Date的自定义gson反序列化器永远不会被调用

Question

据我所知,gson不会自动将java.util.Date对象序列化和反序列化为ISO字符串,如"yyyy-MM-ddTHH:mm:ssZ"或例如"2014-04-15T18:22:00-05" :00" .因此,为了让我在我的客户端(使用Retrofit和gson)和服务器之间正确地交换日期,我需要将DateFormat指定为gson.这就是我所做的:

// code defining the creation of a RestAdapter
// ...
new GsonBuilder()
    .setDateFormat("yyyy-MM-dd'T'HH:mm:ssZ")
    .create()

添加.setDateFormat行足以让gson将时间戳字符串正确反序列化为Date对象.但是,它没有将Date对象序列化为时间戳字符串.所以我假设我必须像这样创建一个自定义序列化器:

// code defining the creation of a RestAdapter
// ...
new GsonBuilder()
    .setDateFormat("yyyy-MM-dd'T'HH:mm:ssZ")
    .registerTypeAdapter(Date.class, new DateSerializer())
    .create()

和DateSerializer类:

class DateSerializer implements JsonSerializer<Date> {
    @Override
    public JsonElement serialize(Date arg0, Type arg1, JsonSerializationContext arg2) {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ", Locale.US);
        return new JsonPrimitive(df.format(arg0));
    }
}

不幸的是,序列化函数被忽略了.相反,gson将日期格式化为字符串,如"Tues Mar 15 18:22:00 EST 2014".所以为了测试,我尝试用以下代码替换serialize函数:

public JsonElement serialize(Date arg0, Type arg1, JsonSerializationContext arg2) {
    throw new RuntimeException("Serialize function called!");
}

但是当然永远不会抛出RuntimeException.

有谁知道为什么我的序列化函数被忽略了？我想我在某处阅读过,对于某些类型,如果为超类定义了一个,则会忽略registerTypeAdapter,但由于这是java.util.Date,如果这是问题,我会感到困惑.我可能只是在做一些愚蠢的事情,但我可能不知道Date或gson足以实现它.

编辑:提供了以下代码的更多上下文:

MyApplication.java

public class MyApplication extends Application {
    public static RestAdapter restAdapter;
    public static The1Api the1Api;

    public static void createRestAdapter(String server_url){
        // enable cookies
        CookieManager cookieManager = new CookieManager();
        cookieManager.setCookiePolicy(CookiePolicy.ACCEPT_ALL);
        CookieHandler.setDefault(cookieManager);

        // create rest adapter
        restAdapter = new RestAdapter.Builder()
            .setEndpoint(server_url)
            .setConverter(new GsonConverter(new GsonBuilder()
                    .setDateFormat("yyyy-MM-dd'T'HH:mm:ssZ")
                    .registerTypeAdapter(Date.class, new DateSerializer())
                    .create()))
            .setLogLevel(LogLevel.FULL)
            .setLog(new ResponseInterceptor())
            .build();

        // create API
        the1Api = restAdapter.create(The1Api.class);
    }
}

The1Api.java

public interface The1Api {
    /* Chat */

    public class PublicMessage {
        String from_user;
        String message;
        Date time;
        Integer microsecond;
        Boolean in_1_percent;
    }
    public class PublicMessageList {
        Integer last_message_id;
        ArrayList<PublicMessage> messages;
    }

    @GET("/chat/get_public_messages/")
    public PublicMessageList getPublicMessages(
            @Query("last_message_id") Integer last_message_id, // optional
            @Query("since") Date since, // optional
            @Query("max") Integer max // optional
            );   

    // ...
}

LoginActivity.java

public class LoginActivity extends Activity {
    // ...

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Crashlytics.start(this);
        MyApplication.createRestAdapter(getString(R.string.server_url));
        setContentView(R.layout.activity_login);
    }

    @Override
    protected void onPostCreate(Bundle savedInstanceState){
        super.onPostCreate(savedInstanceState);

        Thread thread = new Thread(){
            @Override
            public void run(){
                ArrayList<The1Api.PublicMessage> publicMessages = MyApplication.the1Api.getPublicMessages(null, null, null).messages;
                for (The1Api.PublicMessage m : publicMessages){
                    Log.d("The1", "[" + m.time.toString() + "] " + m.from_user + ": " + m.message);
                }
                // when the following line gets executed, my server receives a request including the date below,
                // but the server does not understand the format of the date because it does not get serialized properly
                MyApplication.the1Api.getPublicMessages(null, new Date(1000000000), null);
            }
        };
        thread.start();
    }

    // ...    
}

DateSerializer.java

class DateSerializer implements JsonSerializer<Date> {
    @Override
    public JsonElement serialize(Date arg0, Type arg1, JsonSerializationContext arg2) {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ", Locale.US);
        return new JsonPrimitive(df.format(arg0));
    }
}

编辑2:尚未解决方案,但作为一种解决方法,您可以在发送之前手动将日期转换为其他格式.在评论中,Kalel建议将其转换为String,我将其转换为Long(自UNIX纪元以来的秒数).

Answer 1

您还能重现这个问题吗？我看到 Gson 序列化和反序列化正确。这可能是一个改造问题（我以前没有使用过它），但是查看文档，GsonConverter我发现除了委托给Gson对象中提供的对象之外，没有理由它会执行任何其他操作。

这是一个 SSCCE：

public class GsonDateDemo {
  public static void main(String[] args) {
    Gson gson = new GsonBuilder()
        .setDateFormat("yyyy-MM-dd'T'HH:mm:ssZ")
        .registerTypeAdapter(Date.class, new DateSerializer())
        .create();
    Date d = new Date(1438806977000L);

    System.out.println("Serializing "+d);
    String json = gson.toJson(d);
    System.out.println("JSON: "+json);
    Date d2 = gson.fromJson(json, Date.class);
    System.out.println("Deserialized: "+d2);
    System.out.println("Equal? "+d.equals(d2));
  }

  static class DateSerializer implements JsonSerializer<Date> {
    @Override
    public JsonElement serialize(Date arg0, Type arg1, JsonSerializationContext arg2) {
      System.out.println("Serializer received "+arg0);
      SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ", Locale.US);
      return new JsonPrimitive(df.format(arg0));
    }
  }
}

这输出：

Calling: local.GsonDateDemo.main[]
Serializing Wed Aug 05 16:36:17 EDT 2015
Serializer received Wed Aug 05 16:36:17 EDT 2015
JSON: "2015-08-05T16:36:17-0400"
Deserialized: Wed Aug 05 16:36:17 EDT 2015
Equal? true

如果可以，请修改此 SSCCE 以使用 Retrofit，并查看是否可以通过这种方式复制故障。