【笔记】Feign学习笔记

发表于 2022-10-24 更新于 2022-10-31 分类于 Java后端学习指北阅读次数：

前言

Feign is a Java to HTTP client binder inspired by Retrofit, JAXRS-2.0, and WebSocket. Feign’s first goal was reducing the complexity of binding Denominator uniformly to HTTP APIs regardless of ReSTfulness.（Github）

添加依赖

pom.xml

<dependency>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

在主启动类添加注解

在主启动类上添加@EnableFeignClients启动Feign自动装配

package com;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;

@EnableFeignClients
@SpringBootApplication
@MapperScan("com.dao")
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

}

手动指定客户端类

package com;

import com.clients.UserClients;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;

@EnableFeignClients(clients = UserClients.class)
@SpringBootApplication
public class FeignApiApplication {

    public static void main(String[] args) {
        SpringApplication.run(FeignApiApplication.class, args);
    }

}

创建接口

创建用于发送请求的接口
Feign中的注解与SpringMVC中相同

@FeignClient("")：指定请求的地址（或服务名）
@GetMapping("")：发送Get请求，并指定请求参数
@PathVariable：指定Rest风格的请求参数

src/main/java/com/clients/UserClients.java

package com.clients;

import com.pojo.User;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

@FeignClient("eureka-service-user")
public interface UserClients {

    @GetMapping("/users/{id}")
    User getUserById(@PathVariable int id);
}

通过Feign发送请求

使用Feign代替RestTemplate发送请求

@Autowired
private UserClients userClients;
    
public void method() {
    User user = userClients.getUserById(order.getUserId());
}

修改日志级别

通过配置文件

feign.client.config.default.loggerLevel：设置所有服务的日志级别

NONE：缺省值。没有日志
BASIC：基本信息。包含请求发送时间、请求结束时间、请求耗时
HEADERS：详细信息。包含请求头和响应头
FULL：完整信息。包含请求体和响应体

feign.client.config.服务名.loggerLevel：设置指定服务的日志级别

src/main/resources/application.yml

feign:
  client:
    config:
      default:
        loggerLevel: NONE
      服务名:
        loggerLevel: FULL

通过配置类

创建配置类

package com.conf;

import feign.Logger;
import org.springframework.boot.SpringBootConfiguration;
import org.springframework.context.annotation.Bean;

public class FeignClientConfig {

    @Bean
    public Logger.Level feignLogLevel() {
        return Logger.Level.FULL;
    }
}

在全局应用配置

在主启动类上的注解添加参数

1	@EnableFeignClients(defaultConfiguration = FeignClientConfig.class)

在指定服务应用配置

在FeignClient借口上的注解添加参数

1	@FeignClient(value = "eureka-service-user", configuration = FeignClientConfig.class)

性能优化

将默认的不支持连接池底层实现URLConnection换成支持连接池的底层实现Apache HttpClient

引入依赖

pom.xml

<dependency>
  <groupId>io.github.openfeign</groupId>
  <artifactId>feign-httpclient</artifactId>
</dependency>

配置连接池

feign.httpclient.enabled：启动Feign对HttpClient的支持
feign.httpclient.max-connections：最大连接数
feign.httpclient.max-connections-per-route：每个路径的最大连接数
feign.httpclient.connection-timeout：请求超时时间
feign.httpclient.time-to-live：存活时间

src/main/resource/application.yml

feign:
  httpclient:
    enabled: true
    max-connections: 200
    max-connections-per-route: 50

最佳实践

把Feign抽取为一个服务，当其他服务需要使用Feign客户端时，继承Feign服务，就可以直接使用

抽取模块

创建一个名为FeignAPI的模块
添加依赖

FeignAPI/pom.xml

<dependency>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

在启动类添加注解

FeignAPI/src/main/java/com/FeignApiApplication.java

package com;

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

@EnableFeignClients
@SpringBootApplication
public class FeignApiApplication {

    public static void main(String[] args) {
        SpringApplication.run(FeignApiApplication.class, args);
    }

}

创建实体类

FeignAPI/src/main/java/com/pojo/User.java

package com.pojo;

import lombok.Data;

@Data
public class User {

    private Integer id;
    private String name;

}

创建Feign客户端接口

FeignAPI/src/main/java/com/clients/UserClients.java

package com.clients;

import com.pojo.User;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

@FeignClient(value = "eureka-service-user")
public interface UserClients {

    @GetMapping("/users/{id}")
    User getUserById(@PathVariable int id);
}

使用抽取的模块

在需要利用Feign发送请求的模块中，引入FeignAPI模块作为依赖

Other/pom.xml

<dependency>
  <groupId>com</groupId>
  <artifactId>FeignAPI</artifactId>
  <version>0.0.1-SNAPSHOT</version>
</dependency>

注入对象，通过对象调用方法，发起请求

package com.service;

import com.clients.UserClients;
import com.dao.OrderDao;
import com.pojo.Order;
import com.pojo.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

import java.util.List;

@Service
public class OrderService {

    @Autowired
    private OrderDao orderDao;

    @Autowired
    private UserClients userClients;

    public Order getOrderById(int id) {

        Order order = orderDao.selectById(id);

        User user = userClients.getUserById(order.getUserId());
        order.setUser(user);

        return order;
    }
}

完成

参考文献

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