RMI - Serializing Object with the right constructor..?

Question

Hello, I am trying to usr RMI to send an object that I serialized but I have further porblems than that. The Object that I am using is called FileLineReader and it Extends Buffered Reader. SInce Buffered Reader is not Serializable, I implemented Serializable within FileLineReader, so that I can send it through the RMI.
package musr.client.dbreader;
import java.io.*;
public class FileLineReader extends BufferedReader
          implements LineReader, java.io.Serializable {
String pattern; // The string we are going to be matching.
* Constructor
* Passes the stream to our superclass
public FileLineReader(Reader in) { super(in); }
* This is the filter: call our superclass's readLine() to get the
* actual lines, but only return lines that contain the pattern.
* When the superclass readLine() returns null (EOF), we return null.
public String matchLine(String pattern) throws IOException {
String line;
do { line = super.readLine(); }
while ((line != null) && line.indexOf(pattern) == -1);
return line;
When I use this object to send it through RMI to the Server,
(FileLineReader)inFile = (FileLineReader) obj.senddbFile(openFileTextField1.getText(),openFileTextField2.getText());
I get an exception:
GUI_RMI exception, error unmarshalling return; nested exception is: java.io.InvalidClassException: musr.client.dbreader.FileLineReader; no valid constructor.
I am not sure what the problem is and I have been struggling with it for a while now. The constructor of BufferedReader takes one argument in so I have to pass FileLineReader an argument when I construct it. I think the RMI needs a constructor that takes no arguments and that causes problems. Is that true? In that case, I can't extend my class with BufferedReader.
Or maybe the problem is somthing quite different. Anyone has any suggestions or comments, I'd appreciate help. Thanks Ivan

Answer 1

You will have to create your own stream. (RMI is just a way to call reemote methods; it knows nothing about files or I/O.)
1. You need a RemoteReader. This object should probably have 3 or so methods:
Open(filename) Opens the file
read reads a block from the file and returns it as a byte array.
close()
2. You need a RemoteInputStream object.
o Instantiated on the client.
o Makes calls to the RemoteReader.
o Has some read methods and a close method.
o Implements InputStream.
With these two objects, you have enough underpinnings top - for example - wrap the RemoteINputStream in a BufferedReader or whatever you need.