ServletContextListener execution order for different wars

Question

Is it possible to control order of ServletContextListener execution in different wars?

Suppose there are 3 separate, independent modules A, B, and C in a web service. They can be initialized in any order, and there is no consequences. However, if an optional module D is present, it needs to be initialized first and may impact other modules. Is this configuration possible through Spring? Only thing that comes to mind is having a global ServletContextListener that polls if an init class for every module exists on class path but that solution seems pretty messy.

Answer 1

Managing the startup of applications can be done when they all WAR's are bundled in EAR. It can done by adding <initialize-in-order>true</initialize-in-order> in application.xmkl.

If all WAR's are independent then there is no standard way of doing it. But, there are container specific features that allow you to do that.

References:

• WebsphereManages Startup
• Tomcat Startup ordering

If you want to define dependency between the servlet's of an application. You can define Absolute ordering in web.xml or relative ordering in web-fragment.xml.

Here is how absolute ordering works:

<web-app>
...
    <absolute-ordering>
      <name>A</name>
      <others/>
      <name>B</name>
    <absolute-ordering>
</web-app> 

If there is no absolute ordering in web.xml, the container will look for relative ordering in web-fragment.xml. It looks something like this:

<ordering>
    <before>
    <others />
    </before>
</ordering>