MyBatis安装&入门

MyBatis

创建

在pom.xml中添加依赖

<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.13.2</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.32</version>
</dependency>
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.13</version>
</dependency>

db.properties

jdbc.driverClass=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/数据库名?useUnicode=true&characterEncoding=utf8&serverTimezone=Asia/Shanghai&useSSL=false

配置文件mybatis-config.xml

<?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"> <!-- 有错误 -->
<configuration>
    <!--引入外部配置文件        -->
    <properties resource="db.properties"/>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!-- 连接信息 -->
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql:///数据库名?useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 注册UserMapper.xml  -->
    <mappers>
        <!-- 加载Sql映射文件  -->
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>

Sql映射文件

UserMapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org/DTD Mapper 3.0" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<!-- namespace命名空间 -->
<!--resultType：返回结果类型-->
<mapper namespace="com.cy.mybatis.mapper.UserMapper">
</mapper>

命名空间中的内容的格式

<select id="名" resultType="返回结果类型">
    select * from 表名 where 字段名 = 内容
</select>

• 例

  • <mapper namespace="test">
        <select id="selectUsers" resultType="User">
            select * from demo1;
        </select>
    </mapper>
    

使用

1. 获取SqlSessionFactory对象

try {
    String resource = "mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
    throw new RuntimeException(e);
}

2. 获取sqlSession对象，执行SQL语句

SqlSession sqlSession = sqlSessionFactory.openSession();	

3. 执行SQL语句

List<User> users = sqlSession.selectList("test.selectUsers");
//执行sql语句，此处执行了上文UserMapper.xml示例中的test

方法二：获取Mapper接口的代理对象

4. 释放资源

sqlSession.close();

其他语句

insert

<insert id="add">
    insert into demo1 values(id,name,password);
</insert>