Spring Cloud服务注册与发现
Spring Cloud集成了搭建分布式服务一系列框架，如服务注册与发现Eureka，熔断器Hystrix，路由网关Zuul，链路追踪zipkin，今天主要讲解Eureka的使用。
Eureka是什么？
Eureka是Netflix开源的一款提供服务注册和发现的产品，它提供了完整的Service Registry和Service Discovery实现。也是springcloud体系中最重要最核心的组件之一，我们通过下面这样图就可以了解
1）服务提供方向Eureka注册自己的服务，
2）消费者向Eureka获取自己需要的服务，和提供方建立连接
3) 如果服务方出现故障，Eureka会自动将服务方从注册列表中删除
搭建项目
创建Eureka服务
首先创建一个Maven项目，指定spring boot，spring cloud 版本
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.1.RELEASE</version>
<relativePath/>
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
<spring-cloud.version>Finchley.SR2</spring-cloud.version>
</properties>
创建一个模块，我们称为EurekaServer，使用Eureka只需要引入maven包，然后启动项目就可以了，很方面，如下：
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
</dependency>
</dependencies>
配置application.yml文件
server:
port: 8081
eureka:
instance:
hostname: localhost
client:
registerWithEureka: false
fetchRegistry: false
serviceUrl:
defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
spring:
application:
name: eurka-server
添加注解@EnableEurekaServer，并启动EurekaServer
@SpringBootApplication
@EnableEurekaServer
public class EurakaServerApplication {
public static void main(String[] args) {
SpringApplication.run(EurakaServerApplication.class, args);
}
}
启动EurekaServer，地址为：http://localhost:8081/eureka
创建提供方服务
添加maven依赖
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-zipkin</artifactId>
</dependency>
创建服务接口
@RestController
public class AirportController {
@Autowired
private AirportService airportService;
@RequestMapping("/getAirport")
public AirportBean getAirport(@RequestParam("threeCode") String threeCode) {
return airportService.getAirport(threeCode);
}
}
@Service
public class AirportService {
@Value("${server.port}")
private int port;
public AirportBean getAirport(String threeCode) {
AirportBean bean = new AirportBean();
bean.setName("北京首都国际机场");
bean.setThreeCode(threeCode);
bean.setPort(port);
return bean;
}
}
public class AirportBean {
private String threeCode;
private String name;
private int port;
}
修改application.yml文件
<code>server:
port: 8082
spring:
application:
name: dynamic-service
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8081/eureka/</code>
添加@EnableEurekaClient注解，这里我们为了方便演示负载均衡，同时也启动了两个实例，端口分别为8082，8083
@SpringBootApplication
@EnableEurekaClient
public class DynamicServiceApplication {
public static void main(String[] args) {
SpringApplication.run(DynamicServiceApplication.class, args);
}
}
创建服务消费方
我们再项目下再新建一个模块，称为springcloudclient,添加maven依赖
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
这里我们使用了feign的服务调用方式，Spring cloud有两种服务调用方式，一种是ribbon+restTemplate，另一种是feign，ribbon类似一种rest风格的API调用方式，而feign整合了ribbon，具有负载均衡的能力，通过注解的方式，使代码看起来更加简洁，另外feign整合了Hystrix，具有熔断的能力
调用服务方的接口
@RestController
public class AirportFeignController {
@Autowired
private AirportFeignService airportFeignService;
@RequestMapping(value = "/getAirport",method = RequestMethod.GET)
public AirportBean getAirport(@RequestParam("threeCode") String threeCode) {
return airportFeignService.getAirport(threeCode);
}
}
@FeignClient(value = "dynamic-service", fallback = AirportFeignFallbackService.class)
public interface AirportFeignService {
@RequestMapping(value = "/getAirport",method = RequestMethod.GET)
public AirportBean getAirport(@RequestParam("threeCode") String threeCode);
}
// 服务失败后熔断，调用的方法
public class AirportFeignFallbackService implements AirportFeignService {
@Override
public AirportBean getAirport(String threeCode) {
return null;
}
}
public class AirportBean {
private String threeCode;
private String name;
private int port;
}
配置application.yml文件
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8761/eureka/
server:
port: 8084
spring:
application:
name: service-feign
添加@ EnableEurekaClient，@EnableDiscoveryClient， @EnableFeignClients注解，端口为8084，
@SpringBootApplication
@EnableEurekaClient
@EnableDiscoveryClient
@EnableFeignClients
public class SpringCloudServerApplication {
public static void main(String[] args) {
SpringApplication.run(SpringCloudServerApplication.class, args);
}
}
好了下面可以演示springcloud的服务注册与发现了，通过上面的例子，我们启动了Eureka服务，分别为：8081，同时启动了两个服务提供方，注册到Eureka中，端口分别为8082和8083，接着我们启动了一个服务消费方，端口为8084，我们分别启动他们
可以发现有两个服务方已经注册上了，我们调用消费方的接口，发现消费方会使用负载均衡的方式分别访问服务方
org.springframework.boot spring-boot-starter-parent 2.1.1.RELEASE utf – 8 utf – 8 1.8 Finchley.SR2
