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/fo/expr/FunctionBase.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: FunctionBase.java 1547372 2013-12-03 12:44:41Z vhennebert $ */

package org.apache.fop.fo.expr;

import org.apache.fop.datatypes.PercentBase;
import org.apache.fop.fo.properties.Property;
import org.apache.fop.fo.properties.StringProperty;

/**
 * Abstract Base class for XSL-FO functions
 */
public abstract class FunctionBase implements Function {

    /** {@inheritDoc} */
    public int getOptionalArgsCount() {
        return 0;
    }

    /** {@inheritDoc} */
    public Property getOptionalArgDefault(int index, PropertyInfo pi) throws PropertyException {
        if (index >= getOptionalArgsCount()) {
            PropertyException e = new PropertyException(
                    new IndexOutOfBoundsException("illegal optional argument index"));
            e.setPropertyInfo(pi);
            throw e;
        } else {
            return null;
        }
    }

    /** {@inheritDoc} */
    public boolean hasVariableArgs() {
        return false;
    }

    /** {@inheritDoc} */
    public PercentBase getPercentBase() {
        return null;
    }

    /**
     * @param pi property information instance that applies to property being evaluated
     * @return string property whose value is name of property being evaluated
     */
    protected final Property getPropertyName(PropertyInfo pi) {
        return StringProperty.getInstance(pi.getPropertyMaker().getName());
    }
}

⏎ org/apache/fop/fo/expr/FunctionBase.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)