Spring Cloud 3.x 集成eureka快速入门Demo

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: 8761

eureka:
  instance:
    hostname: node1 # eureka name
    prefer-ip-address: false
  client:
    fetch-registry: false
    register-with-eureka: true
    # eureka url
    service-url:
      defaultZone: http://node2:8762/eureka
spring:
  application:
    name: "eureka-server-ha"

management:
  endpoints:
    web:
      exposure:
        include: "*"

node2

server:
  port: 8762

eureka:
  instance:
    hostname: node2 # eureka name
    prefer-ip-address: false
  client:
    fetch-registry: false
    register-with-eureka: true
    # eureka url
    service-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 {
    @Autowired
    private 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));
    }

    @Override
    public Collection findAll() {
        return studentMap.values();
    }

    @Override
    public Student findById(long id) {
        return (Student) studentMap.get(id);
    }

    @Override
    public void saveOrUpdate(Student student) {
        studentMap.put(student.getId(),student);
    }

    @Override
    public 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: true

management:
  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 {
    @Autowired
    RestTemplate restTemplate;
    @Resource
    private DiscoveryClient discoveryClient;
    @Autowired
    private 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
    @LoadBalanced
    public 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