//DAO层
Public selectById(int id);
//基本数据类型,可以任意写,如果是对象类型,需要写对应的属性名
<select id="selectById" resultType="Integer">
select * from user where user_id = #{id}
</select>
#{}的索引传递多个参数
//DAO层
Public SelectByIdAndUserName(int id,String username);
//对应的xml,#{0}代表接收的是dao层中的第一个参数,#{1}代表dao层中第二参数,更多参数一致
<select id="SelectByIdAndUserName" resulttype="user">
select * from user where id = #{0} and username = #{1}
</select>
@param注解
public interface usermapper {
user SelectByIdAndUserName(@param("id") Integer id,@param("username") string username);
}
然后,就可以如下使用
<select id="SelectByIdAndUserName" resulttype="user">
select * from user where id=#{id} and username = #{username}
</select>
Map、List
//Map如下
Map<String,Object> map=new HasMap<String,Object>();
map.put("name","lucy");
map.put("age",18);
User user = userDao.selectUserByNameAndAge(map);
//Dao层
public User selectUserByNameAndAge(Map map);
//直接使用map存放的键值
<select id="selectUserByNameAndAge" parameterType="Map" resultType="user">
select * from user where name = #{name} and age = #{age}
</select>