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/afp/modca/StreamedResourceGroup.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: StreamedResourceGroup.java 1610839 2014-07-15 20:25:58Z vhennebert $ */

package org.apache.fop.afp.modca;

import java.io.IOException;
import java.io.OutputStream;

import org.apache.fop.afp.Completable;

/**
 * A print-file resource group
 */
public class StreamedResourceGroup extends ResourceGroup implements Completable {
    /** the outputstream to write to */
    private final OutputStream os;

    private boolean started;

    private boolean complete;

    /**
     * Main constructor
     *
     * @param name the resource group name
     * @param os the outputstream
     */
    public StreamedResourceGroup(String name, OutputStream os) {
        super(name);
        this.os = os;
    }

    /**
     * Adds a resource to the external resource group
     *
     * @param namedObject a named object
     * @throws IOException thrown if an I/O exception of some sort has occurred.
     */
    public void addObject(AbstractNamedAFPObject namedObject) throws IOException {
        if (!started) {
            writeStart(os);
            started = true;
        }
        try {
            namedObject.writeToStream(os);
        } finally {
            os.flush();
        }
    }

    /**
     * Closes this external resource group file
     *
     * @throws IOException thrown if an I/O exception of some sort has occurred.
     */
    public void close() throws IOException {
        writeEnd(os);
        complete = true;
    }

    /**
     * Returns the outputstream
     *
     * @return the outputstream
     */
    public OutputStream getOutputStream() {
        return this.os;
    }

    /** {@inheritDoc} */
    public void setComplete(boolean complete) {
        this.complete = complete;
    }

    /** {@inheritDoc} */
    public boolean isComplete() {
        return this.complete;
    }

}

⏎ org/apache/fop/afp/modca/StreamedResourceGroup.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)