While this class is neither feature-rich nor the most performant one, it's sufficient enough - * for its use-case. - */ - public static class JsonObjectBuilder { - - private StringBuilder builder = new StringBuilder(); - - private boolean hasAtLeastOneField = false; - - public JsonObjectBuilder() { - builder.append("{"); - } - - /** - * Appends a null field to the JSON. - * - * @param key The key of the field. - * @return A reference to this object. - */ - public JsonObjectBuilder appendNull(String key) { - appendFieldUnescaped(key, "null"); - return this; - } - - /** - * Appends a string field to the JSON. - * - * @param key The key of the field. - * @param value The value of the field. - * @return A reference to this object. - */ - public JsonObjectBuilder appendField(String key, String value) { - if (value == null) { - throw new IllegalArgumentException("JSON value must not be null"); - } - appendFieldUnescaped(key, "\"" + escape(value) + "\""); - return this; - } - - /** - * Appends an integer field to the JSON. - * - * @param key The key of the field. - * @param value The value of the field. - * @return A reference to this object. - */ - public JsonObjectBuilder appendField(String key, int value) { - appendFieldUnescaped(key, String.valueOf(value)); - return this; - } - - /** - * Appends an object to the JSON. - * - * @param key The key of the field. - * @param object The object. - * @return A reference to this object. - */ - public JsonObjectBuilder appendField(String key, JsonObject object) { - if (object == null) { - throw new IllegalArgumentException("JSON object must not be null"); - } - appendFieldUnescaped(key, object.toString()); - return this; - } - - /** - * Appends a string array to the JSON. - * - * @param key The key of the field. - * @param values The string array. - * @return A reference to this object. - */ - public JsonObjectBuilder appendField(String key, String[] values) { - if (values == null) { - throw new IllegalArgumentException("JSON values must not be null"); - } - String escapedValues = - Arrays.stream(values) - .map(value -> "\"" + escape(value) + "\"") - .collect(Collectors.joining(",")); - appendFieldUnescaped(key, "[" + escapedValues + "]"); - return this; - } - - /** - * Appends an integer array to the JSON. - * - * @param key The key of the field. - * @param values The integer array. - * @return A reference to this object. - */ - public JsonObjectBuilder appendField(String key, int[] values) { - if (values == null) { - throw new IllegalArgumentException("JSON values must not be null"); - } - String escapedValues = - Arrays.stream(values).mapToObj(String::valueOf).collect(Collectors.joining(",")); - appendFieldUnescaped(key, "[" + escapedValues + "]"); - return this; - } - - /** - * Appends an object array to the JSON. - * - * @param key The key of the field. - * @param values The integer array. - * @return A reference to this object. - */ - public JsonObjectBuilder appendField(String key, JsonObject[] values) { - if (values == null) { - throw new IllegalArgumentException("JSON values must not be null"); - } - String escapedValues = - Arrays.stream(values).map(JsonObject::toString).collect(Collectors.joining(",")); - appendFieldUnescaped(key, "[" + escapedValues + "]"); - return this; - } - - /** - * Appends a field to the object. - * - * @param key The key of the field. - * @param escapedValue The escaped value of the field. - */ - private void appendFieldUnescaped(String key, String escapedValue) { - if (builder == null) { - throw new IllegalStateException("JSON has already been built"); - } - if (key == null) { - throw new IllegalArgumentException("JSON key must not be null"); - } - if (hasAtLeastOneField) { - builder.append(","); - } - builder.append("\"").append(escape(key)).append("\":").append(escapedValue); - hasAtLeastOneField = true; - } - - /** - * Builds the JSON string and invalidates this builder. - * - * @return The built JSON string. - */ - public JsonObject build() { - if (builder == null) { - throw new IllegalStateException("JSON has already been built"); - } - JsonObject object = new JsonObject(builder.append("}").toString()); - builder = null; - return object; - } - - /** - * Escapes the given string like stated in https://www.ietf.org/rfc/rfc4627.txt. - * - *
This method escapes only the necessary characters '"', '\'. and '\u0000' - '\u001F'. - * Compact escapes are not used (e.g., '\n' is escaped as "\u000a" and not as "\n"). - * - * @param value The value to escape. - * @return The escaped value. - */ - private static String escape(String value) { - final StringBuilder builder = new StringBuilder(); - for (int i = 0; i < value.length(); i++) { - char c = value.charAt(i); - if (c == '"') { - builder.append("\\\""); - } else if (c == '\\') { - builder.append("\\\\"); - } else if (c <= '\u000F') { - builder.append("\\u000").append(Integer.toHexString(c)); - } else if (c <= '\u001F') { - builder.append("\\u00").append(Integer.toHexString(c)); - } else { - builder.append(c); - } - } - return builder.toString(); - } - - /** - * A super simple representation of a JSON object. - * - *
This class only exists to make methods of the {@link JsonObjectBuilder} type-safe and not - * allow a raw string inputs for methods like {@link JsonObjectBuilder#appendField(String, - * JsonObject)}. - */ - public static class JsonObject { - - private final String value; - - private JsonObject(String value) { - this.value = value; - } - - @Override - public String toString() { - return value; - } - } - } -} \ No newline at end of file