Exception: conversion from UNKNOWN to UNKNOWN is unsupported - sql-server

Question

I'm converting some jdbc code from MySql to SQL Server. When trying to
query = "Update ReportSetup "
+ "set N_ID=?, "
+ "R_Default=?, "
+ "R_Name=?, "
+ "R_Module=? "
+ " where R_ID = ?";
}
PreparedStatement stmt =
(PreparedStatement) con.prepareStatement(query, Statement.RETURN_GENERATED_KEYS);
stmt.setInt(1, ri.getNodeID());
stmt.setInt(2, (ri.isDefault()) ? 1 : 0);
stmt.setString(3, ri.getName());
Object o = ri.getReportModule();
stmt.setObject(4, o);
The last statement stmt.setObject(4,o) throws the exception.
ri.getReportModule returns an instance of a class which implements Externalizable.
The method writeExternal() of that class is implemented as
public final void writeExternal(final ObjectOutput objectOutput) throws IOException {
for (int i=0; i<pdV.size(); i++) {
PropertyDescriptor pd = pdV.elementAt(i);
try {
Method m = pd.getReadMethod();
Object val = pd.getReadMethod().invoke(this);
System.out.print("writing property " + i + ": " + pd.getName() + " = " + val);
objectOutput.writeObject(val);
} catch (Exception e) {
e.printStackTrace();
}
}
}
The database column in question is defined as
varbinary(max), not null
The code works well using MySql but I can't figure out what to do to make it run with Sql Server.
Any suggestions would be very much appreciated

Answer 1

The problem was that sql server is not happy to save a serialization (as done when implementing externalizable). .setObject() fails. The solution is to use setBinaryStream().
// Sql Server can't do an stmt.setObject(4,o) "Conversion from UNKNOWN to UNKNOWN not supported"
// Serialize the object to an output stream and then read it in again into the stmt.
Object o = ri.getReportModule();
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream objectOutput = new ObjectOutputStream(bos);
objectOutput.writeObject(o);
objectOutput.flush();
InputStream objectInput = new ByteArrayInputStream(bos.toByteArray());
stmt.setBinaryStream(4, objectInput);
Cheers
Christian