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Eureka Client使用

Salmon2026/1/15大约 4 分钟EurekaEureka Client服务注册

Eureka Client 使用

一、服务提供者

1.1 创建项目

<?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">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>user-service</artifactId>
    <version>1.0.0</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.18</version>
    </parent>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>2021.0.8</spring-cloud.version>
    </properties>

    <dependencies>
        <!-- Web -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        
        <!-- Eureka Client -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
</project>

1.2 启动类

package com.example.user;

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

@SpringBootApplication
@EnableDiscoveryClient  // 启用服务发现（可省略，自动配置）
public class UserServiceApplication {
    public static void main(String[] args) {
        SpringApplication.run(UserServiceApplication.class, args);
    }
}

1.3 配置文件

server:
  port: 8081

spring:
  application:
    name: user-service  # 服务名称，必须配置

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/
  instance:
    # 使用 IP 地址注册
    prefer-ip-address: true
    # 自定义实例 ID
    instance-id: ${spring.application.name}:${spring.cloud.client.ip-address}:${server.port}

1.4 提供接口

@RestController
@RequestMapping("/user")
public class UserController {
    
    @Value("${server.port}")
    private String port;
    
    @GetMapping("/{id}")
    public Map<String, Object> getUser(@PathVariable Long id) {
        Map<String, Object> user = new HashMap<>();
        user.put("id", id);
        user.put("name", "张三");
        user.put("port", port);
        return user;
    }
    
    @GetMapping("/list")
    public List<Map<String, Object>> listUsers() {
        List<Map<String, Object>> users = new ArrayList<>();
        // 模拟数据
        for (int i = 1; i <= 5; i++) {
            Map<String, Object> user = new HashMap<>();
            user.put("id", i);
            user.put("name", "用户" + i);
            users.add(user);
        }
        return users;
    }
}

二、服务消费者

2.1 创建项目

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
    </dependency>
</dependencies>

2.2 配置文件

server:
  port: 8082

spring:
  application:
    name: order-service

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/
  instance:
    prefer-ip-address: true

2.3 配置 RestTemplate

@Configuration
public class RestTemplateConfig {
    
    @Bean
    @LoadBalanced  // 启用负载均衡
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

2.4 调用服务

@RestController
@RequestMapping("/order")
public class OrderController {
    
    @Autowired
    private RestTemplate restTemplate;
    
    @GetMapping("/{id}")
    public Map<String, Object> getOrder(@PathVariable Long id) {
        // 使用服务名调用（不是 IP:端口）
        String url = "http://user-service/user/" + id;
        Map<String, Object> user = restTemplate.getForObject(url, Map.class);
        
        Map<String, Object> order = new HashMap<>();
        order.put("orderId", id);
        order.put("orderNo", "ORDER" + System.currentTimeMillis());
        order.put("user", user);
        return order;
    }
}

三、服务调用流程

四、使用 DiscoveryClient

4.1 获取服务实例信息

@RestController
@RequestMapping("/discovery")
public class DiscoveryController {
    
    @Autowired
    private DiscoveryClient discoveryClient;
    
    /**
     * 获取所有服务名称
     */
    @GetMapping("/services")
    public List<String> getServices() {
        return discoveryClient.getServices();
    }
    
    /**
     * 获取指定服务的所有实例
     */
    @GetMapping("/instances/{serviceName}")
    public List<ServiceInstance> getInstances(@PathVariable String serviceName) {
        return discoveryClient.getInstances(serviceName);
    }
    
    /**
     * 手动选择实例调用
     */
    @GetMapping("/call/{serviceName}")
    public String callService(@PathVariable String serviceName) {
        List<ServiceInstance> instances = discoveryClient.getInstances(serviceName);
        if (instances.isEmpty()) {
            return "No instances available";
        }
        
        // 简单轮询选择第一个实例
        ServiceInstance instance = instances.get(0);
        String url = instance.getUri() + "/user/1";
        
        RestTemplate restTemplate = new RestTemplate();
        return restTemplate.getForObject(url, String.class);
    }
}

4.2 ServiceInstance 信息

属性说明
serviceId服务名称
host主机地址
port端口号
uri完整 URI
metadata元数据
secure是否 HTTPS

五、元数据配置

5.1 配置元数据

eureka:
  instance:
    metadata-map:
      version: v1.0
      region: beijing
      weight: 10

5.2 读取元数据

@GetMapping("/metadata/{serviceName}")
public List<Map<String, String>> getMetadata(@PathVariable String serviceName) {
    List<ServiceInstance> instances = discoveryClient.getInstances(serviceName);
    return instances.stream()
            .map(ServiceInstance::getMetadata)
            .collect(Collectors.toList());
}

六、健康检查配置

6.1 添加 Actuator 依赖

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

6.2 配置健康检查

eureka:
  client:
    # 启用健康检查
    healthcheck:
      enabled: true

management:
  endpoints:
    web:
      exposure:
        include: health,info
  endpoint:
    health:
      show-details: always

七、多实例部署

7.1 启动多个实例

# 启动实例1
java -jar user-service.jar --server.port=8081

# 启动实例2
java -jar user-service.jar --server.port=8082

# 启动实例3
java -jar user-service.jar --server.port=8083

7.2 IDEA 多实例配置

  1. 复制启动配置
  2. 修改 VM Options：-Dserver.port=8082
  3. 启动多个实例

八、常见配置汇总

eureka:
  client:
    # 是否注册到 Eureka
    register-with-eureka: true
    # 是否获取注册表
    fetch-registry: true
    # Eureka Server 地址
    service-url:
      defaultZone: http://localhost:8761/eureka/
    # 获取注册表间隔（秒）
    registry-fetch-interval-seconds: 30
    # 启用健康检查
    healthcheck:
      enabled: true
      
  instance:
    # 使用 IP 注册
    prefer-ip-address: true
    # 实例 ID
    instance-id: ${spring.application.name}:${server.port}
    # 心跳间隔（秒）
    lease-renewal-interval-in-seconds: 30
    # 服务过期时间（秒）
    lease-expiration-duration-in-seconds: 90
    # 元数据
    metadata-map:
      version: v1.0

九、总结

本章介绍了 Eureka Client 的使用：

  1. 服务提供者：注册服务到 Eureka Server
  2. 服务消费者：从 Eureka 获取服务列表并调用
  3. DiscoveryClient：手动获取服务实例信息
  4. 元数据：自定义服务元信息
  5. 健康检查：配置服务健康状态上报
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贡献者: Salmon