For input string: ""

-- 에러메시지

exception

org.apache.jasper.JasperException: For input string: ""
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:372)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

root cause

java.lang.NumberFormatException: For input string: ""
	java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
	java.lang.Integer.parseInt(Integer.java:489)
	java.lang.Integer.parseInt(Integer.java:518)
	org.apache.jsp.bulletin.poll.poll_005flist_jsp._jspService(poll_005flist_jsp.java:108)
	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

note The full stack trace of the root cause is available in the Apache Tomcat/5.0.30 logs.

String 변수에 숫자형태가 아닌 null 이나 "" 값이 할당 되어있어서 그런거 같습니다.
그부분을 예방하는 차원에서
다음과 같은 차원의 소스코드를 추가하세요.

String str = request.getParameter("str");
if(str == null || str.trim().equals("")){
str = "0";
}