Java笔记，3 - 使用Spring Cloud Zookeeper + Feign实现服务发现

配置映射主机名和IP

为每台虚拟主机的/etc/hosts文件加上如下内容，服务发现需要用到默认主机名作为访问地址，这样可以不用为每个服务实例配置IP

192.168.253.30  megumi-30
192.168.253.31  megumi-31
192.168.253.32  megumi-32

服务提供方

1.Maven依赖

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-zookeeper-all</artifactId>
        </dependency>
    </dependencies>

2. 父模块的依赖管理

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>1.5.3.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-zookeeper-dependencies</artifactId>
                <version>1.1.1.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-netflix-dependencies</artifactId>
                <version>1.3.4.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>io.reactivex</groupId>
                <artifactId>rxjava</artifactId>
                <version>1.3.1</version>
            </dependency>
        </dependencies>
    </dependencyManagement>

3. bootstrap.yml (这里配置应用程序的名称，也就是服务的名称，用于Feign查找服务，启用服务发现和注册)

spring:
  application:
    name: demo-service
  cloud:
    zookeeper:
      connect-string: 192.168.253.30:2181,192.168.253.31:2181,192.168.253.32:2181
      discovery:
        enabled: true
        register: true

4. App.java 用@EnableDiscoveryClient注解配置启用服务发现

package demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

@EnableDiscoveryClient
@SpringBootApplication
public class App {

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

}

5. DemoController.java

package demo;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping(value = "/api/demo")
public class DemoController {

    private static final UUID INSTANCE_UUID = UUID.randomUUID();

    @GetMapping(value = "/instance")
    public Object instance() {
        return INSTANCE_UUID.toString();
    }

}

服务消费方

1. Maven依赖 (和提供方同父模块)

   <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-zookeeper-all</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</artifactId>
        </dependency>
    </dependencies>

2. bootstrap.yml 这里选择不注册服务

spring:
  application:
    name: demo-app
  cloud:
    zookeeper:
      connect-string: 192.168.253.30:2181,192.168.253.31:2181,192.168.253.32:2181
      discovery:
        enabled: true
        register: false

3. App.java 同样用注解启用Feign客户端和服务发现

package demo2;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;

@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class App {

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

}

4. DemoService.java 用注解声明Feign客户端调用的服务名称，与服务提供方yml配置的spring.application.name一致，注意这里虽然能用RequestMapping注解，但是可能引发URL路由注册冲突的问题。

package demo2;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;

@FeignClient(value = "demo-service", path = "/api/demo")
//@RequestMapping(value = "/api/demo")
public interface DemoService {

    @GetMapping(value = "/instance")
    String instance();

}

5. DemoController.java

package demo2;

import java.util.UUID;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping(value = "/api/demo")
public class DemoController {

    private static final UUID INSTANCE_UUID = UUID.randomUUID();
    private final DemoService remoteService;

    public DemoController(final DemoService remoteService) {
        this.remoteService = remoteService;
    }

    @GetMapping(value = "/remote-instance")
    public Object remoteInstance() {
        return this.remoteService.instance();
    }

    @GetMapping(value = "/instance")
    public Object instance() {
        return INSTANCE_UUID.toString();
    }

}

服务启动后，使用zkCli运行 ls /services/demo-service ，可以看到服务的各实例已经被注册到这里。

使用浏览器访问消费方的 /api/demo/remote-instance，不停刷新可以看到值是变化的，说明客户端负载均衡已经在正常工作了。