// -*- mode: java; c-basic-offset: 2; -*-
// Copyright 2009-2011 Google, All Rights reserved
// Copyright 2011-2012 MIT, All rights reserved
// Released under the Apache License, Version 2.0
// http://www.apache.org/licenses/LICENSE-2.0
package com.google.appinventor.components.runtime.util;
import gnu.lists.FString;
import gnu.math.IntFraction;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import org.json.JSONTokener;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
/**
* Provides utility functions to convert between Java object and JSON.
*
*
*/
public class JsonUtil {
/**
* Prevent instantiation.
*/
private JsonUtil() {
}
/**
* Returns a list of String objects from a JSONArray. This
* does not do any kind of recursive unpacking of the array.
* Thus, if the array includes other JSON arrays or JSON objects
* their string representation will be a single item in the
* returned list.
*
* @param jArray The JSONArray to convert.
* @return A List of the String representation of each item in
* the JSON array.
* @throws JSONException if an element of jArray cannot be
* converted to a String.
*/
public static List<String> getStringListFromJsonArray(JSONArray jArray) throws JSONException {
List<String> returnList = new ArrayList<String>();
for (int i = 0; i < jArray.length(); i++) {
String val = jArray.getString(i);
returnList.add(val);
}
return returnList;
}
/**
* Returns a Java Object list of a JSONArray with each item in
* the array converted using convertJsonItem().
*
* @param jArray The JSONArray to convert.
* @return A List of Strings and more Object lists.
* @throws JSONException if an element in jArray cannot be
* converted properly.
*/
public static List<Object> getListFromJsonArray(JSONArray jArray) throws JSONException {
List<Object> returnList = new ArrayList<Object>();
for (int i = 0; i < jArray.length(); i++) {
returnList.add(convertJsonItem(jArray.get(i)));
}
return returnList;
}
/**
* Returns a list containing one two item list per key in jObject.
* Each two item list has the key String as its first element and
* the result of calling convertJsonItem() on its value as the
* second element. The sub-lists in the returned list will appear
* in alphabetical order by key.
*
* @param jObject The JSONObject to convert.
* @return A list of two item lists: [String key, Object value].
* @throws JSONException if an element in jObject cannot be
* converted properly.
*/
// TODO(hal): If we implement dictionaries, we'll need to decode Json
// objects to dictionaires instead.
public static List<Object> getListFromJsonObject(JSONObject jObject) throws JSONException {
List<Object> returnList = new ArrayList<Object>();
Iterator<String> keys = jObject.keys();
List<String> keysList = new ArrayList<String>();
while (keys.hasNext()) {
keysList.add(keys.next());
}
Collections.sort(keysList);
for (String key : keysList) {
List<Object> nestedList = new ArrayList<Object>();
nestedList.add(key);
nestedList.add(convertJsonItem(jObject.get(key)));
returnList.add(nestedList);
}
return returnList;
}
/**
* Returns a Java object representation of objects that are
* encountered inside of JSON created using the org.json package.
* JSON arrays and objects are transformed into their list
* representations using getListFromJsonArray and
* getListFromJsonObject respectively.
*
* Java Boolean values and the Strings "true" and "false" (case
* insensitive) are inserted as Booleans. Java Numbers are
* inserted without modification and all other values are inserted
* as their toString(). value.
*
* @param o An item in a JSON array or JSON object to convert.
* @return A Java Object representing o or the String "null"
* if o is null.
* @throws JSONException if o fails to parse.
*/
public static Object convertJsonItem(Object o) throws JSONException {
if (o == null) {
return "null";
}
if (o instanceof JSONObject) {
return getListFromJsonObject((JSONObject) o);
}
if (o instanceof JSONArray) {
return getListFromJsonArray((JSONArray) o);
}
if (o.equals(Boolean.FALSE) || (o instanceof String &&
((String) o).equalsIgnoreCase("false"))) {
return false;
}
if (o.equals(Boolean.TRUE) || (o instanceof String && ((String) o).equalsIgnoreCase("true"))) {
return true;
}
if (o instanceof Number) {
return o;
}
return o.toString();
}
public static String getJsonRepresentation(Object value) throws JSONException {
if (value == null || value.equals(null)) {
return "null";
}
if (value instanceof FString) {
return JSONObject.quote(value.toString());
}
if (value instanceof YailList) {
return ((YailList) value).toJSONString();
}
// The Json tokener used in getObjectFromJson cannot handle
// fractions. So we Json encode fractions by first converting
// them to doubles. This is an example of value with Kawa type any
// being exposed to the rest of App Inventor by the value being
// passed to a component method, in this case TinyDB or TinyWebDB
// StoreValue. See the "warning" comment in runtime.scm at
// call-component-method.
if (value instanceof IntFraction) {
return JSONObject.numberToString((Number) ((IntFraction)value).doubleValue());
}
if (value instanceof Number) {
return JSONObject.numberToString((Number) value);
}
if (value instanceof Boolean) {
return value.toString();
}
if (value.getClass().isArray()) {
StringBuilder sb = new StringBuilder();
sb.append("[");
String separator = "";
for (Object o: (Object[]) value) {
sb.append(separator).append(getJsonRepresentation(o));
separator = ",";
}
sb.append("]");
return sb.toString();
}
return JSONObject.quote(value.toString());
}
public static Object getObjectFromJson(String jsonString) throws JSONException {
if ((jsonString == null) || jsonString.equals("")) {
// We'd like the empty string to decode to the empty string. Form.java
// relies on this for the case where there's an activity result with no intent data.
// We handle this case explicitly since nextValue() appears to throw an error
// when given the empty string.
return "";
} else {
final Object value = (new JSONTokener(jsonString)).nextValue();
// Note that the JSONTokener may return a value equals() to null.
if (value == null || value.equals(null)) {
return null;
} else if ((value instanceof String) ||
(value instanceof Number) ||
(value instanceof Boolean)) {
return value;
} else if (value instanceof JSONArray) {
return getListFromJsonArray((JSONArray)value);
} else if (value instanceof JSONObject) {
return getListFromJsonObject((JSONObject)value);
}
throw new JSONException("Invalid JSON string.");
}
}
}