On Mon, 18 Mar 2002, Rich Baldwin wrote:
> Date: Mon, 18 Mar 2002 11:51:45 -0500
> From: Rich Baldwin <[EMAIL PROTECTED]>
> Reply-To: Tomcat Users List <[EMAIL PROTECTED]>
> To: Tomcat Users List <[EMAIL PROTECTED]>
> Subject: Adding a system property?
>
> I have a system property which I have added to my build.properties file
> and my build.xml
> file. Ant builds and deploys w/o any errors. However, my tomcat
> servlet cannot "find" this
> new system property. What is the trick here? There is nothing in my
> build.xml file to tell
> tomcat explicitly about this property, but how would I do that? Where
> can system properties be
> set in tomcat?
>
The "build.properties" file is only consulted when you *build* Tomcat, not
when you *run* it.
> To recap
> In build.properties
> metadata.xmlfile=project.xml
>
> In build.xml
> <property name="metadata.path"
> value="${catalina.home}/webapps/${app.name}/${metadata.xmlfile}"/>
>
To get system properties defined at Tomcat runtime, you will need to set
an environment variable -- either CATALINA_OPTS (Tomcat 4.x) or
TOMCAT_OPTS (Tomcat 3.3.x). For example:
CATALINA_OPTS=-Dmetadata.xmlfile=/path/to/the/file.xml
$CATALINA_HOME/bin/startup.sh
However, system properties are not the best way to provide configuration
information to servlets, because they are global to the entire container
and hard to manipulate. You should look at using <context-param> or
servlet initialization parameters inside the web.xml file to provide this
sort of configuration data.
If you want to do this kind of thing without modifying the web.xml file
(which would typically be the case if you're deploying the same webapp in
lots of different environments), here is an apporach that works in Tomcat
4 because it requires the JNDI namespace that Tomcat 4 provides:
* In your web.xml file, declare an <env-entry> element
for the configuration property, optionally with a default value:
<env-entry>
<env-entry-name>metadata.path</env-entry-name>
<env-entry-value>/default/path/to/metadata.xml</env-entry-value>
<env-entry-type>java.lang.String</env-entry-type>
</env-entry>
* In your server.xml file, add a <Context> element that defines
the actual value for *this* installation of the webapp:
<Context path="/mypath" ...>
<Environment name="metadata.path" type="java.lang.String"
value="/the/real/path/to/metadata.xml"/>
</Context>
* In your application, you grab the value you need like this:
IniitalContext ic = new InitialContext();
String metadataPath = (String) ic.lookup("java:comp/env/metadata.path");
(This is the javax.naming.InitialContext class from JNDI. The servlet
spec defines that all environment entries are in the "java:comp/env"
namespace.)
* This will pick up the default value (if nothing was set in server.xml)
or the override value (if you did set it).
The nice thing about this is that it doesn't mess up any other webapp that
might be using the same property name -- environment entries are
per-webapp instead of being global. It also requires zero changes to your
webapp itself (or its web.xml file) to customize behavior differently on
different installations.
> Thanks, Rich
>
Craig
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