Json.NET 可以序列化/反序列化到/来自流吗？
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原文地址: http://stackoverflow.com/questions/8157636/
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Can Json.NET serialize / deserialize to / from a stream?
提问by Omri Gazitt
I have heard that Json.NET is faster than DataContractJsonSerializer, and wanted to give it a try...
我听说 Json.NET 比 DataContractJsonSerializer 快，我想试一试......
But I couldn't find any methods on JsonConvert that take a stream rather than a string.
但是我在 JsonConvert 上找不到任何采用流而不是字符串的方法。
For deserializing a file containing JSON on WinPhone, for example, I use the following code to read the file contents into a string, and then deserialize into JSON. It appears to be about 4 times slower in my (very ad-hoc) testing than using DataContractJsonSerializer to deserialize straight from the stream...
例如，在 WinPhone 上反序列化包含 JSON 的文件，我使用以下代码将文件内容读取为字符串，然后反序列化为 JSON。在我的（非常特别的）测试中，它似乎比使用 DataContractJsonSerializer 从流中直接反序列化慢了大约 4 倍......
// DCJS
DataContractJsonSerializer dc = new DataContractJsonSerializer(typeof(Constants));
Constants constants = (Constants)dc.ReadObject(stream);
// JSON.NET
string json = new StreamReader(stream).ReadToEnd();
Constants constants = JsonConvert.DeserializeObject<Constants>(json);
Am I doing it wrong?
我做错了吗？
采纳答案by Paul Tyng
UPDATE:This no longer works in the current version, see belowfor correct answer (no need to vote down, this is correct on older versions).
更新：这不再适用于当前版本，请参阅下面的正确答案（无需投票，这在旧版本上是正确的）。
Use the JsonTextReaderclass with a StreamReaderor use the JsonSerializeroverload that takes a StreamReaderdirectly:
使用JsonTextReader带有 a的类StreamReader或使用直接JsonSerializer采用 a的重载StreamReader：
var serializer = new JsonSerializer();
serializer.Deserialize(streamReader);
回答by
The current version of Json.net does not allow you to use the accepted answer code. A current alternative is:
当前版本的 Json.net 不允许您使用接受的答案代码。目前的替代方案是：
public static object DeserializeFromStream(Stream stream)
{
var serializer = new JsonSerializer();
using (var sr = new StreamReader(stream))
using (var jsonTextReader = new JsonTextReader(sr))
{
return serializer.Deserialize(jsonTextReader);
}
}
Documentation: Deserialize JSON from a file stream
回答by ygaradon
public static void Serialize(object value, Stream s)
{
using (StreamWriter writer = new StreamWriter(s))
using (JsonTextWriter jsonWriter = new JsonTextWriter(writer))
{
JsonSerializer ser = new JsonSerializer();
ser.Serialize(jsonWriter, value);
jsonWriter.Flush();
}
}
public static T Deserialize<T>(Stream s)
{
using (StreamReader reader = new StreamReader(s))
using (JsonTextReader jsonReader = new JsonTextReader(reader))
{
JsonSerializer ser = new JsonSerializer();
return ser.Deserialize<T>(jsonReader);
}
}
回答by Tok'
I've written an extension class to help me deserializing from JSON sources (string, stream, file).
我编写了一个扩展类来帮助我从 JSON 源（字符串、流、文件）反序列化。
public static class JsonHelpers
{
public static T CreateFromJsonStream<T>(this Stream stream)
{
JsonSerializer serializer = new JsonSerializer();
T data;
using (StreamReader streamReader = new StreamReader(stream))
{
data = (T)serializer.Deserialize(streamReader, typeof(T));
}
return data;
}
public static T CreateFromJsonString<T>(this String json)
{
T data;
using (MemoryStream stream = new MemoryStream(System.Text.Encoding.Default.GetBytes(json)))
{
data = CreateFromJsonStream<T>(stream);
}
return data;
}
public static T CreateFromJsonFile<T>(this String fileName)
{
T data;
using (FileStream fileStream = new FileStream(fileName, FileMode.Open))
{
data = CreateFromJsonStream<T>(fileStream);
}
return data;
}
}
Deserializing is now as easy as writing:
反序列化现在就像编写一样简单：
MyType obj1 = aStream.CreateFromJsonStream<MyType>();
MyType obj2 = "{\"key\":\"value\"}".CreateFromJsonString<MyType>();
MyType obj3 = "data.json".CreateFromJsonFile<MyType>();
Hope it will help someone else.
希望它会帮助别人。
回答by Blake Mitchell
I arrived at this question looking for a way to stream an open ended list of objects onto a System.IO.Streamand read them off the other end, without buffering the entire list before sending. (Specifically I'm streaming persisted objects from MongoDB over Web API.)
我遇到了这个问题，寻找一种方法将对象的开放式列表流式传输到 aSystem.IO.Stream并从另一端读取它们，而无需在发送之前缓冲整个列表。（具体来说，我通过 Web API 从 MongoDB 流式传输持久对象。）
@Paul Tyng and @Rivers did an excellent job answering the original question, and I used their answers to build a proof of concept for my problem. I decided to post my test console app here in case anyone else is facing the same issue.
@Paul Tyng 和 @Rivers 在回答原始问题方面做得非常出色，我使用他们的答案为我的问题构建了概念证明。我决定在这里发布我的测试控制台应用程序，以防其他人面临同样的问题。
using System;
using System.Diagnostics;
using System.IO;
using System.IO.Pipes;
using System.Threading;
using System.Threading.Tasks;
using Newtonsoft.Json;
namespace TestJsonStream {
class Program {
static void Main(string[] args) {
using(var writeStream = new AnonymousPipeServerStream(PipeDirection.Out, HandleInheritability.None)) {
string pipeHandle = writeStream.GetClientHandleAsString();
var writeTask = Task.Run(() => {
using(var sw = new StreamWriter(writeStream))
using(var writer = new JsonTextWriter(sw)) {
var ser = new JsonSerializer();
writer.WriteStartArray();
for(int i = 0; i < 25; i++) {
ser.Serialize(writer, new DataItem { Item = i });
writer.Flush();
Thread.Sleep(500);
}
writer.WriteEnd();
writer.Flush();
}
});
var readTask = Task.Run(() => {
var sw = new Stopwatch();
sw.Start();
using(var readStream = new AnonymousPipeClientStream(pipeHandle))
using(var sr = new StreamReader(readStream))
using(var reader = new JsonTextReader(sr)) {
var ser = new JsonSerializer();
if(!reader.Read() || reader.TokenType != JsonToken.StartArray) {
throw new Exception("Expected start of array");
}
while(reader.Read()) {
if(reader.TokenType == JsonToken.EndArray) break;
var item = ser.Deserialize<DataItem>(reader);
Console.WriteLine("[{0}] Received item: {1}", sw.Elapsed, item);
}
}
});
Task.WaitAll(writeTask, readTask);
writeStream.DisposeLocalCopyOfClientHandle();
}
}
class DataItem {
public int Item { get; set; }
public override string ToString() {
return string.Format("{{ Item = {0} }}", Item);
}
}
}
}
Note that you may receive an exception when the AnonymousPipeServerStreamis disposed, I ignored this as it isn't relevant to the problem at hand.
请注意，您可能会在处理时收到异常AnonymousPipeServerStream，我忽略了这一点，因为它与手头的问题无关。
