Questions about JSP programming 2007-01-15 - By Xuekun Hu
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Thanks Rashmi, Zack, and Pid
Sorry it's my fault. <%@ include file="request.getParameter("f") %>
should not be compiled successfully. I fisrt tested <jsp:include
page../>, it works, TOMCAT translated and generated the .java and
.class file, then I just modified the same jsp file with <%@ ... %>,
TOMCAT compiled it failed. TOMCAT deleted the .java file, but kept the
.class. When I load tested the URL again, Some requests will get 500
error, while most are still get the right response!
Now I understood the two include difference. Thanks again.
Thx, Xuekun
On 1/15/07, Pid <p@(protected)> wrote:
> Firstly, all directives of the following form are executed at compile time:
>
> <%@ ... %>
>
> This means that URL request parameters are not available (yet) to the
> JSP. If the OP was using an include file directive containing the
> string 'request.getParameter("f")' it is unlikely that it ever worked as
> expected.
>
> The JSTL approach below is likely to work - though I can't think of a
> good or safe reason for allowing JSPs to load file system paths.
> (if you're on a unix-like system, try loading '/etc/passwd')
>
>
>
> Secondly, <jsp:include ... > operates at *request time* and may
> therefore be more pertinent to the case here. OP should google for 'JSP
> directive tutorials', the top result was enlightening when I checked.
>
>
>
> Lastly, the OP should report on which tool (if any) he was using to load
> test the URL. It may simply be the case (assuming the above error is
> corrected) that the excessive load caused the machine to run out of
> memory.
>
> The normal approach is to examine the logs to determine the source of
> the 500 error, the list will likely provide more advice on receipt of
> this information.
>
>
> p
>
>
>
> Rashmi Rubdi wrote:
> > Zack,
> >
> > I don't think it's the include directive alone causing a memory error. I'm
guessing that there might be a lot of processes in his application running on
Tomcat, eventually causing an out of memory error or may be the system does not
have minimum required memory to run Tomcat.
> >
> > With Tomcat 5.5, and about 2GB RAM I'm not getting an OutOfMemory error
while running 3 applications simultaneously on Tomcat, when I tried his example
of include directives, I got the error on the screen and it was logged in
Tomcat's logs as well.
> >
> > I ran my test as follows: http://practice:8080/p/test2/test2.jsp?f=page
.html , and test2.jsp had <%@ include file="request.getParameter("f")" %> (which
I believe won't work)
> >
> > Here's parts of the error, if it helps him:
> >
> > HTTP Status 500 -
> > type Exception report
> > message
> > description The server encountered an internal error () that prevented it
from fulfilling this request.
> > exception
> > org.apache.jasper.JasperException  : Unable to load class for JSP
> > org.apache.jasper.JspCompilationContext (JspCompilationContext.java
:598)
> > org.apache.jasper.servlet.JspServletWrapper (JspServletWrapper
.java:137)
> > org.apache.jasper.servlet.JspServletWrapper (JspServletWrapper.java
:305)
> > org.apache.jasper.servlet.JspServlet (JspServlet.java:314)
> > org.apache.jasper.servlet.JspServlet (JspServlet.java:264)
> > javax.servlet.http.HttpServlet (HttpServlet.java:802)
> > root cause
> > java.lang.ClassNotFoundException : org.apache.jsp.p.test2.test2_jsp
> > java.net.URLClassLoader $1.run(URLClassLoader.java:200)
> > java.security.AccessController (Native Method)
> > java.net.URLClassLoader (URLClassLoader.java:188)
> > org.apache.jasper.servlet.JasperLoader (JasperLoader.java:133)
> > org.apache.jasper.servlet.JasperLoader (JasperLoader.java:65)
> > org.apache.jasper.JspCompilationContext (JspCompilationContext.java
:596)
> > org.apache.jasper.servlet.JspServletWrapper (JspServletWrapper
.java:137)
> > org.apache.jasper.servlet.JspServletWrapper (JspServletWrapper.java
:305)
> > org.apache.jasper.servlet.JspServlet (JspServlet.java:314)
> > org.apache.jasper.servlet.JspServlet (JspServlet.java:264)
> > javax.servlet.http.HttpServlet (HttpServlet.java:802)
> >
> >
> > Also, if he sets up JSTL1.1 correctly, the following will also work:
> >
> > <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
> > <c:import url="${param.f}"/>
> >
> > Where param.f , is the equivalent of request.getParameter("f")
> >
> > -Rashmi
> >
> >
> > Rashmi,
> >
> > I'm curious as to why his second approach causes the memory error that
> > he gets, would you have any insight as to why it's happening? I've
> > checked out the docs and they don't indicate anything about the way the
> > include directive uses memory. I'm thinking we might actually have a
> > bug to report.
> >
> > Zack
> >
> >
> >
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