Feign是一個聲明式的僞Http客戶端,它使得寫Http客戶端變得更簡單。使用Feign,只需要創建一個接口並註解。它具有可插拔的註解特性,可使用Feign 註解和JAX-RS註解。Feign支持可插拔的編碼器和解碼器。Feign默認集成了Ribbon,並和Eureka結合,默認實現了負載均衡的效果。
簡而言之:
Feign 採用的是基於接口的註解
Feign 整合了ribbon,具有負載均衡的能力
整合了Hystrix,具有熔斷的能力
方誌朋:https://www.fangzhipeng.com/springcloud/2018/08/03/sc-f3-feign.html
1.準備工作
繼續用上一節的工程, 啓動eureka-server,端口爲8761;
2.創建springboot,名字provider-order-feign-9003,在它的pom文件引入Feign的起步依賴spring-cloud-starter-feign、Eureka的起步依賴spring-cloud-starter-netflix-eureka-client,下面一樣,“三板斧”
a.pom
<?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.jason</groupId>
<artifactId>jason-cloud</artifactId>
<version>1.0-SNAPSHOT</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.jason</groupId>
<artifactId>provider-order-feign-9003</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>provider-order-feign-9003</name>
<description>微服務-order-Feign</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.0.0</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.17</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.6</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<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>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
b.配置。在工程的配置文件application文件配置如下
server.port=9003
#註冊到eureka服務端的微服務名稱
spring.application.name=provider-order
#註冊到eureka服務端的地址
eureka.client.service-url.defaultZone=http://localhost:8761/eureka/
#eureka.client.service-url.defaultZone: http://www.eureka9000.com:9000/eureka/
#點擊具體的微服務,右下角是否顯示ip
eureka.instance.prefer-ip-address=true
#顯示微服務的名稱
eureka.instance.instance-id=provider-order-9003
mybatis.configuration.map-underscore-to-camel-case=true
#配置數據庫
spring.datasource.url=jdbc:mysql://localhost:3306/jason-cloud?serverTimezone=GMT&useUnicode=true&characterEncoding=utf-8
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.username=root
spring.datasource.password=admin
logging.level.com.jason.dao=debug
c.註解。在程序的啓動類ServiceFeignApplication ,加上@EnableFeignClients註解開啓Feign的功能:
3.定義一個feign接口,通過@ FeignClient(“服務名”),來指定調用哪個服務。比如在代碼中調用了provide-order服務的“/queryOrdersByUserId/{userId}”接口,代碼如下:
在Web層的controller層,對外暴露一個”/queryOrdersByUserId/{userId}”的API接口,通過上面定義的Feign客戶端OrderService來消費服務。代碼如下:
4.啓動服務,訪問http://localhost:9003/order/queryOrdersByUserId/1
擴展
1.Feign添加日誌
1.1 創建Feign的配置文件,並在其中設置日誌等級
package com.jason.provider.order.config;
import feign.Logger;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
/**
* @author Jason
* @since 2020/6/2
*/
@Configuration
public class OrderClientConfig {
@Bean
Logger.Level feignLoggerLevel() {
return Logger.Level.HEADERS;
}
}
1.2 在FeignClient接口中指定此配置
1.3 配置文件 application.properties 開啓日誌記錄
## 將Feign接口的日誌級別設置成DEBUG,因爲Feign的logger.Level只對DEBUG做出響應
logging.level.com.jason.provider.order.service.OrderService=debug
訪問接口 http://localhost:9003/order/queryOrdersByUserId/1,控制檯打印請求詳情日誌
如果出現訪問超時,是因爲熔斷器默認1秒未請求到結果即爲超時,此時,面對網絡環境較差情況,則需要調整超時時間。
2.Feign配置 Fallback
2.1 創建回調類 OrderClientFallback,OrderClientFallback回調實現,由spring創建使用@Component(其他的註冊也可以)註解,並且實現OrderService,對 queryOrdersByUserId 方法回調時設置返回值。
package com.jason.provider.order.config;
import com.jason.provider.order.service.OrderService;
import com.jason.provider.order.vo.OrderVo;
import org.springframework.stereotype.Component;
import java.util.ArrayList;
import java.util.List;
/**
* @author Jason
* @since 2020/6/3
*/
@Component
public class OrderClientFallback implements OrderService {
@Override
public List<OrderVo> queryOrdersByUserId(String userId) {
return new ArrayList<>();
}
}
2.2 @FeignClient 配置 fallback
2.3 在配置中開啓 hystrix,feign.hystrix.enabled=true
開啓服務,訪問接口,正常情況如下:
模擬異常,訪問接口: