I have Json response (named as jsonResultAsText):
{
"Title": "Hi all",
"IsSecret": false,
"Agents": [
{
"ID": 3,
"Name": "John F"
},
{
"ID": 7,
"Name": "Jack D"
}
]
}
I want to deserialize it using Google's gson library.
I have classes like:
public class JsonResponse {
public String Title;
public boolean IsSecret;
public List<Agent> Agents;
}
public class Agent {
public int ID;
public String Name;
}
I want to get json data into JsonResponse class.
It's the code that I try to achieve:
JsonResponse response =
new Gson().fromJson(jsonResultAsText, JsonResponse.class);
But my Android application gives that classic error: Unfortunately, < app_name > has stopped.
I know that there are plenty examples about serializing/deserializing via gson class, but I could not find similar problem/example.
Thanks in advance.
I solve the problem.
I had forgotten to specify this line on json text I provide (on each element of Agents array):
"Since": "2012-01-07T19:11:01.719"
and in my Agent class:
public class Agent {
public int ID;
public String Name;
public DateTime Since;
}
Sure I have that import: import org.joda.time.DateTime;
When I change data type of Since variable from DateTime to String, problem gone.
Now I can deserialize it.
I am just going to learn how to send DateTime from Asp.Net Web Api to Java via Json.
Thanks for comments.
Related
I am using vk.com API and in one method in response I am getting something like this:
{
"ts": 1691519416,
"updates": [
[
6,
2000000024,
586731
],
[
4,
586732,
8243,
2000000024,
1512642885,
"income message",
{
"from": "384574802"
}
]
]
}
The problem is I am using Gson and I don't know what type of array I need to use.
For now I have this:
public class Updates {
public int ts;
public Update[] updates;
}
I don`t know what to put inside/instead of updates array.
Found a solution, thank you guys for answers. I just needed to use generics and a 2 dimensional array. The code of Updates class:
public class Updates {
public int ts;
public <?>[][] updates;
}
You can create your class like:
class Response
{
Timestamp ts;
Updates[] updates;
}
And use GSON:
Response response = gson.fromJson(jsonString, Response.class);
Just need to create a generic array.
private Object<?>[] json;
{
"localeCode": "",
"map": {
"DynamicName1": [],
"DynamicName2": [
{
"date": "2016-05-15T00:00:00",
"seqId": 1,
"status": 10
},
{
"date": "2016-05-16T00:00:00",
"seqId": 83,
"status": 10
}
],
"DynamicName3": [],
"DynamicName4": []
},
"respCode": 100,
"respMsg": "success",
"status": 1
}
How to correctly map this kind of json. If you can see that, Dynamic is a dynamic name. So far I have done this :
public class MapModel {
public MapObject map;
public static class MapObject{
public java.util.Map<String, Student> queryStudent;
public static class Student{
public String date;
public String seqId;
public String status;
}
}
}
But when run the app. I'm getting NullPointerException. Can somebody help me?
You're getting the NullPointerException accessing queryStudent of your MapObject inside your MapModel since it's not correctly filled when you're trying to deserialize your Json.
So to solve your problem look at Gson documentation where you can see:
You can serialize the collection with Gson without doing anything
specific: toJson(collection) would write out the desired output.
However, deserialization with fromJson(json, Collection.class) will
not work since Gson has no way of knowing how to map the input to the
types. Gson requires that you provide a genericised version of
collection type in fromJson(). So, you have three options:
Use Gson's parser API (low-level streaming parser or the DOM parser
JsonParser) to parse the array elements and then use Gson.fromJson()
on each of the array elements.This is the preferred approach. Here is
an example that demonstrates how to do this.
Register a type adapter for Collection.class that looks at each of the
array members and maps them to appropriate objects. The disadvantage
of this approach is that it will screw up deserialization of other
collection types in Gson.
Register a type adapter for MyCollectionMemberType and use fromJson()
with Collection.
Since your MapObject containts a java.util.Map but your class itself it's not generic, I think that a good approach for your case is create a Deserializer.
Before this try to clean up your class definition, to provide constructors to make the deserializer easy to build. Your POJO classes could be:
Student class
public class Student{
public String date;
public String seqId;
public String status;
public Student(String date, String seqId, String status){
this.date = date;
this.seqId = seqId;
this.status = status;
}
}
MapObject class
Note: I change you Map definition, since in your Json seems that could be multiple students for each DynamicName (look at DynamicName2 from your question), so I use Map<String,List<Student>> instead of Map<String,Student>:
public class MapObject{
public Map<String,List<Student>> queryStudent;
public MapObject(Map<String,List<Student>> value){
this.queryStudent = value;
}
}
MapModel class
public class MapModel {
public MapObject map;
}
Now create a Deserializer for your MapObject:
public class MapObjectDeserializer implements JsonDeserializer<MapObject> {
public MapObject deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
throws JsonParseException {
Map<String,List<Student>> queryStudents = new HashMap<String,List<Student>>();
// for each DynamicElement...
for (Map.Entry<String,JsonElement> entry : json.getAsJsonObject().entrySet()) {
List<Student> students = new ArrayList<Student>();
// each dynamicElement has an Array so convert and add an student
// for each array entry
for(JsonElement elem : entry.getValue().getAsJsonArray()){
students.add(new Gson().fromJson(elem,Student.class));
}
// put the dinamic name and student on the map
queryStudents.put(entry.getKey(),students);
}
// finally create the mapObject
return new MapObject(queryStudents);
}
}
Finally register the Deserializer and parse your Json:
GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(MapObject.class, new MapObjectDeserializer());
Gson gson = builder.create();
MapModel object = gson.fromJson(YourJson,MapModel.class);
DISCLAIMER: For fast prototyping I test this using groovy, I try to keep the Java syntax but I can forget something, anyway I think that this can put you on the right direction.
Hope it helps,
I know how to deserialize normal JSON object with "Gson" library but I am facing problem to deserialize an JSON array with several JSON object and arrays. I am trying to get the time in the arrival_time JSON object in this simple below but I don't know how to structure my class to accomplish that. Can someone explain me how to do that?
Simple:
[{"route": 1,
"info": [
{"direction": "Surrey Quays"},
{"stops": [{"stops_name": " Tenison Way"},
{"arrival_time":{
"mon-fri": [ "05:38", "06:07","06:37"],
"sat": ["05:34","06:01","06:31"],
"son": ["06:02","06:34","07:04"]
}
}
]
}
]
}]
You can parse this Json using following structure:
class ArrivalTime {
public List<String> mon_fri;
public List<String> sat;
public List<String> son;
}
class Stop {
public String stop_name;
public ArrivalTime arrival_time;
}
class Info {
public String direction;
public List<Stop> stops;
}
class RouteInfo {
public Integer route;
public List<Info> info;
}
and then use it like this:
Gson gson = new Gson();
RouteInfo[] routes = gson.fromJson(/* your json string*/, RouteInfo[].class);
Arrival times will be available at something like this (it is ugly but I just want you to present the sample structure for this json string):
System.out.println(routes[0].info.get(1).stops.get(1).arrival_time.sat.get(0));
To learn the structure you could use a javascript object or a online builder.
http://www.jsonschema2pojo.org/
I am having a JSON coming from response payload of rest API. below is structure of simplified JSON but the actual is much more complex.
{
"hardware": {
"cores": 2,
"cpu": 1,
},
"name": "machine11",
"network": [
{
"interface_name": "intf1",
"interface_ip": "1.1.1.1",
"interface_mac": "aa : aa: aa: aa: aa"
}
]
}
Now I have to write POJO class to bind the JSON structure using JAXB annotations (javax.xml.bind.annotation.*).
Can anyone help me how to write POJO class for a complex JSON structure,converting JSON to XML and then using XML schema to generate class is not helping out is there any other way?
Thanks in advance:-)
As per the above JSON structure, your Java objects will look like this:
public class OutermostClass{
private Hardware hardware;
private String name;
private Set<Network> network = new HashSet<Network>;
}
public class Hardware {
private int cores;
private int cpu;
}
public class Network {
private String interface_name;
private String interface_ip;
private String interface_mac
}
I'm trying to parse a JSON feed using Gson in Android. I know the JSON is valid. I suspect that it is because the format is like this:
"Info":[
{
"Id":"",
"Name":"",
"Description":"",
"Date":""
}
In order to parse this I need to "dot" in. Ex: Info.Name
How can I do this in a serialized DTO?
#SerializedName("Name")
public String name;
#SerializedName("Description")
public String desc;
#SerializedName("Date")
public String date;
I tried to put "Info." in front of each serializedName but that didn't work either. I also know my JSON parsing method works properly, because it's used somewhere else with a different DTO. But in that parsing, I don't have to "dotting" issue.
Can anyone help?
EDIT: I have tried everything you guys posted, and nothing works. The error says:
The JsonDeserializer failed to deserialize json object {"Info":[{".......
SECOND EDIT:
I was able to get rid of the error, but now it returns null. Haha, getting pretty damn frustrated right about now!
I am assuming that the actual JSON you are intaking is valid because the example you provided is not. In your JSON example, you have "Info":[ but there is no outer object containing the "Info" property, which is a must. The valid JSON would be:
{
"Info": [
{
"Id":"",
"Name":"",
"Description":"",
"Date":"",
}
]
}
This is a JSON object that has a property "Info" which has a value that is a list of objects. This list of objects contains one object that has the properties "Id", "Name", "Description", and "Date", all of which have empty-string values.
Here is a quick tutorial on how to use GSON to parse a JSON feed such as the above JSON:
You will need a class to represent the items in the list:
public class InfoItem {
public String Id;
public String Name;
public String Description;
public String Date;
public InfoItem() {}
}
And one to represent the list of Items:
public class InfoItemList extends LinkedList<InfoItem> {
public InfoItemList() { super() };
}
This added complexity is because GSON cannot otherwise get the type of a generic collection from the class data.
And one to represent the overall JSON message:
public class InfoMessage {
public InfoItemList Info;
public InfoMessage() {};
}
And then just:
gson.fromJson(jsonString, InfoMessage.getClass());
If just de-serializing a collection:
Type listType = new TypeToken<List<InfoItem>>() {}.getType();
gson.fromJson(jsonString2, listType);
The Info object is a list because of the []. You have to use the following code to deserialze it:
EDIT:
public class Info {
// as in your question
public String name;
...
}
public class Data {
#SerializedName("Info")
public List<Info> info;
}
Then just use the data class to deserialize your json.