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微服务之同步远程调用(Feign)

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前言

微服务的服务提供者和服务消费者解耦合之后，我们可以借助restTemplate这样的HTTP客户端，向微服务的服务提供者发起远程调用；

但是这样的代码有2大缺陷：

[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:b5737d4b-c67f-494f-ab24-db1b90ce375f

[En]

[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:3670496e-b22f-4e34-b244-549a7696f2bf

* 当URL参数复杂时难以维护

//使用RestTemplate发起远程调用
    @Autowired
    private RestTemplate restTemplate;
    public Order findById(Long orderId) {
        // 1.查询订单
        Order order = orderMapper.selectById(orderId);
        //2.调用user-service服务查询当前订单的用户信息
        //String url = "http://127.0.0.1:8081/user/" + order.getUserId();
        //使用RestTemplate发起远程调用
        String url = "http://user-service/user/" + order.getUserId();
        User user = restTemplate.getForObject(url, User.class);
        //3.user封装到order对象
        order.setUser(user);
        // 4.返回
        return order;
    }

一、SpringCloud项目搭建

[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:d51b9890-ec58-48ff-b942-0c2518ac52f6

[En]

[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:46bfcbf5-3bd0-47fe-8e05-40bae98d9231

如果用户微服务需要查询订单微服务的数据，就需要使用Feign发起远程调用；

在远程调用过程中user-service是消费者order-service是生产者；

1.搭建流程图

微服务之同步远程调用(Feign)

2.搭建父项目

2.1.父项目依赖版本锁定

微服务之同步远程调用(Feign)微服务之同步远程调用(Feign) 
<?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>4.0.0modelVersion>

<span>&lt;</span><span>groupId</span><span>&gt;</span>com.zhanggen<span><span>groupId</span><span>&gt;</span>
<span>&lt;</span><span>artifactId</span><span>&gt;</span>spring-cloud-demo<span><span>artifactId</span><span>&gt;</span>
<span>&lt;</span><span>version</span><span>&gt;</span>1.0-SNAPSHOT<span><span>version</span><span>&gt;</span>

<span>&lt;</span><span>packaging</span><span>&gt;</span>pom<span><span>packaging</span><span>&gt;</span>

<span>&lt;</span><span>parent</span><span>&gt;</span>
    <span>&lt;</span><span>groupId</span><span>&gt;</span>org.springframework.boot<span><span>groupId</span><span>&gt;</span>
    <span>&lt;</span><span>artifactId</span><span>&gt;</span>spring-boot-starter-parent<span><span>artifactId</span><span>&gt;</span>
    <span>&lt;</span><span>version</span><span>&gt;</span>2.3.9.RELEASE<span><span>version</span><span>&gt;</span>
    <span>&lt;</span><span>relativePath</span><span>/&gt;</span>
<span><span>parent</span><span>&gt;</span>

<span>&lt;</span><span>dependencyManagement</span><span>&gt;</span>
    <span>&lt;</span><span>dependencies</span><span>&gt;</span>

        <span>&lt;</span><span>dependency</span><span>&gt;</span>
            <span>&lt;</span><span>groupId</span><span>&gt;</span>org.springframework.cloud<span><span>groupId</span><span>&gt;</span>
            <span>&lt;</span><span>artifactId</span><span>&gt;</span>spring-cloud-dependencies<span><span>artifactId</span><span>&gt;</span>
            <span>&lt;</span><span>version</span><span>&gt;</span>Hoxton.SR10<span><span>version</span><span>&gt;</span>
            <span>&lt;</span><span>type</span><span>&gt;</span>pom<span><span>type</span><span>&gt;</span>
            <span>&lt;</span><span>scope</span><span>&gt;</span>import<span><span>scope</span><span>&gt;</span>
        <span><span>dependency</span><span>&gt;</span>

        <span>&lt;</span><span>dependency</span><span>&gt;</span>
            <span>&lt;</span><span>groupId</span><span>&gt;</span>com.alibaba.cloud<span><span>groupId</span><span>&gt;</span>
            <span>&lt;</span><span>artifactId</span><span>&gt;</span>spring-cloud-alibaba-dependencies<span><span>artifactId</span><span>&gt;</span>
            <span>&lt;</span><span>version</span><span>&gt;</span>2.2.6.RELEASE<span><span>version</span><span>&gt;</span>
            <span>&lt;</span><span>type</span><span>&gt;</span>pom<span><span>type</span><span>&gt;</span>
            <span>&lt;</span><span>scope</span><span>&gt;</span>import<span><span>scope</span><span>&gt;</span>
        <span><span>dependency</span><span>&gt;</span>
    <span><span>dependencies</span><span>&gt;</span>
<span><span>dependencyManagement</span><span>&gt;</span>
<span>&lt;</span><span>modules</span><span>&gt;</span>
    <span>&lt;</span><span>module</span><span>&gt;</span>user-service<span><span>module</span><span>&gt;</span>
    <span>&lt;</span><span>module</span><span>&gt;</span>order-service<span><span>module</span><span>&gt;</span>
<span><span>modules</span><span>&gt;</span>



project>
pom.xml

3.搭建子项目


3.1.子项目依赖导入


微服务之同步远程调用(Feign)微服务之同步远程调用(Feign)

<?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>spring-cloud-demoartifactId>
        <groupId>com.zhanggengroupId>
        <version>1.0-SNAPSHOTversion>
    parent>
    <modelVersion>4.0.0modelVersion>
    <artifactId>order-serviceartifactId>

<span>&lt;</span><span>dependencies</span><span>&gt;</span>

    <span>&lt;</span><span>dependency</span><span>&gt;</span>
        <span>&lt;</span><span>groupId</span><span>&gt;</span>org.springframework.boot<span><span>groupId</span><span>&gt;</span>
        <span>&lt;</span><span>artifactId</span><span>&gt;</span>spring-boot-starter-web<span><span>artifactId</span><span>&gt;</span>
    <span><span>dependency</span><span>&gt;</span>

    <span>&lt;</span><span>dependency</span><span>&gt;</span>
        <span>&lt;</span><span>groupId</span><span>&gt;</span>com.alibaba.cloud<span><span>groupId</span><span>&gt;</span>
        <span>&lt;</span><span>artifactId</span><span>&gt;</span>spring-cloud-starter-alibaba-nacos-discovery<span><span>artifactId</span><span>&gt;</span>
    <span><span>dependency</span><span>&gt;</span>

    <span>&lt;</span><span>dependency</span><span>&gt;</span>
        <span>&lt;</span><span>groupId</span><span>&gt;</span>org.springframework.cloud<span><span>groupId</span><span>&gt;</span>
        <span>&lt;</span><span>artifactId</span><span>&gt;</span>spring-cloud-starter-openfeign<span><span>artifactId</span><span>&gt;</span>
    <span><span>dependency</span><span>&gt;</span>

    <span>&lt;</span><span>dependency</span><span>&gt;</span>
        <span>&lt;</span><span>groupId</span><span>&gt;</span>io.github.openfeign<span><span>groupId</span><span>&gt;</span>
        <span>&lt;</span><span>artifactId</span><span>&gt;</span>feign-httpclient<span><span>artifactId</span><span>&gt;</span>
    <span><span>dependency</span><span>&gt;</span>
<span><span>dependencies</span><span>&gt;</span>



project>
pom

3.2.application配置文件


微服务之同步远程调用(Feign)微服务之同步远程调用(Feign)

server:
  port: 9090
spring:
  application:
    name: order-service
  cloud:
    nacos:
      discovery:
        server-addr: 127.0.0.1:8848



application.yml


二、Feign介绍


Feign是1个声明式的HTTP客户端，通过HTTP协议使得调用远程服务就像调用本地服务一样简单，只需要创建一个接口并添加一个注解即可。


其作用就是帮助我们优雅的实现HTTP请求的发送，解决上面提到的问题。


而且Feign默认集成了Ribbon，所以使用Feign默认就实现了客户端负载均衡的效果。


三、Feign使用


1.引入依赖


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


2.添加 @EnableFeignClients 注解


[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:26b875b6-18fb-4abd-baac-861db9e2acc2



[En]

[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:221a4d6a-f7c5-4a0c-bc22-e67562659ace


在order-service的启动类添加注解开启Feign的功能；


@MapperScan("com.zhanggen.order.mapper")
@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients //开启Feign
public class OrderApplication {
    public static void main(String[] args) {
        SpringApplication.run(OrderApplication.class, args);
    }
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }

}



3.编写Feign的客户端


[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:cd228e7e-7486-4d75-8817-ccef56296f4f



[En]

[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:9b95c824-de80-4e82-88d6-e7b94eb9d8fb


在order-service项目中com.zhanggen.order.mapper 包下新建一个接口，内容如下：


//FeignClient必须和@EnableFeignClients标注的类在同一个包下
//该接口用于向user-service微服务发起远程调用
//Feign底层默认使用HTTP协议发起远程调用
//@FeignClient("user-service")+@GetMapping("/user/{id}")确定服务提供者的URL（http://user-service/user/{id}）
@FeignClient("user-service")
public interface UserClient {
    //根据userId查询用户信息
    @GetMapping("/user/{id}")
    User findById(@PathVariable Long id);
}



这样，Feign就可以帮助我们发送http请求，无需自己使用RestTemplate来发送了。


4.修改OrderService类


是不是看起来优雅多了。


//使用Feign发起远程调用
    @Autowired
    private UserClient userClient;

    public Order findById(Long orderId) {
        // 1.查询订单
        Order order = orderMapper.selectById(orderId);
        //2.调用user-service服务查询当前订单的用户信息
        //String url = "http://127.0.0.1:8081/user/" + order.getUserId();
        //使用RestTemplate发起远程调用
        //String url = "http://user-service/user/" + order.getUserId();
        //User user = restTemplate.getForObject(url, User.class);
        User user = userClient.findById(order.getUserId());
        //3.user封装到order对象
        order.setUser(user);
        // 4.返回
        return order;
    }



四、 Feign配置


Feign可以支持很多的自定义配置，如下表所示：
类型作用说明 feign.Logger.Level修改日志级别包含四种不同的级别：NONE（默认）、BASIC、HEADERS、FULL NONE，不记录。默认选项 BASIC，仅记录请求方法和URL以及响应状态代码和执行时间。 HEADERS，记录基本信息以及请求和响应标头。 FULL，记录请求和响应的标题，正文和元数据。feign.codec.Decoder 响应结果的解析器http远程调用的结果做解析，例如解析json字符串为java对象feign.codec.Encoder 请求参数编码将请求参数编码，便于通过http请求发送，例如POST请求，将请求参数编码到请求体中feign.Contract 支持的注解格式默认是SpringMVC的注解feign.Retryer 失败重试机制请求失败的重试机制，默认是没有，不过会使用Ribbon的重试，例如A服务无法访问，会尝试访问集群中的B服务


一般情况下，Feign的默认配置就能满足我们使用，如果要自定义配置时，只需要创建自定义的@Bean覆盖默认Bean即可。


下面以日志为例来演示如何自定义配置，修改Feign日志有 2 种方式： 配置文件方式、Java代码方式


1.配置文件方式（推荐）


基于配置文件修改feign的日志级别可以针对单个服务：


feign:
  client:
    config:
      user-service: # 针对某个微服务的配置，也可以针对所有服务，这个位置换成default
        loggerLevel: FULL #  日志级别



2.Java代码方式


也可以基于Java代码来修改日志级别，在 com.zhanggen.order.config包下创建类，然后声明一个Logger.Level的对象：


package com.zhanggen.order.config;
import feign.Logger;
import org.springframework.context.annotation.Bean;

public class FeignDefaultConfiguration  {
    @Bean
    public Logger.Level feignLogLevel(){
        return Logger.Level.FULL; // 日志级别为FULL
    }
}



2.1.配置局部


如果我想让以上日志配置在调用某1个服务提供者时生效，在FeigClien接口中修改如下；


@FeignClient(value = "user-service",configuration = FeignDefaultConfiguration.class)
public interface UserClient {
    //根据userId查询用户信息
    @GetMapping("/user/{id}")
    User findById(@PathVariable Long id);
}



2.2.配置全局


[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:794bb111-aebb-46ba-9c5e-fb58ca08d50c



[En]

[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:da1e7a9c-b784-40b2-bc78-e6d039c7e5a7


@EnableFeignClients(defaultConfiguration = FeignDefaultConfiguration.class)
public class OrderApplication {
    public static void main(String[] args) {
        SpringApplication.run(OrderApplication.class, args);
    }



五、Feign连接池


Feign底层发起http请求，依赖于其它的框架。其底层客户端实现包括：
  • URLConnection：默认实现，不支持连接池，每次请求都是新建连接
  • Apache HttpClient ：支持连接池
  • OKHttp：支持连接池

因此提高Feign的性能主要手段就是使用 连接池代替默认的URLConnection。

1.pom引入依赖

<dependency>
    <groupId>io.github.openfeigngroupId>
    <artifactId>feign-httpclientartifactId>
dependency>

2.application.yml配置

max-connections-per-route：再调用某1个服务提供者时，最多从连接池中拿出50个连接发起远程调用，避免服务雪崩；

feign:
  httpclient:
    enabled: true # 开启feign对HttpClient的支持
    max-connections: 200 # 设置最大的连接数
    max-connections-per-route: 50 # 并行接收一个服务的请求数量

六、Feign公共模块

在微服务架构中肯定会存在多个服务消费者，这些服务消费者都需要借助Feign发起远程调用；

在实际的分布式架构开发中我们一般把Feign抽取出来作为1个公共模块，以便于其他微服务模块使用；

微服务之同步远程调用(Feign)

1.创建feign-api公共模块

把之前在order-service中编写的UserClient、User、FeignDefaultConfiguration剪切到feign-api项目中

微服务之同步远程调用(Feign)

在fein-api模块中添加spring-cloud-starter-openfeign依赖

<dependencies>

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

        <dependency>
            <groupId>com.baomidougroupId>
            <artifactId>mybatis-plus-coreartifactId>
            <version>3.4.0version>
        dependency>

        <dependency>
            <groupId>io.github.openfeigngroupId>
            <artifactId>feign-httpclientartifactId>
        dependency>
    dependencies>

2.服务消费者（调用方）

2.1.引入公共模块

服务消费者pom文件引入feign-api公共模块的依赖；

  <dependency>
      <groupId>com.zhanggengroupId>
     <artifactId>fein-apiartifactId>
      <version>1.0-SNAPSHOTversion>
  dependency>

2.2.启动类

服务消费者启动类设置@EnableFeignClients注解一定要设置Feign公共模块中的配置类和Feign公共模块的包；

@EnableFeignClients(defaultConfiguration = FeignDefaultConfiguration.class,
        basePackages = "com.zhanggen.feign")
public class OrderApplication {
    public static void main(String[] args) {
        SpringApplication.run(OrderApplication.class, args);
    }
}

服务消费者配置文件

[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:063fbd2d-c651-49eb-9cda-397ce7575a5e

[En]

[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:fc5b95da-c0c1-48fc-a78b-7745783c3f92

feign:
  client:
    config:
      default:
        #不设置connectTimeout会导致readTimeout设置不生效
        connectTimeout: 3000
        readTimeout: 6000

2.3.Feign常见报错

Did you forget to include spring-cloud-starter-netflix-ribbon?

com.alibaba.cloud
         spring-cloud-starter-alibaba-nacos-discovery

3.服务提供者（被调用方）

创建1个client包专门对内面向Feign远程调用，而controller包专门对外面向前端调用；

微服务之同步远程调用(Feign)

参考

Original: https://www.cnblogs.com/sss4/p/16414981.html
Author: Martin8866
Title: 微服务之同步远程调用(Feign)

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转载文章受原作者版权保护。转载请注明原作者出处！

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