Tomcat and Environment Entries

Adding Environment Entries

Normally, in web.xml, you can add the following environment entries:

<env-entry>
  <env-entry-name>maxExemptions</env-entry-name>
  <env-entry-value>10</env-entry-value>
  <env-entry-type>java.lang.Integer</env-entry-type>
</env-entry>

However, Tomcat has a better way of doing it, thereby providing an opportunity to have different values in a different environment without modifying the deployment descriptor.

This is called context.xml, which can be placed under META-INF\ or under conf\Catalina\localhost\

Here is an example:

<Context>
  ...
  <Environment name="maxExemptions" value="10"
         type="java.lang.Integer" override="false"/>
  ...
</Context>

Reading Environment Entries

Environment Entries are relative to java:comp/env:

Reading one property

Context ctx = new InitialContext();
String url = (String) ctx.lookup("java:comp/env/url");

Reading all properties

for (Enumeration<Binding> e = ctx.listBindings("java:comp/env"); e.hasMoreElements();) {
                Binding bind = e.nextElement();
                System.out.println(bind.getName() + " : " + bind.getObject());
            }

Example

Clone the sample project and execute the following command:

mvn clean package docker:build docker:run

Note: Make sure Docker is installed beforehand.

Here is the output: