How to pass an InputStream via RMI

Consider these two functions:

Function A takes inputStream as parameter.

public void processStream(InputStream stream)
{
  //Do process routine
}

Function B loads a file content to pass it to Function A as InputStream.

pulic void loadFile()
{
 File file =new File("c:\\file.txt");
 //Pass file as InputStream
}

How can I pass file from Function B to Function A as InputStream without reading it on first hand?

I did something like this:

File file = new File("c:\\file.txt");
DataInputStream stream= new DataInputStream(new FileInputStream(file));

This generated the exception below:

java.io.WriteAbortedException: writing aborted; j开发者_C百科ava.io.NotSerializableException: java.io.DataInputStream

EDIT:

loadFile() is passing the InputStream as RMI response.

The following should work just fine

processStream(new FileInputStream(file));

You should only not attempt to serialize an InputStream instance by ObjectOutputStream like as

objectOutputStream.writeObject(inputStream);

which you're apparently doing in processStream() method. That's namely exactly what the exception is trying to tell you. How to solve it properly depends on the sole functional requirement which you omitted from the question.

Update as per the comment

I am passing the InputStream as an RMI response.

There's the problem. You cannot pass non-serializable objects around as RMI response, let alone unread streams. You need to read the InputStream into a ByteArrayOutputStream the usual IO way and then use its toByteArray() to get a byte[] out of it and pass that instead. Something like:

InputStream input = new FileInputStream(file); 
ByteArrayOutputStream output = new ByteArrayOutputStream();
byte[] buffer = new byte[8192];

for (int length = 0; (length = input.read(buffer)) > 0;) {
    output.write(buffer, 0, length);
}

byte[] bytes = output.toByteArray(); // Pass that instead to RMI response.

Be careful with large files though. Every byte of a byte[] eats one byte of JVM's memory.

That exception seems to indicate that you are calling the processStream method on a remote object using something like RMI? if that is the case, you will need to re-visit what you are doing. sending streams of data over RMI is not an easy thing to do. if you are guaranteed to be using small files, you could copy the file data to a byte[] and pass that to the remote method call. if you need to process larger files, however, that will most likely cause memory issues on the client and/or server. in that case, you should use something like rmiio, which provides utilities for streaming data over RMI.

You could just pass the FileInputStream ?

processStream(new FileInputStream(yourFile));

The reason you are getting the exception is because DataInputStream is intended to read primitive Java types