spring cloud openfeign 使用记录1

1、背景

使用 zk 作为注册中心，使用 Spring cloud openfeign 进行远程调用

2、步骤

2.1 service-provider

1.Pom.xml

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!-- Eureka 服务发现与注册客户端依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <!-- Zookeeper 服务发现与注册客户端依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-zookeeper-discovery</artifactId>
        </dependency>
</dependencies>

2. Controller

@RestController
public class EchoSerivceController {

    private final Environment environment;

    public EchoSerivceController(Environment environment) {
        this.environment = environment;
    }

    //获取 随机 端口的 方法
    private String getPort() {
        return environment.getProperty("local.server.port"); //依赖注入时 动态 注入
    }

    @GetMapping("/echo/{message}")
    public String echo(@PathVariable String message) {
        return "[ECHO: "+ getPort() + " ] : " + message;
    }
}

3 properties

spring:
  application:
    name: service-provider
  cloud:
    zookeeper:
      enabled: false # Zookeeper 服务发现与注册失效（默认）

server:
  port: 0 #随机端口

## 默认 profile 关闭自动特性,
eureka:
  client:
    enabled: false # Eureka 服务发现与注册失效（默认）

--- # Profile For Eureka
spring:
  profiles: eureka
# Eureka 客户端配置
eureka:
  server: # 官方不存在的配置（自定义配置）
    host: 127.0.0.1
    port: 12345
  client:
    enabled: true
    serviceUrl:
      defaultZone: http://${eureka.server.host}:${eureka.server.port}/eureka
    registryFetchIntervalSeconds: 5 # 5 秒轮训一次
  instance:  # 自定义 instanceId
    instanceId: ${spring.application.name}:${server.port}

--- # Profile For Zookeeper
spring:
  profiles: zookeeper
  cloud:
    zookeeper:
      enabled: true
      connectString: 127.0.0.1:2181

项目启动 添加 参数。--spring.profiles.active=zookeeper， 是 zk 作为 注册中心失效

2.2 service-client

1.pom.xml

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

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!-- Eureka 服务发现与注册客户端依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <!-- Zookeeper 服务发现与注册客户端依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-zookeeper-discovery</artifactId>
        </dependency>
    </dependencies>

2. 定义 feign接口

/**
 * 定义 feign 接口
 */
@FeignClient("service-provider") //应用(服务)名称， 否则 ClientException: Load balancer does not have available server for client: echoServiceClient
public interface EchoServiceClient {

  //同 service-provider controller
    @GetMapping("/echo/{message}")
    public String echo(@PathVariable String message);
}

3. 定义client controller

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients  //扫描同包 package  使@FeignClient生效
@RestController
public class EchoServiceClientBootstrap {

    @Autowired
    private EchoServiceClient echoServiceClient;

    @GetMapping(value = "/call/echo/{message}")
    public String echo(@PathVariable String message) {

        return echoServiceClient.echo(message);
    }

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

3 测试

前提： 启动 zk

项目启动后，能在 zk 中看到 两个模块

[zk: localhost:2181(CONNECTED) 4] ls /services/service-
service-client     service-provider   

异常一

Field echoServiceClient in com.gupaoedu.client.EchoServiceClientBootstrap required a bean of type 'com.gupaoedu.client.EchoServiceClient' that could not be found.

The injection point has the following annotations:
	- @org.springframework.beans.factory.annotation.Autowired(required=true)


Action:

Consider defining a bean of type 'com.gupaoedu.client.EchoServiceClient' in your configuration.

没有添加。@EnableFeignClients

异常二

[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.RuntimeException: com.netflix.client.ClientException: Load balancer does not have available server for client: echoServiceClient] with root cause

com.netflix.client.ClientException: Load balancer does not have available server for client: echoServiceClient

@FeignClient("service-provider"). Value 不是 生产这的 application.name. 通过 spring.application.name 进行 实例的获取

总结

1、所有的学习，从记录开始； 所有的原理，从 使用开始

2、spring cloud feign的使用过程中，涉及很多细节： Enable 驱动模块、负载均衡实现等，后续 充实，听的时候 似懂非懂，涉及的基础太多了

参考：

小马哥视频