MyBatis - 02映射文件

（1）映射文件解释

<?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"> //1. 映射文件DTD约束头
<mapper namespace="com.bearpx.spring.mybatis.dao.UserDao">   // 2. mapper：根标签  3. namespace：命名空间，与下面的id 共同组成查询标识
    // 4. select：查询操作，还有insert、update、delete    5. resultType：查询结果对应的实体类型    6. findAll： 语句的id标识
    <select id="findAll" resultType="com.bearpx.spring.mybatis.domain.User">
        select * from user     // 7. 要执行的sql语句
    </select>
</mapper>     

找不到userMapper.update1： 命名空间+id 出现不匹配

Caused by: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for userMapper.update1
    at org.apache.ibatis.session.Configuration$StrictMap.get(Configuration.java:888)
    at org.apache.ibatis.session.Configuration.getMappedStatement(Configuration.java:721)
    at org.apache.ibatis.session.Configuration.getMappedStatement(Configuration.java:714)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:197)

 

（2）插入操作

    <!-- 更新-->
    <insert id="save" parameterType="com.bearpx.spring.mybatis.domain.User">
        insert into user values(#{id}, #{username}, #{password})
    </insert>

 

   > 插入语句使用insert标签，使用parameterType属性指定要插入的数据类型

   > sql语句中使用 #{实体属性名} 方式引用实体中的属性值

   > 插入操作使用的API 是 sqlSession.insert("命名空间.id", 实体对象)

   > 插入操作涉及数据库数据变化，要使用sqlSession对象显示的提交事务，即 sqlSession.commit()

    @Test
    public void test2() throws IOException {
        User user = new User();
        user.setUsername("tomi");
        user.setPassword("11111111");
        // 获得核心配置文件
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        // 获得session工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        // 获得session 会话对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        // 执行操作   参数： namespace+id
        int result = sqlSession.insert("userMapper.save", user);
        System.out.println(result);
        // mybatis 执行更新操作 提交事务
        sqlSession.commit();
        // 释放资源
        sqlSession.close();
    }

 

（3）修改操作

    <!-- 修改操作-->
    <update id="update" parameterType="com.bearpx.spring.mybatis.domain.User">
        update user set username=#{username}, password=#{password} where id=#{id}
    </update>

 

 

    @Test
    public void test3() throws IOException {
        User user = new User();
        user.setId(3);
        user.setUsername("firefly");
        user.setPassword("222222");

        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        sqlSession.update("userMapper.update", user);

        sqlSession.commit();
        sqlSession.close();
    }

 

（4）删除操作

    <!--删除操作-->
    <!--<delete id="delete" parameterType="java.lang.Integer">-->
    <delete id="delete" parameterType="int">
        delete from user where id = #{id}
    </delete>

 

 

    @Test
    public void testDelete() throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();

        int result = sqlSession.delete("userMapper.delete", 6);
        sqlSession.commit();

        sqlSession.close();
    }

 

（5）查询操作 findById

    <select id="findById" resultType="user" parameterType="int">
        select * from user where id=#{id}
    </select>

 

 

    @Test
    public void testFindById() throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        User user = sqlSession.selectOne("userMapper.findById", 1);

        System.out.println(user);
        sqlSession.close();
    }