itextpdf.jar is a component in iText 5 Java library to provide core functionalities. iText Java library allows you to generate and manage PDF documents.

The Source Code files are provided at iText GitHub site.

You can compile it to generate your JAR file, using pom.xml as the build configuration file.

The source code of itextpdf-5.5.14.jar is provided below:

⏎ com/itextpdf/text/pdf/FdfWriter.java

/*
 *
 * This file is part of the iText (R) project.
    Copyright (c) 1998-2020 iText Group NV
 * Authors: Bruno Lowagie, Paulo Soares, et al.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License version 3
 * as published by the Free Software Foundation with the addition of the
 * following permission added to Section 15 as permitted in Section 7(a):
 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
 * ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
 * OF THIRD PARTY RIGHTS
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Affero General Public License for more details.
 * You should have received a copy of the GNU Affero General Public License
 * along with this program; if not, see http://www.gnu.org/licenses or write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA, 02110-1301 USA, or download the license from the following URL:
 * http://itextpdf.com/terms-of-use/
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General Public License.
 *
 * In accordance with Section 7(b) of the GNU Affero General Public License,
 * a covered work must retain the producer line in every PDF that is created
 * or manipulated using iText.
 *
 * You can be released from the requirements of the license by purchasing
 * a commercial license. Buying such a license is mandatory as soon as you
 * develop commercial activities involving the iText software without
 * disclosing the source code of your own applications.
 * These activities include: offering paid services to customers as an ASP,
 * serving PDFs on the fly in a web application, shipping iText with a closed
 * source product.
 *
 * For more information, please contact iText Software Corp. at this
 * address: sales@itextpdf.com
 */
package com.itextpdf.text.pdf;

import com.itextpdf.text.DocWriter;
import com.itextpdf.text.ExceptionConverter;
import com.itextpdf.text.Image;
import com.itextpdf.text.log.Counter;
import com.itextpdf.text.log.CounterFactory;
import com.itextpdf.text.pdf.AcroFields.Item;

import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import java.util.StringTokenizer;

/** Writes an FDF form.
 * @author Paulo Soares
 */
public class FdfWriter {
    private static final byte[] HEADER_FDF = DocWriter.getISOBytes("%FDF-1.4\n%\u00e2\u00e3\u00cf\u00d3\n");
    HashMap<String, Object> fields = new HashMap<String, Object>();
    Wrt wrt = null;

    /** The PDF file associated with the FDF. */
    private String file;
    private String statusMessage;

    /** Creates a new FdfWriter. */
    public FdfWriter() {
    }

    public FdfWriter(OutputStream os) throws IOException {
        wrt = new Wrt(os, this);
    }

    /** Writes the content to a stream.
     * @param os the stream
     * @throws IOException on error
     */
    public void writeTo(OutputStream os) throws IOException {
        if (wrt == null)
            wrt = new Wrt(os, this);
        wrt.write();
    }

    public void write() throws IOException {
        wrt.write();
    }

    public String getStatusMessage() {
        return statusMessage;
    }

    public void setStatusMessage(String statusMessage) {
        this.statusMessage = statusMessage;
    }

    @SuppressWarnings("unchecked")
    boolean setField(String field, PdfObject value) {
        HashMap<String, Object> map = fields;
        StringTokenizer tk = new StringTokenizer(field, ".");
        if (!tk.hasMoreTokens())
            return false;
        while (true) {
            String s = tk.nextToken();
            Object obj = map.get(s);
            if (tk.hasMoreTokens()) {
                if (obj == null) {
                    obj = new HashMap<String, Object>();
                    map.put(s, obj);
                    map = (HashMap<String, Object>)obj;
                    continue;
                }
                else if (obj instanceof HashMap)
                    map = (HashMap<String, Object>)obj;
                else
                    return false;
            }
            else {
                if (!(obj instanceof HashMap)) {
                    map.put(s, value);
                    return true;
                }
                else
                    return false;
            }
        }
    }

    @SuppressWarnings("unchecked")
    void iterateFields(HashMap<String, Object> values, HashMap<String, Object> map, String name) {
        for (Map.Entry<String, Object> entry: map.entrySet()) {
            String s = entry.getKey();
            Object obj = entry.getValue();
            if (obj instanceof HashMap)
                iterateFields(values, (HashMap<String, Object>)obj, name + "." + s);
            else
                values.put((name + "." + s).substring(1), obj);
        }
    }

    /** Removes the field value.
     * @param field the field name
     * @return <CODE>true</CODE> if the field was found and removed,
     * <CODE>false</CODE> otherwise
     */
    @SuppressWarnings("unchecked")
    public boolean removeField(String field) {
        HashMap<String, Object> map = fields;
        StringTokenizer tk = new StringTokenizer(field, ".");
        if (!tk.hasMoreTokens())
            return false;
        ArrayList<Object> hist = new ArrayList<Object>();
        while (true) {
            String s = tk.nextToken();
            Object obj = map.get(s);
            if (obj == null)
                return false;
            hist.add(map);
            hist.add(s);
            if (tk.hasMoreTokens()) {
                if (obj instanceof HashMap)
                    map = (HashMap<String, Object>)obj;
                else
                    return false;
            }
            else {
                if (obj instanceof HashMap)
                    return false;
                else
                    break;
            }
        }
        for (int k = hist.size() - 2; k >= 0; k -= 2) {
            map = (HashMap<String, Object>)hist.get(k);
            String s = (String)hist.get(k + 1);
            map.remove(s);
            if (!map.isEmpty())
                break;
        }
        return true;
    }

    /** Gets all the fields. The map is keyed by the fully qualified
     * field name and the values are <CODE>PdfObject</CODE>.
     * @return a map with all the fields
     */
    public HashMap<String, Object> getFields() {
        HashMap<String, Object> values = new HashMap<String, Object>();
        iterateFields(values, fields, "");
        return values;
    }

    /** Gets the field value.
     * @param field the field name
     * @return the field value or <CODE>null</CODE> if not found
     */
    @SuppressWarnings("unchecked")
    public String getField(String field) {
        HashMap<String, Object> map = fields;
        StringTokenizer tk = new StringTokenizer(field, ".");
        if (!tk.hasMoreTokens())
            return null;
        while (true) {
            String s = tk.nextToken();
            Object obj = map.get(s);
            if (obj == null)
                return null;
            if (tk.hasMoreTokens()) {
                if (obj instanceof HashMap)
                    map = (HashMap<String, Object>)obj;
                else
                    return null;
            }
            else {
                if (obj instanceof HashMap)
                    return null;
                else {
                    if (((PdfObject)obj).isString())
                        return ((PdfString)obj).toUnicodeString();
                    else
                        return PdfName.decodeName(obj.toString());
                }
            }
        }
    }

    /** Sets the field value as a name.
     * @param field the fully qualified field name
     * @param value the value
     * @return <CODE>true</CODE> if the value was inserted,
     * <CODE>false</CODE> if the name is incompatible with
     * an existing field
     */
    public boolean setFieldAsName(String field, String value) {
        return setField(field, new PdfName(value));
    }

    /** Sets the field value as a string.
     * @param field the fully qualified field name
     * @param value the value
     * @return <CODE>true</CODE> if the value was inserted,
     * <CODE>false</CODE> if the name is incompatible with
     * an existing field
     */
    public boolean setFieldAsString(String field, String value) {
        return setField(field, new PdfString(value, PdfObject.TEXT_UNICODE));
    }

    /**
     * Sets the field value as a <CODE>PDFAction</CODE>.
     * For example, this method allows setting a form submit button action using {@link PdfAction#createSubmitForm(String, Object[], int)}.
     * This method creates an <CODE>A</CODE> entry for the specified field in the underlying FDF file.
     * Method contributed by Philippe Laflamme (plaflamme)
     * @param field the fully qualified field name
     * @param action the field's action
     * @return <CODE>true</CODE> if the value was inserted,
     * <CODE>false</CODE> if the name is incompatible with
     * an existing field
     * @since	2.1.5
     */
    public boolean setFieldAsAction(String field, PdfAction action) {
    	return setField(field, action);
    }

    public boolean setFieldAsTemplate(String field, PdfTemplate template) {
        try {
            PdfDictionary d = new PdfDictionary();
            if (template instanceof PdfImportedPage)
                d.put(PdfName.N, template.getIndirectReference());
            else {
                PdfStream str = template.getFormXObject(PdfStream.NO_COMPRESSION);
                PdfIndirectReference ref = wrt.addToBody(str).getIndirectReference();
                d.put(PdfName.N, ref);
            }
            return setField(field, d);
        } catch (Exception e) {
            throw new ExceptionConverter(e);
        }
    }

    public boolean setFieldAsImage(String field, Image image) {
        try {
            if (Float.isNaN(image.getAbsoluteX()))
                image.setAbsolutePosition(0, image.getAbsoluteY());
            if (Float.isNaN(image.getAbsoluteY()))
                image.setAbsolutePosition(image.getAbsoluteY(), 0);
            PdfTemplate tmpl = PdfTemplate.createTemplate(wrt, image.getWidth(), image.getHeight());
            tmpl.addImage(image);
            PdfStream str = tmpl.getFormXObject(PdfStream.NO_COMPRESSION);
            PdfIndirectReference ref = wrt.addToBody(str).getIndirectReference();
            PdfDictionary d = new PdfDictionary();
            d.put(PdfName.N, ref);
            return setField(field, d);
        } catch (Exception de) {
            throw new ExceptionConverter(de);
        }
    }

    public boolean setFieldAsJavascript(String field, PdfName jsTrigName, String js) {
        PdfAnnotation dict = wrt.createAnnotation(null, null);
        PdfAction javascript = PdfAction.javaScript(js, wrt);
        dict.put(jsTrigName, javascript);
        return setField(field, dict);
    }

    public PdfImportedPage getImportedPage(PdfReader reader, int pageNumber) {
        return wrt.getImportedPage(reader, pageNumber);
    }

    public PdfTemplate createTemplate(float width, float height) {
        return PdfTemplate.createTemplate(wrt, width, height);
    }

    /** Sets all the fields from this <CODE>FdfReader</CODE>
     * @param fdf the <CODE>FdfReader</CODE>
     */
    public void setFields(FdfReader fdf) {
        HashMap<String, PdfDictionary> map = fdf.getFields();
        for (Map.Entry<String, PdfDictionary> entry: map.entrySet()) {
            String key = entry.getKey();
            PdfDictionary dic = entry.getValue();
            PdfObject v = dic.get(PdfName.V);
            if (v != null) {
                setField(key, v);
            }
            v = dic.get(PdfName.A); // (plaflamme)
            if (v != null) {
            	setField(key, v);
            }
        }
    }

    /** Sets all the fields from this <CODE>PdfReader</CODE>
     * @param pdf the <CODE>PdfReader</CODE>
     */
    public void setFields(PdfReader pdf) {
        setFields(pdf.getAcroFields());
    }

    /** Sets all the fields from this <CODE>AcroFields</CODE>
     * @param af the <CODE>AcroFields</CODE>
     */
    public void setFields(AcroFields af) {
        for (Map.Entry<String, Item> entry: af.getFields().entrySet()) {
            String fn = entry.getKey();
            AcroFields.Item item = entry.getValue();
            PdfDictionary dic = item.getMerged(0);
            PdfObject v = PdfReader.getPdfObjectRelease(dic.get(PdfName.V));
            if (v == null)
                continue;
            PdfObject ft = PdfReader.getPdfObjectRelease(dic.get(PdfName.FT));
            if (ft == null || PdfName.SIG.equals(ft))
                continue;
            setField(fn, v);
        }
    }

    /** Gets the PDF file name associated with the FDF.
     * @return the PDF file name associated with the FDF
     */
    public String getFile() {
        return this.file;
    }

    /** Sets the PDF file name associated with the FDF.
     * @param file the PDF file name associated with the FDF
     *
     */
    public void setFile(String file) {
        this.file = file;
    }

    static class Wrt extends PdfWriter {
        private FdfWriter fdf;

        Wrt(OutputStream os, FdfWriter fdf) throws IOException {
            super(new PdfDocument(), os);
            this.fdf = fdf;
            this.os.write(HEADER_FDF);
            body = new PdfBody(this);
        }

        void write() throws IOException {
            for (PdfReaderInstance element : readerInstances.values()) {
                currentPdfReaderInstance= element;
                currentPdfReaderInstance.writeAllPages();
            }

            PdfDictionary dic = new PdfDictionary();
            dic.put(PdfName.FIELDS, calculate(fdf.fields));
            if (fdf.file != null)
                dic.put(PdfName.F, new PdfString(fdf.file, PdfObject.TEXT_UNICODE));
            if (fdf.statusMessage != null && fdf.statusMessage.trim().length() != 0)
                dic.put(PdfName.STATUS, new PdfString(fdf.statusMessage));
            PdfDictionary fd = new PdfDictionary();
            fd.put(PdfName.FDF, dic);
            PdfIndirectReference ref = addToBody(fd).getIndirectReference();
            os.write(getISOBytes("trailer\n"));
            PdfDictionary trailer = new PdfDictionary();
            trailer.put(PdfName.ROOT, ref);
            trailer.toPdf(null, os);
            os.write(getISOBytes("\n%%EOF\n"));
            os.close();
        }


        @SuppressWarnings("unchecked")
        PdfArray calculate(HashMap<String, Object> map) throws IOException {
            PdfArray ar = new PdfArray();
            for (Map.Entry<String, Object> entry: map.entrySet()) {
                String key = entry.getKey();
                Object v = entry.getValue();
                PdfDictionary dic = new PdfDictionary();
                dic.put(PdfName.T, new PdfString(key, PdfObject.TEXT_UNICODE));
                if (v instanceof HashMap) {
                    dic.put(PdfName.KIDS, calculate((HashMap<String, Object>)v));
                } else if(v instanceof PdfAction) {	// (plaflamme)
                   	dic.put(PdfName.A, (PdfAction)v);
                } else if (v instanceof PdfAnnotation) {
                    dic.put(PdfName.AA, (PdfAnnotation)v);
                } else if (v instanceof PdfDictionary && ((PdfDictionary)v).size() == 1 && ((PdfDictionary)v).contains(PdfName.N)) {
                    dic.put(PdfName.AP, (PdfDictionary)v);
                } else {
                    dic.put(PdfName.V, (PdfObject)v);
                }
                ar.add(dic);
            }
            return ar;
        }
    }

	protected Counter COUNTER = CounterFactory.getCounter(FdfWriter.class);
	protected Counter getCounter() {
		return COUNTER;
	}
}

⏎ com/itextpdf/text/pdf/FdfWriter.java

Or download all of them as a single archive file:

File name: itextpdf-5.5.14-fyi.zip
File size: 2163839 bytes
Release date: 2009-10-09
Download 

⇒ iText-2.1.6.jar - iText, a JAVA-PDF library

⇐ iText layout.jar Source Code

⇑ Download and Install iText Java Library

⇑⇑ iText for PDF Generation