# Vert.x Shell

Vert.x Shell is a command line interface for the Vert.x runtime available from regular terminals using different protocols.

Vert.x Shell provides a variety of commands for interacting live with Vert.x services.

Vert.x Shell can be extended with custom commands in any language supported by Vert.x

## Using Vert.x Shell

Vert.x Shell is a Vert.x Service and can be started programmatically via the `ShellService` or deployed as a service.

### Shell service

The shell can be started as a service directly either from the command line or as a the Vert.x deployment:

Starting a shell service available via Telnet

    vertx run -conf '{"telnetOptions":{"port":5000}}' maven:io.vertx:vertx-shell:3.3.2

or

Starting a shell service available via SSH

    # create a key pair for the SSH server
    keytool -genkey -keyalg RSA -keystore ssh.jks -keysize 2048 -validity 1095 -dname CN=localhost -keypass secret -storepass secret
    # create the auth config
    echo user.admin=password > auth.properties
    # start the shell
    vertx run -conf '{"sshOptions":{"port":4000,"keyPairOptions":{"path":"ssh.jks","password":"secret"},"authOptions":{"provider":"shiro","config":{"properties_path":"file:auth.properties"}}}}' maven:io.vertx:vertx-shell:3.3.2

or

Starting a shell service available via HTTP

    # create a certificate for the HTTP server
    keytool -genkey -keyalg RSA -keystore keystore.jks -keysize 2048 -validity 1095 -dname CN=localhost -keypass secret -storepass secret
    # create the auth config
    echo user.admin=password > auth.properties
    vertx run -conf '{"httpOptions":{"port":8080,"ssl":true,"keyStoreOptions":{"path":"keystore.jks","password":"secret"},"authOptions":{"provider":""shiro,"config":{"properties_path":"file:auth.properties"}}}}' maven:io.vertx:vertx-shell:3.3.2

You can also deploy this service inside your own verticle:

    vertx.deployVerticle("maven:{maven-groupId}:{maven-artifactId}:{maven-version}",
        new DeploymentOptions().setConfig(
            new JsonObject().put("telnetOptions",
                new JsonObject().
                    put("host", "localhost").
                    put("port", 4000))
        )
    );

or

    vertx.deployVerticle("maven:{maven-groupId}:{maven-artifactId}:{maven-version}",
        new DeploymentOptions().setConfig(new JsonObject().
                put("sshOptions", new JsonObject().
                    put("host", "localhost").
                    put("port", 5000).
                    put("keyPairOptions", new JsonObject().
                        put("path", "src/test/resources/ssh.jks").
                        put("password", "wibble")).
                    put("authOptions", new JsonObject().
                        put("provider", "shiro").
                        put("config", new JsonObject().
                            put("properties_path", "file:/path/to/my/auth.properties"))))
        )
    );

or

    vertx.deployVerticle("maven:{maven-groupId}:{maven-artifactId}:{maven-version}",
        new DeploymentOptions().setConfig(new JsonObject().
                put("httpOptions", new JsonObject().
                    put("host", "localhost").
                    put("port", 8080).
                    put("ssl", true).
                    put("keyPairOptions", new JsonObject().
                        put("path", "src/test/resources/server-keystore.jks").
                        put("password", "wibble")).
                    put("authOptions", new JsonObject().
                        put("provider", "shiro").
                        put("config", new JsonObject().
                            put("properties_path", "file:/path/to/my/auth.properties"))))
        )
    );

Note | when Vert.x Shell is already on your classpath you can use `service:io.vertx.ext.shell` instead or `maven:io.vertx:vertx-shell:3.3.2`

### Programmatic service

The `ShellService` takes care of starting an instance of Vert.x Shell.

Starting a shell service available via SSH:

    ShellService service = ShellService.create(vertx,
        new ShellServiceOptions().setSSHOptions(
            new SSHTermOptions().
                setHost("localhost").
                setPort(5000).
                setKeyPairOptions(new JksOptions().
                        setPath("server-keystore.jks").
                        setPassword("wibble")
                ).
                setAuthOptions(new ShiroAuthOptions().
                        setType(ShiroAuthRealmType.PROPERTIES).
                        setConfig(new JsonObject().
                            put("properties_path", "file:/path/to/my/auth.properties"))
                )
        )
    );
    service.start();

Starting a shell service available via Telnet:

    ShellService service = ShellService.create(vertx,
        new ShellServiceOptions().setTelnetOptions(
            new TelnetTermOptions().
                setHost("localhost").
                setPort(4000)
        )
    );
    service.start();

The `TelnetTermOptions` extends the Vert.x Core `NetServerOptions` as the Telnet server implementation is based on a `NetServer`.

Caution | Telnet does not provide any authentication nor encryption at all.

Starting a shell service available via HTTP:

    ShellService service = ShellService.create(vertx,
        new ShellServiceOptions().setHttpOptions(
            new HttpTermOptions().
                setHost("localhost").
                setPort(8080)
        )
    );
    service.start();

## Authentication

The SSH and HTTP connectors provide both authentication built on top of vertx-auth with the following supported providers:

- shiro : provides `.properties` and LDAP backend as seen in the ShellService presentation

- jdbc : JDBC backend

- mongo : MongoDB backend

These options can be created directly using directly `AuthOptions`:

- `ShiroAuthOptions` for Shiro

- `JDBCAuthOptions` for JDBC

- `MongoAuthOptions` for Mongo

As for external service configuration in Json, the `authOptions` uses the `provider` property to distinguish:

    {
      ...
      "authOptions": {
        "provider":"shiro",
        "config": {
          "properties_path":"file:auth.properties"
        }
      }
      ...
    }

## Telnet term configuration

Telnet terms are configured by `setTelnetOptions`, the `TelnetTermOptions` extends the `NetServerOptions` so they have the exact same configuration.

## SSH term configuration

SSH terms are configured by `setSSHOptions`:

- `setPort`: port

- `setHost`: host

Only username/password authentication is supported at the moment, it can be configured with property file or LDAP, see Vert.x Auth for more info:

- `setAuthOptions`: configures user authentication

The server key configuration reuses the key pair store configuration scheme provided by Vert.x Core:

- `setKeyPairOptions`: set `.jks` key pair store

- `setPfxKeyPairOptions`: set `.pfx` key pair store

- `setPemKeyPairOptions`: set `.pem` key pair store

Deploying the Shell Service on SSH with Mongo authentication

    vertx.deployVerticle("maven:{maven-groupId}:{maven-artifactId}:{maven-version}",
        new DeploymentOptions().setConfig(new JsonObject().
                put("sshOptions", new JsonObject().
                    put("host", "localhost").
                    put("port", 5000).
                    put("keyPairOptions", new JsonObject().
                        put("path", "src/test/resources/ssh.jks").
                        put("password", "wibble")).
                    put("authOptions", new JsonObject().
                        put("provider", "mongo").
                        put("config", new JsonObject().
                            put("connection_string", "mongodb://localhost:27018"))))
        )
    );

Running the Shell Service on SSH with Mongo authentication

    ShellService service = ShellService.create(vertx,
        new ShellServiceOptions().setSSHOptions(
            new SSHTermOptions().
                setHost("localhost").
                setPort(5000).
                setKeyPairOptions(new JksOptions().
                        setPath("server-keystore.jks").
                        setPassword("wibble")
                ).
                setAuthOptions(new MongoAuthOptions().setConfig(new JsonObject().
                        put("connection_string", "mongodb://localhost:27018"))
                )
        )
    );
    service.start();

Deploying the Shell Service on SSH with JDBC authentication

    vertx.deployVerticle("maven:{maven-groupId}:{maven-artifactId}:{maven-version}",
        new DeploymentOptions().setConfig(new JsonObject().
                put("sshOptions", new JsonObject().
                    put("host", "localhost").
                    put("port", 5000).
                    put("keyPairOptions", new JsonObject().
                        put("path", "src/test/resources/ssh.jks").
                        put("password", "wibble")).
                    put("authOptions", new JsonObject().
                        put("provider", "jdbc").
                        put("config", new JsonObject()
                            .put("url", "jdbc:hsqldb:mem:test?shutdown=true")
                            .put("driver_class", "org.hsqldb.jdbcDriver"))))
        )
    );

Running the Shell Service on SSH with JDBC authentication

    ShellService service = ShellService.create(vertx,
        new ShellServiceOptions().setSSHOptions(
            new SSHTermOptions().
                setHost("localhost").
                setPort(5000).
                setKeyPairOptions(new JksOptions().
                        setPath("server-keystore.jks").
                        setPassword("wibble")
                ).
                setAuthOptions(new JDBCAuthOptions().setConfig(new JsonObject()
                        .put("url", "jdbc:hsqldb:mem:test?shutdown=true")
                        .put("driver_class", "org.hsqldb.jdbcDriver"))
                )
        )
    );
    service.start();

## HTTP term configuration

HTTP terms are configured by `setHttpOptions`, the http options extends the `HttpServerOptions` so they expose the exact same configuration.

In addition there are extra options for configuring an HTTP term:

- `setAuthOptions`: configures user authentication

- `setSockJSHandlerOptions`: configures SockJS

- `setSockJSPath`: the SockJS path in the router

Deploying the Shell Service on HTTP with Mongo authentication

    vertx.deployVerticle("maven:{maven-groupId}:{maven-artifactId}:{maven-version}",
        new DeploymentOptions().setConfig(new JsonObject().
                put("httpOptions", new JsonObject().
                    put("host", "localhost").
                    put("port", 8080).
                    put("ssl", true).
                    put("keyPairOptions", new JsonObject().
                        put("path", "src/test/resources/server-keystore.jks").
                        put("password", "wibble")).
                    put("authOptions", new JsonObject().
                        put("provider", "mongo").
                        put("config", new JsonObject().
                            put("connection_string", "mongodb://localhost:27018"))))
        )
    );

Running the Shell Service on HTTP with Mongo authentication

    ShellService service = ShellService.create(vertx,
        new ShellServiceOptions().setHttpOptions(
            new HttpTermOptions().
                setHost("localhost").
                setPort(8080).
                setAuthOptions(new MongoAuthOptions().setConfig(new JsonObject().
                        put("connection_string", "mongodb://localhost:27018"))
                )
        )
    );
    service.start();

Deploying the Shell Service on HTTP with JDBC authentication

    vertx.deployVerticle("maven:{maven-groupId}:{maven-artifactId}:{maven-version}",
        new DeploymentOptions().setConfig(new JsonObject().
                put("httpOptions", new JsonObject().
                    put("host", "localhost").
                    put("port", 8080).
                    put("ssl", true).
                    put("keyPairOptions", new JsonObject().
                        put("path", "src/test/resources/server-keystore.jks").
                        put("password", "wibble")).
                    put("authOptions", new JsonObject().
                        put("provider", "jdbc").
                        put("config", new JsonObject()
                            .put("url", "jdbc:hsqldb:mem:test?shutdown=true")
                            .put("driver_class", "org.hsqldb.jdbcDriver"))))
        )
    );

Running the Shell Service on HTTP with JDBC authentication

    ShellService service = ShellService.create(vertx,
        new ShellServiceOptions().setHttpOptions(
            new HttpTermOptions().
                setHost("localhost").
                setPort(8080).
                setAuthOptions(new JDBCAuthOptions().setConfig(new JsonObject()
                        .put("url", "jdbc:hsqldb:mem:test?shutdown=true")
                        .put("driver_class", "org.hsqldb.jdbcDriver"))
                )
        )
    );
    service.start();

## Keymap configuration

The shell uses a default keymap configuration that can be overriden using the `inputrc` property of the various term configuration object:

- `setIntputrc`

- `setIntputrc`

- `setIntputrc`

The `inputrc` must point to a file available via the classloader or the filesystem.

The `inputrc` only function bindings and the available functions are:

- backward-char

- forward-char

- next-history

- previous-history

- backward-delete-char

- backward-delete-char

- backward-word

- end-of-line

- beginning-of-line

- delete-char

- delete-char

- complete

- accept-line

- accept-line

- kill-line

- backward-word

- forward-word

- backward-kill-word

Note | Extra functions can be added, however this is done by implementing functions of the `Term.d` project on which Vert.x Shell is based, for instance the reverse function can be implemented and then declared in a `META-INF/services/io.termd.core.readline.Function` to be loaded by the shell.

## Base commands

To find out the available commands you can use the help builtin command:

1. Verticle commands

   1. verticle-ls: list all deployed verticles

   2. verticle-undeploy: undeploy a verticle

   3. verticle-deploy: deployes a verticle

   4. verticle-factories: list all known verticle factories

2. File system commands

   1. ls

   2. cd

   3. pwd

3. Bus commands

   1. bus-tail: display all incoming messages on an event bus address

   2. bus-send: send a message on the event bus

4. Net commands

   1. net-ls: list all available net servers, including HTTP servers

5. Shared data commands

   1. local-map-put

   2. local-map-get

   3. local-map-rm

6. Various commands

   1. echo

   2. sleep

   3. help

   4. exit

   5. logout

7. Job control

   1. fg

   2. bg

   3. jobs

Note | this command list should evolve in next releases of Vert.x Shell. Other Vert.x project may provide commands to extend Vert.x Shell, for instance Dropwizard Metrics.

## Extending Vert.x Shell

Vert.x Shell can be extended with custom commands in any of the languages supporting code generation.

A command is created by the `CommandBuilder.command` method: the command process handler is called by the shell when the command is executed, this handler can be set with the `processHandler` method:

    CommandBuilder builder = CommandBuilder.command("my-command");
    builder.processHandler(process -> {

      // Write a message to the console
      process.write("Hello World");

      // End the process
      process.end();
    });

    // Register the command
    CommandRegistry registry = CommandRegistry.getShared(vertx);
    registry.registerCommand(builder.build(vertx));

After a command is created, it needs to be registed to a `CommandRegistry`. The command registry holds all the commands for a Vert.x instance.

A command is registered until it is unregistered with the `unregisterCommand`. When a command is registered from a Verticle, this command is unregistered when this verticle is undeployed.

Note | Command callbacks are invoked in the `io.vertx.core.Context` when the command is registered in the registry. Keep this in mind if you maintain state in a command.

The `CommandProcess` object can be used for interacting with the shell.

### Command arguments

The `args` returns the command arguments:

    command.processHandler(process -> {

      for (String arg : process.args()) {
        // Print each argument on the console
        process.write("Argument " + arg);
      }

      process.end();
    });

Besides it is also possible to create commands using `Vert.x CLI`: it makes easier to write command line argument parsing:

- option and argument parsing

- argument validation

- generation of the command usage

    CLI cli = CLI.create("my-command").
        addArgument(new Argument().setArgName("my-arg")).
        addOption(new Option().setShortName("m").setLongName("my-option"));
    CommandBuilder command = CommandBuilder.command(cli);
    command.processHandler(process -> {

      CommandLine commandLine = process.commandLine();

      String argValue = commandLine.getArgumentValue(0);
      String optValue = commandLine.getOptionValue("my-option");
      process.write("The argument is " + argValue + " and the option is " + optValue);

      process.end();
    });

When an option named help is added to the CLI object, the shell will take care of generating the command usage when the option is activated:

    CLI cli = CLI.create("my-command").
        addArgument(new Argument().setArgName("my-arg")).
        addOption(new Option().setArgName("help").setShortName("h").setLongName("help"));
    CommandBuilder command = CommandBuilder.command(cli);
    command.processHandler(process -> {
      // ...
    });

When the command executes the `process` is provided for interacting with the shell. A `CommandProcess` extends `Tty` which is used for interacting with the terminal.

### Terminal usage

#### terminal I/O

The `stdinHandler` handler is used to be notified when the terminal receives data, e.g the user uses his keyboard:

    tty.stdinHandler(data -> {
      System.out.println("Received " + data);
    });

A command can use the `write` to write to the standard output.

    tty.write("Hello World");

#### Terminal size

The current terminal size can be obtained using `width` and `height`.

    tty.write("Current terminal size: (" + tty.width() + ", " + tty.height() + ")");

#### Resize event

When the size of the terminal changes the `resizehandler` is called, the new terminal size can be obtained with `width` and `height`.

    tty.resizehandler(v -> {
      System.out.println("terminal resized : " + tty.width() + " " + tty.height());
    });

#### Terminal type

The terminal type is useful for sending escape codes to the remote terminal: `type` returns the current terminal type, it can be null if the terminal has not advertised the value.

    System.out.println("terminal type : " + tty.type());

### Shell session

The shell is a connected service that naturally maintains a session with the client, this session can be used in commands to scope data. A command can get the session with `session`:

    command.processHandler(process -> {

      Session session = process.session();

      if (session.get("my_key") == null) {
        session.put("my key", "my value");
      }

      process.end();
    });

### Process termination

Calling `end` ends the current process. It can be called directly in the invocation of the command handler or any time later:

    command.processHandler(process -> {
      Vertx vertx = process.vertx();

      // Set a timer
      vertx.setTimer(1000, id -> {

        // End the command when the timer is fired
        process.end();
      });
    });

### Process events

A command can subscribe to a few process events.

#### Interrupt event

The `interruptHandler` is called when the process is interrupted, this event is fired when the user press Ctrl+C during the execution of a command. This handler can be used for interrupting commands blocking the CLI and gracefully ending the command process:

    command.processHandler(process -> {
      Vertx vertx = process.vertx();

      // Every second print a message on the console
      long periodicId = vertx.setPeriodic(1000, id -> {
        process.write("tick\n");
      });

      // When user press Ctrl+C: cancel the timer and end the process
      process.interruptHandler(v -> {
        vertx.cancelTimer(periodicId);
        process.end();
      });
    });

When no interrupt handler is registered, pressing Ctrl+C will have no effect on the current process and the event will be delayed and will likely be handled by the shell, like printing a new line on the console.

#### Suspend/resume events

The `suspendHandler` is called when the process is running and the user press Ctrl+Z, the command is suspended:

- the command can receive the suspend event when it has registered an handler for this event

- the command will not receive anymore data from the standard input

- the shell prompt the user for input

- the command can receive interrupts event or end events

The `resumeHandler` is called when the process is resumed, usually when the user types fg:

- the command can receive the resume event when it has registered an handler for this event

- the command will receive again data from the standard input when it has registered an stdin handler

    command.processHandler(process -> {

      // Command is suspended
      process.suspendHandler(v -> {
        System.out.println("Suspended");
      });

      // Command is resumed
      process.resumeHandler(v -> {
        System.out.println("Resumed");
      });
    });

#### End events

The `endHandler` (io.vertx.core.Handler)} is called when the process is running or suspended and the command terminates, for instance the shell session is closed, the command is terminated.

    command.processHandler(process -> {

      // Command terminates
      process.endHandler(v -> {
        System.out.println("Terminated");
      });
    });

The end handler is called even when the command invokes `end`.

This handler is useful for cleaning up resources upon command termination, for instance closing a client or a timer.

### Command completion

A command can provide a completion handler when it wants to provide contextual command line interface completion.

Like the process handler, the `completion handler` is non blocking because the implementation may use Vert.x services, e.g the file system.

The `lineTokens` returns a list of `tokens` from the beginning of the line to the cursor position. The list can be empty if the cursor when the cursor is at the beginning of the line.

The `rawLine` returns the current completed from the beginning of the line to the cursor position, in raw format, i.e without any char escape performed.

Completion ends with a call to `complete`.

## Shell server

The Shell service is a convenient facade for starting a preconfigured shell either programmatically or as a Vert.x service. When more flexibility is needed, a `ShellServer` can be used instead of the service.

For instance the shell http term can be configured to use an existing router instead of starting its own http server.

Using a shell server requires explicit configuration but provides full flexiblity, a shell server is setup in a few steps:

    ShellServer server = ShellServer.create(vertx); (1)

    Router shellRouter = Router.router(vertx); (2)
    router.mountSubRouter("/shell", shellRouter);
    TermServer httpTermServer = TermServer.createHttpTermServer(vertx, router);

    TermServer sshTermServer = TermServer.createSSHTermServer(vertx); (3)

    server.registerTermServer(httpTermServer); (4)
    server.registerTermServer(sshTermServer);

    server.registerCommandResolver(CommandResolver.baseCommands(vertx)); (5)

    server.listen(); (6)

1. create a the shell server

2. create an HTTP term server mounted on an existing router

3. create an SSH term server

4. register term servers

5. register all base commands

6. finally start the shell server

Besides, the shell server can also be used for creating in process shell session: it provides a programmatic interactive shell.

In process shell session can be created with `createShell`:

    Shell shell = shellServer.createShell();

The main use case is running or testing a command:

    Shell shell = shellServer.createShell();

    // Create a job fo the command
    Job job = shell.createJob("my-command 1234");

    // Create a pseudo terminal
    Pty pty = Pty.create();
    pty.stdoutHandler(data -> {
      System.out.println("Command wrote " + data);
    });

    // Run the command
    job.setTty(pty.slave());
    job.statusUpdateHandler(status -> {
      System.out.println("Command terminated with status " + status);
    });

The `Pty` pseudo terminal is the main interface for interacting with the command when it’s running:

- uses standard input/output for writing or reading strings

- resize the terminal

The `close` closes the shell, it will terminate all jobs in the current shell session.

## Terminal servers

Vert.x Shell also provides bare terminal servers for those who need to write pure terminal applications.

A `Term` handler must be set on a term server before starting it. This handler will handle each term when the user connects.

An `AuthOptions` can be set on `SSHTermOptions` and `HttpTermOptions`. Alternatively, an `AuthProvider` can be `set` directly on the term server before starting it.

### SSH term

The terminal server `Term` handler accepts incoming terminal connections. When a remote terminal connects, the `Term` can be used to interact with connected terminal.

    TermServer server = TermServer.createSSHTermServer(vertx, new SSHTermOptions().setPort(5000).setHost("localhost"));
    server.termHandler(term -> {
      term.stdinHandler(line -> {
        term.write(line);
      });
    });
    server.listen();

The `Term` is also a `Tty`, this section explains how to use the tty.

### Telnet term

    TermServer server = TermServer.createTelnetTermServer(vertx, new TelnetTermOptions().setPort(5000).setHost("localhost"));
    server.termHandler(term -> {
      term.stdinHandler(line -> {
        term.write(line);
      });
    });
    server.listen();

### HTTP term

The `TermServer.createHttpTermServer` method creates an HTTP term server, built on top of Vert.x Web using the SockJS protocol.

    TermServer server = TermServer.createHttpTermServer(vertx, new HttpTermOptions().setPort(5000).setHost("localhost"));
    server.termHandler(term -> {
      term.stdinHandler(line -> {
        term.write(line);
      });
    });
    server.listen();

An HTTP term can start its own HTTP server, or it can reuse an existing Vert.x Web `Router`.

The shell can be found at `/shell.html`.

    TermServer server = TermServer.createHttpTermServer(vertx, router, new HttpTermOptions().setPort(5000).setHost("localhost"));
    server.termHandler(term -> {
      term.stdinHandler(line -> {
        term.write(line);
      });
    });
    server.listen();

The later option is convenient when the HTTP shell is integrated in an existing HTTP server.

The HTTP term server by default is configured for serving:

- the `shell.html` page

- the `term.js` client library

- the `vertxshell.js` client library

The `vertxshell.js` integrates `term.js` is the client side part of the HTTP term.

It integrates `term.js` with SockJS and needs the URL of the HTTP term server endpoint:

    window.addEventListener('load', function () {
      var url = 'http://localhost/shell';
      new VertxTerm(url, {
        cols: 80,
        rows: 24
       });
     });

Straight websockets can also be used, if so, the remote term URL should be suffixed with `/websocket`:

    window.addEventListener('load', function () {
      var url = 'ws://localhost/shell/websocket';
      new VertxTerm(url, {
        cols: 80,
        rows: 24
       });
     });

For customization purpose these resources can be copied and customized, they are available in the Vert.x Shell jar under the `io.vertx.ext.shell` packages.

## Command discovery

The command discovery can be used when new commands need to be added to Vert.x without an explicit registration.

For example, the Dropwizard metrics service, adds specific metrics command to the shell service on the fly.

It can be achieved via the `java.util.ServiceLoader` of a `CommandResolverFactory`.

    public class CustomCommands implements CommandResolverFactory {

      public void resolver(Vertx vertx, Handler<AsyncResult<CommandResolver>> resolverHandler) {
        resolverHandler.handler(() -> Arrays.asList(myCommand1, myCommand2));
      }
    }

The `resolver` method is async, because the resolver may need to wait some condition before commands are resolved.

The shell service discovery using the service loader mechanism:

The service provider file `META-INF/services/io.vertx.ext.shell.spi.CommandResolverFactory`

    my.CustomCommands

This is only valid for the `ShellService`. `ShellServer` don’t use this mechanism.

## Command pack

A command pack is a jar that provides new Vert.x Shell commands.

Such jar just need to be present on the classpath and it is discovered by Vertx. Shell.

    package examples.pack;

    import io.vertx.core.AsyncResult;
    import io.vertx.core.Future;
    import io.vertx.core.Handler;
    import io.vertx.core.Vertx;
    import io.vertx.ext.shell.command.Command;
    import io.vertx.ext.shell.command.CommandBuilder;
    import io.vertx.ext.shell.command.CommandResolver;
    import io.vertx.ext.shell.spi.CommandResolverFactory;

    import java.util.ArrayList;
    import java.util.List;

    public class CommandPackExample implements CommandResolverFactory {

      @Override
      public void resolver(Vertx vertx, Handler<AsyncResult<CommandResolver>> resolveHandler) {
        List<Command> commands = new ArrayList<>();

        // Add commands
        commands.add(Command.create(vertx, JavaCommandExample.class));

        // Add another command
        commands.add(CommandBuilder.command("another-command").processHandler(process -> {
          // Handle process
        }).build(vertx));

        // Resolve with the commands
        resolveHandler.handle(Future.succeededFuture(() -> commands));
      }
    }

The command pack uses command discovery mechanism, so it needs the descriptor:

`META-INF/services/io.vertx.ext.shell.spi.CommandResolverFactory` descriptor

    examples.pack.CommandPackExample