code: protected boolean trigger(final ServletRequest pRequest) {
          // If triggerParams not set, assume always trigger
          if (triggerParams == null) {
              return true;
          }
  
          // Trigger only for certain request parameters
          for (String triggerParam : triggerParams) {
              if (pRequest.getParameter(triggerParam) != null) {
                  return true;
              }
          }
  
          // Didn't trigger
          return false;
      }
docs: Tests if the filter should do image filtering/processing.
  <P/>
  This default implementation uses {@link #triggerParams} to test if:
  <dl>
  <dt>{@code mTriggerParams == null}</dt>
  <dd>{@code return true}</dd>
  <dt>{@code mTriggerParams != null}, loop through parameters, and test
  if {@code pRequest} contains the parameter. If match</dt>
  <dd>{@code return true}</dd>
  <dt>Otherwise</dt>
  <dd>{@code return false}</dd>
  </dl>
  
  
  @param pRequest the servlet request
  @return {@code true} if the filter should do image filtering