Do not fail if the appearance dictionary doesn't contain N entry.

DEVSIX-2902

Author: ars18wrw

forms/src/main/java/com/itextpdf/forms/PdfAcroForm.java

@@ -676,51 +676,56 @@ public void flattenFields() {
                     appDic = fieldObject.getAsDictionary(PdfName.AP);
                 }
             }
-            if (appDic != null) {
+            if (null != appDic) {
                 PdfObject normal = appDic.get(PdfName.N);
-                PdfFormXObject xObject = null;
-                if (normal.isStream()) {
-                    xObject = new PdfFormXObject((PdfStream) normal);
-                } else if (normal.isDictionary()) {
-                    PdfName as = fieldObject.getAsName(PdfName.AS);
-                    if (((PdfDictionary) normal).getAsStream(as) != null) {
-                        xObject = new PdfFormXObject(((PdfDictionary) normal).getAsStream(as));
-                        xObject.makeIndirect(document);
+                if (null == normal) {
+                    Logger logger = LoggerFactory.getLogger(PdfAcroForm.class);
+                    logger.error(LogMessageConstant.N_ENTRY_IS_REQUIRED_FOR_APPEARANCE_DICTIONARY);
+                } else {
+                    PdfFormXObject xObject = null;
+                    if (normal.isStream()) {
+                        xObject = new PdfFormXObject((PdfStream) normal);
+                    } else if (normal.isDictionary()) {
+                        PdfName as = fieldObject.getAsName(PdfName.AS);
+                        if (((PdfDictionary) normal).getAsStream(as) != null) {
+                            xObject = new PdfFormXObject(((PdfDictionary) normal).getAsStream(as));
+                            xObject.makeIndirect(document);
+                        }
                     }
-                }
 
-                if (xObject != null) {
-                    //subtype is required field for FormXObject, but can be omitted in normal appearance.
-                    xObject.put(PdfName.Subtype, PdfName.Form);
-                    Rectangle annotBBox = fieldObject.getAsRectangle(PdfName.Rect);
-                    if (page.isFlushed()) {
-                        throw new PdfException(PdfException.PageAlreadyFlushedUseAddFieldAppearanceToPageMethodBeforePageFlushing);
-                    }
-                    PdfCanvas canvas = new PdfCanvas(page, !wrappedPages.contains(page));
-                    wrappedPages.add(page);
-
-                    // Here we avoid circular reference which might occur when page resources and the appearance xObject's
-                    // resources are the same object
-                    PdfObject xObjectResources = xObject.getPdfObject().get(PdfName.Resources);
-                    PdfObject pageResources = page.getResources().getPdfObject();
-                    if (xObjectResources != null && pageResources != null &&
-                            xObjectResources == pageResources) {
-                        xObject.getPdfObject().put(PdfName.Resources, initialPageResourceClones.get(document.getPageNumber(page)));
-                    }
+                    if (xObject != null) {
+                        //subtype is required field for FormXObject, but can be omitted in normal appearance.
+                        xObject.put(PdfName.Subtype, PdfName.Form);
+                        Rectangle annotBBox = fieldObject.getAsRectangle(PdfName.Rect);
+                        if (page.isFlushed()) {
+                            throw new PdfException(PdfException.PageAlreadyFlushedUseAddFieldAppearanceToPageMethodBeforePageFlushing);
+                        }
+                        PdfCanvas canvas = new PdfCanvas(page, !wrappedPages.contains(page));
+                        wrappedPages.add(page);
+
+                        // Here we avoid circular reference which might occur when page resources and the appearance xObject's
+                        // resources are the same object
+                        PdfObject xObjectResources = xObject.getPdfObject().get(PdfName.Resources);
+                        PdfObject pageResources = page.getResources().getPdfObject();
+                        if (xObjectResources != null && pageResources != null &&
+                                xObjectResources == pageResources) {
+                            xObject.getPdfObject().put(PdfName.Resources, initialPageResourceClones.get(document.getPageNumber(page)));
+                        }
 
-                    if (tagPointer != null) {
-                        tagPointer.setPageForTagging(page);
-                        TagReference tagRef = tagPointer.getTagReference();
-                        canvas.openTag(tagRef);
-                    }
+                        if (tagPointer != null) {
+                            tagPointer.setPageForTagging(page);
+                            TagReference tagRef = tagPointer.getTagReference();
+                            canvas.openTag(tagRef);
+                        }
 
-                    AffineTransform at = calcFieldAppTransformToAnnotRect(xObject, annotBBox);
-                    float[] m = new float[6];
-                    at.getMatrix(m);
-                    canvas.addXObject(xObject, m[0], m[1], m[2], m[3], m[4], m[5]);
+                        AffineTransform at = calcFieldAppTransformToAnnotRect(xObject, annotBBox);
+                        float[] m = new float[6];
+                        at.getMatrix(m);
+                        canvas.addXObject(xObject, m[0], m[1], m[2], m[3], m[4], m[5]);
 
-                    if (tagPointer != null) {
-                        canvas.closeTag();
+                        if (tagPointer != null) {
+                            canvas.closeTag();
+                        }
                     }
                 }
             }

forms/src/test/java/com/itextpdf/forms/FlatteningTest.java

@@ -42,11 +42,14 @@ This file is part of the iText (R) project.
  */
 package com.itextpdf.forms;
 
+import com.itextpdf.io.LogMessageConstant;
 import com.itextpdf.kernel.pdf.PdfDocument;
 import com.itextpdf.kernel.pdf.PdfReader;
 import com.itextpdf.kernel.pdf.PdfWriter;
 import com.itextpdf.kernel.utils.CompareTool;
 import com.itextpdf.test.ExtendedITextTest;
+import com.itextpdf.test.annotations.LogMessage;
+import com.itextpdf.test.annotations.LogMessages;
 import com.itextpdf.test.annotations.type.IntegrationTest;
 import org.junit.Assert;
 import org.junit.BeforeClass;
@@ -79,4 +82,19 @@ public void formFlatteningTestWithAPWithoutSubtype() throws IOException, Interru
         Assert.assertNull(new CompareTool().compareByContent(dest, cmp, destinationFolder, "diff_"));
     }
 
+    @Test
+    @LogMessages(messages = @LogMessage(messageTemplate = LogMessageConstant.N_ENTRY_IS_REQUIRED_FOR_APPEARANCE_DICTIONARY))
+    public void formFlatteningTestWithoutNEntry() throws IOException, InterruptedException {
+        String filename = "formFlatteningTestWithoutNEntry";
+        String src = sourceFolder + filename + ".pdf";
+        String dest = destinationFolder + filename + "_flattened.pdf";
+        String cmp = sourceFolder + "cmp_" + filename + "_flattened.pdf";
+        PdfDocument doc = new PdfDocument(new PdfReader(src), new PdfWriter(dest));
+
+        PdfAcroForm.getAcroForm(doc, false).flattenFields();
+        doc.close();
+
+        Assert.assertNull(new CompareTool().compareByContent(dest, cmp, destinationFolder, "diff_"));
+    }
+
 }

forms/src/test/resources/com/itextpdf/forms/FlatteningTest/cmp_formFlatteningTestWithoutNEntry_flattened.pdf

@@ -125,6 +125,7 @@ public final class LogMessageConstant {
     public static final String MAPPING_IN_STRUCT_ROOT_OVERWRITTEN = "Existing mapping for {0} in structure tree root role map was {1} and it was overwritten with {2}.";
     public static final String METHOD_IS_NOT_IMPLEMENTED_BY_DEFAULT_OTHER_METHOD_WILL_BE_USED = "Method {0} is not implemented by default: please, override and implement it. {1} will be used instead.";
     public static final String NAME_ALREADY_EXISTS_IN_THE_NAME_TREE = "Name \"{0}\" already exists in the name tree; old value will be replaced by the new one.";
+    public static final String N_ENTRY_IS_REQUIRED_FOR_APPEARANCE_DICTIONARY = "\\N entry is required to be present in an appearance dictionary.";
     public static final String NOT_TAGGED_PAGES_IN_TAGGED_DOCUMENT = "Not tagged pages are copied to the tagged document. Destination document now may contain not tagged content.";
     public static final String NO_FIELDS_IN_ACROFORM = "Required AcroForm entry /Fields does not exist in the document. Empty array /Fields will be created.";
     public static final String NUM_TREE_SHALL_NOT_END_WITH_KEY = "Number tree ends with a key which is invalid according to the PDF specification.";