Class JSONTokener

java.lang.Object
com.github.openjson.JSONTokener
public class JSONTokener extends Object
Parses a JSON (RFC 4627) encoded string into the corresponding object. Most clients of this class will use only need the constructor and nextValue() method. Example usage: 
String json = "{"
        + "  \"query\": \"Pizza\", "
        + "  \"locations\": [ 94043, 90210 ] "
        + "}";

JSONObject object = (JSONObject) new JSONTokener(json).nextValue();
String query = object.getString("query");
JSONArray locations = object.getJSONArray("locations");

For the best interoperability and performance use JSON that complies with RFC 4627, such as that generated by JSONStringer. For legacy reasons, this parser is lenient, so a successful parse does not indicate that the input string was valid JSON. All of the following syntax errors will be ignored:

  • End of line comments starting with // or # and ending with a newline character.
  • C-style comments starting with /* and ending with */. Such comments may not be nested.
  • Strings that are unquoted or 'single quoted'.
  • Hexadecimal integers prefixed with 0x or 0X.
  • Octal integers prefixed with 0.
  • Array elements separated by ;.
  • Unnecessary array separators. These are interpreted as if null was the omitted value.
  • Key-value pairs separated by = or =>.
  • Key-value pairs separated by ;.

Each tokener may be used to parse a single JSON string. Instances of this class are not thread safe. Although this class is non-final, it was not designed for inheritance and should not be subclassed. In particular, self-use by overrideable methods is not specified. See Effective Java Item 17, "Design and Document or inheritance or else prohibit it" for further information.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    MAX_NESTING_LEVEL
    Maximum allowed JSON nesting level supported by the parser.

  • Constructor Summary

    Constructors
    Constructor
    Description
    JSONTokener(Reader input)
     
    JSONTokener(String in)
     

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    back()
    Unreads the most recent character of input.
    static int
    dehexchar(char hex)
    Returns the integer [0..15] value for the given hex character, or -1 for non-hex input.
    boolean
    more()
    Returns true until the input has been exhausted.
    char
    next()
    Returns the next available character, or the null character '\0' if all inputs have been exhausted.
    char
    next(char c)
    Returns the next available character if it equals c.
    String
    next(int length)
    Returns the next length characters of the input.
    char
    nextClean()
    Returns the next character that is not whitespace and does not belong to a comment.
    String
    nextString(char quote)
    Returns the string up to but not including quote, unescaping any character escape sequences encountered along the way.
    String
    nextTo(char excluded)
    Equivalent to nextTo(String.valueOf(excluded)).
    String
    nextTo(String excluded)
    Returns the trimmed string holding the characters up to but not including the first of: any character in excluded a newline character '\n' a carriage return '\r'
    Object
    nextValue()
    Returns the next value from the input.
    void
    skipPast(String thru)
    Advances past all input up to and including the next occurrence of thru.
    char
    skipTo(char to)
    Advances past all inputs up to but not including the next occurrence of to.
    JSONException
    syntaxError(String message)
    Returns an exception containing the given message plus the current position and the entire input string.
    String
    toString()
    Returns the current position and the entire input string.

    Methods inherited from class Object

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

  • Field Details

    • MAX_NESTING_LEVEL

      public static final int MAX_NESTING_LEVEL
      Maximum allowed JSON nesting level supported by the parser. Used to avoid StackOverflow errors. For backward compatibility, the value can be changed (globally) using a system property.

  • Constructor Details

    • JSONTokener

      public JSONTokener(String in)
      Parameters:
      in - JSON encoded string. Null is not permitted and will yield a tokener that throws NullPointerExceptions when methods are called.

    • JSONTokener

      public JSONTokener(Reader input) throws IOException
      Throws:
      IOException

  • Method Details

    • nextValue

      public Object nextValue() throws JSONException
      Returns the next value from the input.
      Returns:
      a JSONObject, JSONArray, String, Boolean, Integer, Long, Double or JSONObject.NULL.
      Throws:
      JSONException - if the input is malformed.

    • nextString

      public String nextString(char quote) throws JSONException
      Returns the string up to but not including quote, unescaping any character escape sequences encountered along the way. The opening quote should have already been read. This consumes the closing quote, but does not include it in the returned string.
      Parameters:
      quote - either ' or ".
      Returns:
      The unescaped string.
      Throws:
      JSONException - if the string isn't terminated by a closing quote correctly.

    • syntaxError

      public JSONException syntaxError(String message)
      Returns an exception containing the given message plus the current position and the entire input string.
      Parameters:
      message - The message we want to include.
      Returns:
      An exception that we can throw.

    • toString

      public String toString()
      Returns the current position and the entire input string.
      Overrides:
      toString in class Object

    • more

      public boolean more()
      Returns true until the input has been exhausted.
      Returns:
      true if more input exists.

    • next

      public char next()
      Returns the next available character, or the null character '\0' if all inputs have been exhausted. The return value of this method is ambiguous for JSON strings that contain the character '\0'.
      Returns:
      the next character.

    • next

      public char next(char c) throws JSONException
      Returns the next available character if it equals c. Otherwise, an exception is thrown.
      Parameters:
      c - The character we are looking for.
      Returns:
      the next character.
      Throws:
      JSONException - If the next character isn't c

    • nextClean

      public char nextClean() throws JSONException
      Returns the next character that is not whitespace and does not belong to a comment. If the input is exhausted before such a character can be found, the null character '\0' is returned. The return value of this method is ambiguous for JSON strings that contain the character '\0'.
      Returns:
      The next non-whitespace character.
      Throws:
      JSONException - Should not be possible.

    • next

      public String next(int length) throws JSONException
      Returns the next length characters of the input.

      The returned string shares its backing character array with this tokener's input string. If a reference to the returned string may be held indefinitely, you should use new String(result) to copy it first to avoid memory leaks.

      Parameters:
      length - The desired number of characters to return.
      Returns:
      The next few characters.
      Throws:
      JSONException - if the remaining input is not long enough to satisfy this request.

    • nextTo

      public String nextTo(String excluded)
      Returns the trimmed string holding the characters up to but not including the first of:
      • any character in excluded
      • a newline character '\n'
      • a carriage return '\r'

      The returned string shares its backing character array with this tokener's input string. If a reference to the returned string may be held indefinitely, you should use new String(result) to copy it first to avoid memory leaks.

      Parameters:
      excluded - The limiting string where the search should stop.
      Returns:
      a possibly-empty string

    • nextTo

      public String nextTo(char excluded)
      Equivalent to nextTo(String.valueOf(excluded)).
      Parameters:
      excluded - The limiting character.
      Returns:
      a possibly-empty string

    • skipPast

      public void skipPast(String thru)
      Advances past all input up to and including the next occurrence of thru. If the remaining input doesn't contain thru, the input is exhausted.
      Parameters:
      thru - The string to skip over.

    • skipTo

      public char skipTo(char to)
      Advances past all inputs up to but not including the next occurrence of to. If the remaining input doesn't contain to, the input is unchanged.
      Parameters:
      to - The character we want to skip to.
      Returns:
      The value of to or null.

    • back

      public void back()
      Unreads the most recent character of input. If no input characters have been read, the input is unchanged.

    • dehexchar

      public static int dehexchar(char hex)
      Returns the integer [0..15] value for the given hex character, or -1 for non-hex input.
      Parameters:
      hex - a character in the ranges [0-9], [A-F] or [a-f]. Any other character will yield a -1 result.
      Returns:
      The decoded integer.