Attach file to Pdf/A-3B test case

AttachFileToPdfA3BTest

package itext.playground;

import static com.itextpdf.text.pdf.AFRelationshipValue.Alternative;
import static com.itextpdf.text.pdf.PdfName.AFRELATIONSHIP;
import static com.itextpdf.text.pdf.PdfName.MODDATE;
import static com.itextpdf.text.pdf.PdfName.PARAMS;
import static org.junit.Assert.assertNotNull;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

import org.junit.Before;
import org.junit.Test;

import com.itextpdf.text.DocumentException;
import com.itextpdf.text.pdf.PdfAConformanceLevel;
import com.itextpdf.text.pdf.PdfAStamper;
import com.itextpdf.text.pdf.PdfDate;
import com.itextpdf.text.pdf.PdfDictionary;
import com.itextpdf.text.pdf.PdfFileSpecification;
import com.itextpdf.text.pdf.PdfName;
import com.itextpdf.text.pdf.PdfReader;

public class TestCaseForSo {
   
   byte[] content;
   InputStream inPdf;
   
   @Before
   public void setup(){
      content = "<xml>This is a simle text attachment in </xml>".getBytes();
      inPdf = getClass().getResourceAsStream("/Existing_PDFA3.pdf");
   }

   @Test
   public void append() throws IOException, DocumentException {

     ByteArrayOutputStream result = new ByteArrayOutputStream(16000);
     PdfReader reader = new PdfReader(inPdf);
     PdfAStamper stamper = new PdfAStamper(reader, result, PdfAConformanceLevel.PDF_A_3B);

     stamper.createXmpMetadata();

     // Creating PDF/A-3 compliant attachment.
     PdfDictionary embeddedFileParams = new PdfDictionary();
     embeddedFileParams.put(PARAMS, new PdfName("ZF_NAME"));
     embeddedFileParams.put(MODDATE, new PdfDate());
     PdfFileSpecification fs = PdfFileSpecification.fileEmbedded(stamper.getWriter(), null,"ZF_NAME", content , "text/xml", embeddedFileParams,0);
     fs.put(AFRELATIONSHIP, Alternative);
     stamper.addFileAttachment("file description",fs);

     stamper.close();
     reader.close();
     
     assertNotNull(result.toByteArray());
   }
   
}