jsp参数过滤防注入的解决方法

public static boolean sql_inj(String str)
{
String inj_str = "'|and|exec|insert|select|delete|update|count|*|%|chr|mid|master|truncate|char|declare|;|or|-|+|,";
String inj_stra[] = split(inj_str,"|");
for (int i=0 ; i < inj_stra.length ; i++ )
{
if (str.indexOf(inj_stra)>=0)
{
return true;
}
}
return false;
}

jsp中调用该函数检查是否包函非法字符
<%
if(request.getParameter("userID") != null)
userID = request.getParameter("userID").trim();

if (StringUtil.sql_inj(userID) || StringUtil.sql_inj(pwd)){
%>
<Script Language=javascript>alert('参数中包含非法字符！');history.back(-1);</Script>" ;
<%
}else{
……
}%>