JSP：为什么在EL变量中得到0而不是null？

Question

In servlet I do:

request.setAttribute("field-message", "Message");

In JSP I do:

<p>${field-message}</p>

I see 0 instead of "Message" in result HTML file.

What should I do to get "Message" shown there?

Answer 1

<p>${field-message}</p>

This is the difference between two attributes: "field" and "message". Both are nulls, so the difference is zero...

Either you choose another name for your attribute, or you use the construct <p>${requestScope['field-message']}</p>