Mybatis XML映射文件
mybatis为聚焦于SQL而构建，SQL映射文件常用的顶级元素如
- resultMap，是最复杂也是最强大的元素，用来描述如何从数据库结果集中来加载对象。
- insert，映射插入语句
- update， 映射更新语句
- delete ， 映射删除语句
- select ， 映射查询语句
1）简单的单表映射文件
<?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.mybatis.bean.userMapper">
<select id="getUser" parameterType="int" resultType="com.mybatis.bean.User">
select * from users where id=#{id}
</select>
<insert id="insertUser" parameterType="com.mybatis.bean.User">
insert into users(name,age) values(#{name},#{age});
</insert>
<update id="updateUser" parameterType="com.mybatis.bean.User">
update users set name=#{name} ,age=#{age} where id=#{id}
</update>
<delete id="deleteUser" parameterType="int">
delete from users where id=#{id}
</delete>
<select id="allUser" resultType="com.mybatis.bean.User">
select * from users
</select>
</mapper>
Java对象
public class User {
private int id;
private String name;
private int age;
public int getId() {
return id;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
public void setId(int id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
public void setAge(int age) {
this.age = age;
}
}
2）结果映射resultMap 元素是 MyBatis 中最重要最强大的元素。当列名和属性名没有精确匹配，可以在SELECT语句中对列使用别名，或配置显式的结果映射。
Java对象
public class Classes {
private int id;
private String name;
private Teacher teacher;
// 省略
}
resultMap映射文件、关联对象
<?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.mybatis.bean.ClassMapper">
<select id="getClass" parameterType="int" resultMap="ClassResultMap">
select * from class c,teacher t where c.teacher_id = t.t_id and c.c_id=#{id}
</select>
<resultMap id="ClassResultMap" type="classes">
<id property="id" column="c_id"/>
<result property="name" column="c_name"/>
<association property="teacher" column="teacher_id" javaType="teacher">
<id property="id" column="t_id"/>
<result property="name" column="t_name"/>
</association>
</resultMap>
</mapper>
集合配置
<collection property="posts" ofType="domain.blog.Post"> <id property="id" column="post_id"/> <result property="subject" column="post_subject"/> <result property="body" column="post_body"/> </collection>
