大型JSON数组的前四个元素的有效解析 [英] Efficient parsing of first four elements of large JSON arrays

问题描述

我正在使用 Jackson 从JSON inputStream中解析JSON，如下所示:

I am using Jackson to parse JSON from a json inputStream which looks like following:

[
      [ 36,
        100,
        "The 3n + 1 problem",
         56717,
         0,
         1000000000,
         0,
         6316,
         0,
         0,
         88834,
         0,
         45930,
         0,
         46527,
         5209,
         200860,
         3597,
         149256,
         3000,
         1
      ],
      [
         ........
      ],
      [
         ........
      ],
         .....// and almost 5000 arrays like above
]

这是原始的供稿链接: http://uhunt.felix-halim.net/api /p

This is the original feed link: http://uhunt.felix-halim.net/api/p

我想解析它并仅保留每个数组的前4个元素，并跳过其他18个元素.

I want to parse it and keep only the first 4 elements of every array and skip other 18 elements.

36
100
The 3n + 1 problem
56717

到目前为止我尝试过的代码结构:

Code structure I have tried so far:

while (jsonParser.nextToken() != JsonToken.END_ARRAY) {

        jsonParser.nextToken(); // '['
        while (jsonParser.nextToken() != JsonToken.END_ARRAY) {
            // I tried many approaches here but not found appropriate one
         }

}

由于此供稿非常大，因此我需要以更少的开销和内存来高效地执行此操作. 另外，还有三种用于JSON的模型:流API ，数据绑定和树模型.哪一个适合我的目的?

As this feed is pretty big, I need to do this efficiently with less overhead and memory. Also there are three models to procress JSON: Streaming API, Data Binding and Tree Model. Which one is appropriate for my purpose?

我如何与杰克逊有效地解析此json?如何跳过这18个元素并跳到下一个数组以获得更好的性能?

How can I parse this json efficiently with Jackson? How can I skip those 18 elements and jump to next array for better performance?

(解决方案)

Jackson和GSon几乎都以相同的机制工作(增量模式，因为内容是增量读取和写入的)，我切换到GSON，因为它具有功能skipValue()(非常适合姓名).尽管Jackson的nextToken()将像skipValue()一样工作，但GSON对我来说似乎更灵活.感谢@Kowser bro的建议，我以前曾经了解过GSON，但是以某种方式忽略了它.这是我的工作代码:

Jackson and GSon both works in almost in the same mechanism (incremental mode, since content is read and written incrementally), I am switching to GSON as it has a function skipValue() (pretty appropriate with name). Although Jackson's nextToken() will work like skipValue(), GSON seems more flexible to me. Thanks @Kowser bro for his recommendation, I came to know about GSON before but somehow ignored it. This is my working code:

reader.beginArray();
while (reader.hasNext()) {
   reader.beginArray(); 
   int a = reader.nextInt(); 
   int b = reader.nextInt();
   String c = reader.nextString();
   int d = reader.nextInt();
   System.out.println(a + " " + b + " " + c + " " + d);
   while (reader.hasNext())
      reader.skipValue();
   reader.endArray();
} 
reader.endArray();
reader.close();

推荐答案

这是针对Jackson

关注本教程

明智地使用jasonParser.nextToken()应该可以为您提供帮助.

Judicious use of jasonParser.nextToken() should help you.

while (jasonParser.nextToken() != JsonToken.END_ARRAY) { // might be JsonToken.START_ARRAY?

---

伪代码是

---

The pseudo-code is

1. 找到下一个数组

1. find next array

1. 读取值
2. 跳过其他值
3. 跳过下一个结束令牌

---

这是针对gson的. 请看本教程.考虑考虑教程中的第二个示例.

---

This is for gson. Take a look at this tutorial. Consider following second example from the tutorial.

明智地使用reader.begin* reader.end*和reader.skipValue应该可以为您完成这项工作.

Judicious use of reader.begin* reader.end* and reader.skipValue should do the job for you.

这是 JsonReader

这篇关于大型JSON数组的前四个元素的有效解析的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！