spring-boot-demo  (1個Maven模塊)
├── pom.xml       (僅1個配置文件)
└── src
    └── 所有代碼(controller/service/dao) 都在這

project-parent    (Maven父工程，無代碼，僅管理版本)
├── pom.xml
├── common        (公共模塊：工具類、常量)
├── dao           (數(shù)據(jù)訪問模塊：Mapper、實體)
├── service       (業(yè)務模塊：Service)
└── web           (Web模塊：Controller、啟動類)

cloud-parent      (Maven父工程)
├── pom.xml
├── user-service  (用戶服務：獨立SpringBoot)
├── order-service (訂單服務：獨立SpringBoot)
├── product-service (商品服務：獨立SpringBoot)
└── gateway       (網(wǎng)關服務)

mvn archetype:generate -DgroupId=com.mymulti -DartifactId=spring-boot-mymulti -Dversion=1.0.0 -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

<?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>
  <!-- SpringBoot 父依賴 -->
  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.7.15</version>
    <relativePath/>
  </parent>
  <groupId>com.mymulti</groupId>
  <artifactId>spring-boot-mymulti</artifactId>
  <version>1.0.0</version>
  <!-- ? 父工程必須是 pom 打包 -->
  <packaging>pom</packaging>
  <!-- 子模塊列表（創(chuàng)建子模塊后自動生成） -->
  <modules>
  </modules>
  <properties>
    <java.version>1.8</java.version>
  </properties>
</project>

# common模塊
mvn archetype:generate -DgroupId=com.multi -DartifactId=common -Dversion=1.0.0 -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false
# dao模塊
mvn archetype:generate -DgroupId=com.multi -DartifactId=dao -Dversion=1.0.0 -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false
# service模塊
mvn archetype:generate -DgroupId=com.multi -DartifactId=service -Dversion=1.0.0 -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false
# web模塊
mvn archetype:generate -DgroupId=com.multi -DartifactId=web -Dversion=1.0.0 -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

<!-- 核心依賴 -->
    <dependencies>
        <!-- 依賴業(yè)務層 service -->
        <dependency>
            <groupId>com.mymulti</groupId>
            <artifactId>service</artifactId>
            <version>1.0.0</version>
        </dependency>
        <!-- SpringBoot Web 核心（接口、服務器） -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>
    <!-- SpringBoot 打包插件（唯一啟動模塊需要） -->
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

package com.mymulti.controller;
import com.mymulti.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
// 統(tǒng)一路由前綴 /user
@RestController
@RequestMapping("/user")
public class UserController {
    @Autowired
    private UserService userService;
    // 路由：/user/get/1
    @GetMapping("/get/{id}")
    public Object getUser(@PathVariable Long id) {
        return userService.getUserById(id);
    }
}

package com.mymulti.service;
import com.mymulti.dao.UserMapper;
import com.mymulti.entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class UserService {
    @Autowired
    private UserMapper userMapper;
    public User getUserById(Long id) {
        return userMapper.selectById(id);
    }
}

package com.mymulti.dao;
import com.mymulti.entity.User;
import org.apache.ibatis.annotations.Select;
public interface UserMapper {
    @Select("select * from user where id=#{id}")
    User selectById(Long id);
}

package com.mymulti.entity;
public class User {
    private Long id;
    private String username;
    // getter/setter
}

package com.mymulti.entity;
/**
 * 公共實體類（放在 common 模塊，所有模塊都能用）
 * 對應數(shù)據(jù)庫 user 表
 */
public class User {
    private Long id;
    private String username;
    private String password;
    // getter/setter
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public String getUsername() { return username; }
    public void setUsername(String username) { this.username = username; }
    public String getPassword() { return password; }
    public void setPassword(String password) { this.password = password; }
}

package com.mymulti.mapper;
import com.mymulti.entity.User; // 直接導入 common 模塊的類
import org.apache.ibatis.annotations.Select;
import java.util.List;
/**
 * DAO 層：數(shù)據(jù)庫操作
 * 直接使用了 common 中的 User 實體類
 */
public interface UserMapper {
    // 查詢所有用戶 → 返回的是 common 里的 User 對象
    @Select("select id, username, password from user")
    List<User> findAll();
    // 根據(jù)ID查詢用戶
    @Select("select * from user where id = #{id}")
    User findById(Long id);
}