com.google.api.client.util.escape

Class PercentEscaper

java.lang.Object

com.google.api.client.util.escape.Escaper

com.google.api.client.util.escape.UnicodeEscaper

com.google.api.client.util.escape.PercentEscaper

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) is specified on construction.

For details on escaping URIs for use in web pages, see RFC 3986 - section 2.4 and RFC 3986 - appendix A

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 is true, the space character " " is converted into a plus sign "+".
• All other characters are converted into one or more bytes using UTF-8 encoding. 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 3986 defines the set of unreserved characters as "-", "_", "~", and "." It goes on to state:

URIs that differ in the replacement of an unreserved character with its corresponding percent-encoded US-ASCII octet are equivalent: they identify the same resource. However, URI comparison implementations do not always perform normalization prior to comparison (see Section 6). For consistency, percent-encoded octets in the ranges of ALPHA (%41-%5A and %61-%7A), DIGIT (%30-%39), hyphen (%2D), period (%2E), underscore (%5F), or tilde (%7E) should not be created by URI producers and, when found in a URI, should be decoded to their corresponding unreserved characters by URI normalizers.

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

Since:

1.0

Field Summary

Fields

Modifier and Type	Field and Description
static String	SAFE_PLUS_RESERVED_CHARS_URLENCODER Contains the safe characters plus all reserved characters.
static String	SAFECHARS_URLENCODER A string of safe characters that mimics the behavior of URLEncoder.
static 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 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.
static String	SAFEUSERINFOCHARS_URLENCODER A string of characters that do not need to be encoded when used in URI user info part, as specified in RFC 3986.

Constructor Summary

Constructors

Constructor and Description
PercentEscaper(String safeChars) Constructs a URI escaper with the specified safe characters.
PercentEscaper(String safeChars, boolean plusForSpace) Deprecated. use PercentEscaper(String safeChars) instead which is the same as invoking this method with plusForSpace set to false. Escaping spaces as plus signs does not conform to the URI specification.

Method Summary

Modifier and Type	Method and Description
protected char[]	escape(int cp) Escapes the given Unicode code point in UTF-8.
String	escape(String s) Returns the escaped form of a given literal string.
protected int	nextEscapeIndex(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 com.google.api.client.util.escape.UnicodeEscaper

codePointAt, 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 String SAFECHARS_URLENCODER

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

See Also:

Constant Field Values

SAFEPATHCHARS_URLENCODER

public static final 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

SAFE_PLUS_RESERVED_CHARS_URLENCODER

public static final String SAFE_PLUS_RESERVED_CHARS_URLENCODER

Contains the safe characters plus all reserved characters. This happens to be the safe path characters plus those characters which are reserved for URI segments, namely '/' and '?'.

See Also:

Constant Field Values

SAFEUSERINFOCHARS_URLENCODER

public static final String SAFEUSERINFOCHARS_URLENCODER

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

Since:

1.15

See Also:

Constant Field Values

SAFEQUERYSTRINGCHARS_URLENCODER

public static final 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(String safeChars)

Constructs a URI escaper with the specified safe characters. The space character is escaped to %20 in accordance with the URI specification.

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)

Throws:

IllegalArgumentException - if any of the parameters are invalid

PercentEscaper

@Deprecated
public PercentEscaper(String safeChars,
                                  boolean plusForSpace)

Deprecated. use PercentEscaper(String safeChars) instead which is the same as invoking this method with plusForSpace set to false. Escaping spaces as plus signs does not conform to the URI specification.

Constructs a URI escaper that converts all but the specified safe characters into hexadecimal percent escapes. Optionally space characters can be converted into a plus sign + instead of %20. and optional handling of the space

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:

IllegalArgumentException - if safeChars includes characters that are always safe or characters that must always be escaped

Method Detail

nextEscapeIndex

protected int nextEscapeIndex(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 clear warning to users that your escaper does not validate its input.

See PercentEscaper for an example.

Specified by:

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 String escape(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 ensure your input is valid UTF-16 before calling this method.

Specified by:

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