@Beta @GwtCompatible public abstract class Escaper extends Object
For example, an XML escaper would convert the literal string "Foo<Bar>"
into "Foo<Bar>"
to prevent "<Bar>"
from being confused with an XML tag. When the resulting XML document is parsed, the parser API will return this text as the original literal string "Foo<Bar>"
.
An Escaper
instance is required to be stateless, and safe when used concurrently by multiple threads.
Because, in general, escaping operates on the code points of a string and not on its individual char
values, it is not safe to assume that escape(s)
is equivalent to escape(s.substring(0, n)) + escape(s.substing(n))
for arbitrary n
. This is because of the possibility of splitting a surrogate pair. The only case in which it is safe to escape strings and concatenate the results is if you can rule out this possibility, either by splitting an existing long string into short strings adaptively around surrogate pairs, or by starting with short strings already known to be free of unpaired surrogates.
The two primary implementations of this interface are CharEscaper
and UnicodeEscaper
. They are heavily optimized for performance and greatly simplify the task of implementing new escapers. It is strongly recommended that when implementing a new escaper you extend one of these classes. If you find that you are unable to achieve the desired behavior using either of these classes, please contact the Java libraries team for advice.
Popular escapers are defined as constants in classes like HtmlEscapers
and XmlEscapers
. To create your own escapers, use CharEscaperBuilder
, or extend CharEscaper
or UnicodeEscaper
.
Modifier | Constructor and Description |
---|---|
protected |
Escaper()
Constructor for use by subclasses.
|
Modifier and Type | Method and Description |
---|---|
Function |
asFunction()
Returns a
Function that invokes
escape(String) on this escaper.
|
abstract String |
escape(String
Returns the escaped form of a given literal string.
|
public abstract Stringescape(String string)
Note that this method may treat input characters differently depending on the specific escaper implementation.
UnicodeEscaper
handles UTF-16 correctly, including surrogate character pairs. If the input is badly formed the escaper should throw IllegalArgumentException
. CharEscaper
handles Java characters independently and does not verify the input for well formed characters. A CharEscaper
should not be used in situations where input is not guaranteed to be restricted to the Basic Multilingual Plane (BMP). string
- the literal string to be escaped
string
NullPointerException
- if
string
is null
IllegalArgumentException
- if
string
contains badly formed UTF-16 or cannot be escaped for any other reason
public final Function<String ,String > asFunction()
Function
that invokes
escape(String)
on this escaper.