Parse JSON string in Java without keys

Question

I am new to parsing JSON in java. I have this JSON string:

[
{
 "projectId":5,
 "userName":"clinician",
 "projectName":"r",
 "projectSummary":"r",
 "projectLanguage":"r",
 "contactPersonName":"r",
 "contactPersonCV":"r",
 "contactPersonEmail":"r",
 "contactPersonPhone":"r"
},
[
 {
 "consentFileId":2,
 "projectId":5,
 "consentDescription":"r",
 "consentFileName":"test.pdf",
 "servicePathToGetConsentPdf":null
 },
 {
 "consentFileId":3,
 "projectId":5,
 "consentDescription":"rrr",
 "consentFileName":"test.pdf",
 "servicePathToGetConsentPdf":"localhost:8080/4c_viewFile?consentFileId=3"
 }
],
[
 {
 "anonymized_patient_identifier":"r",
 "projectId":5
 },
 {
 "anonymized_patient_identifier":"2",
 "projectId":5
 },
 {
 "anonymized_patient_identifier":"5",
 "projectId":5
 }
]

]

I have managed to get values from simpler JSON strings but this one has multiple levels and also there is no key in each level. I tried with simple code like this:

 Object obj = parser.parse(data);
 JSONObject jsonObject = (JSONObject) obj;
 resultJson = (String) jsonObject.get("projectId");
 resultJson += "\n";
 resultJson += (String) jsonObject.get("userName");

but I get the error [java.lang.ClassCastException: org.json.simple.JSONArray cannot be cast to org.json.simple.JSONObject] And also I don't understand how I will get the values in lower level without a key. I tried also to save it as a JSONArray but it didn't work.

• Biffen: The outermost element in your JSON is an array, and you're (inexplicably) trying to cast it to an object. Of course it doesn't work.
• Hien Ngo: You should parse it to JSONArray, and then cast it to JSONObject with id.

Answer 1

your root of json is type of JSONArray, the first object stored in the root array is an object, you can retrieve it by using index = 0 .

this is a hack to make your code work:

 JSONArray jsonArray = JSONArray.fromObject(data);
 JSONObject jsonObject=obj.getJSONObject(0);
 resultJson = (String) jsonObject.get("projectId");
 resultJson += "\n";
 resultJson += (String) jsonObject.get("userName");

NOTE:

to convert a String to JSONArray, you can do :

JSONArray array = JSONArray.fromObject(data);

• user1431148: I have another error now. I use netbeans and the error is: cannot find symbol about method getJSONObject(int). I have imported org.json.simple.JSONObject; and I searched it on goole but I only found articles about android.
• nafas: @user1431148 have you imported this : net.sf.json.JSONArray; ? if yes make sure you've downloaded the newest package
• user1431148: I still have the same error. Also I use simple.JSONObject and if I use net.sf.json.JSONArray I get java.lang.ClassCastException: org.json.simple.JSONArray cannot be cast to net.sf.json.JSONArray. So which libraries should I use?
• nafas: you should only use ONE json library. if you haven't done too much with org.json.simple package, then i recommend you replace all your code and start using net.sf.json.JSONArray.
• user1431148: Does it have a parser? Because I can't find it or I have to do it differently than JSONParser parser = new JSONParser(); Object obj = parser.parse(data)

Answer 2

To improve on nafas answer, I would do this to see all the objects in the array:

Object obj = parser.parse(data);
JSONArray jsonArray = (JSONArray) obj;
for (int i = 0; i < jsonArray.size (); i++) {
 JSONObject jsonObject=obj.getJSONObject(i);
 resultJson = (String) jsonObject.get("projectId");
 resultJson += "\n";
 resultJson += (String) jsonObject.get("userName");
}

• Vinze: I don't think it will work, the content of the array is heterogeneous and content are not all objects with that fields...