Q: Tomcat java.lang.IllegalStateException: Parameter count exceeded allowed maximum: 512

A: In most versions of Apache Tomcat, the maxParameterCount is defaulted to 10000, but in some versions
   it is defauled to 512. In the case of RHEL 6, the fix is set

   JAVA_OPTS="$JAVA_OPTS -Dorg.apache.tomcat.util.http.Parameters.MAX_COUNT=10000" 
   in tomcat6.conf.

   In other cases, the fix is to add maxParameterCount to the Connector: 

   <Connector port=... maxParameterCount="10000" />
   in server.xml