JHipster + Spring Boot 微服务架构完整指南：Eureka、Ribbon、Hystrix、Liquibase、Feign 详解

eureka:
  instance:
    prefer-ip-address: true
    hostname: localhost
  client:
    register-with-eureka: true
    fetch-registry: true
    service-url:
      defaultZone: http://admin:admin@localhost:8761/eureka/
  server:
    wait-time-in-ms-when-sync-empty: 0
    enable-self-preservation: false

ribbon:
  ReadTimeout: 3000
  ConnectTimeout: 3000
  OkHttp:
    enabled: true
  
user-service:
  ribbon:
    NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RoundRobinRule

# 解决 Ribbon 调用超时 + 负载均衡 + 重试
ribbon:
  # 1. 解决【连接超时】
  ConnectTimeout: 2000    # 连接超时 2秒
  # 2. 解决【读取超时】
  ReadTimeout: 5000       # 数据读取超时 5秒

  # 3. 解决【连接失败】→ 自动重试
  MaxAutoRetries: 2       # 当前服务器重试2次
  MaxAutoRetriesNextServer: 1 # 换一台服务器重试1次
  OkToRetryOnAllOperations: true # 对所有请求类型都重试

  # 4. 解决【负载不均衡】→ 使用轮询策略
  NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RoundRobinRule

hystrix:
  command:
    default:
      execution:
        isolation:
          thread:
            timeoutInMilliseconds: 10000
      circuitBreaker:
        enabled: true
        requestVolumeThreshold: 20
        sleepWindowInMilliseconds: 5000
        errorThresholdPercentage: 50
      fallback:
        enabled: true

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import org.springframework.web.client.RestTemplate;
// 【调用用户服务的方法】
// 开启Hystrix熔断保护，失败时自动调用降级方法：getUserFallback
@HystrixCommand(fallbackMethod = "getUserFallback")
public User getUserById(Long id) {
    // 调用远程的用户服务（通过Ribbon负载均衡）
    return restTemplate.getForObject(
        "http://user-service/users/" + id,  // 远程服务地址
        User.class                          // 返回类型
    );
}

// 【降级/兜底方法】
// 当用户服务超时、报错、挂了时，自动进入这个方法
// 参数：id = 原方法的参数；ex = 异常信息（可选）
public User getUserFallback(Long id, Throwable ex) {
    // 打印错误日志，方便排查问题
    log.error("调用用户服务失败，服务可能已熔断或超时", ex);
    
    // 构造一个默认用户返回，给前端友好提示
    User user = new User();
    user.setId(id);
    user.setUsername("默认用户");  // 降级返回
    
    return user;
}

<dependency>
    <groupId>org.liquibase</groupId>
    <artifactId>liquibase-core</artifactId>
</dependency>

<?xml version="1.0" encoding="UTF-8"?>
<databaseChangeLog
        xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog
        http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-4.9.xsd">                        <!-- 引入第一个版本的变更 -->    
    <include file="classpath:db/changelog/v1/create_user_table.xml" />
</databaseChangeLog>

<?xml version="1.0" encoding="UTF-8"?>
<databaseChangeLog>
    <!-- 版本号：1 -->
    <changeSet id="v1-create-user-table" author="your-name">
        <!-- 建表语句 -->
        <createTable tableName="sys_user">
            <column name="id" type="BIGINT" autoIncrement="true">
                <constraints primaryKey="true" nullable="false"/>
    </column>
    <column name="username" type="VARCHAR(50)">
        <constraints nullable="false" unique="true"/>
    </column>
        <column name="age" type="INT"/>
    </createTable>
   </changeSet>
</databaseChangeLog>

@FeignClient(name = "user-service", fallback = UserServiceFallback.class)
public interface UserServiceClient {

    @GetMapping("/api/users/{id}")
    UserDTO getUserById(@PathVariable("id") Long id);

    @PostMapping("/api/users")
    UserDTO createUser(@RequestBody UserDTO user);
}

@Component
public class UserServiceFallback implements UserServiceClient {

    @Override
    public UserDTO getUserById(Long id) {
        log.error("调用用户服务失败，id={}", id);
        UserDTO user = new UserDTO();
        user.setId(id);
        user.setUsername("默认用户");
        return user;
    }

    @Override
    public UserDTO createUser(UserDTO user) {
        return null;
    }
}

myapp/
├── jhipster-registry/          # 服务注册中心 (Eureka + Config)
├── gateway/                     # API 网关
├── service-a/                   # 微服务 A
├── service-b/                   # 微服务 B
└── docker/                      # Docker 配置

**#安装 JHipster**
npm install -g generator-jhipster

**#生成服务注册中心**
jhipster jdl jhipster-registry.jdl

**#生成网关**
jhipster jdl gateway.jdl

**#生成微服务**
jhipster jdl service-a.jdl

**#使用 Docker Compose 启动**
cd docker-compose
docker-compose -f app.yml up -d