17

この構造の User オブジェクトがあります。

class User {
    private String id;
    private String name;
    private Map<String, Object> properties;

    // GETTERS & SETTERS
}

この構造の JSON 文字列があります。

{
    "user": {
        "id:"123456789",
        "name:"azerty",
        "emailHash":"123456789", // not used in User class
        "properties": {
            "p1":1,
            "p2":"test",
            "p3":[1, 2, 3, 4],
            "p4":{
               etc...
            }
        }
    }
}

プロパティのキーは文字列です。プロパティの値は、文字列、int、配列、ブール値、マップなどにすることができます。

この JSON 文字列を次のように Gson で逆シリアル化しようとしています。

JsonParser parser = new JsonParser();
JsonElement element = parser.parse(jsonString);
JsonObject object = element.getAsJsonObject();

GsonBuilder builder = new GsonBuilder();
builder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES);
Gson gson = builder.create();
User user = (User) gson.fromJson(object.get("user"), new TypeToken<User>() {}.getType());

フィールド 'id' と 'name' は正しく挿入されますが、フィールド 'properties' は null のままです。

私が間違っていることを知っていますか？よろしくお願いします。

4

1 に答える 1

9

For me this code:

public class Main {
    public static void main(String[] args) throws IOException {
    GsonBuilder builder = new GsonBuilder();
    builder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES);
    Gson gson = builder.create();
    FileInputStream inputStream = new FileInputStream(new File("bobi.json"));
    InputStreamReader reader = new InputStreamReader(inputStream);
    User user = gson.fromJson(reader, User.class);
    System.out.println(user.getName());
    System.out.println(user.getId());
    for (String property : user.getProperties().keySet()) {
        System.out.println("Key: " + property + " value: " + user.getProperties().get(property));
    }
    reader.close();
}

Prints this:

azerty
123456789
Key: p1 value: 1.0
Key: p2 value: test
Key: p3 value: [1.0, 2.0, 3.0, 4.0]
Key: p4 value: {}

However, keep in mind that I have stripped the wrapping json object in the file I parse. The file is:

{
        "id":"123456789",
        "name" : "azerty",
        "emailHash":"123456789", 
        "properties": {
            "p1":1,
            "p2":"test",
            "p3":[1, 2, 3, 4],
            "p4":{

            }
        }
}

Also I added closing double quote for name and id, which you did not have in your sample.

The User class as requested by the OP. I have added getters and setters for the reason of printing:

import java.util.Map;

class User {
    private String id;
    private String name;
    private Map<String, Object> properties;
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Map<String, Object> getProperties() {
        return properties;
    }
    public void setProperties(Map<String, Object> properties) {
        this.properties = properties;
    }
}
于 2013-01-11T08:40:07.270 に答える