I am using the following libraries to create some JSON object.
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
The json I am trying to create is this:
{
"function": "create_contact_group",
"parameters": [{
"user_id": "teer",
"comp_id": "97",
"contact_group_name": "Test01",
"invite_user_list": [{
"invite_user_id": "steve"
}]
}]
}
My function looks like this:
public JSONObject createJSONRequest() {
/* Create json object */
JSONObject jsonObject = new JSONObject();
Map<String, String> map = new HashMap<>();
map.put("user_id", "teer");
map.put("comp_id", "97");
map.put("contact_group_name", "Test01");
List<String> mInviteUserList = new ArrayList<>();
mInviteUserList.add("steve");
/* Create the list of invitee */
Map<String, String> inviteList = new HashMap<>();
for(String user : mInviteUserList) {
inviteList.put("invite_user_id", user);
}
/* Add the invitees into the json array */
JSONArray inviteArray = new JSONArray();
inviteArray.add(inviteList);
/* Add the json array to the json object */
jsonObject.put("invite_user_list", inviteArray);
JSONArray parameterlist = new JSONArray();
parameterlist.add(map);
parameterlist.add(jsonObject);
jsonObject.put("parameters", parameterlist);
jsonObject.put("function", "create_contact_group");
Log.d(TAG, "jsonObject: " + jsonObject.toJSONString());
return jsonObject;
}
However, the function crashes when I get to the following line:
Log.d(TAG, "jsonObject: " + jsonObject.toJSONString())
I think it has something to do with this line here:
parameterlist.add(jsonObject);
Stacktrace:
java.lang.StackOverflowError java.lang.AbstractStringBuilder.enlargeBuffer(AbstractStringBuilder.java:95) at java.lang.AbstractStringBuilder.append0(AbstractStringBuilder.java:132)
at java.lang.StringBuffer.append(StringBuffer.java:126) at org.json.simple.JSONValue.escape(JSONValue.java:266) at org.json.simple.JSONObject.toJSONString(JSONObject.java:116)
Many thanks for any suggestions,
There are a couple of issues in your code.
One issue is that the structure you create in the java code will not match the structure that you show above. This I will try to describe a bit below.
The second issue is that you get a stackoverflow exception (which you know but don't know why).
The stackoverflow exception is thrown cause the program runs out of the stack memory assigned by the computer. Why you ask? Well, cause you create a recursive or cyclic JSON object.
This isn't good, but its not that big a deal cause its kinda easy to fix.
So why does the program throw this exception? Well, look at the following snippet:
JSONArray parameterlist = new JSONArray();
parameterlist.add(map);
parameterlist.add(jsonObject);
jsonObject.put("parameters", parameterlist);
jsonObject.put("function", "create_contact_group");
You create a JSONArray and then add the JSONObject created before to the array.
After that you add the same array to the object that is already in the array.
I expect that you see the issue with that!
So, that should not be done.
And how to fix this? Well, I kinda think its better that I describe how you should write the code to get the structure you are actually asking for, so I'll try do that...
What to do...?
A JSON (JavaScript Object Notation) -object is always declared with this type of brackets: {} a JSON array with [], so, the JSON you are trying to generate should be in the following data types:
{ // <= Root object (a JSON-object).
"function": "create_contact_group", // <= Key in the root-object (where the key is a string and the value a string)
"parameters": [ // <= Key in the root-object (where the key is a string and the value is an array.
{ // <= Object inside the array.
"user_id": "teer", // Key (string/string)
"comp_id": "97", // Key (string/string)
"contact_group_name": "Test01", // Key (string/string)
"invite_user_list": [ // Key (string/array)
{ // Object inside the invite_user_list array
"invite_user_id": "steve" // Key (string/string)
}
]
}
]
}
So when creating the JSON-object in java, you will want to create a root object then add all the diff params inside it.
Adding a value to a JSONObject is done with the JSONObject.put(string, Object) method, where the string is a key and the object a value.
So to start, I would recommend creating the parameters list.
In your case, you use a HashMap for the objects, which is not really wrong, but not really necessary either, I would just stick to a JSONObject, which is not all that different than a HashMap<string, Object>.
So instead of map.put(...), you could do something like:
JSONObject param = new JSONObject();
param.put("user_id", "teer");
param.put("comp_id", "97");
param.put("contact_group_name", "Test01");
Now, one of the objects values should be an array (invite_user_id) and the easiest way to add an array to the object is to create a JSONArray and then just add it.
JSONArray inviteList = new JSONArray();
// Then you need to add an object to the array for each `user` that has invited.
// For-loop here maybe?
JSONObject invitee = new JSONObject();
invitee.put("invite_user_id", user);
inviteList,add(invitee); // This will make it into an array with objects, I.E., [ { "invite_user_id": "Steve" } ]
After creating the invite list, add it to the param object like:
param.put("invite_user_list", inviteList);
// Now, param should be in its own list too, so you should probably create a JSONArray for the params.
// Ill leave that to you, and we pretend we have a list of the param objects named "params".
And then at the end, you create the root object and set its values:
JSONObject root = new JSONObject();
root.put("parameters", params);
root.put("function", "create_contact_group");
And that should be it.
This should create a JSON-string with the structure that you made above. But I would recommend testing (and writing unit tests!) for this (especially as I have written this code in the browser!).
But why?!
I guess I should try to describe why your code was not working as the one I described above.
You start by creating a root object, so far so good (can create it at start or at the time you need it, doesn't really matter), after that you create a HashMap and add the properties to it.
So far this is also legit (you could later create a JSONObject from the map).
In the next part, you create an ArrayList (im not really sure why) and add a name to it, and then another HashMap which you add the single name to (key invite_user_list) inside a for-loop.
This is either not necessary (cause its just one name) or wrong (if there is supposed to be more names in a real life execution of the code), in case of unnecessary, the for-loop shouldn't be there and in case of "not like real life" it should not be added to a Map!
Instead the invieList should have been an array, and each entry added should have been a object which had the "invite_user_id" key set to the name.
After that, you add the inviteList HashMap to a newly created JSONArray, I guess this could be kinda okay, if you only want one object ever in the array, else I would recommend creating it before the loop and add each entry into it!
The inviteArray is then put inside the root object with the key invite_user_list, after that you create another JSONArray and add both the map (your parameters created at the start) and the JSONObject (root) created first of all.
But the thing you do after that, is why you are getting a stackoverflow exception, you add the parameterlist (which contains the jsonObject (root)) to the jsonObject, which makes the jsonObject exist inside an array that is inside itself!
This creates a cyclic JSON structure which will never end if the whole thing was to be unrolled, hence the computer throws the exception.
The structure of the resulting object would also be wrong, cause it would look something like this:
{ // Root (jsonObject)
"invite_user_list": [
{ "invite_user_id": "steve" }
]
"parameters": [
{ // The "map" hashmap
"user_id", "teer",
"comp_id": "97",
"contact_group_name": "Test01"
},
{ // The jsonObject object (which is also the root!)
"invite_user_list": [
{ "invite_user_id": "steve" }
],
"parameters": [
{ // The "map" hashmap
"user_id", "teer",
"comp_id": "97",
"contact_group_name": "Test01"
},
{
// The jsonObject object again (which is also the root and the parent!)
// ... and so on til eternity!
}
],
"function": "create_contact_group"
}
],
"function": "create_contact_group"
}
Extra...
I would like to add here at the end (where I hope you end up after reading the whole wall of text that I wrote above, cause you might have learnt something!) that there is a easier way of doing it.
Now, I haven't used this lib myself, but from what I understand, it should be able to serialize a whole object, the lib can be found at Googles github repos which can be used as a json serializer and convert a class-instance to a json string, then you could just create a class for the whole object and fill it up and serialize it at the end of the function, without using either JSONArray nor JSONObject.
The issue is due to recursion process that occurs when you are trying to add the JsonObject to JsonArray and viceVersa.
The thing you are doing is,
JSONArray parameterlist = new JSONArray();
parameterlist.add(map);
parameterlist.add(jsonObject);
And then
jsonObject.put("parameters", parameterlist);
The problem is when you print the object using jsonObject.toJSONString(), Then at first it will fetch the parameterlist then as jsonObject is part of the keyvalue pair on the parameterlist JsonArray it will refetch the jsonObject which then again fetch the parameterlist and this process continues on and hence causing the StackOverflow Issue.
The Quick Solution is to create new JsonObject while assigning the parameterList,
JSONArray parameterlist = new JSONArray();
parameterlist.add(map);
parameterlist.add(jsonObject);
JSONObject newJson = new JSONObject();
newJson.put("parameters", parameterlist);
System.out.println(newJson.toJSONString());
I'm trying to get one JSON object and iterate it. In this case it should iterate only once because I'm having only one complete JSON object, if it has multiple, it should iterate multiple times. But rather it shows the system.out.println string twice. I don't understand whats wrong in this code?
String str = "{\"userId\":\"1234\",\"businessPrimaryInfo\":{\"53bd2a4\":{\"businessSpecificInfo\":{\"businessType\":\"Manufacturing\",\"tradingPlace\":\"Hyderabad\"}},\"53bd2a4e\":{\"businessSpecificInfo\":{\"businessType\":\"Milling\",\"tradingPlace\":\"Mumbai\"}}}}";
JSONObject jsonObj = new JSONObject(str);
Iterator<String> keys = jsonObj.keys();
// Iterate all the users.
while (keys.hasNext()) {
String key = keys.next();
try {
// If the user has Business primary info as JSON object.
if (jsonObj.has("businessPrimaryInfo")) {
JSONObject jsonBizPrimaryInfo = jsonObj
.getJSONObject("businessPrimaryInfo");
System.out.println("Object is:" + jsonBizPrimaryInfo);
}
} finally {
}
}
Please have a look and let me know where I'm doing wrong.
The two keys that are causing your loop to iterate twice are: userId and businessPrimaryInfo. But you ask the main JSON object if it has a businessPrimaryInfo key. Which it has for every iteration.
What you need to do is check that the current key is businessPrimaryInfo.
Or, you can just ask the primary object if it has a businessPrimaryInfo key, and if so, ask for that child object.
I am new to JSON and getting confused everytime I create a new one.
I am trying to create a JSON array like this :
{
"id":"2003",
"HouseMD" :
{
"Doctor_1": "Thirteen",
"Doctor_2" : "Chase"
"Doctor_n" : "Someone"
}
}
Basically I am trying to add info dynamically from Doctor_1 to Doctor_n" in a for loop. and if I use a JSON Object I am only getting the last value when I finally print it.
How do I get something that I want?
Any help appreciated.
Thanks.
JSON arrays look like this:
{ "id":"2003", "HouseMD" : [{ "Doctor_1": "Thirteen"}, {"Doctor_2" : "Chase"}, {"Doctor_n" : "Someone" }]}
Notice the square bracket that surrounds each JSON object in the array.
Here is the link to the JSON website, which can offer more info:
JSON
Note that in order for the code below to work, you will also need the JSON library, which you can easily download from here Download Java JSON Library
I don't know the approach you are using, but based on the format you want, I would do something like this:
JSONObject data = new JSONObject();
data.put("id", "2003");
JSONObject doctors = new JSONObject();
//here I suppose you have all doctors in a list named doctorList
//and also suppose that you get the name of a doctor by the getName() method
for (int i = 0; i < doctorList.size(); ++i)
{
doctors.put("Doctor_" + (i+1), doctorList.get(i).getName();
}
data.put("HouseMD", doctors);
//then you could write to a file, or on screen just for test
System.out.println(data.toString());
However, I feel you need to become more comfortable with JSON, so try starting here.
I have a JSONObject that I pass to a method to get processed into ArrayLists.
{
"set0" :
{
"title" : "Do you win?",
"answer" : "1",
"imgUrl" : "imag",
"id" : "1"
},
"set1" :
{
"title" : "Did you loose?",
"answer" : "1",
"imgUrl" : "imag",
"id" : "2"
}
}
The method is structured like this:
questions(JSONObject result){
// initialization
for(int i=0;i < result.length();i++){
question_list.add(result.getJSONObject("set"+i).getString("title"));
answer_list.add(result.getJSONObject("set"+i).getString("answer"));
img_list.add(result.getJSONObject("set"+i).getString("imgUrl"));
question_batch.add(result.getJSONObject("set"+i).getInt("id"));
}
// rest of code
}
I normally see the jsonarray being used for the loop condition and not the jsonobject itself, when my jsonobject gets bigger but in the same structure as posted above will result.length() start to yield a wrong result and is this an incorrect implementation for someone who will want to iterate through their jsonobject?
I'm not sure if your implementation is "incorrect", but this is how I generally iterate through JSON.
int i = 0;
boolean continue = true;
while (continue){
if (result.has("set" + i){
JSONObject set = result.get("set" + i.toString());
if (set.has("title"){
question_list.add(set.getString("title");
}
if (set.has("answer"){
answer_list.add(set.getString("answer");
}
if (set.has("imgUrl"){
image_list.add(set.getString("imgUrl");
}
if (set.has("id"){
question_batch.add(set.getInt("id");
}
i++;
}else{
continue = false;
}
}
This is a little more efficient because you don't have to create a new JSON object everytime you want to pull data out.
Also I would make a new class to handle the JSON objects, and make the array list of that type, so you only have to add one object for each iteration. This way, you can be sure that your questions/answers/imageURLs/id's are all kept together. Like this:
JSONObject set = result.get("set" + i.toString());
QuestionObject newQuestion = new QuestionObject();
if (set.has("title"){
newQuestion.setTitle(result.getString("title");
}
if (set.has("answer"){
newQuestion.setAnswer(result.getString("answer");
}
if (set.has("imgUrl"){
newQuestion.setImageURL(result.getString("imgUrl");
}
if (set.has("id"){
newQuestion.setID(result.getInt("id");
}
questionList.add(newQuestion);
Also, in case you didn't notice, you can directly parse integers using json.getInt() for your "id" field instead of string.
You might want to have a look to Jackson also. That is also quite straightforward, and your code might benefit from using it.
I am not sure if it possible or not but I think it can be done using JSONArray.put method.
Heres my problem:
I have got two lists:
ArrayList<Students> nativeStudents;
ArrayList<transferStudents> transferStudents = nativeStudents.getTransferStudentsList();
The JSON that I generate with transferStudents list is right here: http://jsfiddle.net/QLh77/2/ using the following code:
public static JSONObject getMyJSONObject( List<?> list )
{
JSONObject json = new JSONObject();
JsonConfig config = new JsonConfig();
config.addIgnoreFieldAnnotation( MyAppJsonIgnore.class );
if( list.size() > 0 )
{
JSONArray array = JSONArray.fromObject( list, config );
json.put( "students", array );
}
else
{
//Empty Array
JSONArray array = new JSONArray();
json.put( "students",
array );
}
return json;
}
Now what I want to get is JSON data with following structure: http://jsfiddle.net/bsa3k/1/ (Notice the tempRollNumber field in both array elements).
I was thinking of doing: (The if condition here is used for a business logic)
if(transferStudents.getNewStudentDetails().getRollNumber() == nativeStudents.getNativeStudentDetails.getStudentId()){
json.put("tempRollNumber", transferStudents.getNewStudentDetails().getRollNumber());
}
but this would add tempRollNumber outsite the array elements, I want this JSON element to be part of every entry of students array.
PS: I cant edit the transferStudents class in order to add tempRollNumber field.
Since no one has come up with anything better I'll turn my comments above into an answer.
The best way to handle this is to create an object model of your data and not create the JSON output yourself. Your app server or container can handle that for you.
Though you cannot change the objects you receive in the List you can extend the object's class to add your own fields. Those fields would then appear in the JSON when you marshall it.