Dynamically connectable pipes

Question

Hi. I'm having trouble building an application which does text processing. The application is structured as a pipeline with data flowing through a chain of modules. Each module is constructed with a java.io.Reader and java.io.Writer and the module reads from the Reader, does some processing, and writes to the Writer. For a module in the middle of the pipeline, the Reader and Writer are actually a PipedReader and PipedWriter which connect a PipedWriter and PipedReader respectively in an adjacent module.
The problem is that I want to be able to add and remove modules during runtime but the PipedReader and PipedWriter classes only allow you to connect them once. You can't disconnect them and reconnect them in new configurations. So what do I do? I need something that allows me to read from a changing Reader, either a dynamically connectable pipe or something like a BufferedReader except that you change the Reader that it reads from at runtime. Do any know of a solution?
Thanks. Eli

Answer 1

Take a look at FilterInputStream and FilterOutputStream. You can extend those, and then furnish addPipe() and removePipe(). This would be custom functionality. Maintain the list of streams each module is outputtting in a Collection. It would be relatively easy to create a Tee (one FilterOutputStream writing to multiple nested output streams) but harder to do so on the input stream end.
- Saish