checkuser.jsp
<%@page contentType="text/html;charset=utf-8"%>
<%@ include file="include/common.jsp"%>
<%@ include file="include/connectdb.jsp"%>
<%
String username;
username=request.getParameter("username");
if(username==""){ response.sendRedirect("register.html");}
ResultSet rs;
String sql;
smt=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
sql="SELECT *  FROM [user] where username ='"+username+"'";
rs = smt.executeQuery(sql);
if (!rs.next()) 
    {
   out.print("true");
    }else{
out.print("false");
}
       con.close(); 
        rs.close(); 
        smt.close(); 
con=null;
rs=null;
smt=null;
%>
运行该文件返回:
true
//true 的上面出现很多空行
//那个大大跟我说下原因哈~~~~因为我的ajax是从这个页采数据回来的  那么多的空行  处理起来很麻烦