安卓：Gson 性能
我正在尝试使用 gson 在 android 模拟器上进行对象映射。
处理 208 kb 左右的 json 数据时，速度慢得离谱。我的 json 中没有任何层次结构。
对象映射完成后，我可以看到 gson 创建了大约 500 条记录。
在 Android 模拟器上映射输入 json 需要 3 分钟多的时间。
我已经注释了我的实体，它由字符串和几个浮点数组成。
我错过了什么吗？
任何想法、最佳实践都会有很大帮助。
有什么方法可以快速对象映射 json 数据吗？
URL myURL = new URL(url);
/* Open a connection to that URL. */
URLConnection ucon = myURL.openConnection();
/*
* Define InputStreams to read from the URLConnection.
*/
InputStream is = ucon.getInputStream();
InputStreamReader reader = new InputStreamReader(is);
long tickCount = System.currentTimeMillis();
Policy[] policies = new Gson().fromJson(reader, Policy[].class);
long endCount = System.currentTimeMillis() - tickCount;
Log.d("Time to pull policies in milliseconds", "" + endCount);
I am trying to use gson to do my object mapping on the android emulator.
It has been ridiculously slow when processing json data around 208 kb. I do not have any hierarchies in my json.
After the object mapping is done, i can see it that gson created around 500 records.
It is taking it over 3 minutes on the android emulator to map the input json.
I have annotated my entity which comprises of strings and couple of floats.
An I missing something?
Any ideas, best practices would greatly help.
Are there any ways of quickly object mapping the json data?
URL myURL = new URL(url);
/* Open a connection to that URL. */
URLConnection ucon = myURL.openConnection();
/*
* Define InputStreams to read from the URLConnection.
*/
InputStream is = ucon.getInputStream();
InputStreamReader reader = new InputStreamReader(is);
long tickCount = System.currentTimeMillis();
Policy[] policies = new Gson().fromJson(reader, Policy[].class);
long endCount = System.currentTimeMillis() - tickCount;
Log.d("Time to pull policies in milliseconds", "" + endCount);
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我以前见过类似的问题，普遍的共识是 Jackson 比 Gson 快得多。请参阅以下链接了解更多信息：
这是专门讨论 Android 的一个： http:// /ubikapps.net/?p=525
I've seen questions like this come up before, and the general consensus is that Jackson is much faster than Gson. See the following links for more information:
Here is one which specifically discusses Android: http://ubikapps.net/?p=525
您是否尝试过将 GSON 流解析器与 Gson 对象混合？ http://sites.google.com/site/gson/streaming（查找混合读取示例）。
这种方法可能会有所帮助，因为 Gson 读取整个解析树，然后对其进行操作。对于大型数组列表，读取所有元素并尝试解析可能会导致大量内存交换（或颠簸）。这种方法将一次读入一个元素。
希望这有帮助。
Have you tried the mixing the GSON streaming parser with the Gson object? http://sites.google.com/site/gson/streaming (look for the Mixed read example).
This approach may help since Gson reads in an entire parse tree and then acts on it. With a large array list, reading in all elements and attempting to parse may cause lot of memory swaps (or thrashing). This approach will read in one element at a time.
Hope this helps.
如果您将
InputStream包装在一个具有良好大缓冲区的BufferedInputStream中，您可能会获得更好的性能...3 分钟太疯狂了。我很少运行模拟器，但我有一个带有约 1.1MB JSON 资源的应用程序，在硬件上加载和处理大约需要 5 秒。
（这仍然太长，但仍然如此）。
You'd probably get better performance if you wrapped that
InputStreamin aBufferedInputStreamwith a nice big buffer...3 minutes is insane. I seldom run the emulator but I have an app with a ~1.1MB JSON asset and that takes around 5 seconds to load and process on hardware.
(Which is still far too long, but still).
我发现，通过不对 JSON 中不需要的所有元素进行建模，可以显着加快 gson.fromJSON 的速度。 GSON 很乐意只填写您的响应类中指定的内容。
I've found that I can speed up gson.fromJSON quite considerably by not modelling all the elements in the JSON that I won't need. GSON will happily fill in only what is specified in your response classes.
我发现创建 Gson 实例是一个非常昂贵的操作，无论是在 CPU 使用还是内存分配方面。
由于 Gson 实例是线程安全的，因此构造和重用单个静态实例是有回报的，特别是当您经常进行序列化/反序列化时。
I have found that CREATING a Gson instance is a very expensive operation, both in terms of CPU used and memory allocated.
Since Gson instances are thread-safe, constructing and reusing a single static instance pays off, especially if you are serializing / deserializing often.