Resolving the root of a webapp from getResource

Question

I have a file structure like this in my webapp:

webapp/
├── META-INF
└── WEB-INF
    ├── reports
    │   └── info.txt
    └── web.xml

3 directories, 2 files

I need to get /WEB-INF/reports/info.txt from a class like so:

this.getClass().getResource("/WEB-INF/reports/info.txt");

Will this resolve? I'm going to test it, but I'm not sure how Tomcat's classloader resolves things. If this doesn't work, how can I get the file?

Solution 1

Well, first of all, this.getClass().getResource should not work (though I didn't try). It's not a classpath, it's a ServletContext, so you need to use ServletContext.getResource.

Problem is, it is not necessary a file: it can be an entry in a WAR archive. So depending on what exactly you know, the answer may be different.

We use a Spring utility class which handles both files (via ServletContext.getResourcePaths if available) and WARs (via ServletContext.getResource). If you use Spring, that may be the best way. If you don't, you'll probably need to re-implement the solution.

Alternatively, you cal simply use ServletContext.getResourceAsStream—it doesn't care where exactly the resource is stored. So as long as you need its content and not the path, you should be fine.

Solution 2

No, it won't resolve. Class.getResource loads resources from the classpath, and the webapp's root directory is not itself on the classpath.

In order to get hold of that resource, you'll need to get hold of the ServletContext, on which you can then call ServletContext.getResource("/WEB-INF/reports/info.txt"). That should work.

You can obtain the ServletContext using Servlet.getServletConfig().getServletContext().

Alternatively, move your reports directory under the /WEB-INF/classes directory (which is on the classpath). You can then get your file using

getClass().getResource("reports/info.txt");

Comments

[Naftuli Kay]

Yeah, so the thing is that I need this to work inside of and outside of a servlet container. I need a pretty standard API which will let me get a given path whether I'm in Tomcat or in Eclipse's jUnit classpath. What's this API you're using? I'm using Spring 3.

[alf]

If you need it outside the container, keep resources in the classpath, and do not touch the Servlet API.

[Naftuli Kay]

Using Spring's ResourceLoader/ApplicationContext to load files. Awesomeness :)