杰克逊多个对象和巨大的json文件 [英] Jackson multiple objects and huge json files

问题描述

我觉得答案可能与此重复：杰克逊 - Json到POJO有多个条目但我认为这个问题可能不同。我也使用原始数据绑定而不是完整数据绑定。

I get the feeling that the answer might be a duplicate of this: Jackson - Json to POJO With Multiple Entries but I think that potentially the question is different enough. Also I'm using raw data binding rather than full data binding.

所以就像那个问题的提问者一样，我在文件中有多个对象，我正在尝试将它们变成POJO并将它们填入我设计的数据库中，以便我可以快速而不是慢慢地访问数据。

So like the asker of that question, I have multiple objects in a file and I'm trying to turn them into POJOs and stuff them into a database of my design so I can access the data quickly rather than slowly.

这里的文件大小为几十GB，每个文件中有多达数百万个对象。无论如何，这是我到目前为止：

The files here are in the order of tens of GB, with up to millions of objects in each file. Anyway here is what I have so far:

ObjectMapper mapper = new ObjectMapper();
Map<String,Object> data = mapper.readValue(new File("foo.json"), Map.class);
System.out.println(data.get("bar"));

这对于打印foo中第一个对象的bar元素非常有用，但我需要一种方法以一种不会耗尽我所有记忆的方式遍历每个元素。

And this works great for printing the bar element of the first object in foo, but I need a way to iterate through every element in a way that won't eat up all my memory.

谢谢。

推荐答案

使用此代码示例查看基本概念。

Use this code sample to see the basic idea.

final InputStream in = new FileInputStream("json.json");
try {
  for (Iterator it = new ObjectMapper().readValues(
      new JsonFactory().createJsonParser(in), Map.class); it.hasNext();)
    System.out.println(it.next());
}
finally { in.close();} }

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