1.什么是eureka？
Eureka 由 Netflix 开发，是一种基于REST（Representational State Transfer）的服务，用于定位服务（服务注册与发现），以实现中间层服务的负载均衡和故障转移，此服务被称为 Eureka Server。同时，它还附带了基于 Java 的客户端组件：Eureka Client，它使得客户端与 Eureka Server 的交互变得更加的容易。
- Register(服务注册)：把自己的IP和端口注册给Eureka。
- Renew(服务续约)：发送心跳包，每30秒发送一次。告诉Eureka自己还活着。
- Cancel(服务下线)：当provider关闭时会向Eureka发送消息，把自己从服务列表中删除。防止consumer调用到不存在的服务。
- Get Registry(获取服务注册列表)：获取其他服务列表。
- Replicate(集群中数据同步)：eureka集群中的数据复制与同步。
- Make Remote Call(远程调用)：完成服务的远程调用。
Eureka Server
Eureka Server提供服务注册服务，各个节点启动后，会在Eureka Server中进行注册，这样Eureka Server中的服务注册表中将会存储所有可用服务节点的信息，服务节点的信息可以在界面中直观的看到。
Eureka Client
Eureka Client是一个java客户端，用于简化与Eureka Server的交互，客户端同时也具备一个内置的、使用轮询(round-robin)负载算法的负载均衡器。
2.环境搭建
eureka主要作为注册中心使用，搭建2节点集群
pom.xml
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd"><parent><artifactId>eureka</artifactId><groupId>com.et</groupId><version>1.0-SNAPSHOT</version></parent><modelVersion>4.0.0</modelVersion><artifactId>eureka-server</artifactId><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.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-eureka-server</artifactId></dependency></dependencies></project>noode1
server:port: 8761eureka:instance:hostname: node1 # eureka nameprefer-ip-address: falseclient:fetch-registry: falseregister-with-eureka: true# eureka urlservice-url:defaultZone: http://node2:8762/eureka
spring:application:name: "eureka-server-ha"management:endpoints:web:exposure:include: "*"node2
server:port: 8762eureka:instance:hostname: node2 # eureka nameprefer-ip-address: falseclient:fetch-registry: falseregister-with-eureka: true# eureka urlservice-url:defaultZone: http://node1:8761/eureka
spring:application:name: "eureka-server-ha"management:endpoints:web:exposure:include: "*"启动类
package com.et.eureka;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;@EnableEurekaServer
@SpringBootApplication
public class EurekaServerApplication {public static void main(String[] args) {SpringApplication.run(EurekaServerApplication.class, args);}
}启动node1和node2，访问http://node2:8762/
3.代码工程
实验目标
实现消费者调用生产者服务
生产者
提供服务接口 pom.xml
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd"><parent><artifactId>eureka</artifactId><groupId>com.et</groupId><version>1.0-SNAPSHOT</version></parent><modelVersion>4.0.0</modelVersion><artifactId>eureka-provider</artifactId><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.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-eureka-client</artifactId></dependency></dependencies></project>controller
package com.er.eureka.provider.controller;import com.er.eureka.provider.model.Student;
import com.er.eureka.provider.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.*;import java.util.Collection;@RestController
@RequestMapping("/student")
public class StudentHandler {@Autowiredprivate StudentService studentService;@Value("${server.port}")private String port;@GetMapping("/findAll")public Collection findAll(){return studentService.findAll();}@GetMapping("/findById/{id}")public Student findById(@PathVariable("id") long id){return studentService.findById(id);}@PostMapping("/save")public void save(@RequestBody Student student){studentService.saveOrUpdate(student);}@PutMapping("/update")public void update(@RequestBody Student student){studentService.saveOrUpdate(student);}@DeleteMapping("/deleteById/{id}")public void deleteById(@PathVariable("id") long id){studentService.deleteById(id);}@GetMapping("/index")public String index(){return "port："+this.port;}
}service
package com.er.eureka.provider.service;import com.er.eureka.provider.model.Student;import java.util.Collection;public interface StudentService {public Collection findAll();public Student findById(long id);public void saveOrUpdate(Student student);public void deleteById(long id);
}package com.er.eureka.provider.service;import com.er.eureka.provider.model.Student;
import org.springframework.stereotype.Repository;import java.util.Collection;
import java.util.HashMap;
import java.util.Map;@Repository
public class StudentServiceImpl implements StudentService {private static Map studentMap;static {studentMap = new HashMap<>();studentMap.put(1L,new Student(1L,"zhangsan",22));studentMap.put(2L,new Student(2L,"lisi",23));studentMap.put(3L,new Student(3L,"wangwu",24));}@Overridepublic Collection findAll() {return studentMap.values();}@Overridepublic Student findById(long id) {return (Student) studentMap.get(id);}@Overridepublic void saveOrUpdate(Student student) {studentMap.put(student.getId(),student);}@Overridepublic void deleteById(long id) {studentMap.remove(id);}
}application.yaml
server:port: 8011
spring:application:name: provider
eureka:client:service-url:defaultZone: http://localhost:8761/eureka/instance:prefer-ip-address: truemanagement:endpoints:web:exposure:include: "*"启动类
package com.er.eureka.provider;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplication
public class DemoApplication {public static void main(String[] args) {SpringApplication.run(DemoApplication.class, args);}
}消费者
调用服务者提供的接口 pom.xml
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd"><parent><artifactId>eureka</artifactId><groupId>com.et</groupId><version>1.0-SNAPSHOT</version></parent><modelVersion>4.0.0</modelVersion><artifactId>eureka-consumer</artifactId><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.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></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></dependencies>
</project>controller
package com.et.eureka.consumer.controller;import com.et.eureka.consumer.model.Student;
import com.et.eureka.consumer.service.MyFeignClient;
import com.netflix.appinfo.InstanceInfo;
import jakarta.annotation.Resource;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.http.*;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.client.RestTemplate;import java.util.Collection;
import java.util.List;@RestController
@RequestMapping("/consumer")
@Slf4j
public class ConsumerHandler {@AutowiredRestTemplate restTemplate;@Resourceprivate DiscoveryClient discoveryClient;@Autowiredprivate MyFeignClient myFeignClient;@GetMapping("/findAll")public String findAll(){return myFeignClient.findAll();}@GetMapping("/findAll2")public Collection findAll2(){return restTemplate.getForObject("http://PROVIDER/student/findAll",Collection.class);}@GetMapping("/findAll3")public String findAll3(){RestTemplate restTemplate = new RestTemplate();List<ServiceInstance> instances = discoveryClient.getInstances("PROVIDER");if (instances == null || instances.size() == 0) {log.info("instances is empty..");return "";}String uri = instances.get(0).getUri().toString();String serviceUrl = String.format("%s/student/findAll", uri);HttpHeaders headers = new HttpHeaders();headers.setContentType(MediaType.APPLICATION_JSON);HttpEntity entity = new HttpEntity(headers);log.info("uri is :{},formatted url is:{}", uri, serviceUrl);ResponseEntity<String> resultExchange = restTemplate.exchange(serviceUrl, HttpMethod.GET, entity, String.class, "");if (resultExchange == null) {log.info("invoke result is null");return "";}String body = resultExchange.getBody();log.info("body is :{}", body);return body;}@GetMapping("/findById/{id}")public Student findById(@PathVariable("id") long id){return restTemplate.getForEntity("http://PROVIDER/student/findById/{id}",Student.class,id).getBody();}@GetMapping("/findById2/{id}")public Student findById2(@PathVariable("id") long id){return restTemplate.getForObject("http://PROVIDER/student/findById/{id}",Student.class,id);}@PostMapping("/save")public void save(@RequestBody Student student){restTemplate.postForEntity("http://PROVIDER/student/save",student,null).getBody();}@PostMapping("/save2")public void save2(@RequestBody Student student){restTemplate.postForObject("http://PROVIDER/student/save",student,null);}@PutMapping("/update")public void update(@RequestBody Student student){restTemplate.put("http://PROVIDER/student/update",student);}@DeleteMapping("/deleteById/{id}")public void deleteById(@PathVariable("id") long id){restTemplate.delete("http://PROVIDER/student/deleteById/{id}",id);}
}service
package com.et.eureka.consumer.service;import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;@FeignClient(name = "provider")
public interface MyFeignClient {@GetMapping("/student/findAll")String findAll();
}启动类
package com.et.eureka.consumer;import com.netflix.discovery.DiscoveryClient;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class ConsumerApplication {public static void main(String[] args) {SpringApplication.run(ConsumerApplication.class,args);}@Bean@LoadBalancedpublic RestTemplate restTemplate(){return new RestTemplate();}}application.yaml
server:port: 8020
spring:application:name: consumer
eureka:client:service-url:defaultZone: http://localhost:8761/eureka/instance:prefer-ip-address: true
management:endpoints:web:exposure:include: "*"以上只是一些关键代码，所有代码请参见下面代码仓库
代码仓库
- https://github.com/Harries/springcloud-demo(eureka)
4.测试
- 启动node1
- 启动node2
- 启动服务端
- 启动消费端
可以看到服务者和消费者都注册到eureka注册中心上
访问http://127.0.0.1:8020/consumer/findAll，会调用服务服务端接口并返回数据。
5.引用
- Spring Cloud Netflix
