Base64 Encoding and Decoding in Java
Base64 is a binary-to-text encoding scheme that describes binary data in an ASCII string format by translating it into a radix-64 representation. It is primarily used to transfer content-based messages over the Internet.
In this article, you’ll learn how to perform Base64 encoding and decoding by using the Base64 class in Java. This class provides static methods to get encoders and decoders for the Base64 encoding scheme.
- Basic: — This is the standard Base64 encoding that only uses a-z , A-Z , 0-9 , / , and + characters (also called The Base64 Alphabet) for encoding and decoding operation. The encoder does not add the line feed character. If there are characters outside of the Base64 alphabet, the decoder rejects the data.
- URL and Filename safe — This is very much similar to the Basic Base64 encoding except that + and / symbols are replaced with — and _ respectively to make the output URL and filename safe. No line feed character is added by the encoder. The decoder rejects the data if it contains characters outside of a-z , A-Z , 0-9 , — , and _ (known as URL and Filename safe Base64 Alphabet).
- MIME — The MIME variant uses the Basic Base64 Alphabet (characters from a-z , A-Z , 0-9 , / , and + ) for encoding and decoding operation. The encoded output is represented in lines of no more than 76 characters each. Every line, except the last line, is separated from the next line by using a carriage return \r followed by a linefeed \n . The decoder ignores all line separators or other characters not found in the base64 Alphabet.
Now it is time to do the actual Base64 encoding in Java by using the Base64 class. Let us start with the basic encoding example.
The simplest way to Base64 encode a string in Java is by using the basic encoding scheme. The basic encoder keeps the things simple — no line feeds are added to the output and the output is mapped to a set of characters in the Base64 Alphabet ( a-zA-Z0-9+/ ). The getEncoder() method returns the Base64.Encoder class instance that encodes using the Basic type Base64 encoding scheme. Here is an example that shows how to perform basic Base64 encoding in Java:
try // data to encode String data = "This is an example string."; // Base64 encode the string String encodedStr = Base64.getEncoder() .encodeToString(data.getBytes(StandardCharsets.UTF_8.name())); // print the output System.out.println(encodedStr); > catch (UnsupportedEncodingException ex) ex.printStackTrace(); > VGhpcyBpcyBhbiBleGFtcGxlIHN0cmluZy4= By default, the length of the Base64 encoded string must be a multiple of three. If it is not, the encoder adds one or two padding characters ( = ) at the end of the encoded string. While decoding, these padding characters are discarded. It is always recommended to use the padding if you want to decode the string at a later point. But if you are sure that the encoded data will never be decoded, you can skip the padding with withoutPadding() and save a couple of bytes:
try // data to encode String data = "This is an example string."; // Base64 encode the string without padding String encodedStr = Base64.getEncoder() .withoutPadding() .encodeToString(data.getBytes(StandardCharsets.UTF_8.name())); // print the output System.out.println(encodedStr); > catch (UnsupportedEncodingException ex) ex.printStackTrace(); > VGhpcyBpcyBhbiBleGFtcGxlIHN0cmluZy4 The URL and filename safe Base64 encoding is same as the basic Base64 encoding with the exception that + and / characters are replaced with the URL safe characters — and _ in the final output. This encoding variant is particularly useful when you want to include the encoded string to the URL or filename. It uses the URL and filename safe Base64 alphabet ( a-zA-Z0-9-_ ) and does not add any line separation. Just call the getUrlEncoder() method to get a Base64.Encoder instance that encodes using the URL and Filename safe type Base64 encoding scheme:
try // url to encode String data = "Are you a web developer?"; // Base64 url and filename safe encoding String encodedStr = Base64.getUrlEncoder() .encodeToString(data.getBytes(StandardCharsets.UTF_8.name())); // print the output System.out.println(encodedStr); > catch (UnsupportedEncodingException ex) ex.printStackTrace(); > QXJlIHlvdSBhIHdlYiBkZXZlbG9wZXI_ Important: Don’t confuse URL and filename safe Base64 encoding with the URL string encoding. URL string encoding converts a string into a valid URL format only without changing the characters to random ASCII symbols. Whereas URL and filename safe encoding is actually a Base64 encoding with the exception that it only uses URL friendly symbols.
The MIME encoder creates a Base64 encoded string by using the basic alphabet ( a-zA-Z0-9+/ ) but in a MIME friendly format. Each line of the output is no more than 76 characters and ends with a carriage return followed by a linefeed ( \r\n ). You can use the getMimeEncoder() method to get a Base64.Encoder instance that encodes using the MIME type Base64 encoding scheme:
try // create a block of text to encode StringBuilder builder = new StringBuilder(); for (int i = 0; i 10; i++) builder.append(UUID.randomUUID().toString()); > // Base64 MIME encoding String encodedStr = Base64.getMimeEncoder() .encodeToString(builder.toString().getBytes(StandardCharsets.UTF_8.name())); // print the output System.out.println(encodedStr); > catch (UnsupportedEncodingException ex) ex.printStackTrace(); > NmQ2MWIyNTItOGYwYi00MjM1LWE0ZjItOGU3OWRhYzQyNzhmYzQ4NjRiNGUtYzdmYS00MTI3LTlh NDEtNmIwNTlhODNkZWU1MWE3NWYyOGItZmQyMC00NzkwLTkxMDQtODA2MGNlYjJkNGM0YTBiZDlm ZDktZDk4Ni00YzM0LTg4OGQtMzBkNjk1ODJmMjRmNDViNjBmNjEtNDkzMy00MzFhLTk2YTItMTdh YmExMWY4Y2NkMjBkNmQxNTctYzFmOS00MWE3LTk5NTEtNmFiYTRlMjQ4NDYzYzU3NzNlZDYtZTg2 MC00ZWRmLWI4YWQtMDhlYWY2ZjZkMTgwZDNlODRjMzktYzlhMy00OTMyLWFmZGItMjZkOWQzYTFj M2FjZTRhOWJmYmQtZTcxNC00MjBkLTkwYmEtODFmMzE3ZTU3MjdiNTE3ZDRhZTItNGIzNi00YTIx LWFlMWMtNmZiOWZjMzIxOTU4 For every Base64 encoding variant implemented by the Base64 class, there is a decoder to turn the data back to its original form (except without padding encoding).
For Base64 basic decoding, just use the getDecoder() to get a Base64.Decoder instance that decodes using the Basic type Base64 encoding scheme:
try // data to decode String encodedData = "VGhpcyBpcyBhbiBleGFtcGxlIHN0cmluZy4="; // Base64 basic decoding byte[] dataBytes = Base64.getDecoder().decode(encodedData); String data = new String(dataBytes, StandardCharsets.UTF_8.name()); // print the output System.out.println(data); > catch (UnsupportedEncodingException ex) ex.printStackTrace(); > This is an example string. For Base64 URL and filename safe decoding, there is a getUrlDecoder() static method that returns a Base64.Decoder instance to decode by using the URL and Filename safe type Base64 encoding scheme:
try // data to decode String encodedData = "QXJlIHlvdSBhIHdlYiBkZXZlbG9wZXI_"; // Base64 URL and filename safe decoding byte[] dataBytes = Base64.getUrlDecoder().decode(encodedData); String data = new String(dataBytes, StandardCharsets.UTF_8.name()); // print the output System.out.println(data); > catch (UnsupportedEncodingException ex) ex.printStackTrace(); > The getMimeDecoder() utility method returns a Base64.Decoder that decodes using the MIME type Base64 decoding scheme:
try // data to decode String encodedData = "MzcwNDkwZjUtNDk1Ni00YTg1LWJkZjItZWQzNTU2MDI0MjcxCmY2OGMzZWVhLTFhNDItNDkyZC1h\n" + "MzdlLWRjMjJlODk5YjllNAo1YWMzMjExMy0yOWZmLTRhYWYtYmUyYy0zOWVhYjg5YWY4OTMKNzQ3\n" + "ZDE5NTctY2ZhNS00MDcxLTllYjktMjAzMDFkODBhYzc0Cg=="; // Base64 MIME decoding byte[] dataBytes = Base64.getMimeDecoder().decode(encodedData); String data = new String(dataBytes, StandardCharsets.UTF_8.name()); // print the output System.out.println(data); > catch (UnsupportedEncodingException ex) ex.printStackTrace(); > 370490f5-4956-4a85-bdf2-ed3556024271 f68c3eea-1a42-492d-a37e-dc22e899b9e4 5ac32113-29ff-4aaf-be2c-39eab89af893 747d1957-cfa5-4071-9eb9-20301d80ac74 The Apache Commons Codec library provides common encoders and decoders such as Base64, Hex, Phonetic and URLs. To add Commons Codec to your project, add the following dependency to your build.gradle file:
implementation 'commons-codec:commons-codec:1.13' dependency> groupId>commons-codecgroupId> artifactId>commons-codecartifactId> version>1.13version> dependency> Similar to Java 8, Commons Codec provides the Base64 class for Base64 encoding and decoding as defined by RFC 2045. Let us use this class to Base64 encode a string in Java:
try // data to encode String data = "Java programming language."; // create a new instance of Base64 (Commons Codec) Base64 base64 = new Base64(); // Base64 encode byte[] encodedBytes = base64.encode(data.getBytes()); String encodedStr = new String(encodedBytes, StandardCharsets.UTF_8.name()); // print the output System.out.println(encodedStr); // SmF2YSBwcm9ncmFtbWluZyBsYW5ndWFnZS4= > catch (Exception ex) ex.printStackTrace(); > If you do not want to create an instance of Base64 , use the static method Base64.encodeBase64() instead:
try // data to encode String data = "Java programming language."; // Base64 encode String encodedStr = new String(Base64.encodeBase64(data.getBytes()), StandardCharsets.UTF_8.name()); // print the output System.out.println(encodedStr); > catch (Exception ex) ex.printStackTrace(); > Similarly, you can decode the encoded string by using the Base64.decodeBase64() static method:
try // data to decode String encodedSData = "SmF2YSBwcm9ncmFtbWluZyBsYW5ndWFnZS4="; // Base64 decode String data = new String(Base64.decodeBase64(encodedSData), StandardCharsets.UTF_8.name()); // print the output System.out.println(data); > catch (Exception ex) ex.printStackTrace(); > You might also like.
Кодирование и декодирование Base64 в Java
В этом посте будет обсуждаться кодирование и декодирование Base64 с использованием простой Java, Guava и Apache Commons.
Base64 представляет собой группу подобных схем кодирования двоичного кода в текст, представляющих двоичные данные в формате строки ASCII путем преобразования их в radix-64 представление. Каждый Base64 цифра представляет ровно 6 бит данных, что означает, что 3 байта могут быть представлены 4 6-битными Base64 цифры.
Схемы кодирования Base64 обычно используются, когда необходимо кодировать двоичные данные, которые необходимо хранить и передавать через носители, предназначенные для работы с текстовыми данными. Это необходимо для того, чтобы данные оставались неповрежденными без изменений во время транспортировки. Base64 обычно используется в ряде приложений, включая электронную почту через MIME и хранение сложных данных в XML .
1. Использование Java 8
Java 8, наконец, обеспечила поддержку возможностей кодирования и декодирования Base64, предоставив Base64, Base64.Encoder а также Base64.Decoder класс полезности. Base64 класс состоит из статических методов для получения экземпляров энкодеров ( Base64.Encoder ) и декодеры ( Base64.Decoder ) для схемы кодирования Base64.
В следующей программе используется Base64.Encoder.encodeToString() метод для кодирования указанного массива байтов в кодированную строку Base64 и Base64.Decoder.decode() метод обратного декодирования строки в кодировке Base64 во вновь выделенный массив байтов.