I use this OATS OpenScript technique for several advanced script control needs. This example only shows how to stop the "content length is zero" error, though this can be used as a template for any advanced control of virtual users.

MyHTTPService.java

package yourcompanyname.oats.scripting.modules.http.api;
 
import oracle.oats.scripting.modules.basic.api.exceptions.AbstractScriptException;
import oracle.oats.scripting.modules.http.api.HTTPService;
import oracle.oats.scripting.modules.http.api.HTTPService.EncodeOptions;
 
public class MyHTTPService extends HTTPService 
{
   private IteratingVUser m_vu = null;

   public MyHTTPService() 
   {
      super();
   }

   /**
    * @see oracle.oats.scripting.modules.basic.api.IVUserProvider#setCurrentVUser(oracle.oats.scripting.modules.basic.api.IteratingVUser)
    */
   @Override public void setCurrentVUser(IteratingVUser vu) 
   {
      super.setCurrentVUser(vu);
      
      /* Consider this work around to stop those warning while running in OATS OLT Tester
      */
      List<IValidator> httpValidators = this.getValidatorList();
         
      for (int i = 0; i < httpValidators.size();  i++)
      {
         IValidator httpValidator = httpValidators.get(i);
         if (httpValidator != null && 
               httpValidator.getClass().getName().contains("ZeroLengthContentValidator"))
         {
            removeValidator(httpValidator);
            break;
         }
      }


....

Use this OATS OpenScript technique for several advanced script control needs. In your script, change this:

@ScriptService oracle.oats.scripting.modules.http.api.HTTPService http; 

To this:

@ScriptService yourcompanyname.oats.scripting.modules.http.api.MyHTTPService http;

Then add the above Gist MyHTTPService.java to your OATS OpenScript project