从JSP用Javascript发布表单

Question

Question level : Intermediate / Beginner

I created a form with

`method="post" action="eh.do" onsubmit="return Form1_Validator(this)"`

The validation is successful and works fine when I hit submit.

But on the servlet, I have a concatenate function to merge the values together.

When the Javascript is turned on, ie when I write onsubmit="return Form1_Validator(this)" it shows:

java.lang.NullPointerException
    java.lang.String.concat(Unknown Source)
    EditHelper.doPost(EditHelper.java:27)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)

But once the Javascript is disabled ie I delete out onsubmit="return Form1_Validator(this)" , it works fine.

If all conditions are true, my script returns

return (true);

Is this the problem?

I tried return(theForm); but the problem remains the same!

Answer 1

I'd use Firebug to see how the form submit request parameters change if you add your onsubmit handler. I guess your javascript code is somehow influencing those parameters and once you see what happens, it might become obvious why this is.