MyBatis基本用法

素颜马尾好姑娘i 2023-10-12 09:49 22阅读 0赞

1.  定义MyBatis配置文件 `mybatis-config.xml`，其中包含数据库连接信息和MyBatis全局配置。

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-config.dtd">
    <configuration>
        
        <environments default="development">
            <environment id="development">
                <transactionManager type="JDBC"/>
                <dataSource type="POOLED">
                    <property name="driver" value="com.mysql.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql://localhost:3306/test"/>
                    <property name="username" value="root"/>
                    <property name="password" value="123456"/>
                </dataSource>
            </environment>
        </environments>
    
        
        <settings>
            
            <setting name="logImpl" value="STDOUT_LOGGING"/>
            
            <setting name="cacheEnabled" value="true"/>
            
            <typeAliases>
                <typeAlias type="com.example.User" alias="User"/>
            </typeAliases>
        </settings>
    
        
        <mappers>
            <mapper resource="com/example/UserMapper.xml"/>
        </mappers>
    </configuration>

1.  定义Mapper映射文件 `UserMapper.xml`，其中包含SQL语句和映射关系。

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    <mapper namespace="com.example.UserMapper">
        
        <select id="getUserById" parameterType="int" resultType="User">
            SELECT * FROM user WHERE id = #{id}
        </select>
    
        
        <insert id="insertUser" parameterType="User">
            INSERT INTO user(name, age) VALUES(#{name}, #{age})
        </insert>
    
        
        <update id="updateUser" parameterType="User">
            UPDATE user SET name = #{name}, age = #{age} WHERE id = #{id}
        </update>
    
        
        <delete id="deleteUser" parameterType="int">
            DELETE FROM user WHERE id = #{id}
        </delete>
    </mapper>

1.  定义实体类 `User`。

public class User {
        
        private int id;
        private String name;
        private int age;
    
        // 省略getter和setter方法
    }

1.  使用MyBatis API进行数据库操作。

public void testMybatis() {
        
        // 加载MyBatis配置文件
        InputStream inputStream = getClass().getClassLoader().getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    
        // 获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        try {
        
            // 获取Mapper接口
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    
            // 查询用户
            User user = userMapper.getUserById(1);
            System.out.println(user.getName());
    
            // 新增用户
            User newUser = new User();
            newUser.setName("Tom");
            newUser.setAge(20);
            userMapper.insertUser(newUser);
    
            // 更新用户
            user.setName("Jerry");
            user.setAge(30);
            userMapper.updateUser(user);
    
            // 删除用户
            userMapper.deleteUser(user.getId());
    
            // 提交事务
            sqlSession.commit();
        } catch (Exception e) {
        
            // 回滚事务
            sqlSession.rollback();
            e.printStackTrace();
        } finally {
        
            sqlSession.close();
        }
    }

以上示例仅为MyBatis的基本用法，实际使用时还需要根据具体业务需求进行更加复杂的操作。详细的MyBatis使用说明可以参考官方文档：[MyBatis 3 Official Documentation][]。

[MyBatis 3 Official Documentation]: https://mybatis.org/mybatis-3/