问题
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;
}
回答1:
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);
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.
And another bug in the SQL:
SQLiteCommand command = new SQLiteCommand("INSERT into 'dump' ('DTime', 'DBinaryData') VALUES ('" + DateTime.Now.ToString() + "', '" + GetSerializedMessages() + "')", connection);
command.ExecuteNonQuery();
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"
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();
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
}
}
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:
- an error in the code that serializes and stores the data
- truncation inside the database storage
- truncation when reading the BLOB (some connections limit the amount fetched in one go)
- an error in the code that fetches and deserializes the data
The first two are totally fatal: if it is those - the data is toast.
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));
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.
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.
来源：https://stackoverflow.com/questions/15967577/serializationexception-when-deserializing