>
    dependencies>
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• 主类

@SpringBootApplication
@EnableFeignClients(basePackages = "cn.axj.remote.feign.feign")
@EnableDiscoveryClient
public class FeignServiceApplication {

    public static void main(String[] args) {
        SpringApplication.run(FeignServiceApplication.class, args);
    }
}
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@EnableDiscoveryClient默认要注册到注册中心，这个注解可加可不加。

@EnableFeignClients : basePackages 用于OpenFeign扫描定义的FeignClient包路径

• bootstrap.yml

spring:
  application:
    name: remote-feign-service
  cloud:
    nacos:
      discovery:
        group: remote-group
        namespace: remoteinvoke
        server-addr: 192.168.56.102:8848
        weight: 5

server:
  port: 8080
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使用url形式的方式

• 创建LoadBalanceProviderOriginalFeignClient的接口，并利用SpringMvc的特性，将provider提供的服务/service声明成springmvc形式

@FeignClient(url = "http://localhost:8082",name = "remoteFeignSerivce")
public interface LoadBalanceProviderOriginalFeignClient {

    @GetMapping("/service")
    String service();

}
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定义一个url为http://localhost:8082的服务ip/端口的服务，指定该类访问的基础ip地址和端口固定

关于@FeignClient注解,参数释义如下

• 创建入口类Controller

@RestController
public class TestController {

    @Resource
    private LoadBalanceProviderOriginalFeignClient loadBalanceProviderOriginalFeignClient;

    @GetMapping("/test")
    public String test(){
        return loadBalanceProviderOriginalFeignClient.service();
    }
}
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将FeignClient用组件的形式注入到Spring中，类似于Mybatis的Mapper类,OpenFeign会生产代理对象注入到Spring容器中

测试

启动remote-feign-service模块，访问localhost:8080/test,返回

provicer servvice: [from port]:8082
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反复刷新，观察返回情况，可以看到返回信息一直是8082服务器返回的。

二、负载功能

OpenFeign默认开启负载，使用注册到注册中心的服务名称定义FeignClient。

• 在remote-feign-service模块中增加loadBalancer依赖

<dependency>
     <groupId>org.springframework.cloudgroupId>
     <artifactId>spring-cloud-starter-loadbalancerartifactId>
dependency>
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• 创建负载类的LoadBalanceProviderFeignClient接口

@FeignClient(name = "remote-feign-provider") 
public interface LoadBalanceProviderFeignClient {

    @GetMapping("/service")
    String service();
}
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name: 在注册中心中注册的调用服务名称

• 在TestController中注入该FeignClient

@RestController
public class TestController {

    @Resource
    private LoadBalanceProviderOriginalFeignClient loadBalanceProviderOriginalFeignClient;

    @Resource
    private LoadBalanceProviderFeignClient loadBalanceProviderFeignClient;

    @GetMapping("/test")
    public String test(){
        return loadBalanceProviderOriginalFeignClient.service();
    }

    @GetMapping("/test2")
    public String test2(){
        return loadBalanceProviderFeignClient.service();
    }
}
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测试

重启remote-feign-service模块，访问localhost:8080/test2,观察返回

provicer servvice: [from port]:8082
provicer servvice: [from port]:8081
provicer servvice: [from port]:8082
provicer servvice: [from port]:8081
provicer servvice: [from port]:8082
....
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此时已默认加入负载功能

三、熔断降级

当远程服务调用失败时，会采用熔断降级策略，调用熔断降级的方法返回。

熔断降级需要搭配熔断降级组件使用，这里使用hystrix进行熔断

由于springcloud高版本openFeign已经默认移除了hystrix组件，这里需要手动加上hystrix依赖

		<dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-netflix-hystrixartifactId>
            <version>2.2.5.RELEASEversion>
        dependency>
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• bootstrap.yml中增加配置

feign:
  circuitbreaker:
    enabled: true
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• 新建LoadBalanceProviderFeignClientFallback熔断类

@Component
public class LoadBalanceProviderFeignClientFallback implements LoadBalanceProviderFeignClient{
    
    @Override
    public String service() {
        return "error fall back";
    }
}
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tips: 必须将熔断类放入Spring容器中

• 配置FeignClient的熔断类,配置FeignClient fallback属性

@FeignClient(name = "remote-feign-provider",fallback = LoadBalanceProviderFeignClientFallback.class)
public interface LoadBalanceProviderFeignClient {

    @GetMapping("/service")
    String service();
}
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重启remote-feign-service模块，并将remote-feign-provider服务全部关掉。模拟熔断现象产生，访问localhost:8080/test2,观察返回

error fall back
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返回结果是有熔断类逻辑返回