Programmatically Modifying a File in Deployed war

Question

I am new to OAS, so excuse me if this is a stupid question.
We are deploying a custom application that provides access to 3rd party software. To that end, we include the 3rd party JAR file in our WAR file.
This 3rd party software requires a certain file be available in the CLASSPATH. Hence, we have this file in the WEB-INF\classes directory. This file contains configuration parameters that the 3rd party software uses.
However, we also have a requirement that our end users need to be able to modify these parameters to cause the 3rd party software to operate differently. So, what I'd like to do is build a UI for our users that allows them to modify the parameters that are stored in this file and then updates the file which is inside the war (in WEB-INF\classes).
Is it possible to do this in OAS? Does OAS provide any API that can be called from a class inside the war file to update another file in that same war file?
It is not permissible for us to store this configuration file anywhere else, like on a file server. Our end client forbids this. So that is why I am seeking to update the file inside the war.
Thanks.

Answer 1

Let us call the file in your problem "the configuration file". If I understand correctly, the crux of the problem is to get hold of the configuration file programmatically after the deployment of the containing war file. You can then provide some mechanism for your client to manipulate it.
An HttpServlet can be employed to do that. Suppose the web application has an index.html at the top level of the war file. Suppose that after the war has been deployed, that index.html can be accessed by, as usual, http://host:port/myServeletContext/index.html. Then you can get the location of the configuration file by
  String fileLocation = "WEB-INF" + File.separator + "classes" + File.separator + "configurationFile";
  File  indexFile = new File(getServletContext().getRealPath("/index.html"));
  File webRoot = indexFile.getParentFile();
  File configFile = new File(webRoot, fileLocation);This is a common trick to get the path to a file in WEB-INF directory. Hope this helps.