What Is fop.jar? I got it from the fop-2.7-bin.zip.

fop.jar in fop-2.7-bin.zip is the JAR file for FOP 2.7, which is a print formatter driven by XSL formatting objects (XSL-FO). You can obtain fop.jar from the build folder of the fop-2.7-bin.zip file.

Below is the information about the fop.jar (2.2) file:

JAR File Size and Download Location:

JAR name: fop.jar, fop-2.7.jar
Target JDK version: 1.7
File name: fop.jar
File size: 4442817 bytes
Release date: 20-Jan-2022
Download: Apache FOP Website

Java source code files for fop.jar:

⏎ org/apache/fop/render/pdf/PageSequenceStructElem.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/* $Id: PageSequenceStructElem.java 1862557 2019-07-04 13:48:41Z ssteiner $ */

package org.apache.fop.render.pdf;

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

import org.apache.fop.pdf.PDFArray;
import org.apache.fop.pdf.PDFObject;
import org.apache.fop.pdf.PDFStructElem;
import org.apache.fop.pdf.StructureType;

public class PageSequenceStructElem extends PDFStructElem {

    private static final long serialVersionUID = -9146602678931267198L;
    private List<PDFStructElem> regionBefores = new ArrayList<PDFStructElem>();

    private List<PDFStructElem> regionAfters = new ArrayList<PDFStructElem>();

    private List<PDFStructElem> regionStarts = new ArrayList<PDFStructElem>();

    private List<PDFStructElem> regionEnds = new ArrayList<PDFStructElem>();

    private List<PDFStructElem> footnoteSeparator = new ArrayList<PDFStructElem>();

    PageSequenceStructElem(PDFObject parent, StructureType structureType) {
        super(parent, structureType);
    }

    void addContent(String flowName, PDFStructElem content) {
        if (flowName.equals("xsl-region-before")) {
            regionBefores.add(content);
        } else if (flowName.equals("xsl-region-after")) {
            regionAfters.add(content);
        } else if (flowName.equals("xsl-region-start")) {
            regionStarts.add(content);
        } else if (flowName.equals("xsl-region-end")) {
            regionEnds.add(content);
        } else if (flowName.equals("xsl-footnote-separator")) {
            footnoteSeparator.add(content);
        } else {
            addKid(content);
        }
    }

    @Override
    protected boolean attachKids() {
        assert !kids.isEmpty();
        PDFArray k = new PDFArray();
        addRegions(k, regionBefores);
        addRegions(k, regionStarts);
        addRegions(k, kids);
        addRegions(k, regionEnds);
        addRegions(k, footnoteSeparator);
        addRegions(k, regionAfters);
        put("K", k);
        return true;
    }

    private void addRegions(PDFArray k, List<? extends PDFObject> regions) {
        if (!regions.isEmpty()) {
            for (PDFObject kid : regions) {
                k.add(kid);
            }
        }
    }

}

⏎ org/apache/fop/render/pdf/PageSequenceStructElem.java

Or download all of them as a single archive file:

File name: fop-2.7-src.zip
File size: 3401312 bytes
Release date: 2022-01-20
Download 

⇒ "fop" Command in fop-2.7-bin.zip

⇐ What Is fop-2.7-bin.zip

⇑ Download and Installing of FOP 2.x

⇑⇑ FAQ for FOP (Formatting Object Processor)