org.unbescape.json
Class JsonEscape

Object
  org.unbescape.json.JsonEscape

public final class JsonEscape
extends Object

Utility class for performing JSON escape/unescape operations.

Configuration of escape/unescape operations

Escape operations can be (optionally) configured by means of:

• Level, which defines how deep the escape operation must be (what chars are to be considered eligible for escaping, depending on the specific needs of the scenario). Its values are defined by the JsonEscapeLevel enum.
• Type, which defines whether escaping should be performed by means of SECs (Single Escape Characters like \n) or additionally by means of u-based hexadecimal references (\u00E1). Its values are defined by the JsonEscapeType enum.

Unescape operations need no configuration parameters. Unescape operations will always perform complete unescape of SECs (\n) and u-based (\u00E1) hexadecimal escapes.

Features

Specific features of the JSON escape/unescape operations performed by means of this class:

• The JSON basic escape set is supported. This basic set consists of:
  • The Single Escape Characters: \b (U+0008), \t (U+0009), \n (U+000A), \f (U+000C), \r (U+000D), \" (U+0022), \\ (U+005C) and \/ (U+002F). Note that \/ is optional, and will only be used when the / symbol appears after <, as in </. This is to avoid accidentally closing <script> tags in HTML.
  • Two ranges of non-displayable, control characters (some of which are already part of the single escape characters list): U+0000 to U+001F (required by the JSON spec) and U+007F to U+009F (additional).
• U-based hexadecimal escapes (a.k.a. unicode escapes) are supported both in escape and unescape operations: \u00E1.
• Support for the whole Unicode character set: \u0000 to \u10FFFF, including characters not representable by only one char in Java (>\uFFFF).

Input/Output

There are two different input/output modes that can be used in escape/unescape operations:

• String input, String output: Input is specified as a String object and output is returned as another. In order to improve memory performance, all escape and unescape operations will return the exact same input object as output if no escape/unescape modifications are required.
• char[] input, java.io.Writer output: Input will be read from a char array (char[]) and output will be written into the specified java.io.Writer. Two int arguments called offset and len will be used for specifying the part of the char[] that should be escaped/unescaped. These methods should be called with offset = 0 and len = text.length in order to process the whole char[].

Glossary

SEC

Single Escape Character: \b (U+0008), \t (U+0009), \n (U+000A), \f (U+000C), \r (U+000D), \" (U+0022), \\ (U+005C) and \/ (U+002F) (optional, only in </).

UHEXA escapes

Also called u-based hexadecimal escapes or simply unicode escapes: complete representation of unicode codepoints up to U+FFFF, with \u followed by exactly four hexadecimal figures: \u00E1. Unicode codepoints > U+FFFF can be represented in JSON by mean of two UHEXA escapes (a surrogate pair).

Unicode Codepoint

Each of the int values conforming the Unicode code space. Normally corresponding to a Java char primitive value (codepoint <= \uFFFF), but might be two chars for codepoints \u10000 to \u10FFFF if the first char is a high surrogate (\uD800 to \uDBFF) and the second is a low surrogate (\uDC00 to \uDFFF).

References

The following references apply:

• RFC4627: The application/json Media Type for JavaScript Object Notation (JSON) [ietf.org]
• JSON: The JavaScript subset that isn't [timelessrepo.com]
• There is no such thing as a "JSON Object" [benalman.com]

Since:

1.0

Author:

Daniel Fernández

Method Summary

static void	escapeJson(char[] text, int offset, int len, Writer writer) Perform a JSON level 2 (basic set and all non-ASCII chars) escape operation on a char[] input.
static void	escapeJson(char[] text, int offset, int len, Writer writer, JsonEscapeType type, JsonEscapeLevel level) Perform a (configurable) JSON escape operation on a char[] input.
static String	escapeJson(String text) Perform a JSON level 2 (basic set and all non-ASCII chars) escape operation on a String input.
static String	escapeJson(String text, JsonEscapeType type, JsonEscapeLevel level) Perform a (configurable) JSON escape operation on a String input.
static void	escapeJsonMinimal(char[] text, int offset, int len, Writer writer) Perform a JSON level 1 (only basic set) escape operation on a char[] input.
static String	escapeJsonMinimal(String text) Perform a JSON level 1 (only basic set) escape operation on a String input.
static void	unescapeJson(char[] text, int offset, int len, Writer writer) Perform a JSON unescape operation on a char[] input.
static String	unescapeJson(String text) Perform a JSON unescape operation on a String input.

Methods inherited from class Object

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

Method Detail

escapeJsonMinimal

public static String escapeJsonMinimal(String text)

Perform a JSON level 1 (only basic set) escape operation on a String input.

Level 1 means this method will only escape the JSON basic escape set:

• The Single Escape Characters: \b (U+0008), \t (U+0009), \n (U+000A), \f (U+000C), \r (U+000D), \" (U+0022), \\ (U+005C) and \/ (U+002F). Note that \/ is optional, and will only be used when the / symbol appears after <, as in </. This is to avoid accidentally closing <script> tags in HTML.
• Two ranges of non-displayable, control characters (some of which are already part of the single escape characters list): U+0000 to U+001F (required by the JSON spec) and U+007F to U+009F (additional).

This method calls escapeJson(String, JsonEscapeType, JsonEscapeLevel) with the following preconfigured values:

• type: JsonEscapeType.SINGLE_ESCAPE_CHARS_DEFAULT_TO_UHEXA
• level: JsonEscapeLevel.LEVEL_1_BASIC_ESCAPE_SET

This method is thread-safe.

Parameters:

text - the String to be escaped.

Returns:

The escaped result String. As a memory-performance improvement, will return the exact same object as the text input argument if no escaping modifications were required (and no additional String objects will be created during processing). Will return null if text is null.

escapeJson

public static String escapeJson(String text)

Perform a JSON level 2 (basic set and all non-ASCII chars) escape operation on a String input.

Level 2 means this method will escape:

• The JSON basic escape set:
  • The Single Escape Characters: \b (U+0008), \t (U+0009), \n (U+000A), \f (U+000C), \r (U+000D), \" (U+0022), \\ (U+005C) and \/ (U+002F). Note that \/ is optional, and will only be used when the / symbol appears after <, as in </. This is to avoid accidentally closing <script> tags in HTML.
  • Two ranges of non-displayable, control characters (some of which are already part of the single escape characters list): U+0000 to U+001F (required by the JSON spec) and U+007F to U+009F (additional).
• All non ASCII characters.

This escape will be performed by using the Single Escape Chars whenever possible. For escaped characters that do not have an associated SEC, default to \uFFFF Hexadecimal Escapes.

This method calls escapeJson(String, JsonEscapeType, JsonEscapeLevel) with the following preconfigured values:

• type: JsonEscapeType.SINGLE_ESCAPE_CHARS_DEFAULT_TO_UHEXA
• level: JsonEscapeLevel.LEVEL_2_ALL_NON_ASCII_PLUS_BASIC_ESCAPE_SET

This method is thread-safe.

Parameters:

text - the String to be escaped.

Returns:

The escaped result String. As a memory-performance improvement, will return the exact same object as the text input argument if no escaping modifications were required (and no additional String objects will be created during processing). Will return null if text is null.

escapeJson

public static String escapeJson(String text,
                                JsonEscapeType type,
                                JsonEscapeLevel level)

Perform a (configurable) JSON escape operation on a String input.

This method will perform an escape operation according to the specified JsonEscapeType and JsonEscapeLevel argument values.

All other String-based escapeJson*(...) methods call this one with preconfigured type and level values.

This method is thread-safe.

Parameters:

text - the String to be escaped.

type - the type of escape operation to be performed, see JsonEscapeType.

level - the escape level to be applied, see JsonEscapeLevel.

Returns:

The escaped result String. As a memory-performance improvement, will return the exact same object as the text input argument if no escaping modifications were required (and no additional String objects will be created during processing). Will return null if text is null.

escapeJsonMinimal

public static void escapeJsonMinimal(char[] text,
                                     int offset,
                                     int len,
                                     Writer writer)
                              throws IOException

Perform a JSON level 1 (only basic set) escape operation on a char[] input.

Level 1 means this method will only escape the JSON basic escape set:

• The Single Escape Characters: \b (U+0008), \t (U+0009), \n (U+000A), \f (U+000C), \r (U+000D), \" (U+0022), \\ (U+005C) and \/ (U+002F). Note that \/ is optional, and will only be used when the / symbol appears after <, as in </. This is to avoid accidentally closing <script> tags in HTML.
• Two ranges of non-displayable, control characters (some of which are already part of the single escape characters list): U+0000 to U+001F (required by the JSON spec) and U+007F to U+009F (additional).

This method calls escapeJson(char[], int, int, java.io.Writer, JsonEscapeType, JsonEscapeLevel) with the following preconfigured values:

• type: JsonEscapeType.SINGLE_ESCAPE_CHARS_DEFAULT_TO_UHEXA
• level: JsonEscapeLevel.LEVEL_1_BASIC_ESCAPE_SET

This method is thread-safe.

Parameters:

text - the char[] to be escaped.

offset - the position in text at which the escape operation should start.

len - the number of characters in text that should be escaped.

writer - the java.io.Writer to which the escaped result will be written. Nothing will be written at all to this writer if text is null.

Throws:

IOException

escapeJson

public static void escapeJson(char[] text,
                              int offset,
                              int len,
                              Writer writer)
                       throws IOException

Perform a JSON level 2 (basic set and all non-ASCII chars) escape operation on a char[] input.

Level 2 means this method will escape:

• The JSON basic escape set:
  • The Single Escape Characters: \b (U+0008), \t (U+0009), \n (U+000A), \f (U+000C), \r (U+000D), \" (U+0022), \\ (U+005C) and \/ (U+002F). Note that \/ is optional, and will only be used when the / symbol appears after <, as in </. This is to avoid accidentally closing <script> tags in HTML.
  • Two ranges of non-displayable, control characters (some of which are already part of the single escape characters list): U+0000 to U+001F (required by the JSON spec) and U+007F to U+009F (additional).
• All non ASCII characters.

This escape will be performed by using the Single Escape Chars whenever possible. For escaped characters that do not have an associated SEC, default to \uFFFF Hexadecimal Escapes.

This method calls escapeJson(char[], int, int, java.io.Writer, JsonEscapeType, JsonEscapeLevel) with the following preconfigured values:

• type: JsonEscapeType.SINGLE_ESCAPE_CHARS_DEFAULT_TO_UHEXA
• level: JsonEscapeLevel.LEVEL_2_ALL_NON_ASCII_PLUS_BASIC_ESCAPE_SET

This method is thread-safe.

Parameters:

text - the char[] to be escaped.

offset - the position in text at which the escape operation should start.

len - the number of characters in text that should be escaped.

writer - the java.io.Writer to which the escaped result will be written. Nothing will be written at all to this writer if text is null.

Throws:

IOException

escapeJson

public static void escapeJson(char[] text,
                              int offset,
                              int len,
                              Writer writer,
                              JsonEscapeType type,
                              JsonEscapeLevel level)
                       throws IOException

Perform a (configurable) JSON escape operation on a char[] input.

This method will perform an escape operation according to the specified JsonEscapeType and JsonEscapeLevel argument values.

All other char[]-based escapeJson*(...) methods call this one with preconfigured type and level values.

This method is thread-safe.

Parameters:

text - the char[] to be escaped.

offset - the position in text at which the escape operation should start.

len - the number of characters in text that should be escaped.

writer - the java.io.Writer to which the escaped result will be written. Nothing will be written at all to this writer if text is null.

type - the type of escape operation to be performed, see JsonEscapeType.

level - the escape level to be applied, see JsonEscapeLevel.

Throws:

IOException

unescapeJson

public static String unescapeJson(String text)

Perform a JSON unescape operation on a String input.

No additional configuration arguments are required. Unescape operations will always perform complete JSON unescape of SECs and u-based escapes.

This method is thread-safe.

Parameters:

text - the String to be unescaped.

Returns:

The unescaped result String. As a memory-performance improvement, will return the exact same object as the text input argument if no unescaping modifications were required (and no additional String objects will be created during processing). Will return null if text is null.

unescapeJson

public static void unescapeJson(char[] text,
                                int offset,
                                int len,
                                Writer writer)
                         throws IOException

Perform a JSON unescape operation on a char[] input.

No additional configuration arguments are required. Unescape operations will always perform complete JSON unescape of SECs and u-based escapes.

This method is thread-safe.

Parameters:

text - the char[] to be unescaped.

offset - the position in text at which the unescape operation should start.

len - the number of characters in text that should be unescaped.

writer - the java.io.Writer to which the unescaped result will be written. Nothing will be written at all to this writer if text is null.

Throws:

IOException