vpro-shared-util

Shared utilities

Table of Contents

• CommandExecutor
• Batched Receiver
  • Paging
  • Resumption token
• Configuration utility

Simple utilities with little or no dependencies themselves

E.g. - Collection related, like CountedIterator, ClosableIterator, SkippingIterator, TransformingList, BatchedReceiver - Strings related, like TextUtil, HTMLStripper, Strings - JMX related: nl.vpro.jmx - CommandExecutor to convientiently call external commands - …

CommandExecutor

 // initialize
 CommandExecutor convert = CommandExecutorImpl
                 .builder()
                 .executablesPaths("/opt/local/bin/convert", "/bin/convert", "/usr/local/bin/convert")
                 .commonArg("-")
                 .commonArg("png:-")
                 .logger(log)
                 .wrapLogInfo(CharSequence::toString)
                 .build();


  //use
  File out = File.createTempFile(FilenameUtils.removeExtension(pdfFileName), ".png");
  try (OutputStream outputStream = new FileOutputStream(out)) {
      int exitCode = convert.execute(zip, outputStream, LoggerOutputStream.error(log));
      if (exitCode != 0) {
           log.warn("Exit code: {}", exitCode);
      }
  }

Batched Receiver

If an API provides access to huge set of elements, they often do it with some paging mechanism, or by some 'resumption token' formalism. With nl.vpro.util.BatchedReceiver this can be morphed into a simple java.util.Iterator.

Paging

The 'batchGetter' argument should be a java.util.BiFunction, returning an iterator for the page described by given offset and batch size

Iterator<String> i = BatchedReceiver.<String>builder()
    .batchGetter((offset, max) ->
       apiClient.getPage(offset, max).iterator()
    )
    .batchSize(6)
    .build();
i.forEachRemaining(string -> {
      ...<do stuff...>
  });

Resumption token

You simply provide a java.util.Supplier. A lambda would probably not suffice because you might need the previous result the get the next one. E.g. this (using olingo code)

   public Iterator<ClientEntity> iterate(URIBuilder ub) {
        return BatchedReceiver.<ClientEntity>builder()
            .batchGetter(new Supplier<Iterator<ClientEntity>>() {
                ClientEntitySet result;
                @Override
                public Iterator<ClientEntity> get() {
                    if (result != null) {
                        result = query(result.getNext());
                    } else {
                        result = query(ub);
                    }
                    return result.getEntities().iterator();
                }
            })
            .build();
    }

Configuration utility

At vpro we use to place configuration properties file for all project on similar places.

The can be obtained like this:

nl.vpro.util.ConfigUtils#getPropertiesInHome("<my config file>.properties");

Resolves properties in class path and user.home/conf in a standardized way.

We also support a convention to have properties differ per OTAP environment

  Map<String, String> properties =
        ConfigUtils.filtered(env, ConfigUtils.getPropertiesInHome("openskosrepository.properties"));

It is also possible to instantiate obects using reflection.

TODO device examples