Class BCodec

java.lang.Object
org.apache.commons.codec.net.BCodec
All Implemented Interfaces:
Decoder, Encoder, StringDecoder, StringEncoder
public class BCodec extends Object implements StringEncoder, StringDecoder
Identical to the Base64 encoding defined by RFC 1521 and allows a character set to be specified.

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.

Decoding is lenient by default: the Base64 payload can contain ignored characters, noncanonical padding or trailing bits, and data after padding. Different encoded words can therefore decode to the same text. To require a canonical Base64 payload, select CodecPolicy.STRICT: 

BCodec codec = new BCodec(StandardCharsets.UTF_8, CodecPolicy.STRICT);

Strict decoding requires the standard Base64 alphabet, padding for partial blocks, and no whitespace within the payload. Invalid payloads cause a DecoderException. This validates the Base64 payload only; it does not establish a unique representation of the complete encoded word or message header, including its charset label. Applications comparing header values for security decisions must use a consistent representation, and signature verification must follow the signing protocol.

Since:
1.3
See Also:

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    protected final Charset
    charset
    The default Charset used for string decoding and encoding.
    protected static final String
    POSTFIX
    Prefix.
    protected static final String
    PREFIX
    Postfix.
    protected static final char
    SEP
    Separator.

  • Constructor Summary

    Constructors
    Constructor
    Description
    BCodec()
    Constructs a new instance.
    BCodec(String charsetName)
    Constructs a new instance for the selection of a default Charset.
    BCodec(Charset charset)
    Constructs a new instance for the selection of a default Charset.
    BCodec(Charset charset, CodecPolicy decodingPolicy)
    Constructs a new instance for the selection of a default Charset.

  • Method Summary

    Modifier and Type
    Method
    Description
    Object
    decode(Object value)
    Decodes a Base64 object into its original form.
    String
    decode(String value)
    Decodes a Base64 string into its original form.
    protected String
    decodeText(String text)
    Applies an RFC 1522 compliant decoding scheme to the given string of text.
    protected byte[]
    doDecoding(byte[] bytes)
    Decodes an array of bytes using the defined encoding scheme.
    protected byte[]
    doEncoding(byte[] bytes)
    Encodes an array of bytes using the defined encoding scheme.
    Object
    encode(Object value)
    Encodes an object into its Base64 form using the default Charset.
    String
    encode(String strSource)
    Encodes a string into its Base64 form using the default Charset.
    String
    encode(String strSource, String sourceCharset)
    Encodes a string into its Base64 form using the specified Charset.
    String
    encode(String strSource, Charset sourceCharset)
    Encodes a string into its Base64 form using the specified Charset.
    protected String
    encodeText(String text, String charsetName)
    Applies an RFC 1522 compliant encoding scheme to the given string of text with the given charset.
    protected String
    encodeText(String text, Charset charset)
    Applies an RFC 1522 compliant encoding scheme to the given string of text with the given charset.
    Charset
    getCharset()
    Gets the default Charset name used for string decoding and encoding.
    String
    getDefaultCharset()
    Gets the default Charset name used for string decoding and encoding.
    protected String
    getEncoding()
    Gets the codec name (referred to as encoding in the RFC 1522).
    boolean
    isStrictDecoding()
    Tests whether decoding requires a canonical Base64 payload.

    Methods inherited from class Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

  • Constructor Details

    • BCodec

      public BCodec()
      Constructs a new instance.

    • BCodec

      public BCodec(Charset charset)
      Constructs a new instance for the selection of a default Charset.
      Parameters:
      charset - the default string Charset to use.
      Since:
      1.7
      See Also:

    • BCodec

      public BCodec(Charset charset, CodecPolicy decodingPolicy)
      Constructs a new instance for the selection of a default Charset.

      Use CodecPolicy.STRICT to require canonical standard Base64 payloads. The other constructors use CodecPolicy.LENIENT. This policy applies to the Base64 payload, not the complete encoded word; see the class documentation.

      Parameters:
      charset - the default string Charset to use.
      decodingPolicy - The decoding policy.
      Since:
      1.15
      See Also:

    • BCodec

      public BCodec(String charsetName)
      Constructs a new instance for the selection of a default Charset.
      Parameters:
      charsetName - the default Charset to use.
      Throws:
      UnsupportedCharsetException - Thrown if the named Charset is unavailable.
      Since:
      1.7 throws UnsupportedCharsetException if the named Charset is unavailable
      See Also:

  • Method Details

    • decode

      public Object decode(Object value) throws DecoderException
      Decodes a Base64 object into its original form. Escaped characters are converted back to their original representation.

      Uses the decoding policy selected at construction. The default is lenient and does not require a canonical Base64 payload. Use BCodec(Charset, CodecPolicy) with CodecPolicy.STRICT for canonical payload validation.

      Specified by:
      decode in interface Decoder
      Parameters:
      value - Base64 object to convert into its original form.
      Returns:
      original object.
      Throws:
      DecoderException - Thrown if the argument is not a String. Thrown if a failure condition is encountered during the decode process.

    • decode

      public String decode(String value) throws DecoderException
      Decodes a Base64 string into its original form. Escaped characters are converted back to their original representation.

      Uses the decoding policy selected at construction. The default is lenient and does not require a canonical Base64 payload. Use BCodec(Charset, CodecPolicy) with CodecPolicy.STRICT for canonical payload validation.

      Specified by:
      decode in interface StringDecoder
      Parameters:
      value - Base64 string to convert into its original form.
      Returns:
      original string.
      Throws:
      DecoderException - Thrown if a failure condition is encountered during the decoding process.

    • doDecoding

      protected byte[] doDecoding(byte[] bytes) throws DecoderException
      Decodes an array of bytes using the defined encoding scheme.
      Parameters:
      bytes - Data to be decoded.
      Returns:
      A byte array that contains decoded data.
      Throws:
      IllegalArgumentException - Thrown when a problem is detected processing data.
      DecoderException - Thrown if a Decoder encounters a failure condition during the decode process.

    • doEncoding

      protected byte[] doEncoding(byte[] bytes)
      Encodes an array of bytes using the defined encoding scheme.
      Parameters:
      bytes - Data to be encoded.
      Returns:
      A byte array containing the encoded data.

    • encode

      public Object encode(Object value) throws EncoderException
      Encodes an object into its Base64 form using the default Charset. Unsafe characters are escaped.
      Specified by:
      encode in interface Encoder
      Parameters:
      value - object to convert to Base64 form.
      Returns:
      Base64 object.
      Throws:
      EncoderException - Thrown if a failure condition is encountered during the encoding process.

    • encode

      public String encode(String strSource) throws EncoderException
      Encodes a string into its Base64 form using the default Charset. Unsafe characters are escaped.
      Specified by:
      encode in interface StringEncoder
      Parameters:
      strSource - string to convert to Base64 form.
      Returns:
      Base64 string.
      Throws:
      EncoderException - Thrown if a failure condition is encountered during the encoding process.

    • encode

      public String encode(String strSource, Charset sourceCharset) throws EncoderException
      Encodes a string into its Base64 form using the specified Charset. Unsafe characters are escaped.
      Parameters:
      strSource - string to convert to Base64 form.
      sourceCharset - the Charset for value.
      Returns:
      Base64 string.
      Throws:
      EncoderException - Thrown if a failure condition is encountered during the encoding process.
      Since:
      1.7

    • encode

      public String encode(String strSource, String sourceCharset) throws EncoderException
      Encodes a string into its Base64 form using the specified Charset. Unsafe characters are escaped.
      Parameters:
      strSource - string to convert to Base64 form.
      sourceCharset - the Charset for value.
      Returns:
      Base64 string.
      Throws:
      EncoderException - Thrown if a failure condition is encountered during the encoding process.

    • getEncoding

      protected String getEncoding()
      Gets the codec name (referred to as encoding in the RFC 1522).
      Returns:
      name of the codec.

    • isStrictDecoding

      public boolean isStrictDecoding()
      Tests whether decoding requires a canonical Base64 payload.

      Strict decoding raises DecoderException for a noncanonical Base64 payload, including invalid alphabet characters, padding, or trailing bits. The default is lenient. This policy does not establish a canonical representation of the complete encoded word.

      Returns:
      true if using strict decoding.
      Since:
      1.15

    • decodeText

      protected String decodeText(String text) throws DecoderException, UnsupportedEncodingException
      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 doDecoding(byte[]) method of a concrete class to perform the specific decoding.

      Parameters:
      text - A string to decode.
      Returns:
      A new decoded String or null if the input is null.
      Throws:
      DecoderException - Thrown if there is an error condition during the decoding process.
      UnsupportedEncodingException - Thrown if charset specified in the "encoded-word" header is not supported.

    • encodeText

      protected String encodeText(String text, Charset charset) throws EncoderException
      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.

      Parameters:
      text - A string to encode.
      charset - A charset to be used.
      Returns:
      RFC 1522 compliant "encoded-word".
      Throws:
      EncoderException - Thrown if there is an error condition during the encoding process.
      See Also:

    • encodeText

      protected String encodeText(String text, String charsetName) throws EncoderException
      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.

      Parameters:
      text - A string to encode.
      charsetName - The charset to use.
      Returns:
      RFC 1522 compliant "encoded-word".
      Throws:
      EncoderException - Thrown if there is an error condition during the encoding process.
      UnsupportedCharsetException - Thrown if charset is not available.
      See Also:

    • getCharset

      public Charset getCharset()
      Gets the default Charset name used for string decoding and encoding.
      Returns:
      The default Charset name.
      Since:
      1.7

    • getDefaultCharset

      public String getDefaultCharset()
      Gets the default Charset name used for string decoding and encoding.
      Returns:
      The default Charset name.