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Split and delete forms #6277

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255626f
Delete orphaned forms when removing pages and maintain forms correctl…
reecebrowne Apr 30, 2026
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reecebrowne Apr 30, 2026
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reecebrowne Apr 30, 2026
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Merge branch 'main' into bug/splitting-forms
reecebrowne Apr 30, 2026
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79 changes: 79 additions & 0 deletions app/common/src/main/java/stirling/software/common/util/FormUtils.java
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Original file line number Diff line number Diff line change
Expand Up @@ -2289,6 +2289,85 @@ private <T extends PDTerminalField> void registerNewField(
acroForm.getFields().add(field);
}

/** Drops AcroForm fields whose widgets are no longer on any page of {@code document}. */
public void pruneOrphanedFormFields(PDDocument document) {
if (document == null) {
return;
}
PDDocumentCatalog catalog = document.getDocumentCatalog();
if (catalog == null) {
return;
}
PDAcroForm form = catalog.getAcroForm(null);
if (form == null) {
return;
}
List<PDField> fields = form.getFields();
if (fields.isEmpty()) {
return;
}

Set<COSDictionary> liveWidgets = collectLiveWidgetDictionaries(document);
List<PDField> kept = pruneFieldList(fields, liveWidgets);
if (kept.isEmpty()) {
catalog.setAcroForm(null);
} else if (kept.size() != fields.size()) {
form.setFields(kept);
}
}

private Set<COSDictionary> collectLiveWidgetDictionaries(PDDocument document) {
Set<COSDictionary> live = new HashSet<>();
int pageCount = document.getNumberOfPages();
for (int i = 0; i < pageCount; i++) {
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@ConnorYoh ConnorYoh Apr 30, 2026

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Potential place for threaded implementation. If you got a chonky doc that is. May not be worth it

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@reecebrowne reecebrowne May 1, 2026

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I don't think this is worth doing, used very big docs to test and had no issue nad I don't think the overhead for this is all that significant

try {
for (PDAnnotation annotation : document.getPage(i).getAnnotations()) {
if (annotation instanceof PDAnnotationWidget) {
live.add(annotation.getCOSObject());
}
}
} catch (IOException e) {
log.debug("Failed reading page {} annotations: {}", i, e.getMessage());
}
}
return live;
}

private List<PDField> pruneFieldList(List<PDField> fields, Set<COSDictionary> liveWidgets) {
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@ConnorYoh ConnorYoh Apr 30, 2026

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Fancy recursion! What happens if the number of fields get really big?

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@reecebrowne reecebrowne May 1, 2026

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It's on tree depth not field count. This matches how pdf box does it if this fails due to tree depth then we have biger problems

List<PDField> kept = new ArrayList<>(fields.size());
for (PDField field : fields) {
if (field instanceof PDNonTerminalField nonTerminal) {
List<PDField> children = nonTerminal.getChildren();
List<PDField> remaining = pruneFieldList(children, liveWidgets);
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if (remaining.isEmpty()) {
continue;
}
if (remaining.size() != children.size()) {
nonTerminal.setChildren(remaining);
}
kept.add(nonTerminal);
} else if (field instanceof PDTerminalField terminal) {
List<PDAnnotationWidget> widgets = terminal.getWidgets();
List<PDAnnotationWidget> liveOnes = new ArrayList<>(widgets.size());
for (PDAnnotationWidget widget : widgets) {
if (liveWidgets.contains(widget.getCOSObject())) {
liveOnes.add(widget);
}
}
if (liveOnes.isEmpty()) {
continue;
}
if (liveOnes.size() != widgets.size()) {
terminal.setWidgets(liveOnes);
}
kept.add(terminal);
} else {
kept.add(field);
}
}
return kept;
}

// Delegation methods to GeneralFormCopyUtils for form field transformation
public boolean hasAnyRotatedPage(PDDocument document) {
return stirling.software.common.util.GeneralFormCopyUtils.hasAnyRotatedPage(document);
Expand Down
229 changes: 229 additions & 0 deletions app/common/src/test/java/stirling/software/common/util/FormUtilsPruneOrphanedFieldsTest.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,229 @@
package stirling.software.common.util;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertNull;
import static org.junit.jupiter.api.Assertions.assertTrue;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.pdfbox.Loader;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDResources;
import org.apache.pdfbox.pdmodel.common.PDRectangle;
import org.apache.pdfbox.pdmodel.interactive.annotation.PDAnnotationWidget;
import org.apache.pdfbox.pdmodel.interactive.form.PDAcroForm;
import org.apache.pdfbox.pdmodel.interactive.form.PDField;
import org.apache.pdfbox.pdmodel.interactive.form.PDNonTerminalField;
import org.apache.pdfbox.pdmodel.interactive.form.PDTextField;
import org.junit.jupiter.api.Test;

class FormUtilsPruneOrphanedFieldsTest {

@Test
void noAcroFormIsNoOp() throws IOException {
try (PDDocument document = new PDDocument()) {
document.addPage(new PDPage(PDRectangle.A4));
FormUtils.pruneOrphanedFormFields(document);
assertNull(document.getDocumentCatalog().getAcroForm(null));
}
}

@Test
void dropsFieldsWhoseWidgetsAreAllOnRemovedPages() throws IOException {
byte[] pdfBytes = buildPdfWithFieldPerPage(3);

try (PDDocument document = Loader.loadPDF(pdfBytes)) {
document.removePage(2);
document.removePage(0);

FormUtils.pruneOrphanedFormFields(document);

PDAcroForm form = document.getDocumentCatalog().getAcroForm(null);
assertNotNull(form);
List<String> remainingNames = new ArrayList<>();
for (PDField field : form.getFields()) {
remainingNames.add(field.getPartialName());
}
assertEquals(List.of("field_1"), remainingNames);
}
}

@Test
void dropsAcroFormEntirelyWhenNoFieldsSurvive() throws IOException {
byte[] pdfBytes = buildPdfWithFieldPerPage(2);

try (PDDocument document = Loader.loadPDF(pdfBytes)) {
document.removePage(1);
document.removePage(0);
document.addPage(new PDPage(PDRectangle.A4));

FormUtils.pruneOrphanedFormFields(document);

assertNull(document.getDocumentCatalog().getAcroForm(null));
}
}

@Test
void keepsLiveWidgetsAndDropsOrphanWidgetsFromMultiWidgetField() throws IOException {
byte[] pdfBytes = buildPdfWithMultiWidgetField();

try (PDDocument document = Loader.loadPDF(pdfBytes)) {
document.removePage(0);

FormUtils.pruneOrphanedFormFields(document);

PDAcroForm form = document.getDocumentCatalog().getAcroForm(null);
assertNotNull(form);
assertEquals(1, form.getFields().size());
PDField field = form.getFields().get(0);
assertEquals("multi", field.getPartialName());
assertEquals(2, field.getWidgets().size(), "two widgets remain after one is dropped");
}
}

@Test
void survivesRoundTripWithoutOrphanPagesInOutput() throws IOException {
byte[] pdfBytes = buildPdfWithFieldPerPage(3);

byte[] writtenBytes;
try (PDDocument document = Loader.loadPDF(pdfBytes)) {
document.removePage(2);
document.removePage(1);
FormUtils.pruneOrphanedFormFields(document);
try (ByteArrayOutputStream out = new ByteArrayOutputStream()) {
document.save(out);
writtenBytes = out.toByteArray();
}
}

try (PDDocument reloaded = Loader.loadPDF(writtenBytes)) {
assertEquals(1, reloaded.getNumberOfPages());
PDAcroForm form = reloaded.getDocumentCatalog().getAcroForm(null);
assertNotNull(form);
assertEquals(1, form.getFields().size());
assertEquals("field_0", form.getFields().get(0).getPartialName());
}
}

@Test
void prunesNestedNonTerminalFields() throws IOException {
byte[] pdfBytes = buildPdfWithNestedFields();

try (PDDocument document = Loader.loadPDF(pdfBytes)) {
document.removePage(1);

FormUtils.pruneOrphanedFormFields(document);

PDAcroForm form = document.getDocumentCatalog().getAcroForm(null);
assertNotNull(form);
assertEquals(1, form.getFields().size());
PDField group = form.getFields().get(0);
assertEquals("group", group.getPartialName());
assertTrue(group instanceof PDNonTerminalField);
PDNonTerminalField nonTerminal = (PDNonTerminalField) group;
assertEquals(1, nonTerminal.getChildren().size());
assertEquals("kept", nonTerminal.getChildren().get(0).getPartialName());
}
}

private static byte[] buildPdfWithFieldPerPage(int pageCount) throws IOException {
try (PDDocument document = new PDDocument()) {
PDAcroForm acroForm = new PDAcroForm(document);
acroForm.setDefaultResources(new PDResources());
document.getDocumentCatalog().setAcroForm(acroForm);

for (int i = 0; i < pageCount; i++) {
PDPage page = new PDPage(PDRectangle.A4);
document.addPage(page);

PDTextField field = new PDTextField(acroForm);
field.setPartialName("field_" + i);
PDAnnotationWidget widget = new PDAnnotationWidget();
widget.setRectangle(new PDRectangle(50, 50, 100, 20));
widget.setPage(page);
field.setWidgets(List.of(widget));
acroForm.getFields().add(field);
page.getAnnotations().add(widget);
}

try (ByteArrayOutputStream out = new ByteArrayOutputStream()) {
document.save(out);
return out.toByteArray();
}
}
}

private static byte[] buildPdfWithMultiWidgetField() throws IOException {
try (PDDocument document = new PDDocument()) {
PDAcroForm acroForm = new PDAcroForm(document);
acroForm.setDefaultResources(new PDResources());
document.getDocumentCatalog().setAcroForm(acroForm);

List<PDAnnotationWidget> widgets = new ArrayList<>();
for (int i = 0; i < 3; i++) {
PDPage page = new PDPage(PDRectangle.A4);
document.addPage(page);
PDAnnotationWidget widget = new PDAnnotationWidget();
widget.setRectangle(new PDRectangle(50, 50, 100, 20));
widget.setPage(page);
page.getAnnotations().add(widget);
widgets.add(widget);
}

PDTextField field = new PDTextField(acroForm);
field.setPartialName("multi");
field.setWidgets(widgets);
acroForm.getFields().add(field);

try (ByteArrayOutputStream out = new ByteArrayOutputStream()) {
document.save(out);
return out.toByteArray();
}
}
}

private static byte[] buildPdfWithNestedFields() throws IOException {
try (PDDocument document = new PDDocument()) {
PDAcroForm acroForm = new PDAcroForm(document);
acroForm.setDefaultResources(new PDResources());
document.getDocumentCatalog().setAcroForm(acroForm);

PDPage pageA = new PDPage(PDRectangle.A4);
PDPage pageB = new PDPage(PDRectangle.A4);
document.addPage(pageA);
document.addPage(pageB);

PDNonTerminalField group = new PDNonTerminalField(acroForm);
group.setPartialName("group");

PDTextField kept = new PDTextField(acroForm);
kept.setPartialName("kept");
PDAnnotationWidget keptWidget = new PDAnnotationWidget();
keptWidget.setRectangle(new PDRectangle(50, 50, 100, 20));
keptWidget.setPage(pageA);
kept.setWidgets(List.of(keptWidget));
pageA.getAnnotations().add(keptWidget);

PDTextField dropped = new PDTextField(acroForm);
dropped.setPartialName("dropped");
Comment on lines +202 to +213
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@ConnorYoh ConnorYoh May 1, 2026

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Are these names shown to the user? Does it matter if they are english only?

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@reecebrowne reecebrowne May 1, 2026

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These are just for tests. Shouldn't have added this file though it can just be moved to formutilstest

PDAnnotationWidget droppedWidget = new PDAnnotationWidget();
droppedWidget.setRectangle(new PDRectangle(50, 100, 100, 20));
droppedWidget.setPage(pageB);
dropped.setWidgets(List.of(droppedWidget));
pageB.getAnnotations().add(droppedWidget);

group.setChildren(List.of(kept, dropped));
acroForm.getFields().add(group);

try (ByteArrayOutputStream out = new ByteArrayOutputStream()) {
document.save(out);
return out.toByteArray();
}
}
}
}
16 changes: 16 additions & 0 deletions ...core/src/main/java/stirling/software/SPDF/controller/api/RearrangePagesPDFController.java
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Original file line number Diff line number Diff line change
Expand Up @@ -6,8 +6,11 @@
import java.util.List;
import java.util.Locale;

import org.apache.pdfbox.cos.COSName;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDDocumentCatalog;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.interactive.form.PDAcroForm;
import org.springframework.core.io.Resource;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
Expand All @@ -27,6 +30,7 @@
import stirling.software.common.annotations.api.GeneralApi;
import stirling.software.common.service.CustomPDFDocumentFactory;
import stirling.software.common.util.ExceptionUtils;
import stirling.software.common.util.FormUtils;
import stirling.software.common.util.GeneralUtils;
import stirling.software.common.util.TempFileManager;
import stirling.software.common.util.WebResponseUtils;
Expand Down Expand Up @@ -67,6 +71,7 @@ public ResponseEntity<Resource> deletePages(@ModelAttribute PDFWithPageNums requ
int pageIndex = pagesToRemove.get(i);
document.removePage(pageIndex);
}
FormUtils.pruneOrphanedFormFields(document);
return WebResponseUtils.pdfDocToWebResponse(
document,
GeneralUtils.generateFilename(
Expand Down Expand Up @@ -265,6 +270,17 @@ public ResponseEntity<Resource> rearrangePages(@ModelAttribute RearrangePagesReq
rearrangedDocument.addPage(page);
}

PDDocumentCatalog sourceCatalog = document.getDocumentCatalog();
if (sourceCatalog != null) {
PDAcroForm sourceForm = sourceCatalog.getAcroForm(null);
if (sourceForm != null) {
rearrangedDocument
.getDocumentCatalog()
.getCOSObject()
.setItem(COSName.ACRO_FORM, sourceForm.getCOSObject());
}
}

return WebResponseUtils.pdfDocToWebResponse(
rearrangedDocument,
GeneralUtils.generateFilename(
Expand Down
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