idError » JAVA-JSP

IllegalStateException while using JSP

admin — Fri, 20 Mar 2009 10:28:59 +0000

Applies to:
NA

Description:
Signals that a method has been invoked at an illegal or inappropriate time. In other words, the Java environment or Java application is not in an appropriate state for the requested operation.

Cause:
a. The most common cause of this exception is a servlet or JSP attempting to write to the output stream after the response has been committed.
b. Another way this can happen is by attempting to redirect from within the middle of a JSP page:

…

hello world

<%
if ("not logged in")
response.sendRedirect("login.jsp");
%>

more stuff

…

c. Another common place where an IllegalStateException is likely to occur is in a JSP that attempts to stream binary data. JSPs are primarily designed to format output as HTML. With HTML, white space characters are ignored. It is not uncommon for JSP compilers to inject their own white space charaters to the beginning and/or end of the output stream. Line breaks in the developer’s code can also be interpreted as white space in the output stream. These white space characters can interfer with the generated servlet’s ability to create and stream the binary outputdata, resulting in the IllegalStateException.

Java Bean not found

admin — Fri, 20 Mar 2009 10:28:59 +0000

Applies to:
NA

Description:
A common problem which occurs when the class loader cannot find beans that the pages reference.That usually results in an error message like “Class xxx cannot be resolved to a type”

Cause:
The class loader could not find beans that the pages referenced.

EL Or JSTL Not Working As Expected

admin — Fri, 20 Mar 2009 10:28:59 +0000

Applies to:
NA

Description:
Occurs while using EL or JSTL in JSP.

Cause:
Configuration mismatch between the version of JSP that you are using, the version of the JSTL that you employ, and how you have declared your web application in the deployment descriptor (web.xml).

Resource Url Problems

admin — Fri, 20 Mar 2009 10:28:59 +0000

Applies to:
NA

Description:
A common issue is the problem where the external resources for a page, to include images, style sheets and script files, do not load.

Cause:
his problem is frequently caused by using page-relative URLs to these resources.
Within a static web site, the URL to HTML files is formed from the file path to that page. Within a dynamic web application, this is no longer the case; the URLs are usually formed from mappings within the deployment descriptor (web.xml).

Thus, a URL such as

http://some.server.com/command/doSomething

does not reference any particular folder on the file system. Rather, it is referencing a servlet mapped within the deployment descriptor.
When you forward to a JSP from this servlet, the URL remains the same and the browser has no way of knowing that the URL does not reference a folder. And it certainly has no way of knowing in which folder the JSP resides.
Thus, if you use page-relative URLs in the JSP, the browser tries to use the servlet mapping to resolve the path to the file, and of course, that fails.

UnsatisfiedLinkError: no jchli in java.library.path