MyBatis核心概念 + 环境搭建 + CRUD实战详解

// 1. 加载驱动、建立连接
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection(url, user, pwd);
// 2. 编写SQL（硬编码）
String sql = "select * from user where id = ?";
PreparedStatement pstmt = conn.prepareStatement(sql);
// 3. 设置参数
pstmt.setInt(1, id);
// 4. 执行查询
ResultSet rs = pstmt.executeQuery();
// 5. 手动封装结果集
User user = null;
if(rs.next()){
    user = new User();
    user.setId(rs.getInt("id"));
    user.setUsername(rs.getString("username"));
}

<dependencies>
    <!-- MyBatis核心依赖 -->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.9</version>
    </dependency>
    <!-- MySQL驱动 -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.49</version>
    </dependency>
    <!-- 日志包 -->
    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.17</version>
    </dependency>
    <!-- 测试包 -->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.13.2</version>
        <scope>test</scope>
    </dependency>
</dependencies>

<?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>
    <!-- 环境配置：默认使用development -->
    <environments default="development">
        <environment id="development">
            <!-- 事务管理：JDBC事务 -->
            <transactionManager type="JDBC"/>
            <!-- 数据源：POOLED连接池 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis_demo?serverTimezone=Asia/Shanghai&useSSL=false&characterEncoding=utf8"/>
                <property name="username" value="root"/>
                <property name="password" value="abc123"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 加载Mapper映射文件 -->
    <mappers>
        <mapper resource="mapper/UserMapper.xml"/>
    </mappers>
</configuration>

src/main/java
  com.qcby
    ├── dao/          DAO接口层
    ├── entity/       实体类
src/main/resources
  ├── mapper/         Mapper XML映射文件
  ├── sqlMapConfig.xml  MyBatis核心配置

public class User {
    private Integer id;
    private String username;
    private String sex;
    private Date birthday;
    private String address;
    // 无参构造
    public User(){}
    // getter/setter
    // toString()
}

public interface UserDao {
    List<User> findAll();
    User findUserById(Integer id);
}

<!-- namespace：绑定接口全限定名 -->
<mapper namespace="com.qcby.dao.UserDao">
    <!-- id：与接口方法名一致 -->
    <select id="findAll" resultType="com.qcby.entity.User">
        select * from user order by id desc
    </select>
</mapper>

<select id="findUserById" parameterType="Integer" resultType="com.qcby.entity.User">
    select * from user where id = #{id}
</select>

<select id="findAll" resultType="com.qcby.entity.User">
    select * from user
</select>

<select id="findAll" resultType="com.qcby.entity.User">
    select * from user order by id desc;
</select>

List<User> findAll();

<select id="findUserById" parameterType="Integer" resultType="com.qcby.entity.User">
    select * from user where id = #{id};
</select>

User findUserById(Integer id);

<select id="findUserByUserName" parameterType="String" resultType="com.qcby.entity.User">
    select * from user where username like concat('%', #{username}, '%');
</select>

List<User> findUserByUserName(String username);

<insert id="insert" parameterType="com.qcby.entity.User">
    insert into user(username,sex,birthday,address)
    values(#{username},#{sex},#{birthday},#{address});
</insert>

int insert(User user);

<update id="update" parameterType="com.qcby.entity.User">
    update user 
    set username=#{username},sex=#{sex},birthday=#{birthday},address=#{address}
    where id=#{id};
</update>

<delete id="delete" parameterType="Integer">
    delete from user where id=#{id};
</delete>

@Test
public void addUser(){
    User user = new User();
    user.setUsername("张三");
    user.setSex("男");
    // 执行插入
    userDao.insert(user);
    // 必须提交事务
    session.commit();
}

public class MyBatisUtil {
    private static SqlSessionFactory sqlSessionFactory;
    static{
        try {
            String resource = "sqlMapConfig.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    // 获取SqlSession
    public static SqlSession getSession(){
        return sqlSessionFactory.openSession(true); // 自动提交事务
    }
}