<nonpublicExecutionReport xmlns="http://www.fpml.org/FpML-5/recordkeeping" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<header>
  <messageId> 1256399</messageId> 
</header>
<isCorrection>false</isCorrection> 
……..

Document document = DocumentHelper.createDocument();
Namespace xmlns =DocumentHelper.createNamespace("", http://www.fpml.org/FpML-5/recordkeeping");	
Namespace xsi=DocumentHelper.createNamespace("xsi", "http://www.w3.org/2001/XMLSchema-instance");
Element nonpublicExecutionReport = document.addElement( "nonpublicExecutionReport" ); 
    
nonpublicExecutionReport.clearContent();     
nonpublicExecutionReport.add(xmlns);
nonpublicExecutionReport.add(xsi);  

Element header = nonpublicExecutionReport.addElement( "header" );
Element messageId = header.addElement("messageId");
messageId.addText( GetMessageId() );
nonpublicExecutionReport.addElement("isCorrection").setText(isCorrection);  	

<nonpublicExecutionReport xmlns="http://www.fpml.org/FpML-5/recordkeeping" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<header xmlns="">
  <messageId>1256399</messageId> 
</header>
<isCorrection xmlns="">false</isCorrection>