commons-net.jar is the bytecode of Apache Commons Net library, which implements the client side of many basic Internet protocols.

Apache Commons Net Source Code files are provided in the binary packge (commons-net-3.8.0-bin.zip). You can download it at Apache Commons Net Website.

The source code of commons-net-3.8.0.jar is provided below:

⏎ org/apache/commons/net/smtp/SimpleSMTPHeader.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.
 */

package org.apache.commons.net.smtp;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;

/**
 * This class is used to construct a bare minimum
 * acceptable header for an email message.  To construct more
 * complicated headers you should refer to RFC 5322.  When the
 * Java Mail API is finalized, you will be
 * able to use it to compose fully compliant Internet text messages.
 * <p>
 * The main purpose of the class is to faciliatate the mail sending
 * process, by relieving the programmer from having to explicitly format
 * a simple message header.  For example:
 * <pre>
 * writer = client.sendMessageData();
 * if(writer == null) // failure
 *   return false;
 * header =
 *    new SimpleSMTPHeader("foobar@foo.com", "foo@bar.com" "Just testing");
 * header.addCC("bar@foo.com");
 * header.addHeaderField("Organization", "Foobar, Inc.");
 * writer.write(header.toString());
 * writer.write("This is just a test");
 * writer.close();
 * if(!client.completePendingCommand()) // failure
 *   return false;
 * </pre>
 *
 * @see SMTPClient
 */

public class SimpleSMTPHeader
{
    private final String subject;
    private final String from;
    private final String to;
    private final StringBuffer headerFields;
    private boolean hasHeaderDate;
    private StringBuffer cc;

    /**
     * Creates a new SimpleSMTPHeader instance initialized with the given
     * from, to, and subject header field values.
     * <p>
     * @param from  The value of the <code>From:</code> header field.  This
     *              should be the sender's email address.
     *              Must not be null.
     * @param to    The value of the <code>To:</code> header field.  This
     *              should be the recipient's email address.
     *              May be null
     * @param subject  The value of the <code>Subject:</code> header field.
     *              This should be the subject of the message.
     *              May be null
     */
    public SimpleSMTPHeader(final String from, final String to, final String subject)
    {
        if (from == null) {
            throw new IllegalArgumentException("From cannot be null");
        }
        this.to = to;
        this.from = from;
        this.subject = subject;
        this.headerFields = new StringBuffer();
        this.cc = null;
    }

    /**
     * Adds an arbitrary header field with the given value to the article
     * header.  These headers will be written before the From, To, Subject, and
     * Cc fields when the SimpleSMTPHeader is convertered to a string.
     * An example use would be:
     * <pre>
     * header.addHeaderField("Organization", "Foobar, Inc.");
     * </pre>
     * <p>
     * @param headerField  The header field to add, not including the colon.
     * @param value  The value of the added header field.
     */
    public void addHeaderField(final String headerField, final String value)
    {
        if (!hasHeaderDate && "Date".equals(headerField)) {
            hasHeaderDate = true;
        }
        headerFields.append(headerField);
        headerFields.append(": ");
        headerFields.append(value);
        headerFields.append('\n');
    }


    /**
     * Add an email address to the CC (carbon copy or courtesy copy) list.
     * <p>
     * @param address The email address to add to the CC list.
     */
    public void addCC(final String address)
    {
        if (cc == null) {
            cc = new StringBuffer();
        } else {
            cc.append(", ");
        }

        cc.append(address);
    }


    /**
     * Converts the SimpleSMTPHeader to a properly formatted header in
     * the form of a String, including the blank line used to separate
     * the header from the article body.  The header fields CC and Subject
     * are only included when they are non-null.
     * <p>
     * @return The message header in the form of a String.
     */
    @Override
    public String toString()
    {
        final StringBuilder header = new StringBuilder();

        final String pattern = "EEE, dd MMM yyyy HH:mm:ss Z"; // Fri, 21 Nov 1997 09:55:06 -0600
        final SimpleDateFormat format = new SimpleDateFormat(pattern, Locale.ENGLISH);

        if (!hasHeaderDate) {
            addHeaderField("Date", format.format(new Date()));
        }
        if (headerFields.length() > 0) {
            header.append(headerFields.toString());
        }

        header.append("From: ").append(from).append("\n");

        if (to != null) {
            header.append("To: ").append(to).append("\n");
        }

        if (cc != null)
        {
            header.append("Cc: ").append(cc.toString()).append("\n");
        }

        if (subject != null)
        {
            header.append("Subject: ").append(subject).append("\n");
        }

        header.append('\n'); // end of headers; body follows

        return header.toString();
    }
}

⏎ org/apache/commons/net/smtp/SimpleSMTPHeader.java

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File name: commons-net-3.8.0-sources.jar
File size: 437325 bytes
Release date: 2020-01-22
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