An "OOM" error can happen if you have not allocated enough memory for the JVM that runs Tomcat. Tomcat isn't the world's fattest server by far, but when you're running with advanced libraries like Spring, it's a good idea to have at least 512MB available.
Create a file in your CATALINA_BASE/bin directory named "setenv.sh" (or, if you're running Windows, "setenv.bat"). It should contain the following line:
If you still get an OOM exception, make Xmx bigger.
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