在tomcat 5.x上运行的jsp页面中的getParameter文本字段返回null

Question

I am getting a weird error of page constantly fluctuating between nullpointerexception to actual execution on every form submit. I am writing a simple jsp page and running it on tomcat 5.x server. I am taking data from text field of a form and processing it upon form submit. Here is the code I am trying:

form id="mainForm" method=POST action="index.jsp">

<input type="text" name="reportName" size=20> 



<a class="btnBlue btnBlueRight" href="#" onclick="document.getElementById('mainForm').submit();" > 

            <% 
            if(request.getParameter("reportName")!=null){
            //do things
            else
            //print message
            %>

for this code, page address in address bar is localhost:8080/# or localhost:8080/index.jsp for every form submit. I am new to jsp so could not resolve this.

Answer 1

It's because the reportName does not set any where for the first time page load! eg try to navigate

localhost:8080/index.jsp?reportName=all