POI Word Unable to merge newly created cell vertically

Question

I know how to merge cells vertically with Apache POI word. But it seems if a new row is created, the merge won't take effect.

Here is the input table:

I wish to add a new row between old row 2 and old row 3, and have the new row's cell at first column merged into C2, like this:

So I created a new row and added it to the table below old row 2, and attempt to merge the cells

github source code link is here, it can reproduce the problem.

public class POIWordAddSubRowQuestionDemo{
    public static void main(String[] args) throws IOException, XmlException{
        ClassLoader classLoader = POIWordAddSubRowQuestionDemo.class.getClassLoader();
        InputStream inputStream = classLoader.getResourceAsStream("input.docx");
        String outputDocxPath = "F:/TEMP/output.docx";
        assert inputStream != null;
        XWPFDocument doc = new XWPFDocument(inputStream);
        XWPFTable table = doc.getTables().get(0);
        //this is 'old row 2'
        XWPFTableRow secondRow = table.getRows().get(1);

        //create a new row that is based on 'old row 2'
        CTRow ctrow = CTRow.Factory.parse(secondRow.getCtRow().newInputStream());
        XWPFTableRow newRow = new XWPFTableRow(ctrow, table);
        XWPFRun xwpfRun = newRow.getCell(1).getParagraphs().get(0).getRuns().get(0);
        //set row text
        xwpfRun.setText("new row", 0);
        // add new row below 'old row 2'
        table.addRow(newRow, 2);

        //merge cells at first column of 'old row 2', 'new row', and 'old row 3'
        mergeCellVertically(doc.getTables().get(0), 0, 1, 3);

        FileOutputStream fos = new FileOutputStream(outputDocxPath);
        doc.write(fos);
        fos.close();
    }

    static void mergeCellVertically(XWPFTable table, int col, int fromRow, int toRow) {
        for(int rowIndex = fromRow; rowIndex <= toRow; rowIndex++) {
            XWPFTableCell cell = table.getRow(rowIndex).getCell(col);
            CTVMerge vmerge = CTVMerge.Factory.newInstance();
            if(rowIndex == fromRow){
                // The first merged cell is set with RESTART merge value
                vmerge.setVal(STMerge.RESTART);
            } else {
                // Cells which join (merge) the first one, are set with CONTINUE
                vmerge.setVal(STMerge.CONTINUE);
                // and the content should be removed
                for (int i = cell.getParagraphs().size(); i > 0; i--) {
                    cell.removeParagraph(0);
                }
                cell.addParagraph();
            }
            // Try getting the TcPr. Not simply setting an new one every time.
            CTTcPr tcPr = cell.getCTTc().getTcPr();
            if (tcPr == null) tcPr = cell.getCTTc().addNewTcPr();
            tcPr.setVMerge(vmerge);
        }
    }
}

But the merge did not work and I got:

In another attempt, I tried to merge based on the table in picture 3 to get the table in picture 2, and it was a success. The only difference between the 2 attempts is that new row was not newly created, but rather read from the docx document, so I believe creating a new row was the reason why merge failed.

So is there a solution for merging newly created rows? I really don't want to split this operation like this: adding rows > saving docx to disk> read docx from disk> merge rows.

Answer 1

The problem you have is not with mergeCellVertically method but with your approach to copy table row. When copying the underlying CTRow and inserting it in CTTbl.TrArray using XWPFTable.addRow it must be fully complete. Later changings are not written in XML. I told that in my answer java Apache POI Word existing table insert row with cell style and formatting already. And I provided a method commitTableRows in my answer Can't change row text in .docx file once row is added to table. This method needs to be called before writing out the document, so the later changes get written in XML.

So because you are copying second row, which is the start of merging, that setting also gets copied. And the later called mergeCellVertically does not take effect. So your newRow remains new start of merging. This is what you get.

So after all changes and before writing out, call commitTableRows.

Complete example:

import java.io.*;
import org.apache.poi.xwpf.usermodel.*;
import org.openxmlformats.schemas.wordprocessingml.x2006.main.*;


public class WordInsertTableRowAndMerge {
    
 static XWPFTableRow insertNewTableRow(XWPFTableRow sourceTableRow, int pos) throws Exception {
  XWPFTable table = sourceTableRow.getTable();
  CTRow newCTRrow = CTRow.Factory.parse(sourceTableRow.getCtRow().newInputStream());
  XWPFTableRow tableRow = new XWPFTableRow(newCTRrow, table);
  table.addRow(tableRow, pos);
  return tableRow;
 }

 static void commitTableRows(XWPFTable table) {
  int rowNr = 0;
  for (XWPFTableRow tableRow : table.getRows()) {
   table.getCTTbl().setTrArray(rowNr++, tableRow.getCtRow());
  }
 }
    
 static void mergeCellVertically(XWPFTable table, int col, int fromRow, int toRow) {
  for(int rowIndex = fromRow; rowIndex <= toRow; rowIndex++) {
   System.out.println("rowIndex: " + rowIndex);
   XWPFTableCell cell = table.getRow(rowIndex).getCell(col);
   CTVMerge vmerge = CTVMerge.Factory.newInstance();
   if(rowIndex == fromRow){
    // The first merged cell is set with RESTART merge value
    vmerge.setVal(STMerge.RESTART);
   } else {
    // Cells which join (merge) the first one, are set with CONTINUE
    vmerge.setVal(STMerge.CONTINUE);
    // and the content should be removed
    for (int i = cell.getParagraphs().size(); i > 0; i--) {
     cell.removeParagraph(0);
    }
    cell.addParagraph();
   }
   // Try getting the TcPr. Not simply setting an new one every time.
   CTTcPr tcPr = cell.getCTTc().getTcPr();
   if (tcPr == null) tcPr = cell.getCTTc().addNewTcPr();
   tcPr.setVMerge(vmerge);
  }
 }
 
 public static void main(String[] args) throws Exception {

  XWPFDocument doc = new XWPFDocument(new FileInputStream("./source.docx"));
  
  XWPFTable table = doc.getTables().get(0);

  XWPFTableRow row = table.getRow(1);
  XWPFTableRow newRow = insertNewTableRow(row, 2);
  
  XWPFTableCell cell = newRow.getCell(0); if (cell == null) cell = newRow.addNewTableCell();
  // not needed because merged to cell above
  cell = newRow.getCell(1); if (cell == null) cell = newRow.addNewTableCell();
  for (XWPFParagraph paragraph : cell.getParagraphs()) { // only use first text runs in paragraphs
   for (int r = paragraph.getRuns().size()-1; r >= 0; r--) {
    XWPFRun run = paragraph.getRuns().get(r);
    if (r == 0) {
     run.setText("new row 1", 0);
    } else {
     paragraph.removeRun(r); 
    }
   }
  }

  mergeCellVertically(table, 0, 1, 3);

  commitTableRows(table);

  FileOutputStream out = new FileOutputStream("./result.docx");
  doc.write(out);
  out.close();
  doc.close();

 }
}