NullPointerException in itextpdf during Form flattening with Acrofields

Question

I have a six page PDF with some acrofields on each page. I have deleted page 4 and 5 using following code :

List<Integer> pagesToKeep = Arrays.asList(new int[]{ 1, 2, 3 });
pdfReader.selectPages(pagesToKeep);

But then on Form freezing using following command :

 pdfStamper.setFreeTextFlattening(true);
     pdfStamper.close();

I am getting NullPointerException. Reason for this : On Form Flattening , Acro Fields defined on pages are unable to locate the page number, as Page 6 does not exists any more.

Exception Trace :

java.lang.NullPointerException
    at com.itextpdf.text.pdf.PdfStamperImp.flatFields(PdfStamperImp.java:1019)
    at com.itextpdf.text.pdf.PdfStamperImp.close(PdfStamperImp.java:227)
    at com.itextpdf.text.pdf.PdfStamper.close(PdfStamper.java:231)
    at com.ally.bankapi.service.impl.DocumentServiceImpl.generateDocument(DocumentServiceImpl.java:1272)
    at com.ally.bankapi.service.impl.DocumentServiceImplTest.testGenerateDocumentSuccess(DocumentServiceImplTest.java:111)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
    at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
    at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl.run(JUnit45AndHigherRunnerImpl.java:37)
    at org.mockito.runners.MockitoJUnitRunner.run(MockitoJUnitRunner.java:62)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

Answer 1

I got a workaround it , instead of removing the pages from current PDF, copy the selected pages in new PDF using PdfCopy as shown in below comment : – Narendra Apr 6 '16 at 18:18

pdfStamper.setFormFlattening(true);
pdfStamper.close();
pdfReader.close();
//Create a new pdfReader which reads the existing baos
pdfReader = new PdfReader(baos.toByteArray());
Document document = new com.itextpdf.text.Document();
PdfCopy copy = null;
ByteArrayOutputStream copyBaos = new ByteArrayOutputStream();
//Create Copy of the same.
copy = new PdfCopy(document, copyBaos);
document.open();
// Keep only selected pages
copy.addDocument(pdfReader, pagesToKeep);