> can i store large vectors in session
you can store any object in the session. The size is only limited by the amount of memory assigned to java.
> how to retrieve vectors from servlet in my jsp
Store the vectors in the request using request.setAttribute():
request.setAttribute("myvector", vector);
Forward to the JSP and in the JSP you can do this:
<c:forEach items="${requestScope.myvector}" var="current">
${current}
</c:forEach>