SSM框架的sql中参数注入（#和$的区别）

<select id="findUsersByUserName2" resultType="java.util.Map" parameterType="Params">
 SELECT
 id as uid,
 username as uname,
 password as pwd,
 account as act,
 telephone,
 idcard,
 create_time as createTime,
  is_delete as isDelete,
  male,
  birthday,
  email,
  address,
  update_time as updateTime,
  teacher_id as teacherId,
  subject_id as subjectId,
  age,
  status,
  type
  FROM
  tz_user
  WHERE
  username LIKE '%${username}%'
  AND `password` = #{password}
  ORDER BY ${order}
  </select>
ORDER BY ${order} 和模糊查询 username LIKE '%${username}%' 是用$符号，其他的大多是用 #{} 来获取传递的参数。
ORDER BY 还可以用#{}符号传递参数。

#{} 将传入的数据都当成一个字符串，会对自动传入的数据加一个双引号。如：order by #{userId}，如果传入的值是111, 那么解析成sql时的值为order by "111", 如果传入的值是id，则解析成的sql为order by "id".

${} 将传入的数据直接显示生成在sql中，是什么就是什么，没有加双引号：select * from table1 where id=${id} 若 id = 4，则就是：select * from table1 where id = 4;

最好是能用 #{} 就用它，因为它可以防止sql注入，且是预编译的，在需要原样输出时才使用 ${}

记住一点：单引号里面的用 ${} 符号，ORDER BY 可以用${}或者#{}符号，用 #{} 的不能加单引号，因为默认加了引号