Certain values are lost or altered upon submitting a large form

Issue

• For very long forms, some input values may be unexpectedly lost or modified after submission.
• Some fields are submitted correctly, but from a certain point onwards, they start persisting with incorrect values (usually the default value, unless it's a calculated field).

Environment

• Any Liferay DXP version
• Tomcat

Resolution

• The most probable cause is that you have reached the maxParameterCount limit (see doc) for your Connector:

  The maximum total number of request parameters (including uploaded files) obtained from the query string and,
  for POST requests, the request body if the content type is application/x-www-form-urlencoded or multipart/form-data.
  Request parameters beyond this limit will be ignored.

• If you have activate Tomcat logging, you would observe messages like this:

  org.apache.tomcat.util.http.Parameters processParameters
  INFO: More than the maximum number of request parameters (GET plus POST) for a single request ([1,000]) were detected. 
  Any parameters beyond this limit have been ignored. 
  To change this limit, set the maxParameterCount attribute on the Connector.​​​

• To fix this issue, you'll need to modify the server.xml file and increase the value of the maxParameterCount attribute of your Connector. For instance, if the current value is 1000, you can try setting it to 2000:

  <Connector port="8080" protocol="HTTP/1.1"
             redirectPort="8443"
             maxParameterCount="2000"
             />

Additional Information

• Tomcat has changed this behavior starting from version 11 (see doc), so it will be easy to notice it:

  Requests that exceed this limit will be rejected.