HTTP Error 404 on Your Java Web App?

Somebody in the JUG-ID mailing list was asking where does this HTTP Error 404 comes from? He has successfully run the application before, but now get this error when hitting the page.

For me, I would run through these diagnostic process:

1. Because the browser returned error HTTP status 404, means that the application server is there serving the HTTP request; make sure that the application server serving there is the Tomcat/JBoss/WebLogic/WebSphere that you intended to get the data from; typical mistakes would be that you are trying to get the data from your application server, ended up that you hit an Oracle XE web console running on the same port, or you are hitting something else other than what you intended to.


2. Check whether your application has been deployed. The error could come because your application actually has not been deployed to the application server. Use Tomcat Manager for Apache Tomcat, use WebLogic console, or Glassfish console, or whatever console your application server provides.


3. Check whether there are some failure in the deployment process. This time you or your IDE deployed the application, yet there are some failure that causes the deployment to stop. It is typical for example, on finding error on your Spring context configuration or your Hibernate context configuration, your application will cease to deploy. It is also common when you have something wrong in your web.xml file, the application server will refuse to deploy. Check what error you get from your console and application server's log.


4. And if you find out that the application has been successfully deployed, check whether the URL is actually available: check whether your web application uses filter (check the web.xml file), and check whether the JSP file exists (if it hits the JSP file directly), or check whether the action request is configured property (in action based MVC framework such as Struts1.x, WebWork, Struts2, Spring MVC, etc).

Better luck next time.