Question

Environment: Java (Java EE), Tomcat container

At work the vast majority of our apps run in a Glassfish-container and (as typical) we have a lot of properties externalized from our apps and injected into our Glassfish-environment via the use of an app.properties file where Glassfish then exposes them to our app by making a standard system call something like this:

System.getProperty( "myProp" );

We have one particular app, however, than was deployed on a Tomcat-container (and due to the large bureaucracy here, that’s not going to change anytime soon); the original author also didn’t invest the time to research how to do a similar property-externalization using Tomcat as what is done with Glassfish. The result is that there are several things in this app where you have to comment-out some lines of code when you deploy it to our test-server and comment-out different lines of code when you deploy it to our production-server. A real pain, and potential-cause of trouble.

So I’m trying to fix that.
From my research it seems that the way to do this in Tomcat is via Tomcat’s server.xml file, something like this:

 <Environment name="myProp" type="java.lang.String" value="This is my value"/>

Then, from what I’ve read here, accessing ‘myProp’ should be the same thing as accessing an <env-entry> in the web.xml, so image I have an entry like this:

 <env-entry>
        <env-entry-name>myOtherProp</env-entry-name>
        <env-entry-type>java.lang.String</env-entry-type>
        <env-entry-value>This is my other value</env-entry-value>
  </env-entry>

Then I have implemented the following code in my Spring#handleRequestInternal():

Context ctx = new InitialContext();

String myProp = "<not found>";
try {
      myProp = (String) ctx.lookup( "java:comp/env/myProp" );  // from Tomcat's server.xml
} catch( Exception e ) { ... }

String myOtherProp = "<not found>";
try {
      myOtherProp = (String) ctx.lookup( "java:comp/env/myOtherProp" ); // from web.xml
} catch( Exception e ) { ... }

Yet when I log ‘myProp’ and ‘myOtherProp’, the one from my web.xml returns the correct value while the one from Tomcat’s server.xml is not found (caught by the try/catch).

What gives?
How do I set an environment-variable outside of my app via the Tomcat-container and retrieve it from within my app?

Answer 1

Instead of putting this in server.xml it belongs in the Context.xml file for the servlet containter you’re configuring. See the tomcat Context configuration webpage. For more details.