Question

我似乎无法让gson在Java中将Date转换为UTC时间.... 这是我的代码......

Gson gson = new GsonBuilder().setDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'").create();
//This is the format I want, which according to the ISO8601 standard - Z specifies UTC - 'Zulu' time

Date now=new Date();          
System.out.println(now);       
System.out.println(now.getTimezoneOffset());
System.out.println(gson.toJson(now));

这是我的输出

Thu Sep 25 18:21:42 BST 2014           // Time now - in British Summer Time 
-60                                    // As expected : offset is 1hour from UTC    
"2014-09-25T18:21:42.026Z"             // Uhhhh this is not UTC ??? Its still BST !!

我想要的gson结果和我期待的结果

"2014-09-25T17:21:42.026Z"

我可以清楚地在调用Json之前减去1小时，但这似乎是一个黑客。如何将gson配置为始终转换为UTC？

Answer 1

经过一些进一步的研究，看来这是一个已知的问题。 gson默认序列化程序始终默认为您的本地时区，并且不允许您指定时区。请参阅以下链接.....

https://code.google.com/p/google-gson/issues/detail?id=281

解决方案是创建一个自定义的gson类型适配器，如链接中所示：

// this class can't be static
public class GsonUTCDateAdapter implements JsonSerializer<Date>,JsonDeserializer<Date> {

    private final DateFormat dateFormat;

    public GsonUTCDateAdapter() {
      dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", Locale.US);      //This is the format I need
      dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));                               //This is the key line which converts the date to UTC which cannot be accessed with the default serializer
    }

    @Override public synchronized JsonElement serialize(Date date,Type type,JsonSerializationContext jsonSerializationContext) {
        return new JsonPrimitive(dateFormat.format(date));
    }

    @Override public synchronized Date deserialize(JsonElement jsonElement,Type type,JsonDeserializationContext jsonDeserializationContext) {
      try {
        return dateFormat.parse(jsonElement.getAsString());
      } catch (ParseException e) {
        throw new JsonParseException(e);
      }
    }
}

然后注册如下：

  Gson gson = new GsonBuilder().registerTypeAdapter(Date.class, new GsonUTCDateAdapter()).create();
  Date now=new Date();
  System.out.println(gson.toJson(now));

现在可以正确输出UTC中的日期

"2014-09-25T17:21:42.026Z"

感谢链接作者。

Answer 2

对我来说这个问题的解决方案是创建一个自定义日期适配器（P.S小心，以便导入java.util.Date而不是java.sql.Date！）

public class ColonCompatibileDateTypeAdapter implements JsonSerializer<Date>, JsonDeserializer< Date> {
private final DateFormat dateFormat;

public ColonCompatibileDateTypeAdapter() {
  dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ") {
        @Override
        public StringBuffer format(Date date, StringBuffer toAppendTo, FieldPosition pos) {
            StringBuffer rfcFormat = super.format(date, toAppendTo, pos);
            return rfcFormat.insert(rfcFormat.length() - 2, ":");
        }

        @Override
        public Date parse(String text, ParsePosition pos) {
            if (text.length() > 3) {
                text = text.substring(0, text.length() - 3) + text.substring(text.length() - 2);
            }
            return super.parse(text, pos);
        }
    };


}

@Override public synchronized JsonElement serialize(Date date, Type type,
    JsonSerializationContext jsonSerializationContext) {
  return new JsonPrimitive(dateFormat.format(date));
}

@Override public synchronized Date deserialize(JsonElement jsonElement, Type type,
    JsonDeserializationContext jsonDeserializationContext) {
  try {
      return dateFormat.parse(jsonElement.getAsString());
  } catch (ParseException e) {
    throw new JsonParseException(e);
  }
}}

然后在创建GSON对象时使用它

Gson gson = new GsonBuilder().registerTypeAdapter(Date.class, new ColonCompatibileDateTypeAdapter()).create();

Answer 3

日期格式中的Z是单引号，必须不加引号才能被实际时区替换。

此外，如果您希望以UTC格式表示日期，请先转换它。

Answer 4

我调整了标记solution并对DateFormat

进行了参数化

import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonParseException;
import com.google.gson.JsonPrimitive;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;

import java.lang.reflect.Type;
import java.text.DateFormat;
import java.text.ParseException;
import java.util.Date;

public class GsonDateFormatAdapter implements JsonSerializer<Date>, JsonDeserializer<Date> {

    private final DateFormat dateFormat;

    public GsonDateFormatAdapter(DateFormat dateFormat) {
        this.dateFormat = dateFormat;
    }

    @Override
    public synchronized JsonElement serialize(Date date, Type type, JsonSerializationContext jsonSerializationContext) {
        return new JsonPrimitive(dateFormat.format(date));
    }

    @Override
    public synchronized Date deserialize(JsonElement jsonElement, Type type,JsonDeserializationContext jsonDeserializationContext) {
        try {
            return dateFormat.parse(jsonElement.getAsString());
        } catch (ParseException e) {
            throw new JsonParseException(e);
        }
    }
}

使用gson将Java日期转换为UTC

4 个答案: