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org.netbeans.modules.sendopts/2 2.36

Command Line Parsing API
Official

See: Description

Command Line Parsing API 
Package Description
org.netbeans.api.sendopts
Start here if you are in a standalone application and you want to parse a command line using the sendopts infrastructure.
org.netbeans.spi.sendopts
Package for those that want to write a command line handler that can participate on handling parts of a command line send to the application.

SendOptsAPI allows anyone to parse an array of strings - e.g. a command line. The infrastracture of the module then locates all providers registered using the SendOptsSPI and distributes the parts of the command line to their handlers. It is expected that the handlers do not know about each other and are in fact provided by different modules. The goal of the sendopts framework is to get the description of the handlers, apply the gained knowledge to the actual content of the command line and distribute the parts of the command line arguments to the designated handlers. Beyond this optimal state the error handling and help composition is also supported by this infrastructure.

What is New (see all changes)?

Use Cases

Just Parse the Command Line
There needs to be a simple API for someone who has an array of strings and wants to parse them. One does not need to search for providers, just ask the infrastructure to do the parse and get the result.

The correct way to achieve this is to call CommandLine.getDefault().process(args).
Parse the Command Line with Own Options
Since version 2.20 one can define own classes with fields and annotate them with @Arg annotation. Those classes can then be passed into a factory method that creates new command line. One can then process the arguments as many times as needed via the process method. Example:
public final class MyOption implements Runnable {
  @Arg(longName="hello")
  public String name;

  public void run() {
    System.out.println("Hello " + name + "!");
  }
  
  public static void main(String... args) {
    CommandLine line = CommandLine.create(MyOption.class);
    line.process(args);
  }
}

If the above main class is called with parameters --hello World it will print out Hello World!.

Short and Long options with or without an argument
The standard getopts supports short form of options - e.g. a dash followed with one letter - or long form using two dashes followed with a word. Moreover the long form is optimized for abbrevations. If there are no conflicts between multiple options, then one can only use double dash followed with a prefix of a long option.

When using the declarative annotation style one can always specify @Arg(longName="text", shortName='t'). The longName attribute is required, but if there is supposed to be no long version of the argument, it can be set to empty string.

One can create an Option by calling any of its factory methods (like withoutArgument) and provider char for the one letter option and/or string for the long getopts option.
Options with or without an argument
There are three types of options. Those without an argument, those with a required one and those with optional one. Each one can be created by appropriate factory method in the Option class.

When using the declarative annotation style one needs to annotate a field of type boolean to create an option without an argument.
Support for --
The getopts compliant command line parsers support --. If these characters do appear on the command line, the rest of it is treated as extra arguments and not processed. The sendopts infrastructure supports this as well.
Multiple Independent CLI Handlers
The handlers for the options need not know about each other and still have to be able to process the command line successfully. Any module which wishes to provide its own options can register its OptionProcessor with @ServiceProvider annotation. Alternatively the module can use the @Arg annotation of its fields and it will be registered as well.
Extensible Options Set

Q: How shall one write an OptionProcessor that recognizes set of basic options, however contains one open slot? The processor wants other modules to provide recognizers for that slot and wants to communicate with them. For example, by default the processor recognizes option --channel <name_of_the_channel> which describes a source of data, and stores such data into a sink. There can be multiple sinks - discard the output, save it to file, show it on stdout, stream it to network. The processor itself can handle the copying of data, but does not itself know all the possible sink types.

To implement OptionProcessor like this one shall define an additional interface to communicate with the sink providers:

   package my.module;
   public interface SinkProvider {
     /** gets the option (even composite) that this sink needs on command line */
     public Option getOption();

     /** processes the options and creates a "sink" */
     public OutputStream createSink(Env env, Map<Option,String[]> values) throws CommandException;
   }
       

Other modules would then registered implementations of this interface in the META-INF/services/my.module.SinkProvider files. The OptionProcessor itself would just look all the implementations up, queried for the sinks, and then did the copying:

   class CopyingProvider extends OptionProvider {
     public Option getOption() {
        List<Option> l = ...;
        for (SinkProvider sp : Lookup.getDefault().lookupAll(SinkProvider.class)) {
          l.add(sp.getOption());
        }

        // we need only one provider to be present
        Option oneOfSinks = OptionGroups.oneOf(l.toArray(new Option[0]));

        // our channel option
        Option channel = ...;

        // the channel option needs to be present as well as a sink
        return OptionGroups.allOf(channel, oneOfSinks);
     }

     public void process(Env env, Map<Option,String[]> values) throws CommandException {
        OutputStream os = null;
        for (SinkProvider sp : Lookup.getDefault().lookupAll(SinkProvider.class)) {
          if (values.containsKey(sp.getOption())) {
            os = sp.createSink(env, values);
            break;
          }
        }
        if (os == null) {
          throw CommandException.exitCode(2);
        }

        // process the channel option and
        // handle the copying to the sink os
     }
   }
       

Another possible approach how to allow sharing of one option between multiple modules is to expose the option definition and its handling code as an interface to other modules, and then let the modules to write their own OptionProcessors. Necessary condition is that each of the processor is uniquely identified by some additional option, so when the shared option appears the infrastructure knows which processor to delegate to. This is demonstrated in the SharedOptionTest which basically does the following:

   /** the shared option, part of an interface of some module */
   public static final Option SHARED = ...;
   /** finds value(s) associated with the SHARED option and 
   * creates a JPanel based on them */
   public static JPanel getSharedPanel(Map<Option,String[]> args) { ... }
       

Then each module who wishes to reuse the SHARED option and the factory method that knows how to process their values for their own processing can just:

  public static final class ShowDialog extends OptionProcessor {
    private static final Option DIALOG = Option.withoutArgument('d', "dialog");

    protected Set<Option> getOptions() {
        // the following says that this processor should be invoked
        // everytime --dialog appears on command line, if the SHARED
        // option is there, then this processor wants to consume it 
        // as well...
        return Collections.singleton(Option.allOf(DIALOG, Option.anyOf(SHARED)));
    }

    protected void process(Env env, Map<Option, String[]> optionValues) throws CommandException {
        JPanel p = getSharedPanel(optionvalues);
        if (p == null) {
           // show empty dialog
        } else {
           // show some dialog containing the panel p
        }
    }
  }
       

The other modules are then free to write other processors refering to SHARED, for example one can write ShowFrame that does the same, just shows the panel in a frame, etc. The infrastructure guarantees that the exactly one provider which matches the command line options is called.

Printing Full Help Text
Althrough the handlers are provided by independent parties, it must be possible to generate resonable and consistent help description from all of them, so for the end user it appears as well formated and easily understandable. That is why every option can be associated with a short description providing info about what it is useful for using Option.shortDescription method. When using the @Arg style, there is an additional @Description annotation which can be used to declaratively associate a localized display name and short description with the option. To get such descriptions for all available options one can use CommandLine.getDefault().usage(java.io.PrintWriter).
Finding and Reporting when Options Are Not Correct
In case the command line cannot be processed a clean error for programmatic consumation and also one that can be shown to the end user of the command line must be given. This is handled by throwing CommandException with appropriate message description and exit code.
Processing Extra Command Line Arguments
There can be non-option arguments in the command line and they can freely mix with the option ones. For example the getopts would treat the following command line arguments as the same:
       --open X.java Y.java Z.txt
       X.java Y.java --open Z.txt
       
if the option open handles extra arguments. The sendopts infrastructure must distinquish between them and pass the non-option ones to the only one handler (active because it processed an option) that knowns how to parse them. It is an error if more than one or no handler expresses an interest in extra arguments and those are given. One can register such option by using the Option.additionalArgument factory method.

When using the declarative annotation style one may annotate a field of type String[] which then means this field should be filled with all additional arguments.
Handling Input and Output
Handler's shall not use the input and output streams directly for their execution, they should rely on the framework provided ones. This allows NetBeans based application to transfer the I/O from second started instance to the master one which is already running. From the client side there is the CommandLine.getDefault().parse methods taking additional arguments like input and output streams. This gets transfered to providers as an Env argument of their methods.
Returning Exit Code
When Handler's get execute (in the order defined by the order of options on the command line), each of them can either execute successfully, or fail. If a handler succeeds, next one is executed, if it fails, the execution is terminated and its return code is returned to the caller. The error can be notified by creating and throwing CommandException.exitCode(int errorCode).
Processing Only Extra Command Line Arguments
Sometimes it is desirable to process non-option arguments like file names without providing any option. Handlers can declare interest in such arguments. It is an error if such non-options are provided and no or more than one handler is around to handle them. One can create such option by using Option.defaultArguments factory method. With the declarative annotation style one can annotate a field of type String[] and specify that it is supposed to be implicit.
Only those processor need to process the options are created
For purposes of usage in NetBeans, it is needed to not-initialize those handlers that are not really needed to process certain command line. The infrastructure decides which of them are going to be needed and instantiates only those. This is supported only when using the declarative annotation style - information about these options is recorded in declarative way and the system can decide without loading the provider classes whether they are present on the command line or not.
Complex Option Relations
Certain CLI processors may need more than one option before they can process the input. For example it is necesary to tune the radio and then also tell what to do with the output. It is unconvenient to process that as one option with argument(s), that is why one can use the OptionGroups.allOf, OptionGroups.someOf, for example like:
class PP extends OptionProcessor {
    private static Option tune = Option.requiredArgument(Option.NO_SHORT_NAME, "tune");
    private static Option stream = Option.requiredArgument(Option.NO_SHORT_NAME, "stream");
    
    public Set<Option> getOptions() {
      return Collections.singleton(
        OptionGroups.allOf(tune, stream)
      );
    }
    
    public void process(Env env, Map>Option,String[]> values) throws CommandException {
        String freq = values.get(tune)[0];
        String output = values.get(stream)[0];

        // XXX handle what is needed here
    }
}
When the two options are registered and command line like --tune 91.9 --stream radio1.mp3 is being processed, the PP's process method is going to get called with values 91.9 and radio1.mp3.

This kind of grouping is not currently supported with the declarative annotation style registration.
Alternative Options
Sometimes there may different ways to specify the same option and just one of them or none of them can be provided at given time. For example is there is a way to tune the radio with direct frequency or with name of the station. Just one can be provided and one is needed. This can be specified by using OptionGroups.oneOf factory methods:
Option freq = Option.requiredArgument(Option.NO_SHORT_NAME, "tune");
Option station = Option.requiredArgument(Option.NO_SHORT_NAME, "station");
Option tune = OptionGroups.oneOf(freq, station);    
The option tune then signals that just one of the station or freq options can appear and that they both are replaceable.

Exported Interfaces

This table lists all of the module exported APIs with defined stability classifications. It is generated based on answers to questions about the architecture of the module. Read them all...
Group of java interfaces
Interface NameIn/OutStabilitySpecified in What Document?
SendOptsAPIExportedOfficial .../api/sendopts/package-summary.html

SendOptsSPIExportedOfficial .../spi/sendopts/package-summary.html

Group of lookup interfaces
Interface NameIn/OutStabilitySpecified in What Document?
OptionProcessorExportedStable .../spi/sendopts/OptionProcessor.html

The sendopts module uses Lookup to get list of all registered OptionProcessors.

Implementation Details

Where are the sources for the module?

The sources for the module are in the NetBeans Mercurial repositories.

What do other modules need to do to declare a dependency on this one, in addition to or instead of a plain module dependency?

Nothing.

Read more about the implementation in the answers to architecture questions.

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