Mybatis 集成

在现代Web应用开发中，数据库操作是不可或缺的一部分。Feat Cloud 与 MyBatis 的深度集成使得数据库操作变得简单而高效。本文将通过一个完整的用户管理示例，详细介绍如何在 Feat Cloud 中集成和使用 MyBatis。

教程概述

在本教程中，我们将构建一个简单的用户管理系统，涵盖以下内容：

• 配置 MyBatis 环境
• 创建数据库表结构
• 定义实体类
• 实现数据访问层（Mapper）
• 构建业务逻辑层（Service）
• 创建 REST API 控制器（Controller）
• 测试 API 接口

有关完整示例，请参见 Gitee 仓库中的 MyBatis 示例

下面是整个系统的架构概览：

graph TD A[客户端] --> B[Controller层] B --> C[Service层] C --> D[Mapper层] D --> E[(数据库)] style A fill:#FFE4B5,stroke:#333 style B fill:#87CEEB,stroke:#333 style C fill:#98FB98,stroke:#333 style D fill:#FFB6C1,stroke:#333 style E fill:#DDA0DD,stroke:#333

环境准备

添加 Maven 依赖

在开始之前，请确保在项目的 pom.xml 中添加以下依赖：

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.15</version>
</dependency>

<!-- 使用内存数据库进行演示 -->
<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <version>2.2.224</version>
</dependency>

第一步：配置 MyBatis

创建 MyBatis 配置文件

在 src/main/resources/mybatis 目录下创建 mybatis-config.xml：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="h2_mem">
        <environment id="h2_mem">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="org.h2.Driver"/>
                <property name="url" value="jdbc:h2:mem:feat-demo;NON_KEYWORDS=value;mode=mysql;"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <package name="tech.smartboot.feat.demo.mybatis.mapper"/>
    </mappers>
</configuration>

提示

配置文件可以放置在任意子目录下，例如 src/main/resources/mybatis/mybatis-config.xml。建议将配置文件放在专门的目录中以便管理。

创建数据库表结构

在 src/main/resources/mybatis/ddl 目录下创建 schema.sql：

schema.sql

-- 用户信息表
CREATE TABLE IF NOT EXISTS user_info
(
    username    varchar(32)  NOT NULL COMMENT '用户名',
    password    varchar(128) NOT NULL COMMENT '密码',
    `desc`      varchar(256) COMMENT '备注',
    role        varchar(32) COMMENT '角色',
    create_time timestamp DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
    edit_time   timestamp DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '更新时间',
    INDEX       idx_user_password (username, password),
    PRIMARY KEY (username)
);

-- 插入初始数据
insert ignore into user_info(username, password, role, `desc`)
values ('feat', 'feat', 'admin', '超级账户');

insert ignore into user_info(username, password, role, `desc`)
values ('admin', 'admin123', 'admin', '管理员用户');

insert ignore into user_info(username, password, role, `desc`)
values ('user1', 'password1', 'user', '普通用户1');

第二步：创建核心组件

实例化 SessionFactory Bean

创建一个 Bootstrap 类来初始化 SqlSessionFactory：

@Bean
public class Bootstrap {
    @Bean
    public SqlSessionFactory sessionFactory() throws IOException {
        // 加载 MyBatis 配置文件
        InputStream inputStream = Resources.getResourceAsStream("mybatis/mybatis-config.xml");
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        // 初始化数据库表结构
        ScriptRunner runner = new ScriptRunner(sessionFactory.openSession().getConnection());
        runner.setLogWriter(null);
        runner.runScript(Resources.getResourceAsReader("mybatis/ddl/schema.sql"));
        return sessionFactory;
    }

    public static void main(String[] args) {
        FeatCloud.cloudServer().listen();
    }
}

警告

生成的 SqlSessionFactory 对象 bean 名称必须为 sessionFactory。这是 Feat Cloud 约定的固定名称。

定义实体类

创建 User 实体类，对应数据库中的 user_info 表：

User.java

public class User {
    private String username;
    private String password;
    private String desc;
    private String role;
    private Date createTime;
    private Date editTime;

    // Constructors
    public User() {}

    public User(String username, String password, String desc, String role) {
        this.username = username;
        this.password = password;
        this.desc = desc;
        this.role = role;
    }

    // 省略 getter 和 setter 方法
    // ...

    @Override
    public String toString() {
        return "User{" +
                "username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", desc='" + desc + '\'' +
                ", role='" + role + '\'' +
                ", createTime=" + createTime +
                ", editTime=" + editTime +
                '}';
    }
}

第三步：实现数据访问层

创建 Mapper 接口

使用 MyBatis 注解方式定义 UserMapper 接口：

UserMapper.java

@Mapper
public interface UserMapper {
    @Select("SELECT * FROM user_info WHERE username = #{username}")
    @Results({
            @Result(property = "username", column = "username"),
            @Result(property = "password", column = "password"),
            @Result(property = "desc", column = "desc"),
            @Result(property = "role", column = "role"),
            @Result(property = "createTime", column = "create_time"),
            @Result(property = "editTime", column = "edit_time")
    })
    User selectByUsername(@Param("username") String username);

    @Select("SELECT * FROM user_info")
    @Results({
            @Result(property = "username", column = "username"),
            @Result(property = "password", column = "password"),
            @Result(property = "desc", column = "desc"),
            @Result(property = "role", column = "role"),
            @Result(property = "createTime", column = "create_time"),
            @Result(property = "editTime", column = "edit_time")
    })
    List<User> selectAll();

    @Insert("INSERT INTO user_info(username, password, `desc`, role) VALUES(#{username}, #{password}, #{desc}, #{role})")
    int insert(User user);

    @Update("UPDATE user_info SET password=#{password}, `desc`=#{desc}, role=#{role} WHERE username=#{username}")
    int update(User user);

    @Delete("DELETE FROM user_info WHERE username = #{username}")
    int deleteByUsername(@Param("username") String username);

    @Select("SELECT * FROM user_info WHERE role = #{role}")
    @Results({
            @Result(property = "username", column = "username"),
            @Result(property = "password", column = "password"),
            @Result(property = "desc", column = "desc"),
            @Result(property = "role", column = "role"),
            @Result(property = "createTime", column = "create_time"),
            @Result(property = "editTime", column = "edit_time")
    })
    List<User> selectByRole(@Param("role") String role);
}

第四步：构建业务逻辑层

创建 Service 类

创建 UserService 类处理业务逻辑：

UserService.java

@Bean
public class UserService {
    @Autowired
    private UserMapper userMapper;

    public User findByUsername(String username) {
        return userMapper.selectByUsername(username);
    }

    public List<User> findAll() {
        return userMapper.selectAll();
    }

    public List<User> findByRole(String role) {
        return userMapper.selectByRole(role);
    }

    public boolean insert(User user) {
        try {
            return userMapper.insert(user) > 0;
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
    }

    public boolean update(User user) {
        try {
            return userMapper.update(user) > 0;
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
    }

    public boolean deleteByUsername(String username) {
        try {
            return userMapper.deleteByUsername(username) > 0;
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
    }
}

第五步：创建 REST API

创建 Controller 类

创建 UserController 类提供 RESTful API：

UserController.java

@Controller
public class UserController {
    @Autowired
    private UserService userService;

    @RequestMapping("/users")
    public RestResult<List<User>> getAllUsers() {
        List<User> users = userService.findAll();
        return RestResult.ok(users);
    }

    @RequestMapping("/users/{username}")
    public RestResult<User> getUserByUsername(@PathParam("username") String username) {
        User user = userService.findByUsername(username);
        if (user != null) {
            return RestResult.ok(user);
        } else {
            return RestResult.fail("User not found");
        }
    }

    @RequestMapping("/users/role/{role}")
    public RestResult<List<User>> getUsersByRole(@PathParam("role") String role) {
        List<User> users = userService.findByRole(role);
        return RestResult.ok(users);
    }

    @RequestMapping(value = "/users", method = RequestMethod.POST)
    public RestResult<String> createUser(User user) {
        boolean success = userService.insert(user);
        if (success) {
            return RestResult.ok("User created successfully");
        } else {
            return RestResult.fail("Failed to create user");
        }
    }

    @RequestMapping(value = "/users", method = RequestMethod.PUT)
    public RestResult<String> updateUser(User user) {
        boolean success = userService.update(user);
        if (success) {
            return RestResult.ok("User updated successfully");
        } else {
            return RestResult.fail("Failed to update user");
        }
    }

    @RequestMapping(value = "/users/{username}", method = RequestMethod.DELETE)
    public RestResult<String> deleteUser(@PathParam("username") String username) {
        boolean success = userService.deleteByUsername(username);
        if (success) {
            return RestResult.ok("User deleted successfully");
        } else {
            return RestResult.fail("Failed to delete user");
        }
    }
}

数据流转过程

数据在整个系统中的流转过程如下所示：

sequenceDiagram participant Client as 客户端 participant Controller as Controller层 participant Service as Service层 participant Mapper as Mapper层 participant Database as 数据库 Client->>Controller: 发起HTTP请求 Controller->>Service: 调用业务方法 Service->>Mapper: 调用数据访问方法 Mapper->>Database: 执行SQL语句 Database-->>Mapper: 返回结果 Mapper-->>Service: 返回对象 Service-->>Controller: 返回业务结果 Controller-->>Client: 返回HTTP响应

测试 API 接口

启动应用后，可以通过以下 HTTP 请求测试 API：

### 获取所有用户
GET http://localhost:8080/users

### 根据用户名获取特定用户
GET http://localhost:8080/users/feat

### 根据角色获取用户列表
GET http://localhost:8080/users/role/admin

### 创建新用户
POST http://localhost:8080/users
Content-Type: application/json

{
  "username": "newuser",
  "password": "password123",
  "desc": "New test user",
  "role": "user"
}

### 更新用户信息
PUT http://localhost:8080/users
Content-Type: application/json

{
  "username": "newuser",
  "password": "newpassword123",
  "desc": "Updated test user",
  "role": "user"
}

### 删除特定用户
DELETE http://localhost:8080/users/newuser

最佳实践建议

1. 错误处理

在实际项目中，应该更优雅地处理异常，而不是简单地打印堆栈跟踪：

public boolean insert(User user) {
    try {
        return userMapper.insert(user) > 0;
    } catch (Exception e) {
        LOGGER.error("Failed to insert user: " + user.getUsername(), e);
        return false;
    }
}

2. 事务管理

由于 Feat 目前没有提供事务注解功能，需要手动管理事务。以下是一个示例：

@Bean
public class UserService {
    @Autowired
    private SqlSessionFactory sqlSessionFactory;

    // 手动管理事务的批量插入方法
    public boolean batchInsert(List<User> users) {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        try {
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            for (User user : users) {
                userMapper.insert(user);
            }
            sqlSession.commit(); // 提交事务
            return true;
        } catch (Exception e) {
            sqlSession.rollback(); // 回滚事务
            LOGGER.error("Failed to batch insert users", e);
            return false;
        } finally {
            sqlSession.close(); // 关闭会话
        }
    }
}

3. 分页查询

对于可能返回大量数据的查询，应该实现分页功能：

@Select("SELECT * FROM user_info LIMIT #{offset}, #{limit}")
@Results({
    @Result(property = "username", column = "username"),
    @Result(property = "password", column = "password"),
    @Result(property = "desc", column = "desc"),
    @Result(property = "role", column = "role"),
    @Result(property = "createTime", column = "create_time"),
    @Result(property = "editTime", column = "edit_time")
})
List<User> selectWithPagination(@Param("offset") int offset, @Param("limit") int limit);

总结

通过本教程，我们学习了如何在 Feat Cloud 中集成 MyBatis 并构建一个完整的用户管理系统。整个过程包括：

1. 配置 MyBatis 环境和数据库连接
2. 创建数据库表结构和初始化数据
3. 实现实体类、Mapper 接口、Service 类和 Controller 类
4. 提供 RESTful API 接口
5. 测试 API 功能

这种分层架构使代码更加清晰，便于维护和扩展。MyBatis 的注解方式使得 SQL 语句与 Java 代码紧密结合，提高了开发效率。

有关完整示例，请参见 Gitee 仓库中的 MyBatis 示例