反序列化时出现SerializationException [英] SerializationException when deserializing
问题描述
此代码反序列化来自SQLite的对象.我从DBinaryData(BLOB)字段获取序列化的对象.但是获取System.Runtime.Serialization.SerializationException:在解析完成之前遇到流的结尾.该如何解决?
This code deserialize object from SQLite. I'm get serialized object from DBinaryData (BLOB) field. But get System.Runtime.Serialization.SerializationException: end of stream encountered before parsing was completed. How to fix this?
public void Dump()
{
try
{
const string databaseName = @"C:\Code\C#\WcfService\WcfService\mainDB.db3";
SQLiteConnection connection = new SQLiteConnection(string.Format("Data Source={0};", databaseName));
connection.Open();
try
{
SQLiteCommand command = new SQLiteCommand("INSERT into 'dump' ('DTime', 'DBinaryData') VALUES ('" + DateTime.Now.ToString() + "', '" + GetSerializedMessages() + "')", connection);
command.ExecuteNonQuery();
}
finally
{
connection.Close();
}
}
catch (Exception e)
{
Logger.Log(e.Message);
}
}
public void Restore()
{
try
{
const string databaseName = @"C:\Code\C#\WcfService\WcfService\mainDB.db3";
SQLiteConnection connection = new SQLiteConnection(string.Format("Data Source={0};", databaseName));
connection.Open();
try
{
SQLiteCommand command = new SQLiteCommand("SELECT * FROM dump ORDER BY DId DESC limit 1", connection);
SQLiteDataReader reader = command.ExecuteReader();
while (reader.Read())
{
Queue<Message> deserializedData = GetDeserializedMessages((byte[])reader["DBinaryData"]);
var data = MergeQueueMessage(deserializedData);
Logger.Log(data.ToString());
}
}
finally
{
connection.Close();
}
}
catch (Exception e)
{
Logger.Log(e.Message);
}
}
public byte[] GetSerializedMessages()
{
byte[] result = null;
MemoryStream memoryStream = new MemoryStream();
BinaryFormatter formatter = new BinaryFormatter();
try
{
lock (MessageQueue.Instance.Messages)
{
formatter.Serialize(memoryStream, MessageQueue.Instance.Messages);
}
result = new byte[memoryStream.GetBuffer().Length];
memoryStream.GetBuffer().CopyTo(result, 0);
}
catch (SerializationException e)
{
Logger.Log("Failed to serialize. Reason: " + e.Message);
}
finally
{
memoryStream.Close();
}
return result;
}
public Queue<Message> GetDeserializedMessages(byte[] source)
{
Queue<Message> messages = null;
using (MemoryStream memoryStream = new MemoryStream(source))
{
BinaryFormatter formatter = new BinaryFormatter();
messages = (Queue<Message>)formatter.Deserialize(memoryStream);
}
return messages;
}
private IEnumerable<Message> MergeQueueMessage(Queue<Message> source)
{
IEnumerable<Message> result = MessageQueue.Instance.Messages.Union(source, new EqualityComparator());
return result;
}
推荐答案
通过您的这是一个错误(尽管不确定是否是"the"错误):
With your edit: here's a bug (not sure if it is "the" bug, though):
result = new byte[memoryStream.GetBuffer().Length];
memoryStream.GetBuffer().CopyTo(result, 0);
缓冲区的长度无关紧要. memoryStream.Length是否重要.坦白地说，这应该是result = memoryStream.ToArray();-这将为您提供正确的结果.
The length of the buffer is irrelevant. If is the memoryStream.Length that matters. Frankly, this should just be result = memoryStream.ToArray(); - which would give you the correct result.
SQL中的另一个错误:
And another bug in the SQL:
SQLiteCommand command = new SQLiteCommand("INSERT into 'dump' ('DTime', 'DBinaryData') VALUES ('" + DateTime.Now.ToString() + "', '" + GetSerializedMessages() + "')", connection);
command.ExecuteNonQuery();
串联从来都不是一个好主意，但在这里却是致命的.因为GetSerializedMessages()返回null(失败时-不是一个好主意；应该抛出)或byte[]，所以这样做很简单.如果连接byte[]，则输出将不是您期望的:
Concatenation is never a good idea, but here it is fatal; since GetSerializedMessages() returns either null (on failure - not a good idea; should have just thrown) or a byte[], this does simple concatenation. If you concatenate a byte[] the output is not what you expect:
byte[] b = {1,2,3};
string s = "a " + b + " c";
// gives: "a System.Byte[] c"
很明显不包含您想要的实际数据，所以很乱.理想情况下，您应该在此处为数据和日期使用参数:
that clearly doesn't contain the actual data you wanted, so is gibberish. Ideally you should be using parameters here for both the data and the date:
SQLiteCommand command = new SQLiteCommand("INSERT into 'dump' ('DTime', 'DBinaryData') VALUES (@when, @data)", connection);
// note: not sure if SQLiteCommand has an "AddWithValue", but the overall usage
// should be something like this
command.Parameters.AddWithValue("when", DateTime.Now);
command.Parameters.AddWithValue("data", GetSerializedMessages());
command.ExecuteNonQuery();
最后:不要吞下问题；不要吞下任何东西.您的序列化代码应该更像(IMO)
Finally: don't swallow problems; your serialization code should be (IMO) more like
public byte[] GetSerializedMessages()
{
try {
using(MemoryStream memoryStream = new MemoryStream())
{
BinaryFormatter formatter = new BinaryFormatter();
// skipped: serialize etc
return memoryStream.ToArray();
}
} catch(Exception ex) {
Logger.Log("Failed to serialize. Reason: " + ex.Message);
throw; // it doesn't stop being a problem just because we logged it
}
}
首先要看的是(通过reader["DBinaryData"])通过byte[]是否与最初序列化时的byte[] 100％相同.如果您没有为此进行测试，那么所有的选择都将落空.从错误中得知，它们似乎并不相同-这可能是由于:
The first thing to look at is whether the byte[] you get out (via reader["DBinaryData"]), is 100% identical to the byte[] you had when you originally serialized. If you don't have a test for that, all bets are off. From the error, it sounds like they're not identical - this could be because of:
- 序列化和存储数据的代码中的错误
- 数据库存储内部的截断
- 读取BLOB时出现截断(某些连接限制了一次获取的数量)
- 获取和反序列化数据的代码错误
前两个完全是致命的:如果是致命的-数据就是吐司.
The first two are totally fatal: if it is those - the data is toast.
在集成测试中比较两个byte[]的一种惰性方法是比较十六进制:
A lazy way to compare two byte[] in an integration test is to compare the hex:
// here expected should be the raw data just after serializing; actual should
// be what you get after storing it in the db and fetching it back, using
// your code
Assert.AreEqual(BitConverter.ToString(expected), BitConverter.ToString(actual));
给出了任意增量的十六进制输出.您没有显示如何序列化和存储消息，所以我不能告诉您那里是否存在任何明显的问题，但是请参阅
which gives a nice hex output of any delta. You don't show how you serialize and store the messages, so I can't tell you whether there are any obvious issues there, but please see http://marcgravell.blogspot.com/2013/02/how-many-ways-can-you-mess-up-io.html for a list of common issues here.
最后，我强烈建议: 为此停止使用BinaryFormatter .请参阅类似的问题，以了解其他人的痛苦:基本上，他们不能在以后恢复数据甚至很小的更改(或有时只是重建).基于合同的序列化器会更安全-我倾向于protobuf-net，但我有很大的偏见.
Finally, I strongly advise: stop using BinaryFormatter for this. See questions like this to see other people's pain: basically they can't get their data back after even minor changes (or sometimes just rebuilds). Contract-based serializers would be much safer - I lean towards protobuf-net, but I'm hugely biased.
这篇关于反序列化时出现SerializationException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！
