org.apache.tapestry.json
Class JSONTokener

java.lang.Object
  org.apache.tapestry.json.JSONTokener

Direct Known Subclasses:

HTTPTokener, XMLTokener

public class JSONTokener
extends Object

A JSONTokener takes a source string and extracts characters and tokens from it. It is used by the JSONObject and JSONArray constructors to parse JSON source strings.

The toString() method has been modified from its original form to provide easier to understand exception reporting.

Version:

1

Author:

JSON.org, jkuhnert

Constructor Summary

JSONTokener(String s)
Construct a JSONTokener from a string.

Method Summary

void	back() Back up one character.
static int	dehexchar(char c) Get the hex value of a character (base16).
boolean	more() Determine if the source string still contains characters that next() can consume.
char	next() Get the next character in the source string.
char	next(char c) Consume the next character, and check that it matches a specified character.
String	next(int n) Get the next n characters.
char	nextClean() Get the next char in the string, skipping whitespace and comments (slashslash, slashstar, and hash).
String	nextString(char quote) Return the characters up to the next close quote character.
String	nextTo(char d) Get the text up but not including the specified character or the end of line, whichever comes first.
String	nextTo(String delimiters) Get the text up but not including one of the specified delimeter characters or the end of line, whichever comes first.
Object	nextValue() Get the next value.
void	skipPast(String to) Skip characters until past the requested string.
char	skipTo(char to) Skip characters until the next character is the requested character.
ParseException	syntaxError(String message) Make a ParseException to signal a syntax error.
String	toString() Make a printable string of this JSONTokener.
static String	unescape(String s) Convert %hh sequences to single characters, and convert plus to space.

Methods inherited from class java.lang.Object

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

Constructor Detail

JSONTokener

public JSONTokener(String s)

Construct a JSONTokener from a string.

Parameters:

s - A source string.

Method Detail

back

public void back()

Back up one character. This provides a sort of lookahead capability, so that you can test for a digit or letter before attempting to parse the next number or identifier.

dehexchar

public static int dehexchar(char c)

Get the hex value of a character (base16).

Parameters:

c - A character between '0' and '9' or between 'A' and 'F' or between 'a' and 'f'.

Returns:

An int between 0 and 15, or -1 if c was not a hex digit.

more

public boolean more()

Determine if the source string still contains characters that next() can consume.

Returns:

true if not yet at the end of the source.

next

public char next()

Get the next character in the source string.

Returns:

The next character, or 0 if past the end of the source string.

next

public char next(char c)
          throws ParseException

Consume the next character, and check that it matches a specified character.

Parameters:

c - The character to match.

Returns:

The character.

Throws:

ParseException - if the character does not match.

next

public String next(int n)
            throws ParseException

Get the next n characters.

Parameters:

n - The number of characters to take.

Returns:

A string of n characters.

Throws:

ParseException - Substring bounds error if there are not n characters remaining in the source string.

nextClean

public char nextClean()
               throws ParseException

Get the next char in the string, skipping whitespace and comments (slashslash, slashstar, and hash).

Returns:

A character, or 0 if there are no more characters.

Throws:

ParseException

nextString

public String nextString(char quote)
                  throws ParseException

Return the characters up to the next close quote character. Backslash processing is done. The formal JSON format does not allow strings in single quotes, but an implementation is allowed to accept them.

Parameters:

quote - The quoting character, either " (double quote) or ' (single quote).

Returns:

A String.

Throws:

ParseException - Unterminated string.

nextTo

public String nextTo(char d)

Get the text up but not including the specified character or the end of line, whichever comes first.

Parameters:

d - A delimiter character.

Returns:

A string.

nextTo

public String nextTo(String delimiters)

Get the text up but not including one of the specified delimeter characters or the end of line, whichever comes first.

Parameters:

delimiters - A set of delimiter characters.

Returns:

A string, trimmed.

nextValue

public Object nextValue()
                 throws ParseException

Get the next value. The value can be a Boolean, Double, Integer, JSONArray, JSONObject, or String, or the JSONObject.NULL object.

Returns:

An object.

Throws:

ParseException - The source does not conform to JSON syntax.

skipTo

public char skipTo(char to)

Skip characters until the next character is the requested character. If the requested character is not found, no characters are skipped.

Parameters:

to - A character to skip to.

Returns:

The requested character, or zero if the requested character is not found.

skipPast

public void skipPast(String to)

Skip characters until past the requested string. If it is not found, we are left at the end of the source.

Parameters:

to - A string to skip past.

syntaxError

public ParseException syntaxError(String message)

Make a ParseException to signal a syntax error.

Parameters:

message - The error message.

Returns:

A ParseException object, suitable for throwing

toString

public String toString()

Make a printable string of this JSONTokener.

Overrides:

toString in class Object

Returns:

" at character [this.myIndex] of [this.mySource]"

unescape

public static String unescape(String s)

Convert %hh sequences to single characters, and convert plus to space.

Parameters:

s - A string that may contain + (plus) and %hh sequences.

Returns:

The unescaped string.