http://commons.apache.org/proper/commons-codec/: The Apache Commons Codec package contains simple encoder and decoders for various formats such as Base64 and Hexadecimal. In addition to these widely used encoders and decoders, the codec package also maintains a collection of phonetic encoding utilities. (The Apache Software Foundation)
  • Christopher O'Brien
  • Martin Redington
  • Jeffery Dever
  • Steve Zimmermann
  • Benjamin Walstrum
  • Oleg Kalnichevski
  • Dave Dribin
  • Alex Karasulu
  • Matthew Inger
  • Jochen Wiedmann
  • Sebastian Bazley
  • Matthew Pocock
  • Colm Rice 
/*
 * 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.codec.net;

import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;

import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.EncoderException;
import org.apache.commons.codec.binary.StringUtils;


Implements methods common to all codecs defined in RFC 1522.


RFC 1522 describes techniques to allow the
encoding of non-ASCII text in various portions of a RFC 822 [2] message header, in a manner which
is unlikely to confuse existing message handling software.


This class is immutable and thread-safe.

See Also:
Since:1.3
Version:$Id$
/**
 * Implements methods common to all codecs defined in RFC 1522.
 * <p>
 * <a href="http://www.ietf.org/rfc/rfc1522.txt">RFC 1522</a> describes techniques to allow the
 * encoding of non-ASCII text in various portions of a RFC 822 [2] message header, in a manner which
 * is unlikely to confuse existing message handling software.
 * <p>
 * This class is immutable and thread-safe.
 *
 * @see <a href="http://www.ietf.org/rfc/rfc1522.txt">MIME (Multipurpose Internet Mail Extensions) Part Two:
 *          Message Header Extensions for Non-ASCII Text</a>
 *
 * @since 1.3
 * @version $Id$
 */
abstract class RFC1522Codec {

    
Separator. 
/** Separator. */
    protected static final char SEP = '?';

    
Prefix. 
/** Prefix. */
    protected static final String POSTFIX = "?=";

    
Postfix. 
/** Postfix. */
    protected static final String PREFIX = "=?";

    
Applies an RFC 1522 compliant encoding scheme to the given string of text with the given charset.

 This method constructs the "encoded-word" header common to all the RFC 1522 codecs and then invokes doEncoding(byte[]) method of a concrete class to perform the specific encoding. 
Params:
  • text – 
           a string to encode
  • charset – 
           a charset to be used
Throws:
  • EncoderException – 
            thrown if there is an error condition during the Encoding process.
See Also:
Returns:RFC 1522 compliant "encoded-word"
/**
     * Applies an RFC 1522 compliant encoding scheme to the given string of text with the given charset.
     * <p>
     * This method constructs the "encoded-word" header common to all the RFC 1522 codecs and then invokes
     * {@link #doEncoding(byte [])} method of a concrete class to perform the specific encoding.
     *
     * @param text
     *            a string to encode
     * @param charset
     *            a charset to be used
     * @return RFC 1522 compliant "encoded-word"
     * @throws EncoderException
     *             thrown if there is an error condition during the Encoding process.
     * @see <a href="http://download.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
     */
    protected String encodeText(final String text, final Charset charset) throws EncoderException {
        if (text == null) {
            return null;
        }
        final StringBuilder buffer = new StringBuilder();
        buffer.append(PREFIX);
        buffer.append(charset);
        buffer.append(SEP);
        buffer.append(this.getEncoding());
        buffer.append(SEP);
        final byte [] rawData = this.doEncoding(text.getBytes(charset));
        buffer.append(StringUtils.newStringUsAscii(rawData));
        buffer.append(POSTFIX);
        return buffer.toString();
    }

    
Applies an RFC 1522 compliant encoding scheme to the given string of text with the given charset.

 This method constructs the "encoded-word" header common to all the RFC 1522 codecs and then invokes doEncoding(byte[]) method of a concrete class to perform the specific encoding. 
Params:
  • text – 
           a string to encode
  • charsetName – 
           the charset to use
Throws:
See Also:
Returns:RFC 1522 compliant "encoded-word"
/**
     * Applies an RFC 1522 compliant encoding scheme to the given string of text with the given charset.
     * <p>
     * This method constructs the "encoded-word" header common to all the RFC 1522 codecs and then invokes
     * {@link #doEncoding(byte [])} method of a concrete class to perform the specific encoding.
     *
     * @param text
     *            a string to encode
     * @param charsetName
     *            the charset to use
     * @return RFC 1522 compliant "encoded-word"
     * @throws EncoderException
     *             thrown if there is an error condition during the Encoding process.
     * @throws UnsupportedEncodingException
     *             if charset is not available
     *
     * @see <a href="http://download.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
     */
    protected String encodeText(final String text, final String charsetName)
            throws EncoderException, UnsupportedEncodingException {
        if (text == null) {
            return null;
        }
        return this.encodeText(text, Charset.forName(charsetName));
    }

    
Applies an RFC 1522 compliant decoding scheme to the given string of text.

 This method processes the "encoded-word" header common to all the RFC 1522 codecs and then invokes doEncoding(byte[]) method of a concrete class to perform the specific decoding. 
Params:
  • text – 
           a string to decode
Throws:
Returns:A new decoded String or null if the input is null.
/**
     * Applies an RFC 1522 compliant decoding scheme to the given string of text.
     * <p>
     * This method processes the "encoded-word" header common to all the RFC 1522 codecs and then invokes
     * {@link #doEncoding(byte [])} method of a concrete class to perform the specific decoding.
     *
     * @param text
     *            a string to decode
     * @return A new decoded String or <code>null</code> if the input is <code>null</code>.
     * @throws DecoderException
     *             thrown if there is an error condition during the decoding process.
     * @throws UnsupportedEncodingException
     *             thrown if charset specified in the "encoded-word" header is not supported
     */
    protected String decodeText(final String text)
            throws DecoderException, UnsupportedEncodingException {
        if (text == null) {
            return null;
        }
        if (!text.startsWith(PREFIX) || !text.endsWith(POSTFIX)) {
            throw new DecoderException("RFC 1522 violation: malformed encoded content");
        }
        final int terminator = text.length() - 2;
        int from = 2;
        int to = text.indexOf(SEP, from);
        if (to == terminator) {
            throw new DecoderException("RFC 1522 violation: charset token not found");
        }
        final String charset = text.substring(from, to);
        if (charset.equals("")) {
            throw new DecoderException("RFC 1522 violation: charset not specified");
        }
        from = to + 1;
        to = text.indexOf(SEP, from);
        if (to == terminator) {
            throw new DecoderException("RFC 1522 violation: encoding token not found");
        }
        final String encoding = text.substring(from, to);
        if (!getEncoding().equalsIgnoreCase(encoding)) {
            throw new DecoderException("This codec cannot decode " + encoding + " encoded content");
        }
        from = to + 1;
        to = text.indexOf(SEP, from);
        byte[] data = StringUtils.getBytesUsAscii(text.substring(from, to));
        data = doDecoding(data);
        return new String(data, charset);
    }

    
Returns the codec name (referred to as encoding in the RFC 1522).

Returns:name of the codec
/**
     * Returns the codec name (referred to as encoding in the RFC 1522).
     *
     * @return name of the codec
     */
    protected abstract String getEncoding();

    
Encodes an array of bytes using the defined encoding scheme.

Params:
  • bytes – 
           Data to be encoded
Throws:
  • EncoderException – 
            thrown if the Encoder encounters a failure condition during the encoding process.
Returns:A byte array containing the encoded data
/**
     * Encodes an array of bytes using the defined encoding scheme.
     *
     * @param bytes
     *            Data to be encoded
     * @return A byte array containing the encoded data
     * @throws EncoderException
     *             thrown if the Encoder encounters a failure condition during the encoding process.
     */
    protected abstract byte[] doEncoding(byte[] bytes) throws EncoderException;

    
Decodes an array of bytes using the defined encoding scheme.

Params:
  • bytes – 
           Data to be decoded
Throws:
  • DecoderException – 
            A decoder exception is thrown if a Decoder encounters a failure condition during the decode process.
Returns:a byte array that contains decoded data
/**
     * Decodes an array of bytes using the defined encoding scheme.
     *
     * @param bytes
     *            Data to be decoded
     * @return a byte array that contains decoded data
     * @throws DecoderException
     *             A decoder exception is thrown if a Decoder encounters a failure condition during the decode process.
     */
    protected abstract byte[] doDecoding(byte[] bytes) throws DecoderException;
}