Google Cloud端点以JSON中的字符串形式返回Java

问题描述：

我使用的是Google App Engine最新版本1.9.30，并且按如下所示定义了我的云终结点

I am using google app engine latest version 1.9.30 and I define my cloud endpoint as follows

@Api(name="app", version="v1", transformers={EndpointDateTransformer.class})
public class MyEndpoints {

    @ApiMethod(name="dummy", path="dummy", httpMethod=HttpMethod.GET)
    public Map<String, Object> dummy(){
        Map<String, Object> dummy = Maps.newHashMap();
        dummy.put("date", DateUtil.getCurrentTimestamp());
        dummy.put("number", 5L);
        return dummy;
    }

}

此处EndpointDateTransformer将Date转换为Long值，并且来自端点的JSON响应为

here EndpointDateTransformer converts Date to Long value and the JSON response from endpoint is

{
    "number": "5",
    "date": "1452751174672"
}

但是如果我将5L更改为5，那么我会看到JSON响应

But if I change that 5L to 5 then I see JSON response as

{
    "number": 5,
    "date": "1452751174672"
}

为什么云端点将Long值转换为JSON中的字符串.当我使用旧版App Engine 1.9.19时，它曾经可以工作.以及在JSON上的长渲染.我在这里想念什么吗?

Why cloud endpoints converting Long values as string in JSON. When I was working on old app engine versions 1.9.19 it used to work. Long rendered as long on JSON as well. Am I missing anything here?

答

JSON是JavaScript对象符号，实际上是有效的Javascript.因此，它应该遵循javascript标准.

JSON is JavaScript Object Notation, it's a valid Javascript actually. So it should follow javascript standards.

JavaScript的编号是54位，从-(2^53 - 1)到(2^53 - 1).但是Java的long是64位数字，从-2^63到2^63-1.

Javascript's Number is 54 bit number, from -(2^53 - 1) to (2^53 - 1). But Java's long is 64 bit number, from -2^63 to 2^63-1.

查看区别:

Java Long Max         = 9223372036854775807
Javascript Number Max = 9007199254740992

您根本无法将Java Long转换为Javascript Number，因为它不适用于所有值.因此，将使用字符串表示形式.

You simply cannot convert Java Long to Javascript Number because it doesn't work for all values. So a string representation is used instead.

您有两种可能的解决方案:

You have two possible solutions:

将您的价值定义为Integer
使用具有自定义转换器的实体对象，请参见 https://cloud .google.com/appengine/docs/java/endpoints/annotations#apitransformer

define your value as Integer
use an entity object with custom transformer, see https://cloud.google.com/appengine/docs/java/endpoints/annotations#apitransformer

或者如果您真的想要日期，最好在UTC时区将其格式化为yyyy-MM-dd\'T\'HH:mm:ss.它与Javascript日期格式兼容.

Or if you really want Date, it's better to format it as yyyy-MM-dd\'T\'HH:mm:ss within UTC timezone. It's compatible with Javascript date format.

规格:

Javascript- https://developer.mozilla. org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number
Java- https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html
Javascript日期- https://developer.mozilla .org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Date

Javascript - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number
Java - https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html
Javascript Date - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date

Google Cloud端点以JSON中的字符串形式返回Java

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