mybatis基础02

一、Mybatis的获取参数的方式

方式1：${} 字符串拼接

方式2：#{} 占位符

1.Mapper接口参数为单个参数

Integer deleteById(Integer id);

 
 
    <delete id="deleteById" parameterType="int">
 
        delete from user  where id = #{id}
 
    delete>

2.Mapper接口参数是多个参数的获取

User selectUserByUserNameAndPassword(String username,String password);

<select id="selectUserByUserNameAndPassword" resultType="user">
        select  * from user where user_name = #{arg0} and password = #{arg1}
 select>

3.将参数设为map集合进行数据的传递

User selectUserByMap(Map map);

<select id="selectUserByMap" resultType="cn.kgc.mybatis.entity.User">
        select  * from user where user_name = #{username} and password = #{password}
select>

4.通过注解@param("键名")设置参数的获取名字

Integer addUser(@Param("username") String username,@Param("password") String password);

<insert id="addUser" >
         insert into user(username,password)values(#{username},#{password})
    insert>

5.将多个参数设置成对象进行数据的传递

int insertUser(User user);

 <insert id="insertUser" parameterType="user" useGeneratedKeys="true" keyProperty="id" >
         insert into user values ( #{id},#{userName},#{password})
 insert>

二、Mybatis中的模糊查询

方式1：

SELECT * FROM tableName WHERE name LIKE #{text};
 
-- 传递的参数需要拼接  ‘%text%’

方式2：

SELECT * FROM tableName WHERE name LIKE '%${text}%';
 -- 使用$替代# 参数无需在拼接%  存在sql注入

方式3

SELECT * FROM tableName WHERE name LIKE CONCAT('%', #{text}), '%');
-- 使用mysql的函数  实现拼接

批量删除

int deleteMore(String ids);

 <delete id="deleteMore">
        delete from user where id in(${ids})
   delete>

mapper中自定义映射

自定义映射的用法之一，解决表格查询的字段名和实体类中不一致的情况

<resultMap id="userMap" type="user">
        <id column="id" property="id">id>
        <result column="user_name" property="userName">result>
        <result column="password" property="password">result>
resultMap>

mybatis对象的关联关系

一对多关系处理(一方)

<resultMap id="selectByEIdMap" type="cn.kgc.mybatis.entity.Emp">
        <result column="id" property="dept.id" >result>
        <result column="dname" property="dept.dName">result>
 resultMap>
 
 
    <resultMap id="selectByEIdMap2" type="cn.kgc.mybatis.entity.Emp">
        <id column="eid" property="eId">id>
        <result column="ename" property="EName">result>
        <result column="age" property="age">result>
        <result column="deptno" property="deptNo">result>
        
       <association property="dept" javaType="dept">
           <id column="id" property="id">id>
           <result column="dname" property="dName">result>
       association>
    resultMap>
 
	
    <resultMap id="selectByEIdMap3" type="cn.kgc.mybatis.entity.Emp">
        <id column="eid" property="eId">id>
        <result column="ename" property="EName">result>
        <result column="age" property="age">result>
        <result column="deptno" property="deptNo">result>
        <association property="dept" select="cn.kgc.mybatis.mapper.DeptMapper.selectById" 
                                    column="deptno" 
                                    fetchType="eager">
        association>
    resultMap>
 
注：延迟加载设置  ：
		1. <setting name="lazyLoadingEnabled" value="true"/> 
		2. <setting name="aggressiveLazyLoading" value="false"/>  3.4.1之前的版本需要设置
 
    <select id="selectByEId" resultMap="selectByEIdMap2">
            select  * from emp left  join  dept on  emp.deptno = dept.id  where eid = #{eid}
    select>
 
    <select id="selectByEId2" resultMap="selectByEIdMap3">
            select  * from emp  where eid = #{eid}
    select>

一对多关系处理(多方)

<resultMap id="BaseResultMap" type="cn.kgc.mybatis.entity.Dept">
            <id property="id" column="id" />
            <result property="dName" column="dname" />
            <collection property="emps" ofType="emp">
                <id column="eid" property="eId">id>
                <result column="ename" property="EName">result>
                <result column="age" property="age">result>
                <result column="deptno" property="deptNo">result>
            collection>
    resultMap>
 
 
    <resultMap id="BaseResultMap2" type="cn.kgc.mybatis.entity.Dept">
        <id property="id" column="id" />
        <result property="dName" column="dname" />
        <collection property="emps" select="cn.kgc.mybatis.mapper.EmpMapper.selectByDeptId" column="id">collection>
    resultMap>
 
    <select id="selectById" resultType="dept">
        select  * from dept where id = #{id}
    select>
 
    <select id="selectById2" resultMap="BaseResultMap">
        select emp.* ,dept.* from dept left join emp on dept.id = emp.deptno where id = #{id}
    select>
 
    <select id="selectById3" resultMap="BaseResultMap2">
        select dept.* from dept  where id = #{id}
    select>