JSP radio button values gives java.lang.NullPointerException

Question

I have a form to which radio inputs are generated using js code. But when I try to submit the form, the selected value is not being sent to servlet and I am getting null pointer exception.

onMyPage.jsp

<form action="generate" method="post">
<%
for (Monitor mtr : maInfo.getMonitor()) {
    out.println("<input style=\"margin-left:20px\" type=\"radio\" name=\"monitor\" value=\""+mtr.getMonitorAbbr()+"\"/>"+mtr.getMonitorAbbr()+"<br>");
}
%>
<input type="submit" value="Submit" onclick="this.disabled=true"/>
</form>

On servlet.java

String variable = (String) request.getAttribute("monitor");

Error message:

java.lang.NullPointerException: Cannot invoke "Object.toString()" because the return value of "javax.servlet.http.HttpServletRequest.getAttribute(String)" is null

Instead of request.getAttribute("monitor") use request.getParameter("monitor"). — Swati
– Swati, Commented Jan 21, 2021 at 5:42

novice · Accepted Answer · 2021-01-22 22:08:22Z

0

Request.getAttribute() is basically used to get Request Header or field values in request. Attribute can be also be used to set some objects in Request scope. This helps in request forwards.

Request.getParameter() is used to retrieve form parameters of HTTP Request.

pls refer HTTPServletRequest documentation

edited Jan 22, 2021 at 22:08

answered Jan 22, 2021 at 11:15

novice

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