Maven: Including a META-INF folder in the classes folder

Question

I have a very simple WAR project and I want to include a directory named META-INF at the top of the classes output folder where all the compiled Java classes are. I'm using Maven, but it seems that by default Maven won't include anything that is not a Java class. So it ignores my META-INF directory that is sitting at the top of the src directory. The META-INF directory contains a file named persistence.xml. Any quick pointers on how to instruct Maven to put this directory and file into the output folder?

Answer 1

In general, for a Java-based Maven project, non-source files should go in the src/main/resources sub-directory of the project. The contents of that resources directory are copied to the output directory (by default, target/classes) during the process-resources phase of the build.

For Maven WAR projects, it is slightly more complicated: there is also the src/main/webapp directory, wherein Maven expects to find WEB-INF/web.xml. To build your WAR file, that file must exist; otherwise, you'll see an error message like this:

[INFO] ------------------------------------------------------------------------
[ERROR] BUILD ERROR
[INFO] ------------------------------------------------------------------------
[INFO] Error assembling WAR: webxml attribute is required (or pre-existing WEB-INF/web.xml if executing in update mode)

As the WEB-INF directory must exist under src/main/webapp, I'd recommend avoiding defining it again in src/main/resources. Although this is perfectly valid and the contents of the two directories will be merged, it can get confusing if a file is defined in both. The contents of src/main/resources will take precedence as they are copied over the top of the contents from src/main/webapp.