In your json fromat the JSON array contains mixed types. Deserialization with fromJson() 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:
Option 1: Use Gson's parser API.
Option 2: Register a type adapter for Collection.class.
Option 3: Register a type adapter for MyCollectionMemberType. This approach is practical only if the array appears as a top-level element.
Here in your case option 3 is best because array is on the top level elements of response object. I've followed mixed approach option 1 & 3.
For further detail see
Serializing and Deserializing Collection with Objects of Arbitrary Types using Gson
Gson Collections Limitations
The complex part in your json format is deserialize total record number
in Wall class object
Here is the tricky part to deserialize the json in java objects.
GsonBuilder b = new GsonBuilder();
b.registerTypeAdapter(WallResponse.class,new JsonDeserializer<WallResponse>() {
@Override
public WallResponse deserialize(JsonElement jsonElement,Type typeOf, JsonDeserializationContext context) throws JsonParseException {
final Gson g = new Gson();
final JsonObject jsonObject = jsonElement.getAsJsonObject();
final WallResponse wallResponse = new WallResponse(new Response());
final Entry<String, JsonElement> entry = jsonObject.entrySet().iterator().next();
final JsonElement element = entry.getValue();
final JsonObject jsonObject2 = element.getAsJsonObject();
final Entry<String, JsonElement> entry2 = jsonObject2.entrySet().iterator().next();
final JsonArray jsonArray = entry2.getValue().getAsJsonArray();
final Iterator<JsonElement> jsonElement2 = jsonArray.iterator();
int totalRecord=-1;
while (jsonElement2.hasNext()) {
final JsonElement element2 = jsonElement2.next();
if (element2.isJsonPrimitive())
totalRecord=element2.getAsInt();
if (element2.isJsonObject()) {
final Wall wall = g.fromJson(element2, Wall.class);
wall.setTotalRecord(totalRecord);
List<Wall> walls= new ArrayList<>();
walls.add(wall);
wallResponse.getResponse().setWall(walls);
}
}
return wallResponse;
}
});
WallResponse response = b.create().fromJson(reader, WallResponse.class);
Java models classes are like below according to json format
WallResponse Class
public class WallResponse {
private Response response;
public WallResponse() { super();{
public WallResponse(Response response) {super();this.response = response;}
public Response getResponse() { return this.response;}
public void setResponse(Response response) { this.response = response; }
@Override
public String toString() { return "WallResponse [response=" + response + "]"; }
}
Response Class
public class Response {
private List<Wall> wall;
public List<Wall> getWall() { return this.wall; }
public void setWall(List<Wall> wall) { this.wall = wall; }
@Override
public String toString() { return "Response [wall=" + wall + "]"; }
}
Wall Class
public class Wall {
private int totalRecord;
private Media media;
private Attachment attachment;
private List<Attachments> attachments;
@SerializedName(value = "post_source")
private PostSource postSource;
private Comments comments;
@SerializedName(value = "likes")
private Like like;
@SerializedName(value = "reposts")
private Repost repost;
private String id;
private String from_id;
private String to_id;
private String date;
private String post_type;
private String text;
private String can_delete;
private String reply_count;
private String online;
// setter getter here
}
Media Class
public class Media {
private String type;
private String owner_id;
private String item_id;
private String thumb_src;
//setter getter here
@Override
public String toString() {
return "Media [type=" + type + ", owner_id=" + owner_id + ", item_id="
+ item_id + ", thumb_src=" + thumb_src + "]";
}
}
Attachment Class
public class Attachment {
private String type;
private Photo photo;
// setter getter here
@Override
public String toString() {
return "Attachment [type=" + type + ", photo=" + photo + "]";
}
}
Attachments
public class Attachments {
private String type;
private Photo photo;
// getter setter here
@Override
public String toString() {
return "Attachment [type=" + type + ", photo=" + photo + "]";
}
}
Photo Class composed by Attachment and Attachments class
public class Photo {
private String pid;
private String aid;
private String owner_id;
private String src;
private String src_big;
private String src_small;
private String src_xbig;
private String width;
private String height;
private String text;
private String created;
private String access_key;
// setter getter here
@Override
public String toString() {
return "Photo [pid=" + pid + ", aid=" + aid + ", owner_id=" + owner_id
+ ", src=" + src + ", src_big=" + src_big + ", src_small="
+ src_small + ", src_xbig=" + src_xbig + ", width=" + width
+ ", height=" + height + ", text=" + text + ", created="
+ created + ", access_key=" + access_key + "]";
}
}
Base Model Class for common properties in Comments,Report and Like class.
public class BaseModel {
private String type;
private int count;
public void setType(String type) { this.type = type; }
public String getType() {return type;}
public int getCount() { return count;}
public void setCount(int count) {this.count = count;}
@Override
public String toString() {return "BaseModel [type=" + type + ", count=" + count + "]";}
}
Comments Class
public class Comments extends BaseModel {
private String can_post;
@Override
public String toString() {
return "Comments [count=" + getCount() + ", can_post=" + can_post + "]";
}
}
Like Class
public class Like extends BaseModel {
private int user_likes;
private String can_like;
private String can_publish;
@Override
public String toString() {
return "Like [user_likes=" + user_likes + ", can_like=" + can_like
+ ", can_publish=" + can_publish + ", count =" + getCount()
+ "]";
}
}
Report Class
public class Repost extends BaseModel {
private String user_reposted;
@Override
public String toString() {
return "Repost [user_reposted=" + user_reposted + ", count=" + getCount() + "]";
}
}
Finally your object graph will look like this
// wallResponse object.
WallResponse [ // response object
response=Response
[wall= // wall object
[Wall [totalRecord=10, media=Media [type=photo, owner_id=21454540, item_id=314573297, thumb_src=http://cs313417.vk.me/v313417540/6cc9/Ze-8KY9tYfc.jpg],
attachment=Attachment [type=photo,
// photo object inside attachment
photo=Photo [pid=314573297, aid=-5, owner_id=21454540, src=http://cs313417.vk.me/v313417540/6cc9/Ze-8KY9tYfc.jpg, src_big=http://cs313417.vk.me/v313417540/6cca/ndKUage2w4I.jpg, src_small=http://cs313417.vk.me/v313417540/6cc8/A5m7zXxTAlQ.jpg, src_xbig=http://cs313417.vk.me/v313417540/6ccb/gaW8MQhFiFQ.jpg, width=760, height=606, text=, created=1384634699, access_key=bafb734c3dd74c5656]],
attachments=[Attachment [type=photo,
// photo object inside attachements
photo=Photo [pid=314573297, aid=-5, owner_id=21454540, src=http://cs313417.vk.me/v313417540/6cc9/Ze-8KY9tYfc.jpg, src_big=http://cs313417.vk.me/v313417540/6cca/ndKUage2w4I.jpg, src_small=http://cs313417.vk.me/v313417540/6cc8/A5m7zXxTAlQ.jpg, src_xbig=http://cs313417.vk.me/v313417540/6ccb/gaW8MQhFiFQ.jpg, width=760, height=606, text=, created=1384634699, access_key=bafb734c3dd74c5656]]],
// postSource object
postSource=PostSource [getType()=vk],
// comments object
comments=Comments [count=0, can_post=1], like=Like [user_likes=0, can_like=1, can_publish=0, count =1],
//report object
repost=Repost [user_reposted=0, count=0],
// wall data...
id=727, from_id=21454540, to_id=52158932, date=1384634706, post_type=post, text=, can_delete=1, reply_count=0, online=0]]]]
Enjoy! :)
