1 使用

// 1. 添加依赖
// Spring Cloud 2020.x 之后需要额外引入 loadbalancer
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-loadbalancer</artifactId>
</dependency>

// 2. 启用Feign
@SpringBootApplication
@EnableFeignClients
public class Application { ... }

// 3. 定义接口
@FeignClient(name = "user-service")
public interface UserClient {
    @GetMapping("/users/{id}")
    User getUser(@PathVariable Long id);
}

// 4. 注入使用
@RestController
public class UserController {
    @Autowired
    private UserClient userClient;
    
    @GetMapping("/proxy/users/{id}")
    public User getUser(@PathVariable Long id) {
        return userClient.getUser(id);
    }
}

2 超时调用控制

# application.yml
openfeign:
  client:
    config:
      default:  # 全局默认配置
        connectTimeout: 5000  # 连接超时(ms)
        readTimeout: 30000    # 读取超时(ms)
      user-service:  # 针对单个服务进行配置
        connectTimeout: 2000
        readTimeout: 5000 

3 重试机制

@Configuration
public class FeignConfig {

		// 默认实现不进行重试
		@Bean
		public Retryer feignRetryer() {
		    // 参数：间隔时间(ms)，最大间隔时间(ms)，最大尝试次数(含第一次)
		    return new Retryer.Default(100, 1000, 3);
		}

		// 开启feign的日志
    @Bean
    public Logger.Level feignLoggerLevel() {
        return Logger.Level.FULL;  // 设置日志级别
    }
}

4 性能优化

# application.yml
openfeign:
  client:
    config:
      default:  # 全局默认配置
        connectTimeout: 10000  # 连接超时(ms)
        readTimeout: 20000    # 读取超时(ms)
    httpclient:
      hc5:               # 使用http5进行优化
        enabled: true
    compression:
      request:
        enabled: true
        mime-types: text/xml,application/xml,application/json  #触发压缩的数据类型
        min-request-size: 2048       #最小处罚压缩大小
      response:
        enabled: true

引入依赖

<!-- HttpClient5 核心依赖 -->
<dependency>
    <groupId>org.apache.httpcomponents.client5</groupId>
    <artifactId>httpclient5</artifactId>
    <version>5.3</version>
</dependency>

<!-- Feign对HttpClient5的适配器 -->
<dependency>
    <groupId>io.github.openfeign</groupId>
    <artifactId>feign-hc5</artifactId>
    <version>13.1</version>
</dependency>