- * 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.
- * @author JSON.org
- * @version 2016-08-08
- */
-public class JSONWriter {
- private static final int maxdepth = 200;
-
- /**
- * The comma flag determines if a comma should be output before the next
- * value.
- */
- private boolean comma;
-
- /**
- * The current mode. Values:
- * 'a' (array),
- * 'd' (done),
- * 'i' (initial),
- * 'k' (key),
- * 'o' (object).
- */
- protected char mode;
-
- /**
- * The object/array stack.
- */
- private final JSONObject stack[];
-
- /**
- * The stack top index. A value of 0 indicates that the stack is empty.
- */
- private int top;
-
- /**
- * The writer that will receive the output.
- */
- protected Appendable writer;
-
- /**
- * Make a fresh JSONWriter. It can be used to build one JSON text.
- */
- public JSONWriter(Appendable w) {
- this.comma = false;
- this.mode = 'i';
- this.stack = new JSONObject[maxdepth];
- this.top = 0;
- this.writer = w;
- }
-
- /**
- * Append a value.
- * @param string A string value.
- * @return this
- * @throws JSONException If the value is out of sequence.
- */
- private JSONWriter append(String string) throws JSONException {
- if (string == null) {
- throw new JSONException("Null pointer");
- }
- if (this.mode == 'o' || this.mode == 'a') {
- try {
- if (this.comma && this.mode == 'a') {
- this.writer.append(',');
- }
- this.writer.append(string);
- } catch (IOException e) {
- // Android as of API 25 does not support this exception constructor
- // however we won't worry about it. If an exception is happening here
- // it will just throw a "Method not found" exception instead.
- throw new JSONException(e);
- }
- if (this.mode == 'o') {
- this.mode = 'k';
- }
- this.comma = true;
- return this;
- }
- throw new JSONException("Value out of sequence.");
- }
-
- /**
- * 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.
- * @return 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).
- */
- public JSONWriter array() throws JSONException {
- if (this.mode == 'i' || this.mode == 'o' || this.mode == 'a') {
- this.push(null);
- this.append("[");
- this.comma = false;
- return this;
- }
- throw new JSONException("Misplaced array.");
- }
-
- /**
- * End something.
- * @param m Mode
- * @param c Closing character
- * @return this
- * @throws JSONException If unbalanced.
- */
- private JSONWriter end(char m, char c) throws JSONException {
- if (this.mode != m) {
- throw new JSONException(m == 'a'
- ? "Misplaced endArray."
- : "Misplaced endObject.");
- }
- this.pop(m);
- try {
- this.writer.append(c);
- } catch (IOException e) {
- // Android as of API 25 does not support this exception constructor
- // however we won't worry about it. If an exception is happening here
- // it will just throw a "Method not found" exception instead.
- throw new JSONException(e);
- }
- this.comma = true;
- return this;
- }
-
- /**
- * End an array. This method most be called to balance calls to
- * array.
- * @return this
- * @throws JSONException If incorrectly nested.
- */
- public JSONWriter endArray() throws JSONException {
- return this.end('a', ']');
- }
-
- /**
- * End an object. This method most be called to balance calls to
- * object.
- * @return this
- * @throws JSONException If incorrectly nested.
- */
- public JSONWriter endObject() throws JSONException {
- return this.end('k', '}');
- }
-
- /**
- * Append a key. The key will be associated with the next value. In an
- * object, every value must be preceded by a key.
- * @param string A key string.
- * @return this
- * @throws JSONException If the key is out of place. For example, keys
- * do not belong in arrays or if the key is null.
- */
- public JSONWriter key(String string) throws JSONException {
- if (string == null) {
- throw new JSONException("Null key.");
- }
- if (this.mode == 'k') {
- try {
- JSONObject topObject = this.stack[this.top - 1];
- // don't use the built in putOnce method to maintain Android support
- if(topObject.has(string)) {
- throw new JSONException("Duplicate key \"" + string + "\"");
- }
- topObject.put(string, true);
- if (this.comma) {
- this.writer.append(',');
- }
- this.writer.append(JSONObject.quote(string));
- this.writer.append(':');
- this.comma = false;
- this.mode = 'o';
- return this;
- } catch (IOException e) {
- // Android as of API 25 does not support this exception constructor
- // however we won't worry about it. If an exception is happening here
- // it will just throw a "Method not found" exception instead.
- throw new JSONException(e);
- }
- }
- throw new JSONException("Misplaced key.");
- }
-
-
- /**
- * 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.
- * @return 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).
- */
- public JSONWriter object() throws JSONException {
- if (this.mode == 'i') {
- this.mode = 'o';
- }
- if (this.mode == 'o' || this.mode == 'a') {
- this.append("{");
- this.push(new JSONObject());
- this.comma = false;
- return this;
- }
- throw new JSONException("Misplaced object.");
-
- }
-
-
- /**
- * Pop an array or object scope.
- * @param c The scope to close.
- * @throws JSONException If nesting is wrong.
- */
- private void pop(char c) throws JSONException {
- if (this.top <= 0) {
- throw new JSONException("Nesting error.");
- }
- char m = this.stack[this.top - 1] == null ? 'a' : 'k';
- if (m != c) {
- throw new JSONException("Nesting error.");
- }
- this.top -= 1;
- this.mode = this.top == 0
- ? 'd'
- : this.stack[this.top - 1] == null
- ? 'a'
- : 'k';
- }
-
- /**
- * Push an array or object scope.
- * @param jo The scope to open.
- * @throws JSONException If nesting is too deep.
- */
- private void push(JSONObject jo) throws JSONException {
- if (this.top >= maxdepth) {
- throw new JSONException("Nesting too deep.");
- }
- this.stack[this.top] = jo;
- this.mode = jo == null ? 'a' : 'k';
- this.top += 1;
- }
-
- /**
- * 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.
- *
- * @param value
- * The value to be serialized.
- * @return 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.
- */
- public static String valueToString(Object value) throws JSONException {
- if (value == null || value.equals(null)) {
- return "null";
- }
- if (value instanceof JSONString) {
- Object object;
- try {
- object = ((JSONString) value).toJSONString();
- } catch (Exception e) {
- throw new JSONException(e);
- }
- if (object instanceof String) {
- return (String) object;
- }
- throw new JSONException("Bad value from toJSONString: " + object);
- }
- if (value instanceof Number) {
- // not all Numbers may match actual JSON Numbers. i.e. Fractions or Complex
- final String numberAsString = JSONObject.numberToString((Number) value);
- try {
- // Use the BigDecimal constructor for it's parser to validate the format.
- @SuppressWarnings("unused")
- BigDecimal unused = new BigDecimal(numberAsString);
- // Close enough to a JSON number that we will return it unquoted
- return numberAsString;
- } catch (NumberFormatException ex){
- // The Number value is not a valid JSON number.
- // Instead we will quote it as a string
- return JSONObject.quote(numberAsString);
- }
- }
- if (value instanceof Boolean || value instanceof JSONObject
- || value instanceof JSONArray) {
- return value.toString();
- }
- if (value instanceof Map) {
- Map map = (Map) value;
- return new JSONObject(map).toString();
- }
- if (value instanceof Collection) {
- Collection coll = (Collection) value;
- return new JSONArray(coll).toString();
- }
- if (value.getClass().isArray()) {
- return new JSONArray(value).toString();
- }
- if(value instanceof Enum){
- return JSONObject.quote(((Enum)value).name());
- }
- return JSONObject.quote(value.toString());
- }
-
- /**
- * Append either the value true or the value
- * false.
- * @param b A boolean.
- * @return this
- * @throws JSONException
- */
- public JSONWriter value(boolean b) throws JSONException {
- return this.append(b ? "true" : "false");
- }
-
- /**
- * Append a double value.
- * @param d A double.
- * @return this
- * @throws JSONException If the number is not finite.
- */
- public JSONWriter value(double d) throws JSONException {
- return this.value(Double.valueOf(d));
- }
-
- /**
- * Append a long value.
- * @param l A long.
- * @return this
- * @throws JSONException
- */
- public JSONWriter value(long l) throws JSONException {
- return this.append(Long.toString(l));
- }
-
-
- /**
- * Append an object value.
- * @param object The object to append. It can be null, or a Boolean, Number,
- * String, JSONObject, or JSONArray, or an object that implements JSONString.
- * @return this
- * @throws JSONException If the value is out of sequence.
- */
- public JSONWriter value(Object object) throws JSONException {
- return this.append(valueToString(object));
- }
-}