Class URLDecoder

java.lang.Object

java.net.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 charset 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

See Also:

• Charset.defaultCharset()

Method Summary

Modifier and Type	Method	Description
static String	decode(String s)	Deprecated. The resulting string may vary depending on the default charset.
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

Method Details

decode

@Deprecated
public static String decode(String s)

Deprecated.

The resulting string may vary depending on the default charset. Instead, use the decode(String,String) method to specify the encoding.

Decodes a x-www-form-urlencoded string. The default charset 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

Throws:

IllegalArgumentException - if the implementation encounters malformed escape sequences

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.

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

IllegalArgumentException - if the implementation encounters malformed escape sequences

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 escape sequences of the form "%xy". Erroneous bytes are replaced with the supplied Charset's replacement value.

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

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 malformed escape sequences

Since:

10

External Specifications

• HTML 4.01 Specification

See Also:

• URLEncoder.encode(java.lang.String, Charset)