Gson和数组

Question

I'm building a client server web application and stuck on this:

I'm getting an array of users "FriendsIDList:":

"data":{
    "name":"anna",
    "BirthDate":"2010-01-01",
    "FriendsIDList":{
        "email":"anna1@gmail.com",
        "email":"anna2@gmail.com"
    }
}}

Without the array I have no problem reading the data like this:

GsonBuilder gb = new GsonBuilder();
gb.setDateFormat("yyyy-MM-dd");
gson = gb.create();
newUser= gson.fromJson(data, user.class);

How can I read this array? I'm using LinkedList in my user class:

LinkedList FriendsIDList;

Answer 1

In case you have a single user that contains the FriendList then your last line will work as you have mentioned.

Try defining you FriendList property as follows:

LinkedList<Email> FriendList;

And create Email Class:

public class Email {
  private String email;
}

Answer 2

The JSON spec says this:

A name is a string. A single colon comes after each name, separating the name from the value. A single comma separates a value from a following name. The names within an object SHOULD be unique.

Unfortunately Gson doesn't natively support non-unique names in name/value pairs. So it cannot properly handle your 'email' properties:

{"email":"anna1@gmail.com","email":"anna2@gmail.com"}

You can work-around this by writing your own TypeAdapter . Your implementation should accumulate email strings into a list. You'll probably want to use a special wrapper object in your data model like EmailAddressList to make this easy.

static class FriendsIDList {
  List<String> emails;
}

static TypeAdapter<FriendsIDList> friendsIDListAdapter
        = new TypeAdapter<FriendsIDList>() {
    ... // code to read and write emails
}