How to insert a sdt before a given paragraph by using POI?

I want to generate a TOC before main body in a existed word file. I have redefined a custom XWPFDocument.createTOC function to generate a TOC whose styles accord with my needs. But in the createTOC function, "this.getDocument().getBody().addNewSdt()" only can insert a sdt at the last of body. I spend lots time to find a method to change the position of sdt element. I find this method can work eventually.

Node body_node = doc.getDocument().getDomNode().item(0);
NodeList nodeList = body_node.getChildNodes();
Node sdt_xxx = nodeList.item(8);
body_node.removeChild(sdt_xxx);
body_node.insertBefore(sdt_xxx ,nodeList.item(0));

This method can modify the position of sdt. But this method works with the CT class, so the variable in XWPFDocument (such as List<XWPFSDT>, List<XWPFParagraph>) do not change after I modify the CT class. And I don't know how to modify the bodyelements in XWPFDocument, which is a unmodifiable variable. I don't know how to reload the XWPFDocument object after I modify CT variable.

(When reopen file after write the modified object to a new file, the XWPFDocument object can update. But I don't want to do this, this method seems too stupid.)

So, who knows how to add a sdt (TOC) into a given position using POI? Thanks a lot.

Solution

You say you have extended XWPFDocument with your own createTOC method. So you also could provide a createTOC(org.apache.xmlbeans.XmlCursor cursor) along the lines of insertNewParagraph(org.apache.xmlbeans.XmlCursor cursor). There the cursor determines where the TOC is inserted.

And because of updating the bodyelements lists, the extended XWPFDocument could provide a recreateBodyElementLists method. This method then recreates all necessary bodyelements lists when called.

Complete example to show the principle:

import java.io.FileOutputStream;
import java.io.FileInputStream;

import org.apache.poi.xwpf.usermodel.*;
import org.openxmlformats.schemas.wordprocessingml.x2006.main.CTStyles;
import org.openxmlformats.schemas.wordprocessingml.x2006.main.CTStyle;
import org.openxmlformats.schemas.wordprocessingml.x2006.main.CTSimpleField;

import org.apache.xmlbeans.XmlCursor;

public class CreateWordTOC {
    
 static String cTStyleTOC1 =
  "<w:style xmlns:w=\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\" w:type=\"paragraph\" w:styleId=\"TOC1\">"
+ "<w:name w:val=\"toc 1\"/>"
+ "<w:basedOn w:val=\"Normal\"/>"
+ "<w:next w:val=\"Normal\"/>"
+ "<w:autoRedefine/><w:unhideWhenUsed/>"
+ "<w:rPr><w:b/><w:bCs/><w:caps/><w:color w:val=\"C00000\"/><w:sz w:val=\"32\"/><w:szCs w:val=\"32\"/></w:rPr>"
+ "</w:style>";

 static String cTStyleTOC2 =
  "<w:style xmlns:w=\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\" w:type=\"paragraph\" w:styleId=\"TOC2\">"
+ "<w:name w:val=\"toc 2\"/>"
+ "<w:basedOn w:val=\"Normal\"/>"
+ "<w:next w:val=\"Normal\"/>"
+ "<w:autoRedefine/><w:unhideWhenUsed/>"
+ "<w:rPr><w:i/><w:iCs/><w:sz w:val=\"28\"/><w:szCs w:val=\"28\"/></w:rPr>"
+ "</w:style>";

 public static void main(String[] args) throws Exception {

  //XWPFDocument document = new XWPFDocument(new FileInputStream("./WordDocument.docx"));
  MyXWPFDocument document = new MyXWPFDocument(new FileInputStream("./WordDocument.docx"));

  XWPFStyles styles = document.createStyles(); 
  CTStyles cTStyles = CTStyles.Factory.parse(cTStyleTOC1);
  CTStyle cTStyle = cTStyles.getStyleArray(0);
  styles.addStyle(new XWPFStyle(cTStyle));
  cTStyles = CTStyles.Factory.parse(cTStyleTOC2);
  cTStyle = cTStyles.getStyleArray(0);
  styles.addStyle(new XWPFStyle(cTStyle));
  
  System.out.println(document.getBodyElements().size());
  System.out.println(document.getContentControls().size());
 
  //TOC before first parahraph
  XWPFParagraph paragraph = document.getParagraphs().get(0);
  XmlCursor cursor = paragraph.getCTP().newCursor();
  //document.createTOC(cursor, "Heading");
  document.createTOC(cursor, "berschrift"); // German style Ids are "berschrift1", "berschrift2", ... (from "Überschrift" umlaut is not used in Id)
  cursor.dispose();
  //TOC as last element in body
  //document.createTOC(null, "Heading");
  document.createTOC(null, "berschrift");
  
  System.out.println(document.getBodyElements().size());
  System.out.println(document.getContentControls().size());
  if (document.getContentControls().size() > 0 )
   System.out.println(document.getContentControls().get(0).getContent());


  FileOutputStream out = new FileOutputStream("./WordDocumentNew.docx");   
  document.write(out);
  out.close();
  document.close();

 }

}

MyXWPFDocument.java:

import java.io.*; 
import java.math.BigInteger;
import org.apache.poi.util.POILogFactory;
import org.apache.poi.util.POILogger;
import org.apache.poi.xwpf.usermodel.*; 
import org.openxmlformats.schemas.wordprocessingml.x2006.main.*;

import org.apache.xmlbeans.XmlCursor;
import org.apache.xmlbeans.XmlObject;

import java.util.List;
import java.util.ArrayList;
import java.util.Collections;

public class MyXWPFDocument extends XWPFDocument {
    
 private static final POILogger LOG = POILogFactory.getLogger(XWPFDocument.class);
    
 public MyXWPFDocument(InputStream is) throws IOException {
  super(is);   
 }
    
 public void createTOC(XmlCursor cursor, String headingStyleIdPrefix) {
  CTSdtBlock block = null;
  if (cursor != null && isCursorInBody(cursor)) {
   String uri = CTSdtBlock.type.getName().getNamespaceURI();
   String localPart = "sdt";
   cursor.beginElement(localPart, uri);
   cursor.toParent();
   block = (CTSdtBlock) cursor.getObject(); 
  } else {
   block = this.getDocument().getBody().addNewSdt();
  }
  TOC toc = new TOC(block);
  int bookmarkId = 0;
  String tocIdPrefix = "123456";
  for (XWPFParagraph par : paragraphs) {
   String parStyleId = par.getStyle();
   if (parStyleId != null && parStyleId.toLowerCase().startsWith(headingStyleIdPrefix.toLowerCase())) {
    try {
     int level = Integer.parseInt(parStyleId.substring(headingStyleIdPrefix.length()));
     par.getCTP().addNewBookmarkStart();
     par.getCTP().getBookmarkStartArray(0).setId(BigInteger.valueOf(bookmarkId));
     par.getCTP().getBookmarkStartArray(0).setName("_Toc" + tocIdPrefix + bookmarkId);
     par.getCTP().addNewBookmarkEnd().setId(BigInteger.valueOf(bookmarkId));
     toc.addRow(level, par.getText(), 1, "" + tocIdPrefix + bookmarkId);
     bookmarkId++;
    } catch (Exception e) {
     LOG.log(POILogger.ERROR, "can't create TOC item", e);
    }
   }
  }
  recreateBodyElementLists();
 }

 protected void recreateBodyElementLists() {
  bodyElements = new ArrayList<>();
  paragraphs = new ArrayList<>();
  tables = new ArrayList<>();
  contentControls = new ArrayList<>();
  // parse the document with cursor and add
  // the XmlObject to its lists
  XmlCursor docCursor = this.getDocument().newCursor();
  docCursor.selectPath("./*");
  while (docCursor.toNextSelection()) {
   XmlObject o = docCursor.getObject();
   if (o instanceof CTBody) {
    XmlCursor bodyCursor = o.newCursor();
    bodyCursor.selectPath("./*");
    while (bodyCursor.toNextSelection()) {
     XmlObject bodyObj = bodyCursor.getObject();
     if (bodyObj instanceof CTP) {
      XWPFParagraph p = new XWPFParagraph((CTP) bodyObj, this);
      bodyElements.add(p);
      paragraphs.add(p);
     } else if (bodyObj instanceof CTTbl) {
      XWPFTable t = new XWPFTable((CTTbl) bodyObj, this);
      bodyElements.add(t);
      tables.add(t);
     } else if (bodyObj instanceof CTSdtBlock) {
      XWPFSDT c = new XWPFSDT((CTSdtBlock) bodyObj, this);
      bodyElements.add(c);
      contentControls.add(c);
     }
    }
    bodyCursor.dispose();
   }
  }
  docCursor.dispose();
 }
 
 public List<XWPFSDT> getContentControls() {
  return Collections.unmodifiableList(contentControls);
 }
            
 private boolean isCursorInBody(XmlCursor cursor) {
  XmlCursor verify = cursor.newCursor();
  verify.toParent();
  boolean result = (verify.getObject() == getDocument().getBody());
  verify.dispose();
  return result;
 }
}

In my opinion org.apache.poi.xwpf.usermodel.TOC also is incomplete and needs to be extended. But this is another thing then.