Detailed introduction of mybatis
mybatis
usermapper.xml<?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.easytopit.demo.mybatis.mapper.UserMapper"><insert id="insert" useGeneratedKeys="true" keyProperty="id" >INSERT INTO et_user (username, truename, login_time) VALUES(#{username}, #{truename}, #{loginTime});</insert>
<update id="update">UPDATE et_user SET username=#{username}, truename=#{truename}, login_time=#{loginTime} WHERE id=#{id}</update>
<delete id="delete" parameterType="int">delete from et_user where id=#{id}</delete>
<select id="queryAll" resultType="com.easytopit.demo.mybatis.bean.User">SELECT id, username, truename, login_time loginTime FROM et_user LIMIT 10</select><select id="queryAllByPage" parameterType="java.util.HashMap" resultType="com.easytopit.demo.mybatis.bean.User"><!-- SELECT id, username, truename, login_time loginTime FROM et_user LIMIT #{param1}, #{param2} --> SELECT id, username, truename, login_time loginTime FROM et_user LIMIT #{pageOffset}, #{pageSize}</select><select id="query" resultType="com.easytopit.demo.mybatis.bean.User">SELECT id, username, truename, login_time loginTime FROM et_user WHERE id = #{id}</select></mapper> namespace： AI-powered app for creating realistic nude photos Online AI tool for removing clothes from photos. Undress images for free AI clothes remover Swap faces in any video effortlessly with our completely free AI face swap tool! Easy-to-use and free code editor Chinese version, very easy to use Powerful PHP integrated development environment Visual web development tools God-level code editing software (SublimeText3)
是为了解决相同名字的sql操作问题，有标识的作用
例如如果访问的路径是/add.do,如果namespace为/user，则访问路径为/user/add.do
select id="selectid"
id是为了唯一标识sql语句
resultType=java.util.map
标识当行记录的类型
// 手工查询(根据命名空间 - 命名空间与Mapper接口一致) -> com/easytopit/demo/mybatis/mapper/persistent/UserMapperNS.xml
users = session.selectList("NS.queryAll");
参数的三种方法
1：使用#{0}索引
2：使用参数#{param1} 从1开始
3：注解 @param（“name”）
jdk1.8支持参数注解，其他的不支持 参数名字和param（“”）名字一致
注意事项
#{} 实际上使用的jdbc的？占位符，是安全的
11:41:56.728 [http-bio-8080-exec-10] DEBUG c.e.c.m.AlbumMapper.deletelAlbum - ==> Preparing: delete from ab_album where id = ?
${} 底层实际上使用的替换，要记得加单引号，是不安全的
11:47:29.831 [http-bio-8080-exec-10] DEBUG c.e.c.m.AlbumMapper.deletelAlbum - ==> Preparing: delete from ab_album where id = 67
结果集映射
resulttype
映射一个具体的类
resultmap
先定义一个resultmap，然后映射
多对一映射
相当于先查询一个属性，然后自动使用属性作为参数调用其他的方法，再讲结果返回
column ''deptno ,property='dept',javaType=dept.class,one = @one(select = "命名空间.方法名")
一对多映射
懒加载
设置
需要的时候加载
出现的原因在于，应为一对多情况，有可能出现内存不足，所以当需要的时候，重新发起sql语句
insert selectkey标签
先通过sql语法，查询当前的列的最大值+1，放入到map中，然后insert into语句
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