config.getInitParameter() still returning null

[Michael . Murphy]

The config.getInitParameter() called from within a JSP page is returning null. After changing the web.xml file numerous times and trying all the suggestions from java.sun.com and the tomcat archives I still cannot resolve this problem.
Does anyone know why we can't access the init parameters?
thanks in advance

Here is what my web.xml file looks like (does not work):

web-app
  servlet
servlet-name
 Error
/servlet-name
servlet-class
  org.apache.jasper.runtime.JspServlet
/servlet-class
init-param
  param-namedebug/param-name
  param-valuetrue/param-value
/init-param
  /servlet
/web-app

and my JSP code:
%
String s = config.getInitParameter(debug);
if (s == null) {
out.println(Init param must be null!);
}
else{
out.println(Init param is +s);
}
%

Re: config.getInitParameter() still returning null

[Michael . Murphy]

Just to clear up what i'm trying to do:
not having any problems getting init parameters using servlets, the following code in web.xml will achieve that:

servlet
servlet-nameMyServlet/servlet-name
servlet-classMyServlet/servlet-class
init-param
param-namedebug/param-name
param-valuetrue/param-value
/init-param
/servlet

The problem is accessing init-params exclusively in JSPs without any servlets at all. In theory this should be possible as a JSP is a servlet but it's proving very difficult to do this.

Right now i'm working on a background servlet for the JSP to make these init-params possible. I'll post solution when it's done.






Bo Xu [EMAIL PROTECTED]
03/08/01 10:09 AM
Please respond to tomcat-user


To:[EMAIL PROTECTED]
cc:
Subject:Re: config.getInitParameter() still returning null


Milt Epstein wrote:

 [ ... ]

 I could be wrong, but I don't believe you have to define
 servlet-mapping's to get init-param's to work, just having defined the
 servlet is sufficient. However, in the URL, you do need to use the
 specific servlet-name you used in the servlet definition. (That's
 because you can define the same servlet class multiple times, with
 different servlet-name's and different init-param's.)

 So, according to the above web.xml, the URL that should be used is:

 http://your.domain.com/yourwebappname/servlet/Error
 [...]

thanks for your email :-) and now I find mistake in my last email,
the following is my new understanding about Servlet(not JSP) with
jakarta-tomcat-4.0-b1 :

0 if we don't define any named servlet definition
  in webapps/myapp/WEB-INF/web.xml, then we can invoke
  MyServlet with the following way:
  http://localhost:8080/myapp/servlet/MyServlet
  it will invoke the default/non-named servlet definition

1 if we define the following in webapps/myapp/WEB-INF/web.xml:
   ...
   servlet-nameMyServlet_sn /servlet-name
   ...
  then we Also can invoke this servlet definition with this servlet-name:
  http://localhost:8080/myapp/servlet/MyServlet_sn

2 if we also define a servlet-mapping:
  servlet-mapping
   servlet-nameMyServlet_sn /servlet-name
url-pattern /MyServlet_up/url-pattern
  /servlet-mapping
  then we Also can invoke this servlet definition with this url-pattern:
  http://localhost:8080/myapp/MyServlet_up

  and 1 and 2 will invoke the same named servlet definition whose
  name is MyServlet_sn.

3 from a email in List.this ^_^ , I find:
  if we directly use MyServlet as the servlet-name, and we invoke
  with the following way:
  http://localhost:8080/myapp/servlet/MyServlet
  we will goto that named servlet definition whose name is
  MyServlet- we will Not goto that default/non-named
  servlet definition.

hope the above is right, otherwise I need to correct my
experience notebook Again :-) or I need to use a pencial
instead of a pen? :-)


Bo
Mar.08, 2001



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solved-Re: config.getInitParameter() still returning null

[Michael . Murphy]

OK this is how to get init-params working for JSP

Include this in your web.xml file

web-app
context-param
param-name
 foo
/param-name
param-value
 bar
/param-value
/context-param
/web-app

And then in your JSP page:

String s = application.getInitParameter(foo);








Milt Epstein [EMAIL PROTECTED]
03/08/01 08:00 AM
Please respond to tomcat-user


To:[EMAIL PROTECTED]
cc:
Subject:Re: config.getInitParameter() still returning null


On Thu, 8 Mar 2001, Bo Xu wrote:

 [EMAIL PROTECTED] wrote:
 
  The config.getInitParameter() called from within a JSP page is
  returning null. After changing the web.xml file numerous times and
  trying all the suggestions from java.sun.com and the tomcat archives I
  still cannot resolve this problem.
  Does anyone know why we can't access the init parameters?
  thanks in advance
 
  Here is what my web.xml file looks like (does not work):
 
  web-app
servlet
  servlet-name
   Error
  /servlet-name
  servlet-class
org.apache.jasper.runtime.JspServlet
  /servlet-class
  init-param
param-namedebug/param-name
param-valuetrue/param-value
  /init-param
/servlet
  /web-app
 
  and my JSP code:
  %
  String s = config.getInitParameter(debug);
  if (s == null) {
  out.println(Init param must be null!);
  }
  else{
  out.println(Init param is +s);
  }
  %
 
 Hi :-) I didn't ever use jsp to get init parameters, but I guess
 the reasons is: in your WEB_INF/web.xml, you only define
 a servlet definition with some init parameters, but you didn't
 define a servlet-mapping; and/so I guess you invoked your
 servlet without url-pattern(servlet-mapping name) - I guess
 you use: http://localhost:8080/myapp/servlet/Myservlet ,
 so if you use Servlet, the following will return null:
 - config.getInitParameter(...)
 - this.getInitParameter(...)
[ ... ]

I could be wrong, but I don't believe you have to define
servlet-mapping's to get init-param's to work, just having defined the
servlet is sufficient. However, in the URL, you do need to use the
specific servlet-name you used in the servlet definition. (That's
because you can define the same servlet class multiple times, with
different servlet-name's and different init-param's.)

So, according to the above web.xml, the URL that should be used is:

http://your.domain.com/yourwebappname/servlet/Error

(No, I haven't tested this.)

However, I just noticed that the original poster said that this is all
happening in a JSP (JSP page is redundant :-) -- that throws a
monkey wrench into the situation, and I'm not sure how it changes
things. For example, I don't know how to set up init-param's in a
JSP. Also, upon re-reading the above servlet definition, I'm not sure
that's the right way to set up a JSP -- i.e. putting
org.apache.jasper.runtime.JspServlet as the servlet-class (I assume
that's the tomcat/jasper servlet that handles JSP's). I think you
want to name your JSP something.jsp, and just tell tomcat somewhere
that it's a JSP. But again, I'm not sure how you'd set up
init-param's for it (maybe you do have to fallback on the suggestion
to use context init-param's, instead of servlet init-param's).

Well, I think I may have just raised more confusion, but perhaps this
will lead to some helpful discussion/ideas, and/or someone will post
clearing things up.

...

Hold on. I decided to do a google newsgroup search on this, to see if
I can get more definite information, and looks like I found the
answers. Check out the following posts:

http://groups.google.com/groups?q=init-param+jsphl=enlr=safe=offrnum=1seld=964886773ic=1
http://groups.google.com/groups?hl=enlr=safe=offth=9eb4e0cd3b0f1fb6rnum=9seld=958627636ic=1

Actually, I don't know if these URLs will work outside the context of
my search -- if not, go to the google advanced newsgroups search page
at:

http://groups.google.com/advanced_group_search

and enter init-param jsp in the with all of the words box (without
the quotes) and hanna in the Author box (again, without the
quotes).

Basically, it looks like a servlet definition can specify *either*
servlet-class or a jsp-file (those are the actual names of the tags
used in web.xml). Note the warnings about what form of URL to use
when you set things up this way, though.

Milt Epstein
Research Programmer
Software/Systems Development Group
Computing and Communications Services Office (CCSO)
University of Illinois at Urbana-Champaign (UIUC)
[EMAIL PROTECTED]


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