Pipes

Light-weight data processing pipelines for Java.

Pipes is provided under the Apache License Version 2.0.

Example

This example uses Pipes to read an arbitrary set of text files and output their contents line-by-line.

public static void main(final String... args) throws StreamException
{
    // A pipe to convert arguments to paths
    final Pipe<String[],Path> argsToPaths = (i,o) -> {
        for(String arg : i) o.accept(Paths.get(arg));
    };
    // A pipe to open paths as byte streams
    final Pipe<Path, InputStream> pathToStream = (i,o) -> {
    try {
      o.accept(Files.newInputStream(i, StandardOpenOption.READ));
    } catch (final IOException e) {
      throw new PipeException(e);
    }
    };
    // A pipe to read lines of text from byte streams
    final Pipe<InputStream, String> streamToLines = (i,o) -> {
    try(final BufferedReader reader = new BufferedReader(new InputStreamReader(i, StandardCharsets.UTF_8))) {
      for(String line = reader.readLine(); line != null; line = reader.readLine()){
        o.accept(line);
      }
    } catch (final IOException e) {
      throw new PipeException(e);
    }
    };
    // A predicate to filter out any blank lines or lines starting with '#'.
    final PipePredicate<String> nonComments = line -> line != null && !line.isEmpty() && !line.matches("\\s*(#.*)?");

    // Build the pipeline
    final Pipe<String, String> filteredLines = argToPath.append(pathToStream)
                                                      .append(streamToLines)
                                                      .filter(nonComments);

    // Consume the pipeline by printing to standard out.
    filteredLines.flush(args, line -> System.out.println(line));
}