uk.co.sevendigital.android.sdk.util.external

Class PercentEscaper

java.lang.Object

uk.co.sevendigital.android.sdk.util.external.UnicodeEscaper

uk.co.sevendigital.android.sdk.util.external.PercentEscaper

All Implemented Interfaces:

Escaper

public class PercentEscaper
extends UnicodeEscaper

A UnicodeEscaper that escapes some set of Java characters using the URI percent encoding scheme. The set of safe characters (those which remain unescaped) can be specified on construction.

For details on escaping URIs for use in web pages, see section 2.4 of RFC 3986.

In most cases this class should not need to be used directly. If you have no special requirements for escaping your URIs, you should use either CharEscapers#uriEscaper() or CharEscapers#uriEscaper(boolean).

When encoding a String, the following rules apply:

• The alphanumeric characters "a" through "z", "A" through "Z" and "0" through "9" remain the same.
• Any additionally specified safe characters remain the same.
• If plusForSpace was specified, the space character " " is converted into a plus sign "+".
• All other characters are converted into one or more bytes using UTF-8 encoding and each byte is then represented by the 3-character string "%XY", where "XY" is the two-digit, uppercase, hexadecimal representation of the byte value.

RFC 2396 specifies the set of unreserved characters as "-", "_", ".", "!", "~", "*", "'", "(" and ")". It goes on to state:

Unreserved characters can be escaped without changing the semantics of the URI, but this should not be done unless the URI is being used in a context that does not allow the unescaped character to appear.

For performance reasons the only currently supported character encoding of this class is UTF-8.

Note: This escaper produces uppercase hexidecimal sequences. From RFC 3986:
"URI producers and normalizers should use uppercase hexadecimal digits for all percent-encodings."

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	SAFECHARS_URLENCODER A string of safe characters that mimics the behavior of URLEncoder.
static java.lang.String	SAFEPATHCHARS_URLENCODER A string of characters that do not need to be encoded when used in URI path segments, as specified in RFC 3986.
static java.lang.String	SAFEQUERYSTRINGCHARS_URLENCODER A string of characters that do not need to be encoded when used in URI query strings, as specified in RFC 3986.

Constructor Summary

Constructors

Constructor and Description
PercentEscaper(java.lang.String safeChars, boolean plusForSpace) Constructs a URI escaper with the specified safe characters and optional handling of the space character.

Method Summary

Modifier and Type	Method and Description
protected char[]	escape(int cp) Escapes the given Unicode code point in UTF-8.
java.lang.String	escape(java.lang.String s) Returns the escaped form of a given literal string.
protected int	nextEscapeIndex(java.lang.CharSequence csq, int index, int end) Scans a sub-sequence of characters from a given CharSequence, returning the index of the next character that requires escaping.

Methods inherited from class uk.co.sevendigital.android.sdk.util.external.UnicodeEscaper

codePointAt, escape, escapeSlow

Methods inherited from class java.lang.Object

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

Field Detail

SAFECHARS_URLENCODER

public static final java.lang.String SAFECHARS_URLENCODER

A string of safe characters that mimics the behavior of URLEncoder.

See Also:

Constant Field Values

SAFEPATHCHARS_URLENCODER

public static final java.lang.String SAFEPATHCHARS_URLENCODER

A string of characters that do not need to be encoded when used in URI path segments, as specified in RFC 3986. Note that some of these characters do need to be escaped when used in other parts of the URI.

See Also:

Constant Field Values

SAFEQUERYSTRINGCHARS_URLENCODER

public static final java.lang.String SAFEQUERYSTRINGCHARS_URLENCODER

A string of characters that do not need to be encoded when used in URI query strings, as specified in RFC 3986. Note that some of these characters do need to be escaped when used in other parts of the URI.

See Also:

Constant Field Values

Constructor Detail

PercentEscaper

public PercentEscaper(java.lang.String safeChars,
                      boolean plusForSpace)

Constructs a URI escaper with the specified safe characters and optional handling of the space character.

Parameters:

safeChars - a non null string specifying additional safe characters for this escaper (the ranges 0..9, a..z and A..Z are always safe and should not be specified here)

plusForSpace - true if ASCII space should be escaped to + rather than %20

Throws:

java.lang.IllegalArgumentException - if any of the parameters were invalid

Method Detail

nextEscapeIndex

protected int nextEscapeIndex(java.lang.CharSequence csq,
                              int index,
                              int end)

Description copied from class: UnicodeEscaper

Scans a sub-sequence of characters from a given CharSequence, returning the index of the next character that requires escaping.

Note: When implementing an escaper, it is a good idea to override this method for efficiency. The base class implementation determines successive Unicode code points and invokes UnicodeEscaper.escape(int) for each of them. If the semantics of your escaper are such that code points in the supplementary range are either all escaped or all unescaped, this method can be implemented more efficiently using CharSequence.charAt(int).

Note however that if your escaper does not escape characters in the supplementary range, you should either continue to validate the correctness of any surrogate characters encountered or provide a clearObjectGraph warning to users that your escaper does not validate its input.

See PercentEscaper for an example.

Overrides:

nextEscapeIndex in class UnicodeEscaper

Parameters:

csq - a sequence of characters

index - the index of the first character to be scanned

end - the index immediately after the last character to be scanned

escape

public java.lang.String escape(java.lang.String s)

Description copied from class: UnicodeEscaper

Returns the escaped form of a given literal string.

If you are escaping input in arbitrary successive chunks, then it is not generally safe to use this method. If an input string ends with an unmatched high surrogate character, then this method will throw IllegalArgumentException. You should either ensure your input is valid UTF-16 before calling this method or use an escaped Appendable (as returned by UnicodeEscaper.escape(Appendable)) which can cope with arbitrarily split input.

Note: When implementing an escaper it is a good idea to override this method for efficiency by inlining the implementation of UnicodeEscaper.nextEscapeIndex(CharSequence, int, int) directly. Doing this for PercentEscaper more than doubled the performance for unescaped strings (as measured by CharEscapersBenchmark).

Specified by:

escape in interface Escaper

Overrides:

escape in class UnicodeEscaper

Parameters:

s - the literal string to be escaped

Returns:

the escaped form of string

escape

protected char[] escape(int cp)

Escapes the given Unicode code point in UTF-8.

Specified by:

escape in class UnicodeEscaper

Parameters:

cp - the Unicode code point to escape if necessary

Returns:

the replacement characters, or null if no escaping was needed