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/extensions/AbstractPDFExtensionElement.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: AbstractPDFExtensionElement.java 1610822 2014-07-15 19:27:58Z vhennebert $ */

package org.apache.fop.render.pdf.extensions;

import org.apache.fop.fo.FONode;
import org.apache.fop.fo.extensions.ExtensionAttachment;

/**
 * Base class for the PDF-specific extension elements.
 */
public abstract class AbstractPDFExtensionElement extends FONode {

    /**Extension attachment. */
    protected PDFExtensionAttachment attachment;

    /**
     * Default constructor
     *
     * @param parent parent of this node
     * @see org.apache.fop.fo.FONode#FONode(FONode)
     */
    public AbstractPDFExtensionElement(FONode parent) {
        super(parent);
    }

    /** {@inheritDoc} */
    public String getNamespaceURI() {
        return PDFElementMapping.NAMESPACE;
    }

    /** {@inheritDoc} */
    public String getNormalNamespacePrefix() {
        return "pdf";
    }

    /**
     * Returns the extension attachment.
     * @return the extension attachment if one is created by the extension element, null otherwise.
     * @see org.apache.fop.fo.FONode#getExtensionAttachment()
     */
    public ExtensionAttachment getExtensionAttachment() {
        if (attachment == null) {
            this.attachment = (PDFExtensionAttachment)instantiateExtensionAttachment();
        }
        return this.attachment;
    }

    /**
     * Instantiates extension attachment object.
     * @return extension attachment
     */
    protected ExtensionAttachment instantiateExtensionAttachment() {
        return null;
    }

}

⏎ org/apache/fop/render/pdf/extensions/AbstractPDFExtensionElement.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)