【愚公系列】2023年03月 Java教学课程 116-Mybatis（动态代理和动态SQL）

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

<!--
    mapper：核心根标签
    namespace属性：名称空间
-->
<mapper namespace="com.itheima.mapper.StudentMapper">

    <sql id="select" >SELECT * FROM student</sql>

    <!--
        select：查询功能的标签
        id属性：唯一标识
        resultType属性：指定结果映射对象类型
        parameterType属性：指定参数映射对象类型
    -->
    <select id="selectAll" resultType="student">
        <include refid="select"/>
    </select>

    <select id="selectById" resultType="student" parameterType="int">
        <include refid="select"/> WHERE id = #{id}
    </select>

    <insert id="insert" parameterType="student">
        INSERT INTO student VALUES (#{id},#{name},#{age})
    </insert>

    <update id="update" parameterType="student">
        UPDATE student SET name = #{name},age = #{age} WHERE id = #{id}
    </update>

    <delete id="delete" parameterType="int">
        DELETE FROM student WHERE id = #{id}
    </delete>

    <select id="selectCondition" resultType="student" parameterType="student">
        <include refid="select"/>
        <where>
            <if test="id != null">
                id = #{id}
            </if>
            <if test="name != null">
                AND name = #{name}
            </if>
            <if test="age != null">
                AND age = #{age}
            </if>
        </where>
    </select>

    <select id="selectByIds" resultType="student" parameterType="list">
        <include refid="select"/>
        <where>
            <foreach collection="list" open="id IN (" close=")" item="id" separator=",">
                #{id}
            </foreach>
        </where>
    </select>
</mapper>

public class Test01 {
    @Test
    public void selectByIds() throws Exception{
        //1.加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");

        //2.获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);

        //3.通过工厂对象获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);

        //4.获取StudentMapper接口的实现类对象
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);

        List<Integer> ids = new ArrayList<>();
        ids.add(1);
        ids.add(2);
        ids.add(3);

        //5.调用实现类的方法，接收结果
        List<Student> list = mapper.selectByIds(ids);

        //6.处理结果
        for (Student student : list) {
            System.out.println(student);
        }

        //7.释放资源
        sqlSession.close();
        is.close();
    }

    @Test
    public void selectCondition() throws Exception{
        //1.加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");

        //2.获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);

        //3.通过工厂对象获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);

        //4.获取StudentMapper接口的实现类对象
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);

        Student stu = new Student();
        stu.setId(2);
        stu.setName("李四");
        //stu.setAge(24);

        //5.调用实现类的方法，接收结果
        List<Student> list = mapper.selectCondition(stu);

        //6.处理结果
        for (Student student : list) {
            System.out.println(student);
        }

        //7.释放资源
        sqlSession.close();
        is.close();
    }
}