How Can Json.NET Stream JSON Deserialization to Process Large Files Efficiently?

Efficient processing of large JSON files: Json.NET streaming deserialization

Efficient parsing is critical when dealing with large JSON data sets that cannot be fully loaded into memory. Json.NET provides a powerful streaming JSON data processing solution through its JsonReader.

Problem Overview

A JSON file contains a sequence of identical objects, the goal is to read one object at a time without loading the entire file into memory.

Failed attempt

Initially trying to deserialize the file resulted in an exception because a JSON array was expected, not an object. Deserializing the array into a list solved the error but resulted in high memory consumption.

Streaming Solutions

To work around these limitations, the proposed solution reads the JSON file character by character and only deserializes the object when the reader encounters the "{" character indicating the start of the object.

Code Example

Here is the optimized code for streaming a JSON file using JsonReader:

JsonSerializer serializer = new JsonSerializer();
MyObject o;
using (FileStream s = File.Open("bigfile.json", FileMode.Open))
using (StreamReader sr = new StreamReader(s))
using (JsonReader reader = new JsonTextReader(sr))
{
    while (reader.Read())
    {
        // 仅当流中存在 "{" 字符时才反序列化
        if (reader.TokenType == JsonToken.StartObject)
        {
            o = serializer.Deserialize<MyObject>(reader);
            // 对 o 对象进行处理
        }
    }
}

This code reads the file efficiently, deserializing objects as they are encountered in the stream, without taking up too much RAM. Note that myobject should be replaced with your actual object type MyObject. Handling of o objects has been added to the code so that each object can be manipulated after deserialization.

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