mybatis映射文件mapper.xml的写法(collections...)
转自:https://blog.csdn.net/two_people/article/details/51759881
在学习mybatis的时候我们通常会在映射文件这样写:
<?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="com.qbd.mapper.StudentMappers"> <select id="findbyid" parameterType="Integer" resultMap="StudentResult"> select *from student where id=#{id} </select> <select id="findbygradeid" parameterType="Integer" resultMap="StudentResult"> select *from student where gid=#{gid} </select> <resultMap type="Student" id="StudentResult"> <id property="id" column="id"/> <result property="name" column="name"/> <result property="age" column="age"/> <association property="address" column="addid" select="com.qbd.mapper.AddressMappers.findbyid"> </association> <association property="grade" column="gid" select="com.qbd.mapper.GradeMappers.findbyid"> </association> </resultMap> </mapper>
来读取配置文件
另一种方法就是:
直接在mapper.xml中的这一部分写成dao<mapper namespace="com.qbd.mapper.StudentMappers">如下
<?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="com.qbd.ssm.dao.UserDao"> <!-- 定义缓存 一般是一级缓存,如果用同一个sqlsession 那么相同查询直接会从缓存中查找 <cache size="1024" flushInterval="60000" eviction="LRU" readOnly="false"></cache> --> <!-- 查找所有 --> <select id="find" parameterType="Map" resultMap="StudentResult"> select * from user <where> <if test="uname!=null and uname!='' "> and uname like #{uname} </if> </where> <if test="start!=null and size!=null"> limit #{start},#{size} </if> </select> <select id="getTotal" parameterType="Map" resultType="Long"> select count(*) from user <where> <if test="uname!=null and uname!='' "> and uname like #{uname} </if> </where> </select> <!-- 按照用户名和密码查找 --> <select id="getUser" resultMap="StudentResult" parameterType="Map"> select *from user where uname=#{uname} and upassword=#{upassword} </select> <!-- 删除 --> <delete id="delete" parameterType="Map"> delete from user where uid=#{uid} </delete> <!-- 修改 --> <update id="update" parameterType="User"> update user <set> <if test="uname!=null"> uname=#{uname}, </if> <if test="upassword!=null"> upassword=#{upassword}, </if> <if test="upower!=null"> upower=#{upower}, </if> </set> where uid=#{uid} </update> <!-- 增加 --> <insert id="add" parameterType="User"> insert into user values(null,#{uname},#{upassword},#{upower}) </insert> <resultMap type="User" id="StudentResult"> <id property="uid" column="uid"/> <result property="uname" column="uname"/> <result property="upassword" column="upassword"/> </resultMap> </mapper>
那么就不用写dao的实现在service中就能掉用 mybatis默认会把mapper.xml映射为dao的实现