Class JSONStringer

java.lang.Object
com.github.openjson.JSONStringer

public class JSONStringer extends Object
Implements JSONObject.toString() and JSONArray.toString(). Most application developers should use those methods directly and disregard this API. For example:
 JSONObject object = ...
 String json = object.toString();

Stringers only encode well-formed JSON strings. In particular:

  • The stringer must have exactly one top-level array or object.
  • Lexical scopes must be balanced: every call to array() must have a matching call to endArray() and every call to object() must have a matching call to endObject().
  • Arrays may not contain keys (property names).
  • Objects must alternate keys (property names) and values.
  • Values are inserted with either literal value calls, or by nesting arrays or objects.
Calls that would result in a malformed JSON string will fail with a JSONException.

This class provides no facility for pretty-printing (ie. indenting) output. To encode indented output, use JSONObject.toString(int) or JSONArray.toString(int).

Some implementations of the API support at most 20 levels of nesting. Attempts to create more than 20 levels of nesting may fail with a JSONException.

Each stringer may be used to encode a single top level value. Instances of this class are not thread safe. Although this class is nonfinal, 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 Details

    • out

      protected final StringBuilder out
      The output data, containing at most one top-level array or object.
    • stack

      private final List<JSONStringer.Scope> stack
      Unlike the original implementation, this stack isn't limited to 20 levels of nesting.
    • indent

      private final String indent
      A string containing a full set of spaces for a single level of indentation, or null for no pretty printing.
  • Constructor Details

    • JSONStringer

      public JSONStringer()
    • JSONStringer

      public JSONStringer(int indentSpaces)
  • Method Details

    • array

      public JSONStringer array() throws JSONException
      Begins encoding a new array. Each call to this method must be paired with a call to endArray().
      Returns:
      this stringer.
      Throws:
      JSONException - On internal errors. Shouldn't happen.
    • endArray

      public JSONStringer endArray() throws JSONException
      Ends encoding the current array.
      Returns:
      this stringer.
      Throws:
      JSONException - On internal errors. Shouldn't happen.
    • object

      public JSONStringer object() throws JSONException
      Begins encoding a new object. Each call to this method must be paired with a call to endObject().
      Returns:
      this stringer.
      Throws:
      JSONException - On internal errors. Shouldn't happen.
    • endObject

      public JSONStringer endObject() throws JSONException
      Ends encoding the current object.
      Returns:
      this stringer.
      Throws:
      JSONException - On internal errors. Shouldn't happen.
    • open

      JSONStringer open(JSONStringer.Scope empty, String openBracket) throws JSONException
      Enters a new scope by appending any necessary whitespace and the given bracket.
      Throws:
      JSONException
    • close

      JSONStringer close(JSONStringer.Scope empty, JSONStringer.Scope nonempty, String closeBracket) throws JSONException
      Closes the current scope by appending any necessary whitespace and the given bracket.
      Throws:
      JSONException
    • peek

      private JSONStringer.Scope peek() throws JSONException
      Returns the value on the top of the stack.
      Throws:
      JSONException
    • replaceTop

      private void replaceTop(JSONStringer.Scope topOfStack)
      Replace the value on the top of the stack with the given value.
    • value

      public JSONStringer value(Object value) throws JSONException
      Encodes value.
      Parameters:
      value - a JSONObject, JSONArray, String, Boolean, Integer, Long, Double or null. May not be NaNs or infinities.
      Returns:
      this stringer.
      Throws:
      JSONException - On internal errors. Shouldn't happen.
    • value

      public JSONStringer value(boolean value) throws JSONException
      Encodes value to this stringer.
      Parameters:
      value - The value to encode.
      Returns:
      this stringer.
      Throws:
      JSONException - On internal errors. Shouldn't happen.
    • value

      public JSONStringer value(double value) throws JSONException
      Encodes value to this stringer.
      Parameters:
      value - a finite value. May not be NaNs or infinities.
      Returns:
      this stringer.
      Throws:
      JSONException - On internal errors. Shouldn't happen.
    • value

      public JSONStringer value(long value) throws JSONException
      Encodes value to this stringer.
      Parameters:
      value - The value to encode.
      Returns:
      this stringer.
      Throws:
      JSONException - If we have an internal error. Shouldn't happen.
    • entry

      public JSONStringer entry(Map.Entry<String,Object> entry)
      Encodes key/value pair to this stringer.
      Parameters:
      entry - The entry to encode.
      Returns:
      this stringer.
      Throws:
      JSONException - If we have an internal error. Shouldn't happen.
    • string

      private void string(String value)
    • newline

      private void newline()
    • createKey

      protected JSONStringer createKey(String name)
      Creates String representation of the key (property name) to this stringer Override this method to provide your own representation of the name.
      Parameters:
      name - the name of the forthcoming value.
      Returns:
      this stringer.
    • key

      public JSONStringer key(String name) throws JSONException
      Encodes the key (property name) to this stringer.
      Parameters:
      name - the name of the forthcoming value. May not be null.
      Returns:
      this stringer.
      Throws:
      JSONException - on internal errors, shouldn't happen.
    • beforeKey

      private void beforeKey() throws JSONException
      Inserts any necessary separators and whitespace before a name. Also adjusts the stack to expect the key's value.
      Throws:
      JSONException
    • beforeValue

      private void beforeValue() throws JSONException
      Inserts any necessary separators and whitespace before a literal value, inline array, or inline object. Also adjusts the stack to expect either a closing bracket or another element.
      Throws:
      JSONException
    • toString

      public String toString()
      Returns the encoded JSON string.

      If invoked with unterminated arrays or unclosed objects, this method's return value is undefined.

      Warning: although it contradicts the general contract of Object.toString(), this method returns null if the stringer contains no data.

      Overrides:
      toString in class Object