MyBatis快速入门

MyBatis

快速入门

创建xml文件：mybatis-config.xml

配置

java 复制代码

 <?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="${driver}"/>
         <property name="url" value="${url}"/>
         <property name="username" value="${username}"/>
         <property name="password" value="${password}"/>
       </dataSource>
     </environment>
   </environments>
   <mappers>
     <mapper resource="org/mybatis/example/BlogMapper.xml"/>
   </mappers>
 </configuration>

创建xml文件，namespace作用域，id唯一标识符，传入sqlSession的方法中执行

java 复制代码

 <?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="org.mybatis.example.BlogMapper">
   <select id="selectBlog" resultType="Blog">
     select * from Blog where id = #{id}
   </select>
 </mapper>

创建SqlSessionFactory以及SqlSession

java 复制代码

 String resource = "org/mybatis/example/mybatis-config.xml";
 InputStream inputStream = Resources.getResourceAsStream(resource);
 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 
 SqlSession sqlSession = sqlSessionFactory.openSession();
 //硬编码问题，下一节解决
 sqlSession.selectOne("org.mybatis.example.BlogMapper.selectBlog", 101);
 sqlSession.selectList();                                                                      
 sqlSession.close();

Mapper代理开发

定义Mapper接口：xml文件要和接口在同一目录下，例如resources创建top/zendee/mapper

命名空间改为Mapper接口

java 复制代码

 <!DOCTYPE mapper
   PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
   "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 <mapper namespace="top.zendee.mapper.UserMapper">
   <select id="selectBlog" resultType="Blog">
     select * from Blog where id = #{id}
   </select>
 </mapper>

映射文件的id 和方法名 相同，返回值相同

使用接口

java 复制代码

 BlogMapper mapper = session.getMapper(BlogMapper.class);
 Blog blog = mapper.selectBlog(101);

MyBatisX插件

功能：XML 和接口方法 相互跳转，根据接口方法生成statement

字段映射

起别名：在xml文件的sql语句中给列起别名，例如brand_name as brandName。

sql片段：

java 复制代码

 <sql id = user>`
 id , user_name as userName, phone, email`
 </sql>
 
 <select id = selectAll resultType = "user">
     select
         <include refid="user"/>
     from user;
 </select>

resultMap映射：id :主键，result：一般列。

java 复制代码

 <resultMap type="User" id="userResultMap">
     <id property="userId" column="user_id" javaType="int" jdbcType="int"/>
     <result property="name" column="name" javaType="String" jdbcType="VARCHAR"/>
 </resultMap>
 //也可如下：
 <resultMap type="User" id="userResultMap">
     //主键字段映射
     <id property="userId" column="user_id"/>
     //一般字段映射
     <result property="name" column="name"/>
 </resultMap>
     
 //同时修改resultType -> resultMap
 <select id = selectAll resultMap = "userResultMap">
     select *
     from user;
 </select>

查询

查询所有数据
产看单个数据

java 复制代码

 <!DOCTYPE mapper
   PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
   "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 <mapper namespace="top.zendee.mapper.UserMapper">
     
     <resultMap id="userResultMap" type="top.zendee.entity.User">
         <id column="user_id" property="userId">
         <result column="user_name" property="userName">
     </resultMap>
     
     //$存在sql注入问题，在表名或者列名不确定可以使用
     <select id="selectUserById" resultMap="userResultMap">
         select * from user where user_id = #{id}
     </select>
 </mapper>

多重判断模糊查询

java 复制代码

//mapper接口
List<Brand> selectByCondition(@Param("status")int status, @Param("brandName")String brandName);
//或者
List<Brand> selectByCondition(Brand brand);
//或者
List<Brand> selectByCondition(Map map);

//XML文件,模糊查询%和_，在java函数中进行处理，例如华为->%华为%
<select id="selectByCondition" resultMap="brandResultMap">
    select * from brand
    where 
    	status like #{status}
		and brand_name like #{brandName}
</select>

特殊字符处理

转义字符：&lt，例如&lt <(小于)
<! [CDATA[ 特殊字符 ]]>：例如<! [CDATA[ <(小于) ]]>

动态查询

java 复制代码

<select id="findActiveBlogWithTitleLike" resultType="Blog">
  SELECT * FROM BLOG
  WHERE state = 'ACTIVE'
  <if test="title != null">
    AND title like #{title}
  </if>
</select>
      
<select id="findActiveBlogLike" resultType="Blog">
  SELECT * FROM BLOG WHERE state = 'ACTIVE'
  <if test="title != null">
    AND title like #{title}
  </if>
  <if test="author != null and author.name != null">
    AND author_name like #{author.name}
  </if>
</select>

choose-when-otherwise

java 复制代码

//只匹配一个条件。类似switch语句
<select id="findActiveBlogLike"
     resultType="Blog">
  SELECT * FROM BLOG WHERE state = 'ACTIVE'
  <choose>
    <when test="title != null">
      AND title like #{title}
    </when>
    <when test="author != null and author.name != null">
      AND author_name like #{author.name}
    </when>
    <otherwise>
      AND 1 = 1
    </otherwise>
  </choose>
</select>

where-if

java 复制代码

//只有传入参数不为空时，才进行where语句判断
<select id="findActiveBlogLike"
     resultType="Blog">
  SELECT * FROM BLOG
  <where>
    <if test="state != null">
         state = #{state}
    </if>
    <if test="title != null">
        AND title like #{title}
    </if>
    <if test="author != null and author.name != null">
        AND author_name like #{author.name}
    </if>
  </where>
</select>

最终版

java 复制代码

<select id="findActiveBlogLike"
     resultType="Blog">
  SELECT * FROM BLOG
  <where>
      <choose>
        <when test="title != null">
          title like #{title}
        </when>
        <when test="author != null and author.name != null">
          AND author_name like #{author.name}
        </when>
      </choose>
  </where>
</select>

联表查询

java 复制代码

<!-- 定义结果映射 -->
<resultMap id="studentWithCoursesResultMap" type="Student">
    <id property="id" column="id"/>
    <result property="name" column="name"/>
    <!-- 使用collection处理课程列表 -->
    <collection property="courses" ofType="Course">
        <id property="id" column="course_id"/>
        <result property="courseName" column="course_name"/>
    </collection>
</resultMap>

<!-- 查询语句 -->
<select id="findStudentByNameWithCourses" resultMap="studentWithCoursesResultMap">
    SELECT 
        s.id,
        s.name,
        c.id AS course_id,
        c.course_name
    FROM 
        student s
    LEFT JOIN student_course sc ON s.id = sc.student_id
    LEFT JOIN course c ON sc.course_id = c.id
    WHERE s.name = #{name};
</select>

添加

添加结果可通过异常捕获判断，需要手动提交事务sqlSession.commit()

openSessio()：默认开启事务，需要手动提交
openSessio(true)：自动提交事务

java 复制代码

<insert id = "addUser">
   insert into user(name, status)
    values(#{name}, #{status});
</insert>

主键返回

java 复制代码

<insert id = "addUser" useGeneratedKey="true" keyProPerty="id">

修改

可以返回void ，也可以返回int

java 复制代码

<update id="updateUser">
	update user
	set
		name = #{name},
		status = #{status}
	where id = #{id};
</update>

动态修改

set标签

java 复制代码

<update id="updateUser">
	update user
	<set>
		<if test="name != null and name != ''">
			name = #{name},
		</if>
		<if test="status != null and status != ''">
			status = #{status}
		</if>
      </set>
	where id = #{id};
</update>

删除

java 复制代码

<delete id = "deleteUserById">
	delete from user where id = #{id}
</delete>

批量删除

前端封装数组int[] ids

java 复制代码

//可以用@Param('ids')起别名代替array,separator分隔符
<delete id = "deleteUserById">
	delete from user 
	where id in
	<foreach collection="array" item="id" separator=",">
		id = #{id}
	</foreach>
        ;
</delete>