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Create JSON object from List in Java

I have a List<String> where each element represents a node and a String which is the value that corresponds to the last node of that list. The list represents the path to the value. So, basically each element of the list is the value of the previous element. I would like to create a JSON object from it using Jackson. However, this needs to be done dynamically, not explicitly setting the nodes of the JSON object, because the list will not always be the same.
So, I am wondering if there is a way to convert or iterate through the list and create the JSON object.
So, if my list looks like this:
["user", "car", "brand"] and the value is "BMW", the JSON object should look like this:
{
"user":
{
"car":
{
"brand": "BMW"
}
}
}

Iterate through the list in reverse and upon each iteration create a new JsonNode for the list element, add the previous JsonNode as a child to the new JsonNode and overwrite the original reference with the new JsonNode. Rinse and repeat.
Something like...
final String value = "BMW"; // whatever the final "value" is.
final ObjectMapper objectMapper = new ObjectMapper();
ObjectNode json = null;
for (int i = list.size() - 1; i >= 0; i--) {
final String prop = list.get(i);
final ObjectNode objectNode = objectMapper.createObjectNode();
if (json == null) {
objectNode.put(prop, value);
} else {
objectNode.put(prop, json);
}
json = objectNode;
}

Here is the piece of code which you need
package uk.co.vishal;
import com.fasterxml.jackson.core.JsonProcessingException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class Answer {
public static void main(String[] args) throws JsonProcessingException {
List<String> data = new ArrayList<>();
data.add("user");
data.add("car");
data.add("brand");
System.out.println(data.toString());
Map<String, String> mydata = new HashMap<>();
Map<String, JSONObject> newdata = new HashMap<>();
JSONObject result = new JSONObject();
boolean flag = true;
for (int i = data.size() - 1; i >= 0; i--) {
if (flag) {
mydata.put(data.get(i), "BMW");
result = generateJson(mydata);
flag = false;
} else {
newdata.put(data.get(i), result);
result = generateJson(newdata);
newdata.clear();
}
}
System.out.println(result);
/*
* Here is the output:
* {
"user": {
"car": {
"brand": "BMW"
}
}
}
*
* */
}
private static JSONObject generateJson(Map data) {
return new JSONObject(data);
}
}
I hope you will be sorted !!

Java: Append key value pair to nested json object

I am given three inputs .
A JSON object (nested)
A node structure
key value pair
My task is to append the key value pair to a node by looking at the node structure and updating the original JSON.
For example, if the inputs are,
JSON Object
{
a:
{
b:
{
c:{}
}
}
}
Node structure
a.b.
Key k and value v
The final updated JSON should look like
{
a:
{
b:
{
key:val
c:{}
}
}
}
Please note that the original JSON can be {} also. Then I have to build the whole JSON by looking at the node structure.
Here is my code
making a key value pair
public JSONObject makeEV(String ele, String val) throws JSONException{
JSONObject json =new JSONObject();
json.put(ele, val);
return json;
}
Appending it to JSON
public void modifiedJSON(JSONObject orgJson, String nodeStruct, JSONObject ev) throws JSONException{
JSONObject newJson = new JSONObject();
JSONObject copyJson = newJson;
char last = nodeStruct.charAt(nodeStruct.length()-1);
String lastNode = String.valueOf(last);
int i = 0;
while(orgJson.length() != 0 || i< nodeStruct.length()){
if(orgJson.length() ==0){
if(nodeStruct.charAt(i) == last){
newJson.put(String.valueOf(last), ev.toString());
}else{
newJson.put(String.valueOf(nodeStruct.charAt(i)), "");
}
newJson = newJson.getJSONObject(String.valueOf(nodeStruct.charAt(i)));
}
else if(i >= nodeStruct.length()){
if(orgJson.has(lastNode)){
newJson.put(String.valueOf(last), ev.toString());
}else{
}
}
}
}
I am stuck here. Please help. Thanks in advance.

It could be done using String#split(regex) as next:
public void modifiedJSON(JSONObject orgJson, String nodeStruct,
String targetKey, String value) {
// Split the keys using . as separator
String[] keys = nodeStruct.split("\\.");
// Used to navigate in the tree
// Initialized to the root object
JSONObject target = orgJson;
// Iterate over the list of keys from the first to the key before the last one
for (int i = 0; i < keys.length - 1; i++) {
String key = keys[i];
if (!target.has(key)) {
// The key doesn't exist yet so we create and add it automatically
target.put(key, new JSONObject());
}
// Get the JSONObject corresponding to the current key and use it
// as new target object
target = target.getJSONObject(key);
}
// Set the last key
target.put(targetKey, value);
}

How to store a JsonArray in a Map?

I have used the following Code
JSONArray jsonArray = new JSONArray(incomingData);
Map<String,String> map=new HashMap<String,String>();
for(int i=0;i<jsonArray.length();i++){
JSONObject j = jsonArray.getJSONObject(i);
Iterator<?> it = j.keys();
while (it.hasNext()) {
String n = it.next().toString();
map.put(n, j.getString(n));
}
}
But when I execute this code it's throwing an Exception.
org.json.JSONException: JSONObject["low_stock_date"] not a string.
JsonArray Used
[
{
"item_id": "1",
"product_id": "1",
"stock_id": "1",
"qty": "99.0000",
"low_stock_date": null
},
{
"item_id": "2",
"product_id": "2",
"stock_id": "1",
"qty": "100.0000",
"low_stock_date": null
}
]
Please help me to over come this issue.

The value of low_stock_date is null. thats why it is throwing this error.
Just add one check for null before adding it into Map.
if(!j.isNull(n)){
map.put(n, j.getString(n));
}
else{
map.put(n, null);
}

for(int i=0;i<jsonArray.length();i++){
JSONObject j = jsonArray.getJSONObject(i);
Iterator<?> it = j.keys();
while (it.hasNext()) {
String n = it.next().toString();
map.put(n, j.getString(n));
}
}
You are doing the above, inside for loop & storing the key/value pair in Map.
As same keys are there in every JSONObject so only values in last jsonobject would be there in for Map keys.
As an alternate you can create an ArrayList for storing these Maps, which you can get while converting each JSONObject to Map
One more thing you can do here is using a parser like Jackson Parser
HashMap<String,String> result =
new ObjectMapper().readValue(JSON_SOURCE, HashMap.class);
(where JSON_SOURCE is a File, input stream, reader, or json content String).
That would be quick & better way of doing the what you want.

This is actually how the method is implemented:
/**
* Get the string associated with a key.
*
* #param key
* A key string.
* #return A string which is the value.
* #throws JSONException
* if there is no string value for the key.
*/
public String getString(String key) throws JSONException {
Object object = this.get(key);
if (object instanceof String) {
return (String) object;
}
throw new JSONException("JSONObject[" + quote(key) + "] not a string.");
}
You could check the type of the to-be-loaded object to see if it is null:
j.isNull(n);
and then act accordingly:
if (j.isNull(n)) {
// do something
} else {
// do something else
}

How to get dynamically changed Key's value in Json String using java

I'm trying to parse Json string using java, I have stuck up with some scenario.
See below is my JSON String:
"NetworkSettings": {
"Ports": {
"8080/tcp": [ // It will change dynamically like ("8125/udp" and "8080/udp" etc....)
{
"HostIp": "0.0.0.0",
"HostPort": "8080"
}
]
}
}
I try to parse the above json string by using the following code:
JsonObject NetworkSettings_obj=(JsonObject)obj.get("NetworkSettings");
if(NetworkSettings_obj.has("Ports"))
{
JsonObject ntw_Ports_obj=(JsonObject)NetworkSettings_obj.get("Ports");
if(ntw_Ports_obj.has("8080/tcp"))
{
JsonArray arr_ntwtcp=(JsonArray)ntw_Ports_obj.get("8080/tcp");
JsonObject ntwtcp_obj=arr_ntwtcp.get(0).getAsJsonObject();
if(ntwtcp_obj.has("HostIp"))
{
ntw_HostIp=ntwtcp_obj.get("HostIp").toString();
System.out.println("Network HostIp = "+ntw_HostIp);
}
if(ntwtcp_obj.has("HostPort"))
{
ntw_HostPort=ntwtcp_obj.get("HostPort").toString();
System.out.println("Network HostPort = "+ntw_HostPort);
}
}
else
{
ntw_HostIp="NA";
ntw_HostPort="NA";
}
}
else
{
ntw_HostIp="NA";
ntw_HostPort="NA";
}
In my code I have used this code
JsonArray arr_ntwtcp=(JsonArray)ntw_Ports_obj.get("8080/tcp");
to get the value of "8080/tcp"
How can I get the values of dynamically changing key like ("8125/udp","8134/udp", etc...)
Note: I'm using gson library for parsing
After modification
public static void main(String args[])
{
try
{
JsonParser parser = new JsonParser();
JsonObject obj=(JsonObject)parser.parse(new FileReader("sampleJson.txt"));
System.out.println("obj = "+obj);
JsonObject NetworkSettings_obj=(JsonObject)obj.get("NetworkSettings");
if(NetworkSettings_obj.has("Ports"))
{
JsonObject ntw_Ports_obj=(JsonObject)NetworkSettings_obj.get("Ports");
System.out.println("ntw_Ports_obj = "+ntw_Ports_obj);
Object keyObjects = new Gson().fromJson(ntw_Ports_obj, Object.class);
List keys = new ArrayList();
System.out.println(keyObjects instanceof Map); //**** here the statement prints false
if (keyObjects instanceof Map) // *** so controls doesn't enters into the if() condition block *** //
{
Map map = (Map) keyObjects;
System.out.println("Map = "+map);
keys.addAll(map.keySet());
String key = (String) keys.get(0);
JsonArray jArray = (JsonArray) ntw_Ports_obj.get(key);
System.out.println("Array List = "+jArray);
}
}
}
catch(Exception e)
{
}
}

You can do something like that (not tested but should be ok) :
if (ntw_Ports_obj.isJsonArray()) {
Iterator it = ntw_Ports_obj.getAsJsonArray().iterator();
while (it.hasNext()) {
JsonElement element = (JsonElement) it.next();
if(element.isJsonArray()){
JsonArray currentArray = element.getAsJsonArray();
// Do something with the new JsonArray...
}
}
}

So your problem is the key 8080/tcp is not fixed and it may change. when this situation you can try like this to get the value of the Dynamic key.
Set<Map.Entry<String, JsonElement>> entrySet = ntw_Ports_obj
.entrySet();
for (Map.Entry<String, JsonElement> entry : entrySet) {
String key = entry.getKey();
JsonArray jArray = (JsonArray) ntw_Ports_obj.get(key);
System.out.println(jArray);
}
Edit:
Object keyObjects = new Gson().fromJson(ntw_Ports_obj, Object.class);
List keys = new ArrayList();
/** for the given json there is a one json object within the 'Ports' so the 'keyObjects' will be the 'Map'**/
if (keyObjects instanceof Map) {
Map map = (Map) keyObjects;
keys.addAll(map.keySet());
/**
* keys is a List it may contain more than 1 value, but for the given
* json it will contain only one value
**/
String key = (String) keys.get(0);
JsonArray jArray = (JsonArray) ntw_Ports_obj.get(key);
System.out.println(jArray);
}

How to sort GSON Array based on a key?

Consider the following is my Array
[
{"id":10,"name":"name10","valid":true},
{"id":12,"name":"name12","valid":false},
{"id":11,"name":"name11","valid":false},
{"id":9,"name":"name9","valid":true}
]
Created a JsonArray out of it, like following code does:
//Create a JSON Parser using GSON library
objJsonParser = new JsonParser();
String strArrayText = [{"id":9,"name":"name9","valid":true}, ...]
JsonArray jsonArrayOfJsonObjects = objJsonParser.parse(strArrayText).getAsJsonArray();
Now, I am trying to sort jsonArrayOfJsonObjects based on name field.
Desired Output:
[
{"id":9,"name":"name9","valid":true},
{"id":10,"name":"name10","valid":false},
{"id":11,"name":"name11","valid":false},
{"id":12,"name":"name12","valid":true}
]
Could anyone help to sort this out with best apporach with respect to Java & Gson?
Your inputs are greatly appreciated.

First of all, the proper way to parse your JSON is to create a class to encapsulate your data, such as:
public class MyClass {
private Integer id;
private String name;
private Boolean valid;
//getters & setters
}
And then:
Type listType = new TypeToken<List<MyClass>>() {}.getType();
List<MyClass> myList = new Gson().fromJson(strArrayText, listType);
Now you have a List and you want to sort it by the value of the attribute id, so you can use Collections as explained here:
public class MyComparator implements Comparator<MyClass> {
#Override
public int compare(MyClass o1, MyClass o2) {
return o1.getId().compareTo(o2.getId());
}
}
And finally:
Collections.sort(myList, new MyComparator());

Try this library method as a simple JSON-level alternative to model classes creation:
/**
* Sort JSON-array by a given key name (numbers or text expected).
*
* #param jsonArray JSON-array to sort.
* #param keyNameToSort Key name to sort by. Expected are integer type
* (sorted ascending) or string type (sorted
* alphabetically).
*/
public static JsonArray
sortJsonArrayByKey(
JsonArray jsonArray,
String keyNameToSort) {
JsonArray sortedJsonArray = new JsonArray();
JsonObject jsonObject = null;
int jsonElementIndex;
TreeMap<Integer, JsonObject> integerSortedObjects = new TreeMap<>();
TreeMap<String, JsonObject> stringSortedObjects = new TreeMap<>();
for (
jsonElementIndex = 0;
jsonElementIndex < jsonArray.size();
jsonElementIndex++) {
try {
// A JSON-Object from JSON-array:
jsonObject =
jsonArray
.get(
jsonElementIndex)
.getAsJsonObject();
} catch (Exception notAnObject) {
}
for (Entry<String, JsonElement> entry : jsonObject.entrySet()) {
// Look for the given key in the JSON-object:
if (
entry.getKey()
.equals(keyNameToSort)) {
try {
// If key is of integer type:
integerSortedObjects.put(
entry
.getValue()
.getAsInt(),
jsonObject);
} catch (Exception notAnInt) {
try {
// If key is of string type:
stringSortedObjects.put(
entry
.getValue()
.getAsString(),
jsonObject);
} catch (Exception neitherIntNorString) {
}
}
}
}
}
// Add sorted by number values first:
for (Integer key : integerSortedObjects.keySet()) {
sortedJsonArray.add(
integerSortedObjects.get(
key));
}
// Add sorted by string values second:
for (String key : stringSortedObjects.keySet()) {
sortedJsonArray.add(
stringSortedObjects.get(
key));
}
return sortedJsonArray;
}

you can use Gson library https://sites.google.com/site/gson/gson-user-guide
to get the Array(the class should implement comparable) and sort with arrays.sort();
Thanks