ibatis中$和#的区别

ibatis中$和#的区别

作者：lg

1根据来源

通过看ibatis-2.3.4.726源码com.ibatis.sqlmap.engine.execution.SqlExecutor可以看到方法

executeQuery(StatementScope statementScope,Connection conn, String sql, Object[] parameters, int skipResults, intmaxResults, RowHandlerCallback callback) throws SQLException {了解一些内部实现，下面逐步介绍

2 方法调用

publicstaticvoid main(String[] args)throws SQLException{ Map map = new HashMap(); map.put("tablename","c_admin"); map.put("password","admin"); map.put("passwordtype","1"); List list = testMain.selectAdmintByName(map); int len = list.size(); for(int i=0;i<len;i++){ System.out.println(list.get(i)); } // System.out.println(testMain.searchAdminTotal(map)); }

3如果配成$

可以查看com.ibatis.sqlmap.engine.execution.SqlExecutor---497行

3.1 sqlmap配置文件

<sqlMapnamespace="defaultBusiness"> <resultMapid="cadminresult"class="java.util.HashMap"> <resultproperty="admin"column="admin"/> <resultproperty="password"column="password"/> <resultproperty="passwordtype"column="passwordtype"/> </resultMap> <selectid="searchAdminList"parameterClass="java.util.Map"resultMap="cadminresult"> <dynamicprepend=""> <isNotEmptyproperty="tablename"prepend=""> SELECT * FROM $tablename$ WHERE 1=1 </isNotEmpty> <isNotNullprepend="AND"property="password"> password = $password$ </isNotNull> <isNotNullprepend="AND"property="passwordtype"> passwordtype = $passwordtype$ </isNotNull> </dynamic> </select> </sqlMap>

3.2 ibatis会平凑出sql

SELECT * FROM c_admin WHERE 1=1 AND password = admin AND passwordtype = 1

4如果配成#

4.1 sqlmap配置文件

<sqlMapnamespace="defaultBusiness"> <resultMapid="cadminresult"class="java.util.HashMap"> <resultproperty="admin"column="admin"/> <resultproperty="password"column="password"/> <resultproperty="passwordtype"column="passwordtype"/> </resultMap> <selectid="searchAdminList"parameterClass="java.util.Map"resultMap="cadminresult"> <dynamicprepend=""> <isNotEmptyproperty="tablename"prepend=""> SELECT * FROM $tablename$ WHERE 1=1 </isNotEmpty> <isNotNullprepend="AND"property="password"> password = #password# </isNotNull> <isNotNullprepend="AND"property="passwordtype"> passwordtype = #passwordtype# </isNotNull> </dynamic> </select> </sqlMap>

4.2 ibatis会拼凑sql

SELECT * FROM c_admin WHERE 1=1 AND password = ? AND passwordtype = ?

5 分析结果

从1,2,3,4可以看出，#被解析出？，$被直接替换成了裸露的值admin（如上例），所以tablename不能用#来包括，其ibatis的最低层是借助我们熟悉的PreparedStatementps
= conn.prepareStatement(sql);来执行的，通过ps.setString(i, param);等方法来设置的？里面的条件，ibatic会根据传入参数，并借助StringTypeHandler.java，LongTypeHandler.java 等类来保持参数的原始类型，譬如password是java.lang.String ,passwordtype是java.lang.Interger，再分别调用ps.setString(i, param);和ps.setInt(i, param);来设置参数
这样就很好理解#和$用法了。

以上个人调查结果仅供参考，如果有问题及时联系，非常感谢！