Class URLDecoder

public class URLDecoder
extends Object

Utility class for HTML form decoding. This class contains static methods for decoding a String from the application/x-www-form-urlencoded MIME format.

The conversion process is the reverse of that used by the URLEncoder class. It is assumed that all characters in the encoded string are one of the following: "a" through "z", "A" through "Z", "0" through "9", and "-", "_", ".", and "*". The character "%" is allowed but is interpreted as the start of a special escaped sequence.

The following rules are applied in the conversion:

  • The alphanumeric characters "a" through "z", "A" through "Z" and "0" through "9" remain the same.
  • The special characters ".", "-", "*", and "_" remain the same.
  • The plus sign "+" is converted into a space character " " .
  • A sequence of the form "%xy" will be treated as representing a byte where xy is the two-digit hexadecimal representation of the 8 bits. Then, all substrings that contain one or more of these byte sequences consecutively will be replaced by the character(s) whose encoding would result in those consecutive bytes. The encoding scheme used to decode these characters may be specified, or if unspecified, the default encoding of the platform will be used.

There are two possible ways in which this decoder could deal with illegal strings. It could either leave illegal characters alone or it could throw an IllegalArgumentException. Which approach the decoder takes is left to the implementation.

Since:
1.2

Constructor Summary

Constructors
Constructor Description
URLDecoder()

Method Summary

All Methods Static Methods Concrete Methods Deprecated Methods
Modifier and Type Method Description
static String decode​(String s)

Deprecated.

The resulting string may vary depending on the platform's default encoding.
static String decode​(String s, String enc)

Decodes an application/x-www-form-urlencoded string using a specific encoding scheme.
static String decode​(String s, Charset charset)

Decodes an application/x-www-form-urlencoded string using a specific Charset.

Methods declared in class java.lang.Object

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

Constructor Detail

URLDecoder

public URLDecoder()

Method Detail

decode

@Deprecated
public static String decode​(String s)
Deprecated.
The resulting string may vary depending on the platform's default encoding. Instead, use the decode(String,String) method to specify the encoding.

Decodes a x-www-form-urlencoded string. The platform's default encoding is used to determine what characters are represented by any consecutive sequences of the form "%xy".

Parameters:
s - the String to decode
Returns:
the newly decoded String

decode

public static String decode​(String s,
                            String enc)
                     throws UnsupportedEncodingException

Decodes an application/x-www-form-urlencoded string using a specific encoding scheme.

This method behaves the same as decode(java.lang.String,java.nio.charset.Charset) except that it will look up the charset using the given encoding name.

Implementation Note:
This implementation will throw an IllegalArgumentException when illegal strings are encountered.
Parameters:
s - the String to decode
enc - The name of a supported character encoding.
Returns:
the newly decoded String
Throws:
UnsupportedEncodingException - If character encoding needs to be consulted, but named character encoding is not supported
Since:
1.4
See Also:
URLEncoder.encode(java.lang.String, java.lang.String)

decode

public static String decode​(String s,
                            Charset charset)

Decodes an application/x-www-form-urlencoded string using a specific Charset. The supplied charset is used to determine what characters are represented by any consecutive sequences of the form "%xy".

Note: The World Wide Web Consortium Recommendation states that UTF-8 should be used. Not doing so may introduce incompatibilities.

Implementation Note:
This implementation will throw an IllegalArgumentException when illegal strings are encountered.
Parameters:
s - the String to decode
charset - the given charset
Returns:
the newly decoded String
Throws:
NullPointerException - if s or charset is null
IllegalArgumentException - if the implementation encounters illegal characters
Since:
10
See Also:
URLEncoder.encode(java.lang.String, java.nio.charset.Charset)