ibatis 中 $与#的区别

在sql配置中比如in(#rewr#) 与in ($rewr$)

在Ibatis中我们使用SqlMap进行Sql查询时需要引用参数，在参数引用中遇到的符号#和$之间的区分为，#可以进行与编译，进行类型匹配，而$不进行数据类型匹配，例如： 

select * from table where id = #id# ，其中如果字段id为字符型，那么#id#表示的就是'id'类型，如果id为整型，那么#id#就是id类型。 

select * from table where id = $id$ ，如果字段id为整型，Sql语句就不会出错，但是如果字段id为字符型，那么Sql语句应该写成 select * from table where id = '$id$'


<span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">$ 的作用实际上是字符串拼接， </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">select * from $tableName$ </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">等效于 </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">StringBuffer sb = new StringBuffer(256); </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">sb.append("select * from ").append(tableName); </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">sb.toString(); </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">#用于变量替换 </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">select * from table where id = #id# </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">等效于 </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">prepareStement = stmt.createPrepareStement("select * from table where id = ?") </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">prepareStement.setString(1,'abc'); </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">------------------------------------------------ </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">说道这里， 总结一下， 什么时候用$，什么时候 用 # </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">对于变量部分， 应当使用#， 这样可以有效的防止sql注入， 未来，# 都是用到了prepareStement，这样对效率也有一定的提升 </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">$只是简单的字符拼接而已，对于非变量部分， 那只能使用$， 实际上， 在很多场合，$也是有很多实际意义的 </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">例如 </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">select * from $tableName$ 对于不同的表执行统一的查询 </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">update $tableName$ set status = #status# 每个实体一张表，改变不用实体的状态 </span><br style="line-height: 25px; color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53;" /><span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, simsun, u5b8bu4f53; line-height: 25px;">特别提醒一下， $只是字符串拼接， 所以要特别小心sql注入问题。</span>