Consider this example:
<% int testNumber = 1; %>
//Some HTML goes here
<%=testNumber%>
I get compile error:
testNumber cannot be resolved to a variable
Can someone explain what is going on?
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You are not importing int class.(java.lang.Integer). Writing Java code inside JSP is not a good way.vikiiii– vikiiii2012-05-01 16:25:21 +00:00Commented May 1, 2012 at 16:25
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@vikiiii If I do everything in a single pair of <% %> then it works. Amit Bhargava - That is the content of my test.jsp file.Eleeist– Eleeist2012-05-01 16:28:33 +00:00Commented May 1, 2012 at 16:28
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2 Answers
You need to make sure that you understand variable scoping. It's in scriptlets the same as in normal Java classes.
So if you actually have for example
<%
if (someCondition) {
int testNumber = 1;
}
%>
...
<%=testNumber%>
Then you will get exactly this error (also in a normal Java class!). To fix this, you'd need to make sure that the variable is declared in the very same scope, if necessary with a default value.
<%
int testNumber = 0;
if (someCondition) {
testNumber = 1;
}
%>
...
<%=testNumber%>
Unrelated to the concrete problem, using scriptlets is considered poor practice.
3 Comments
Eleeist
What if I need HTML to go between declaration and variable use?
BalusC
It should not matter. The point is that the variable needs to be declared in the same scope as where you need to access it. You've apparently declared the variable in a different and narrower scope (e.g. inside
if or for block, etc) while you're trying to access it from outside. It's not different from in a normal Java class. Using a normal Java class is only easier to understand and maintain the code.Eleeist
BalusC, thanks for the link. It contained a lot of useful info I had no idea about. In that case I will have to rewrite my code to remove all/most scriptlets.
Design problems aside, try declaring the variable as a global:
<%! int testNumber = 0; %>
2 Comments
Bogdan
This is a very bad idea! Instead of a local variable in the service method this gets placed as a member on the servlet class. Threads will mess this up on concurrent requests. Servlets are not thread safe so you will get into issues if you add state to a servlet instance.
Alexander Pavlov
I never said it was a good idea (and I also mentioned this in the foreword to the answer), just suggested an alternative solution for the particular problem in question, leaving it up to the OP to decide.