Package org.json

Class JSONWriter

  • Direct Known Subclasses:
    JSONStringer
    public class JSONWriter
extends java.lang.Object
    JSONWriter provides a quick and convenient way of producing JSON text. The texts produced strictly conform to JSON syntax rules. No whitespace is added, so the results are ready for transmission or storage. Each instance of JSONWriter can produce one JSON text.

    A JSONWriter instance provides a value method for appending values to the text, and a key method for adding keys before values in objects. There are array and endArray methods that make and bound array values, and object and endObject methods which make and bound object values. All of these methods return the JSONWriter instance, permitting a cascade style. For example, 

     new JSONWriter(myWriter)
     .object()
         .key("JSON")
         .value("Hello, World!")
     .endObject();
    which writes 
     {"JSON":"Hello, World!"}

    The first method called must be array or object. There are no methods for adding commas or colons. JSONWriter adds them for you. Objects and arrays can be nested up to 200 levels deep.

    This can sometimes be easier than using a JSONObject to build a string.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected char mode
      The current mode.
      protected java.lang.Appendable writer
      The writer that will receive the output.

    • Constructor Summary

      Constructors 
      Constructor Description
      JSONWriter​(java.lang.Appendable w)
      Make a fresh JSONWriter.

    • Field Detail

      • mode

        protected char mode
        The current mode. Values: 'a' (array), 'd' (done), 'i' (initial), 'k' (key), 'o' (object).

      • writer

        protected java.lang.Appendable writer
        The writer that will receive the output.

    • Constructor Detail

      • JSONWriter

        public JSONWriter​(java.lang.Appendable w)
        Make a fresh JSONWriter. It can be used to build one JSON text.
        Parameters:
        w - an appendable object

    • Method Detail

      • array

        public JSONWriter array()
                 throws JSONException
        Begin appending a new array. All values until the balancing endArray will be appended to this array. The endArray method must be called to mark the array's end.
        Returns:
        this
        Throws:
        JSONException - If the nesting is too deep, or if the object is started in the wrong place (for example as a key or after the end of the outermost array or object).

      • endArray

        public JSONWriter endArray()
                    throws JSONException
        End an array. This method most be called to balance calls to array.
        Returns:
        this
        Throws:
        JSONException - If incorrectly nested.

      • endObject

        public JSONWriter endObject()
                     throws JSONException
        End an object. This method most be called to balance calls to object.
        Returns:
        this
        Throws:
        JSONException - If incorrectly nested.

      • key

        public JSONWriter key​(java.lang.String string)
               throws JSONException
        Append a key. The key will be associated with the next value. In an object, every value must be preceded by a key.
        Parameters:
        string - A key string.
        Returns:
        this
        Throws:
        JSONException - If the key is out of place. For example, keys do not belong in arrays or if the key is null.

      • object

        public JSONWriter object()
                  throws JSONException
        Begin appending a new object. All keys and values until the balancing endObject will be appended to this object. The endObject method must be called to mark the object's end.
        Returns:
        this
        Throws:
        JSONException - If the nesting is too deep, or if the object is started in the wrong place (for example as a key or after the end of the outermost array or object).

      • valueToString

        public static java.lang.String valueToString​(java.lang.Object value)
                                      throws JSONException
        Make a JSON text of an Object value. If the object has an value.toJSONString() method, then that method will be used to produce the JSON text. The method is required to produce a strictly conforming text. If the object does not contain a toJSONString method (which is the most common case), then a text will be produced by other means. If the value is an array or Collection, then a JSONArray will be made from it and its toJSONString method will be called. If the value is a MAP, then a JSONObject will be made from it and its toJSONString method will be called. Otherwise, the value's toString method will be called, and the result will be quoted.

        Warning: This method assumes that the data structure is acyclical.

        Parameters:
        value - The value to be serialized.
        Returns:
        a printable, displayable, transmittable representation of the object, beginning with { (left brace) and ending with } (right brace).
        Throws:
        JSONException - If the value is or contains an invalid number.

      • value

        public JSONWriter value​(boolean b)
                 throws JSONException
        Append either the value true or the value false.
        Parameters:
        b - A boolean.
        Returns:
        this
        Throws:
        JSONException - if a called function has an error

      • value

        public JSONWriter value​(double d)
                 throws JSONException
        Append a double value.
        Parameters:
        d - A double.
        Returns:
        this
        Throws:
        JSONException - If the number is not finite.

      • value

        public JSONWriter value​(long l)
                 throws JSONException
        Append a long value.
        Parameters:
        l - A long.
        Returns:
        this
        Throws:
        JSONException - if a called function has an error

      • value

        public JSONWriter value​(java.lang.Object object)
                 throws JSONException
        Append an object value.
        Parameters:
        object - The object to append. It can be null, or a Boolean, Number, String, JSONObject, or JSONArray, or an object that implements JSONString.
        Returns:
        this
        Throws:
        JSONException - If the value is out of sequence.