problem in retriving string data using jsp

[Manas Das]

my code is

ps=con.prepareStatement("SELECT * FROM LIBUCE WHERE BOOKID=?");
String bk=request.getParameter("t7");
ps.setString(4,bk);
rs=ps.executeQuery();
if(rs.next())
{
do
{
String nm=rs.getString(1);
int rl=rs.getInt(2);
String yr=rs.getString(3);
String br=rs.getString(4);

%>

while retriving ROLL which is an integer ,its working fine.
but in case of BOOKID which is a string data,i am getting error like
sql statement not ended properly.
plz help me how to do this with string.
Is there anything other than getParameter() for retreiving strings.

[mtyoung]

why is 4 in ps.setString(4,bk);