from :   http://blog.csdn.net/doctor_who2004/article/details/43027181

What is the difference between #{...} and ${...}?

mybatis3中mapper文件中 #{...} 和 ${...}有什么不同．

MyBatis interprets #{...} as a parameter marker in a JDBC prepared statement. MyBatis interprets ${...} as 

mybatis3对于#{...}是JDBC prepared statement参数的占位符标志，其值会有对应typehandler针对不同类型设值．

string substitution. It is important to know the difference because parameter markers cannot be used in certain places 

而${...}在mybatis3中仅仅是字符串替换，这也是以前web编程sql注入发生的地发．

in SQL statements.
For example, you cannot use a parameter marker to specify a table name.
Given the following code:

MyBatis will generate the following prepared statement:

Important: note that use of ${...} (string substitution) presents a risk for SQL injection attacks. Also, string substitution can be problematical for complex types like dates. For these reasons, we recommend using the #{...} form whenever possible.