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Dynamic way to access JSON nested values in Java

I have this JSON object:
{
"maindrawer":
{
"enabled": true,
"actions":
[
{
"type": "Section",
"title": "Section 1"
},
{
"id": 1,
"type": "Primary",
"title": "Title 1",
"badge":
{
"enabled": false,
"value": 0,
"textColor": "#000000",
"badgeColor": "#ff0990"
},
"subActions":
[
{
"id": 1,
"type": "Primary",
"title": "Sub Title 1"
}
]
}
]
}
}
This is the code I'm using to access the badge -> textColor value:
public void loadJSONFromRaw(Context context, int id)
{
json = null;
try
{
//read and return json sting
InputStream is = context.getResources().openRawResource(id);
int size = is.available();
byte[] buffer = new byte[size];
is.read(buffer);
is.close();
json = new String(buffer, "UTF-8");
//convert json to object
Type type = new TypeToken<Map<String, Object>>() {}.getType();
Map<String, Object> data = new Gson().fromJson(json, type);
//access maindrawer property
Map<String, Object> maindrawer = (Map<String, Object>)data.get("maindrawer");
//access actions list
List<Object> actions = (List<Object>)maindrawer.get("actions");
//return first item in the list
Map<String, Object> action = (Map<String, Object>) actions.get(1);
//return badge object
Map<String, String> badge = (Map<String, String>) action.get("badge");
//access badge -> textColor value
String textColor = badge.get("textColor");
}
catch (IOException e)
{
e.printStackTrace();
}
}
Is there a better/faster or more dynamic way to access JSON nested properties using java/android? I'm using Gson library for this task and don't mind to switch to any other solution to make it easier as this is too much of code to write just to access a single variable.
Ideally, I'm looking for something like:
String textColor = data.get("maindrawer").get("actions").get(1).get("badge").get("textColor");
Also I'm not very interested in using POJO for now.
Lastly, I'm still new to Java so I'm probably missing something here or maybe there are some limitations? anyways thanks for you help!!

Found what I need using JsonPath library. It looks like it does similar to what I need. Here's a sample code I found:
String textColor = JsonPath.parse(json).read("$.maindrawer.actions[1].badge.textColor");
Very clean and straightforward. Hopes this will save someone else's time as well.

Since you are accessing json file locally, it means you know its structure.
So instead of using -
Map<String, Object> data = new Gson().fromJson(json, type);
You can use something like this-
Map<String, MainDrawer> data = new Gson().fromJson(json, type);
where MainDrawer is a class with member variables - enabled, actions and array of another type.
That would make easier to fetch your values like using -
mainDrawer.isEnabled()

Here are two solutions without importing a new library.
Write a simple path parser:
String textColor = (String)parse(data, "maindrawer", "actions", 1, "badge", "textColor");
//...
static Object parse(Object root, Object... params) {
Object current = root;
for (Object p : params) {
if (p instanceof Number) {
current = ((List<?>)current).get(((Number)p).intValue());
} else {
current = ((Map<?,?>)current).get(p.toString());
}
}
return current;
}
Or parse and walk through Gson's JsonElement:
JsonElement root = new Gson().fromJson(json, JsonElement.class);
String textColor = root
.getAsJsonObject().get("maindrawer")
.getAsJsonObject().get("actions")
.getAsJsonArray().get(1)
.getAsJsonObject().get("badge")
.getAsJsonObject().get("textColor")
.getAsString();

You can also do this with BSON using a single line query. You have to cast the object to the type as you go down into Nested JSON objects.
//import java.util.ArrayList;
//import org.bson.Document;
Document root = Document.parse("{ \"maindrawer\" : { \"enabled\" : true, \"actions\" : [{ \"type\" : \"Section\", \"title\" : \"Section 1\" }, { \"id\" : 1, \"type\" : \"Primary\", \"title\" : \"Title 1\", \"badge\" : { \"enabled\" : false, \"value\" : 0, \"textColor\" : \"#000000\", \"badgeColor\" : \"#ff0990\" }, \"subActions\" : [{ \"id\" : 1, \"type\" : \"Primary\", \"title\" : \"Sub Title 1\" }] }] } }");
System.out.println(((String)((Document)((Document)((ArrayList)((Document)root.get("maindrawer")).get("actions")).get(1)).get("badge")).get("textColor")));

Java Jackson - how to parse list of objects with an arbatrary identifier tag

I have a JSON record that looks like this:
{"ActionRecord": {
"101": {
"Desc": "string 1",
"Done": 1,
"MaxTimes": 2,
"Point": 30,
"Times": 4
},
"102": {
"Desc": "string 2",
"Done": 1,
"MaxTimes": 3,
"Point": 15,
"Times": 13
},
"103": {
"Desc": "string 3.",
"Done": 1,
"MaxTimes": 5,
"Point": 15,
"Times": 24
}, ... }
I can get Jackson to parse this if i create a hacky intermediate class that contains a field for each number, and then use something like this in the class:
#JsonProperty( value = "101" )
public MyClass hundred_one;
#JsonProperty( value = "102" )
public MyClass hundred_two;
#JsonProperty( value = "103" )
public MyClass hundred_three;
But I have to type out all the expected values, so it would be much easier to be able to use an array list of objects, and insert the numeric id into the POJO with Jackson's mapper.
Is there a way have Jackson automatically map it into a class like this? :
public enum ActionRecord {
Something ( "101" ),
SomethingElse( "102" ),
AnotherSomething ( "103" ),
;
String _id;
EK_DailyTaskInfo_ActionRecord( String id )
{
_id = id;
}
public String getId()
{
return _id;
}
public String Desc; // "some string.",
public boolean Done; // 1,
public int Times; // 4
public int MaxTimes; // 2,
public int Point; // 30,
}
It does not have to be an enum this was just something I was trying before I gave up

Jackson can decode it into a Map<String, Record> for you, e.g.
public class Record {
public String Desc; // "some string.",
public boolean Done; // 1,
public int Times; // 4
public int MaxTimes; // 2,
public int Point; // 30,
}
public class ActionRecords {
public Map<String, Record> ActionRecord
}

well I am using GSON library in shown example, Android has it's own api to handle the JSON where a iterator is very useful, code is also available on github
What i want to propose is that you should read all the keys with respect to it's key's and get the JsonObject from there, you you have a JsonList which is not an array this is what you can do
JsonParser parser = new JsonParser();
JsonElement element = parser.parse(result); // result is your json data
JsonObject obj = element.getAsJsonObject();
System.out.println(obj.toString());
JsonObject jsonObject = obj.getAsJsonObject("ActionRecord"); // this will get the JsonObject with the key ActionRecord
System.out.println(jsonObject);
Set<Map.Entry<String, JsonElement>> stringSet = jsonObject.entrySet(); // this will map all the JsonObject with it's keys
for (Map.Entry<String, JsonElement> key :stringSet) {
System.out.println(jsonObject.getAsJsonObject(key.getKey()).toString());
}
Once you have the key with it's corresponding JSONObject, you can create populate your own type for that object.
well this is for Gson, you might want to look for equivalent of this in Jackson
output
{"Desc":"string 1","Done":1,"MaxTimes":2,"Point":30,"Times":4}
{"Desc":"string 2","Done":1,"MaxTimes":3,"Point":15,"Times":13}
{"Desc":"string 3.","Done":1,"MaxTimes":5,"Point":15,"Times":24}

Java - JSON Parser Error

I am creating an application which it will send http request to a web server. The return will be in json. Here is how the json look like
[//I used a tool to make it beautiful and easy to read.
{
"item_name": "Adame",
"item_type": "Special",
"item": "Chestplate",
"item_min_lvl": "50",
"enchantment": {
"health": "0.3",
"dam": "24%",
"life": "0.1",
"xp": "24%",
"loot": "22%"
},
"def": "73"
},
{
"item_name": "Sticks'",
"item_type": "Unique",
"item": "Stick",
"item_min_lvl": "4",
"enchantment": {
"health": "0.6",
"mana": "1",
"dam": "12%",
"life": "0.3",
"xp": "17%",
"loot": "17%"
},
"min_dam": "39",
"max_dam": "34"
},
{
"item_name": "Sword'",
"item_type": "Unique",
"item": "Sword",
"item_min_lvl": "8",
"enchantment": [], //colonm 30 is [
"min_dam": "9",
"max_dam": "10"
}
]
Are you can see, the data inside the array are different. I got this error, Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 30. This is my code:
MyJSON[] data = gson.from(jsonString, MyJSON[].class);
class MyJSON {
String item_name;
String item_type;
String item;
String item_min_lvl;
Enchantment enchantment;
String min_dam;
String max_dam;
#Override
public String toString() {
StringBuilder builder = new StringBuilder();
builder.append("\nitem_name:").append(item_name);
builder.append("\nitem_type:").append(item_type);
builder.append("\nitem:").append(item);
builder.append("\nitem_min_lvl:").append(item_min_lvl);
builder.append("\n\nEnchantment Details:");
builder.append("\nhealth:").append(enchantment.health);
builder.append("\ndam:").append(enchantment.dam);
builder.append("\nlife:").append(enchantment.life);
builder.append("\nxp:").append(enchantment.xp);
builder.append("\nloot:").append(enchantment.loot);
return builder.toString();
}
}
class Enchantment {
String health;
String dam;
String life;
String xp;
String loot;
String mana;
}
Can anyone help me to improve my code so my code an parse the json in different case. Thanks in advanced. (P.s. that's not my web server so I can't do anything with the json)

Basically this line of JSON
"enchantment": [], //colonm 30 is [
doesn't match your POJO. You're expecting an Enchantment object, but the JSON is giving you an array. Fix your JSON to return an empty JSON object or nothing at all for the enchantment pair.
"enchantment": {}

This is a Valid JSON unless you have added comments just to show lines where is the issue?
Comments should not be part of JSON.
Here is the code that I have already shared you at you another post Java - Json deserialize data [].
You have to use ArrayList<Map<String, Object>> because the entries in the JSON string are not symmetric. You can't convert it into POJO in this case.
StringBuilder builder = new StringBuilder();
BufferedReader reader = new BufferedReader(new FileReader(new File("resources/json2.txt")));
String line = null;
while ((line = reader.readLine()) != null) {
builder.append(line);
}
reader.close();
Gson gson = new Gson();
Type listType = new TypeToken<ArrayList<Map<String, Object>>>() {
}.getType();
ArrayList<Map<String, Object>> list = gson.fromJson(builder.toString(), listType);
for (Map<String, Object> json : list) {
for (String key : json.keySet()) {
System.out.println(key + ":" + json.get(key));
}
System.out.println("===========");
}
output:
item_name:Adame
item_type:Special
item:Chestplate
item_min_lvl:50
enchantment:{health=0.3, dam=24%, life=0.1, xp=24%, loot=22%}
def:73
===========
item_name:Sticks'
item_type:Unique
item:Stick
item_min_lvl:4
enchantment:{health=0.6, mana=1, dam=12%, life=0.3, xp=17%, loot=17%}
min_dam:39
max_dam:34
===========
item_name:Sword'
item_type:Unique
item:Sword
item_min_lvl:8
enchantment:[]
min_dam:9
max_dam:10
===========
EDIT
enchantment return something like
enchantment:{health=0.6, mana=1, dam=12%, life=0.3, xp=17%, loot=17%}.
How can I get for example health?
Type mapType = new TypeToken<Map<String, String>>() {
}.getType();
String string = "{health=0.6, mana=1, dam=12%, life=0.3, xp=17%, loot=17%}";
Map<String, String> map = new Gson().fromJson(string, mapType);
for (String key : map.keySet()) {
System.out.println(key + ":" + map.get(key));
}
output:
health:0.6
mana:1
dam:12%
life:0.3
xp:17%
loot:17%

You can create a custom list type in Gson's fromJson() method to map it to a list of POJOs
Type listType = new TypeToken<ArrayList<Enhancement>>() {}.getType();
List<Enhancement> enhancements = new Gson().fromJson(jsonString, listType);
You will get a List<Enhancement>.

Parsing Json in Android with out using any external libraries

I converted a map to a Json String using the code below
String msg = new JSONObject(map).toString();
How do I parse the above Json String to get the map back in Android with out using any external libraries?

If you have pairs of String/String you can easily restore it this way:
JSONObject obj = new JSONObject(msg);
Iterator<String> keys = obj.keys();
HashMap<String, String> map = new HashMap<String, String>();
while(keys.hasNext()) {
String key = keys.next();
map.put(key, obj.optString(key));
}

You are asking how to parse but I don't see any JSON to parse in your question.
An example parsing method without any library looks like that:
JSONObject jo = new JSONObject(response);
JSONArray rootArray= jo.getJSONArray("jArray");
int rootArrayLength=rootArray.length();
for(int i=0;i<rootArrayLength;i++){
int id= rootArray.getJSONObject(i).getInt("value");
// do same for others too and create an object
}
// create object and make a list
You can also check from my other answer to compare:
Convert String to JsonArray

You can check my answer here for JSON Parsing:
https://stackoverflow.com/questions/21872643/about-json-parsing-exchange-data-with-rest-services/21872688#21872688
For completeness, please find the details below:
JSONObject is the key class for JSON Parsing. This class represent JSON data in key/value pair where values can be of any type: JSONObjects, JSONArrays, Strings, Booleans, Integers, Longs, Doubles
You create JSONObject as:
JSONObject jObject = new JSONObject(result);
where result is the response you obtain from your HTTPRequest.
Use this jObject to get different types using the specific names:
String:
String jsonString = jObject.getString("NAME");
Array:
JSONArray jsonArray = jObject.getJSONArray("NAME");
Eg. For parsing the places results I used following function, where JSON is something like:
"results" : [
{
"geometry" : {
"location" : {
"lat" : 36.817729,
"lng" : 10.18206
}
},
"icon" : "http://maps.gstatic.com/mapfiles/place_api/icons/generic_business-71.png",
"id" : "35a4f720fff88e2cfb94d64bfd7dbe95a8b4a632",
"name" : "Banque Al-Baraka",
"reference" : "CoQBcwAAAJbocdTKVg8I8CzgDdNtBQQaMsaghRlks-IWYl9eDNmFtftPHMgEfVeek_NHJZ2AN9JbiMda1WvREmoeIHBHsNdz9i7gtBaLM1xB93uhema_oswpqD-eRQ9b3fvTo4MhTOeIa7cRJ70BSEtDMONZqFyjqlGvL-5WsiwmqI1F3Vp_EhArWzyFuNrJdly2cHRBNxUJGhQjlcyHs-U2F0ILpN-ce-PHEesdqA",
"types" : [ "bank", "finance", "establishment" ],
"vicinity" : "88 P9, Tunis"
},
{
"geometry" : {
"location" : {
"lat" : 36.861635,
"lng" : 10.164628
}
},
"icon" : "http://maps.gstatic.com/mapfiles/place_api/icons/generic_business-71.png",
"id" : "da42093835270f902f64bc870154e6787fffbc7b",
"name" : "Agence Ennasr",
"reference" : "CnRwAAAAoh-XuMXghUKtv2UtHQJiRXB0ZugUnAkJIyP-vBd2YzTj5GdwIb5XhUS9x5-uY9_OwyQUdMmUeDHYm4KXHFNvOoj7diOOHAGBu-xCI4svIxcCwQ2w063mc2G3lohiScYMNpbKhwnCaggt0H1iknZY6xIQxDvNwVN0wWkVwO8zf_El5hoUwHgmgFflE31LDLj2_rr0uc1zvZM",
"types" : [ "bank", "finance", "establishment" ],
"vicinity" : "Avenue de Hédi Nouira, Ariana"
},
]
Parsing JSON Array
public ArrayList<HashMap<String,String>> parseResult(JSONObject jsonObject) throws JSONException {
JSONArray jsonArray = jsonObject.getJSONArray(Constants.RESULTS);
ArrayList<HashMap<String, String>> placesList = new ArrayList<HashMap<String,String>>();
for (int i = 0; i < jsonArray.length(); i++) {
Object object = jsonArray.get(i);
if (object instanceof JSONObject) {
placesList.add(parsePlaceInfo((JSONObject) object));
}
}
return placesList;
}
Parsing simple JSON Object
private HashMap<String, String> parsePlaceInfo(JSONObject place) throws JSONException {
String name = place.getString(Constants.NAME);
String icon = place.getString(Constants.ICON);
String vicinity = place.getString(Constants.VICINITY);
JSONObject locationObject = place.getJSONObject(Constants.GEOMETRY).getJSONObject(Constants.LOCATION);
String lat = locationObject.getString(Constants.LAT);
String lng = locationObject.getString(Constants.LNG);
HashMap<String, String> placeDetails = new HashMap<String, String>();
placeDetails.put(Constants.NAME, name);
placeDetails.put(Constants.ICON, icon);
placeDetails.put(Constants.VICINITY, vicinity);
placeDetails.put(Constants.LAT, lat);
placeDetails.put(Constants.LNG, lng);
return placeDetails;
}
Please note that this is not a complete code. I am providing you main details. Please let me know if you need any specific details regarding the code. Thanks!

Convert complex Java object to Json using Gson

I am using GSON to serialize Java object.
I have a Java class with following properties.
String property1;
Map<String, HashMap> property2 = new HashMap<>();
Map<String, ArrayList<String>> property3 = new HashMap<>();
Map<String, String[]> property4 = new HashMap<>();
I want to convert this to Json. Because of the maps with HashMaps inside, it has become difficult. I know I can get Json of a map with gsonObject.toJson(map). But I want all these properties in the Json Object. (all in one. not Concatenating many objects)
Can anyone help me to get this done?

I don't see what the problem is. Gson can serialize Maps just fine.
Assuming your class is named Test
Test test = new Test();
test.property1 = "some value";
HashMap<String, Integer> map = new HashMap<>();
map.put("one", 1);
map.put("fourty two", 42);
test.property2.put("property2-key", map);
ArrayList<String> strings = new ArrayList<>(Arrays.asList("string1",
"string2", "string3"));
test.property3.put("property3-key", strings);
String[] stringArray = { "array1", "array2", "array3" };
test.property4.put("property4-key", stringArray);
Gson gson = new Gson();
String json = gson.toJson(test);
System.out.println(json);
It generates the following
{
"property1": "some value",
"property2": {
"property2-key": {
"fourty two": 42,
"one": 1
}
},
"property3": {
"property3-key": [
"string1",
"string2",
"string3"
]
},
"property4": {
"property4-key": [
"array1",
"array2",
"array3"
]
}
}