Json.Net 反序列化内存不足问题

GCSettings.LargeObjectHeapCompactionMode = GCLargeObjectHeapCompactionMode.CompactOnce.

此设置允许压缩大型对象堆，并可能减少由于地址空间碎片导致的内存不足错误.

This setting allows the large object heap to be compacted and may reduce out-of-memory errors due to address space fragmentation.

不过，第二个问题可以通过流式反序列化来解决，如 this answer to this question 中所示a href="https://stackoverflow.com/users/2318354/dilip0165">Dilip0165;使用 HttpClient 和 JSON.NET 的高效 api 调用 作者:John Thiriet;性能提示:优化内存使用 由 Newtonsoft 提供；和 使用新的 .NET HttpClient 和 HttpCompletionOption 进行流式传输Tugberk Ugurlu 的 .ResponseHeadersRead.综合这些来源的信息，您的代码应如下所示:

The second problem, however, can be addressed by streaming deserialization, as shown in this answer to this question by Dilip0165; Efficient api calls with HttpClient and JSON.NET by John Thiriet; Performance Tips: Optimize Memory Usage by Newtonsoft; and Streaming with New .NET HttpClient and HttpCompletionOption.ResponseHeadersRead by Tugberk Ugurlu. Pulling together the information from these sources, your code should look something like:

Result result;
var requestJson = JsonConvert.SerializeObject(message); // Here we assume the request JSON is not too large
using (var requestContent = new StringContent(requestJson, Encoding.UTF8, "application/json"))
using (var request = new HttpRequestMessage(HttpMethod.Post, client.BaseAddress) { Content = requestContent })
using (var response = client.SendAsync(request, HttpCompletionOption.ResponseHeadersRead).Result)
using (var responseStream = response.Content.ReadAsStreamAsync().Result)
{
    if (response.IsSuccessStatusCode)
    {
        using (var textReader = new StreamReader(responseStream))
        using (var jsonReader = new JsonTextReader(textReader))
        {
            result = JsonSerializer.CreateDefault().Deserialize<Result>(jsonReader);
        }
    }
    else
    {
        // TODO: handle an unsuccessful response somehow, e.g. by throwing an exception
    }
}

或者，使用 async/await:

Result result;
var requestJson = JsonConvert.SerializeObject(message); // Here we assume the request JSON is not too large
using (var requestContent = new StringContent(requestJson, Encoding.UTF8, "application/json"))
using (var request = new HttpRequestMessage(HttpMethod.Post, client.BaseAddress) { Content = requestContent })
using (var response = await client.SendAsync(request, HttpCompletionOption.ResponseHeadersRead))
using (var responseStream = await response.Content.ReadAsStreamAsync())
{
    if (response.IsSuccessStatusCode)
    {
        using (var textReader = new StreamReader(responseStream))
        using (var jsonReader = new JsonTextReader(textReader))
        {
            result = JsonSerializer.CreateDefault().Deserialize<Result>(jsonReader);
        }
    }
    else
    {
        // TODO: handle an unsuccessful response somehow, e.g. by throwing an exception
    }
}           

我上面的代码没有经过全面测试，并且 错误和取消处理需要实现.您可能还需要设置超时，如下所示这里 和 这里.Json.NET 的 JsonSerializer 不支持异步反序列化，使其与 HttpClient 的异步编程模型有点尴尬.

My code above isn't fully tested, and error and cancellation handling need to be implemented. You may also need to set the timeout as shown here and here. Json.NET's JsonSerializer does not support async deserialization, making it a slightly awkward fit with the asynchronous programming model of HttpClient.

最后，作为使用 Json.NET 从 JSON 文件读取大量 Base64 块的替代方法，您可以使用 JsonReaderWriterFactory 确实支持阅读可管理的块中的 Base64 数据.有关详细信息，请参阅 this answer to 通过流式传输 json 的某些部分来解析巨大的 OData JSON 以避免 LOH 以解释如何使用此阅读器流式传输巨大的 JSON 文件，以及 this answer to 从 XmlReader 读取流，base64 解码并将结果写入文件 了解如何使用 XmlReader.ReadElementContentAsBase64

Finally, as an alternative to using Json.NET to read a huge Base64 chunk from a JSON file, you could use the reader returned by JsonReaderWriterFactory which does support reading Base64 data in manageable chunks. For details, see this answer to Parse huge OData JSON by streaming certain sections of the json to avoid LOH for an explanation of how stream through a huge JSON file using this reader, and this answer to Read stream from XmlReader, base64 decode it and write result to file for how to decode Base64 data in chunks using XmlReader.ReadElementContentAsBase64

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