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/PRAcroForm.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 java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;

/**
 * This class captures an AcroForm on input. Basically, it extends Dictionary
 * by indexing the fields of an AcroForm
 * @author Mark Thompson
 */

public class PRAcroForm extends PdfDictionary {

    /**
     * This class holds the information for a single field
     */
    public static class FieldInformation {
    	String fieldName;
        PdfDictionary info;
        PRIndirectReference ref;

        FieldInformation(String fieldName, PdfDictionary info, PRIndirectReference ref) {
            this.fieldName = fieldName;
        	this.info = info;
            this.ref = ref;
        }
        
        /**
         * Returns the name of the widget annotation (the /NM entry).
         * @return	a String or null (if there's no /NM key)
         */
        public String getWidgetName() {
        	PdfObject name = info.get(PdfName.NM);
        	if (name != null)
        		return name.toString();
        	return null;
        }
        
        /**
         * Returns the full name of the field.
         * @return	a String or null
         */
        public String getName() {
        	return fieldName;
        }
        
        public PdfDictionary getInfo() {
        	return info;
        }
        
        public PRIndirectReference getRef() {
        	return ref;
        }
    };
    ArrayList<FieldInformation> fields;
    ArrayList<PdfDictionary> stack;
    HashMap<String, FieldInformation> fieldByName;
    PdfReader reader;

    /**
     * Constructor
     * @param reader reader of the input file
     */
    public PRAcroForm(PdfReader reader) {
        this.reader = reader;
        fields = new ArrayList<FieldInformation>();
        fieldByName = new HashMap<String, FieldInformation>();
        stack = new ArrayList<PdfDictionary>();
    }
    /**
     * Number of fields found
     * @return size
     */
    @Override
    public int size() {
        return fields.size();
    }

    public ArrayList<FieldInformation> getFields() {
        return fields;
    }

    public FieldInformation getField(String name) {
        return fieldByName.get(name);
    }

    /**
     * Given the title (/T) of a reference, return the associated reference
     * @param name a string containing the path
     * @return a reference to the field, or null
     */
    public PRIndirectReference getRefByName(String name) {
        FieldInformation fi = fieldByName.get(name);
        if (fi == null) return null;
        return fi.getRef();
    }
    /**
     * Read, and comprehend the acroform
     * @param root the document root
     */
    public void readAcroForm(PdfDictionary root) {
        if (root == null)
            return;
        hashMap = root.hashMap;
        pushAttrib(root);
        PdfArray fieldlist = (PdfArray)PdfReader.getPdfObjectRelease(root.get(PdfName.FIELDS));
        if (fieldlist != null) {
            iterateFields(fieldlist, null, null);
        }
    }

    /**
     * After reading, we index all of the fields. Recursive.
     * @param fieldlist An array of fields
     * @param fieldDict the last field dictionary we encountered (recursively)
     * @param parentPath the pathname of the field, up to this point or null
     */
    protected void iterateFields(PdfArray fieldlist, PRIndirectReference fieldDict, String parentPath) {
        for (Iterator<PdfObject> it = fieldlist.listIterator(); it.hasNext();) {
            PRIndirectReference ref = (PRIndirectReference)it.next();
            PdfDictionary dict = (PdfDictionary) PdfReader.getPdfObjectRelease(ref);

            // if we are not a field dictionary, pass our parent's values
            PRIndirectReference myFieldDict = fieldDict;
            String fullPath = parentPath;
            PdfString tField = (PdfString)dict.get(PdfName.T);
            boolean isFieldDict = tField != null;

            if (isFieldDict) {
                myFieldDict = ref;
                if (parentPath == null) {
                	fullPath = tField.toString();
                }
                else {
                	fullPath = parentPath + '.' + tField.toString();
                }
            }

            PdfArray kids = (PdfArray)dict.get(PdfName.KIDS);
            if (kids != null) {
                pushAttrib(dict);
                iterateFields(kids, myFieldDict, fullPath);
                stack.remove(stack.size() - 1);   // pop
            }
            else {          // leaf node
                if (myFieldDict != null) {
                    PdfDictionary mergedDict = stack.get(stack.size() - 1);
                    if (isFieldDict)
                        mergedDict = mergeAttrib(mergedDict, dict);

                    mergedDict.put(PdfName.T, new PdfString(fullPath));
                    FieldInformation fi = new FieldInformation(fullPath, mergedDict, myFieldDict);
                    fields.add(fi);
                    fieldByName.put(fullPath, fi);
                }
            }
        }
    }
    /**
     * merge field attributes from two dictionaries
     * @param parent one dictionary
     * @param child the other dictionary
     * @return a merged dictionary
     */
    protected PdfDictionary mergeAttrib(PdfDictionary parent, PdfDictionary child) {
        PdfDictionary targ = new PdfDictionary();
        if (parent != null) targ.putAll(parent);

        for (Object element : child.getKeys()) {
            PdfName key = (PdfName) element;
            if (key.equals(PdfName.DR) || key.equals(PdfName.DA) ||
            key.equals(PdfName.Q)  || key.equals(PdfName.FF) ||
            key.equals(PdfName.DV) || key.equals(PdfName.V)
            || key.equals(PdfName.FT) || key.equals(PdfName.NM)
            || key.equals(PdfName.F)) {
                targ.put(key,child.get(key));
            }
        }
        return targ;
    }
    /**
     * stack a level of dictionary. Merge in a dictionary from this level
     */
    protected void pushAttrib(PdfDictionary dict) {
        PdfDictionary dic = null;
        if (!stack.isEmpty()) {
            dic = stack.get(stack.size() - 1);
        }
        dic = mergeAttrib(dic, dict);
        stack.add(dic);
    }
}

⏎ com/itextpdf/text/pdf/PRAcroForm.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