I am trying to create the below header with the help of XWPFDocument and merging cells

I am trying to create the below header with the help of XWPFDocument and merging cells .

Below Image shows the image for the header I am trying to create

*XWPFDocument document = new XWPFDocument();
XWPFTable table = document.createTable(1, 8);*
CTTblBorders borders = table.getCTTbl().getTblPr().addNewTblBorders();
borders.addNewBottom().setVal(STBorder.THICK);
borders.addNewLeft().setVal(STBorder.NONE);
borders.addNewRight().setVal(STBorder.NONE);
borders.addNewTop().setVal(STBorder.THICK);
borders.addNewInsideV().setVal(STBorder.THICK);
table.getCTTbl().getTblPr().setTblBorders(borders);
table.setWidth(1440);

for (int col = 0 ; col < 8; col++) {
CTTblWidth tblWidth = table.getRow(0).getCell(col).getCTTc().addNewTcPr().addNewTcW();
tblWidth.setW(BigInteger.valueOf(1440));
//STTblWidth.DXA is used to specify width in twentieths of a point.
tblWidth.setType(STTblWidth.DXA);
}    
**mergeCellHorizontally(table, 0, 0, 1);**
XWPFTableCell cell = table.getRow(0).getCell(1);
CTTcPr ctTcPr = cell.getCTTc().getTcPr();
CTTcBorders ctTcBorders = ctTcPr.addNewTcBorders();
ctTcBorders.addNewRight().setVal(STBorder.NONE);
ctTcBorders.addNewBottom().setVal(STBorder.NONE);

Solution

First question for such table problems is always: How many columns will the table have at maximum? Or in other words: How many columns counts the row having the most columns in the table? If that answer is known, then the table should be created having that maximum column count. All other then will be possible by setting column widths, cell borders and or by merging cells.

But in your special case, I cannot see how merging cells could help. Assuming the maximum column count is 8, then creating your sample table should be possible by setting column widths and cell borders.

Example:

import java.io.File;
import java.io.FileOutputStream;

import java.math.BigInteger;

import org.apache.poi.xwpf.usermodel.*;

import org.openxmlformats.schemas.wordprocessingml.x2006.main.*;

public class CreateWordTableSpecial {

 static void setColumnWidth(XWPFTable table, int row, int col, int width) {
  CTTblWidth tblWidth = CTTblWidth.Factory.newInstance();
  tblWidth.setW(BigInteger.valueOf(width));
  tblWidth.setType(STTblWidth.DXA);
  CTTcPr tcPr = table.getRow(row).getCell(col).getCTTc().getTcPr();
  if (tcPr != null) {
   tcPr.setTcW(tblWidth);
  } else {
   tcPr = CTTcPr.Factory.newInstance();
   tcPr.setTcW(tblWidth);
   table.getRow(row).getCell(col).getCTTc().setTcPr(tcPr);
  }
 }

 static void setCellBorders(XWPFTableCell cell, STBorder.Enum[] borderTypesLTRB) {
  CTTcBorders borders = CTTcBorders.Factory.newInstance();
  borders.addNewLeft().setVal(borderTypesLTRB[0]);
  borders.addNewTop().setVal(borderTypesLTRB[1]);
  borders.addNewRight().setVal(borderTypesLTRB[2]);
  borders.addNewBottom().setVal(borderTypesLTRB[3]);
  CTTcPr tcPr = cell.getCTTc().getTcPr();
  if (tcPr != null) {
   tcPr.setTcBorders(borders);
  } else {
   tcPr = CTTcPr.Factory.newInstance();
   tcPr.setTcBorders(borders);
   cell.getCTTc().setTcPr(tcPr);
  }
 }

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

  XWPFDocument document= new XWPFDocument();

  XWPFParagraph paragraph = document.createParagraph();
  XWPFRun run = paragraph.createRun();  
  run.setText("The table:");

  //create table
  XWPFTable table = document.createTable(3, 8);
  table.setWidth(1*1440*8); // table width = 8 inches

  //defining the column widths for the grid
  //column width values are in unit twentieths of a point (1/1440 of an inch)
  int defaultColWidth = 1*1440*8/8; // 8 columns fits to 8 inches 

  int[] colunmWidths = new int[] {
   defaultColWidth*3/4, defaultColWidth*2/4, defaultColWidth*8/4, defaultColWidth*3/4, 
   defaultColWidth*3/4, defaultColWidth*2/4, defaultColWidth*8/4, defaultColWidth*3/4
  };

  //create CTTblGrid for this table with widths of the 8 columns. 
  //necessary for Libreoffice/Openoffice to accept the column widths.
  //first column
  table.getCTTbl().addNewTblGrid().addNewGridCol().setW(BigInteger.valueOf(colunmWidths[0]));
  setColumnWidth(table, 0, 0, colunmWidths[0]);
  //other columns
  for (int col = 1; col < colunmWidths.length; col++) {
   table.getCTTbl().getTblGrid().addNewGridCol().setW(BigInteger.valueOf(colunmWidths[col]));
   setColumnWidth(table, 0, col, colunmWidths[col]);
  }

  //set cell borders
  for (int col = 0; col < 3; col++) {
   setCellBorders(table.getRow(0).getCell(col), new STBorder.Enum[] {STBorder.NIL, STBorder.THICK, STBorder.NIL, STBorder.NIL}); 
  } 
  setCellBorders(table.getRow(0).getCell(3), new STBorder.Enum[] {STBorder.NIL, STBorder.THICK, STBorder.THICK, STBorder.NIL}); 
  setCellBorders(table.getRow(0).getCell(4), new STBorder.Enum[] {STBorder.THICK, STBorder.THICK, STBorder.NIL, STBorder.NIL}); 
  for (int col = 5; col < 8; col++) {
   setCellBorders(table.getRow(0).getCell(col), new STBorder.Enum[] {STBorder.NIL, STBorder.THICK, STBorder.NIL, STBorder.NIL}); 
  }

  for (int col = 0; col < 3; col++) {
   setCellBorders(table.getRow(1).getCell(col), new STBorder.Enum[] {STBorder.NIL, STBorder.NIL, STBorder.NIL, STBorder.THICK}); 
  } 
  setCellBorders(table.getRow(1).getCell(3), new STBorder.Enum[] {STBorder.NIL, STBorder.NIL, STBorder.THICK, STBorder.THICK}); 
  setCellBorders(table.getRow(1).getCell(4), new STBorder.Enum[] {STBorder.THICK, STBorder.NIL, STBorder.NIL, STBorder.THICK}); 
  for (int col = 5; col < 8; col++) {
   setCellBorders(table.getRow(1).getCell(col), new STBorder.Enum[] {STBorder.NIL, STBorder.NIL, STBorder.NIL, STBorder.THICK}); 
  }

  for (int col = 0; col < 8; col++) {
   setCellBorders(table.getRow(2).getCell(col), new STBorder.Enum[] {STBorder.NIL, STBorder.NIL, STBorder.NIL, STBorder.NIL}); 
  }

  table.getRow(0).setHeight(28*20); // 28pt row height
  table.getRow(0).getCtRow().getTrPr().getTrHeightArray(0).setHRule(STHeightRule.EXACT);

  XWPFTableCell cell = table.getRow(0).getCell(0);
  paragraph = (cell.getParagraphs().size() > 0)?cell.getParagraphs().get(0):cell.addParagraph();
  paragraph.setIndentationLeft(5*20); // 10pt left indentation
  run = (paragraph.getRuns().size() > 0)?paragraph.getRuns().get(0):paragraph.createRun();
  run.setBold(true);
  run.setText("Species:");

  cell = table.getRow(0).getCell(2);
  paragraph = (cell.getParagraphs().size() > 0)?cell.getParagraphs().get(0):cell.addParagraph();
  paragraph.setIndentationLeft(5*20); // 10pt left indentation
  paragraph.setAlignment(ParagraphAlignment.RIGHT);
  run = (paragraph.getRuns().size() > 0)?paragraph.getRuns().get(0):paragraph.createRun();
  run.setBold(true);
  run.setText("Greater silver smelt");

  cell = table.getRow(0).getCell(4);
  paragraph = (cell.getParagraphs().size() > 0)?cell.getParagraphs().get(0):cell.addParagraph();
  paragraph.setIndentationLeft(5*20); // 10pt left indentation
  run = (paragraph.getRuns().size() > 0)?paragraph.getRuns().get(0):paragraph.createRun();
  run.setBold(true);
  run.setText("Zone:");

  cell = table.getRow(0).getCell(6);
  paragraph = (cell.getParagraphs().size() > 0)?cell.getParagraphs().get(0):cell.addParagraph();
  paragraph.setIndentationLeft(5*20); // 10pt left indentation
  run = (paragraph.getRuns().size() > 0)?paragraph.getRuns().get(0):paragraph.createRun();
  run.setBold(true);
  run.setText("Union and international waters of 1 and 2");

  table.getRow(1).setHeight(28*20); // 28pt row height
  table.getRow(1).getCtRow().getTrPr().getTrHeightArray(0).setHRule(STHeightRule.EXACT);

  cell = table.getRow(1).getCell(2);
  paragraph = (cell.getParagraphs().size() > 0)?cell.getParagraphs().get(0):cell.addParagraph();
  paragraph.setIndentationLeft(5*20); // 10pt left indentation
  paragraph.setAlignment(ParagraphAlignment.RIGHT);
  run = (paragraph.getRuns().size() > 0)?paragraph.getRuns().get(0):paragraph.createRun();
  run.addBreak();
  run = paragraph.createRun();
  run.setItalic(true);
  run.setText("Argentinia silos");

  cell = table.getRow(1).getCell(6);
  paragraph = (cell.getParagraphs().size() > 0)?cell.getParagraphs().get(0):cell.addParagraph();
  paragraph.setIndentationLeft(5*20); // 10pt left indentation
  run = (paragraph.getRuns().size() > 0)?paragraph.getRuns().get(0):paragraph.createRun();
  run.addTab();
  run = paragraph.createRun();
  run.addTab();
  run = paragraph.createRun();
  run.setText("(2)");
  run.addBreak();
  run = paragraph.createRun();
  run.setText("(ARU/1/2)");
 
  paragraph = document.createParagraph();

  CTSectPr sectPr = document.getDocument().getBody().getSectPr();
  if (sectPr == null) sectPr = document.getDocument().getBody().addNewSectPr();
  CTPageSz pageSz = sectPr.addNewPgSz();
  pageSz.setOrient(STPageOrientation.LANDSCAPE);
  pageSz.setH(BigInteger.valueOf(12240)); //12240 Twips = 12240/20 = 612 pt = 612/72 = 8.5"
  pageSz.setW(BigInteger.valueOf(15840)); //15840 Twips = 15840/20 = 792 pt = 792/72 = 11"

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

 }
}

Result: