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   <div class="content">
 <article class="doc">
 <h1 class="page">RFC 147 Overview</h1>
 <div id="preamble">
 <div class="sectionbody">
 <div class="paragraph">
 <p>The RFC-147 draft is not yet publicly available.
 It used to be called RFC-132, which can be found in an <a href="http://www.osgi.org/download/osgi-4.2-early-draft.pdf">early specification draft</a></p>
 </div>
 <div class="paragraph">
 <p>This is an overview of its main features:</p>
 </div>
 </div>
 </div>
 <div class="sect1">
 <h2 id="_standard_way_to_implement_and_run_commands_for_any_osgi_4_2_framework"><a class="anchor" href="#_standard_way_to_implement_and_run_commands_for_any_osgi_4_2_framework"></a>Standard way to implement and run commands for any OSGi 4.2 framework</h2>
 <div class="sectionbody">
 <div class="paragraph">
 <p>Commands are registered via service attributes, you don&#8217;t have to register a specific service.
 This allows commands to be registered by existing services, just by adding the new attributes:</p>
 </div>
 <div class="listingblock">
 <div class="content">
 <pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java"> Dictionary&lt;String, Object&gt; dict = new Hashtable&lt;String, Object&gt;();
  dict.put(CommandProcessor.COMMAND_SCOPE, "shell");
  dict.put(CommandProcessor.COMMAND_FUNCTION, new String[] {"sleep", "grep"});
  context.registerService(name, service, dict);</code></pre>
 </div>
 </div>
 <div class="paragraph">
 <p>Scope is used to provide a namespace for commands.
 The commands above can be invoked as <code>shell:sleep</code> and <code>shell:grep</code>.
 If the scope is omitted (e.g.
 <code>sleep</code> and <code>grep</code>) then the first matching command is invoked.</p>
 </div>
 <div class="sect2">
 <h3 id="_commands_can_have_any_signature"><a class="anchor" href="#_commands_can_have_any_signature"></a>Commands can have any signature</h3>
 <div class="paragraph">
 <p>Arguments are coerced to call the best matching method using reflection.
 A <code>CommandSession</code> argument is inserted if required:</p>
 </div>
 <div class="listingblock">
 <div class="content">
 <pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">public void sleep(long millis) throws InterruptedException{
     Thread.sleep(millis);
 }

 public void sleep(String[] args) throws Exception;

 public boolean grep(CommandSession session, String[] args) throws Exception;</code></pre>
 </div>
 </div>
 <div class="paragraph">
 <p>The <code>CommandSession</code> interface provides methods for executing commands and getting and setting session variables:</p>
 </div>
 <div class="listingblock">
 <div class="content">
 <pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java"> public interface org.apache.felix.service.command.CommandSession {
      Object execute(CharSequence commandline) throws Exception;
      Object get(String name);
      void put(String name, Object value);
      ...
  }</code></pre>
 </div>
 </div>
 </div>
 <div class="sect2">
 <h3 id="_easy_to_use_interactively_no_unnecessary_syntax"><a class="anchor" href="#_easy_to_use_interactively_no_unnecessary_syntax"></a>Easy to use interactively - no unnecessary syntax</h3>
 <div class="ulist">
 <ul>
 <li>
 <p>basic commands</p>
 </li>
 </ul>
 </div>
 <div class="paragraph">
 <p>[source,sh]ell
    g! echo hello world
    hello world</p>
 </div>
 <div class="ulist">
 <ul>
 <li>
 <p>session variables</p>
 </li>
 </ul>
 </div>
 <div class="paragraph">
 <p>[source,sh]ell
    g! msg = "hello world"
    g! echo $msg
    hello world</p>
 </div>
 <div class="ulist">
 <ul>
 <li>
 <p>execution quotes <code>()</code> - similar to bash backquotes</p>
 </li>
 </ul>
 </div>
 <div class="paragraph">
 <p>[source,sh]ell
    g! (bundle 1) location
    file:/Users/derek/Downloads/felix-framework-3.0.0/bundle/org.apache.felix.bundlerepository-1.6.2.jar</p>
 </div>
 </div>
 <div class="sect2">
 <h3 id="_lists_maps_pipes_and_closures"><a class="anchor" href="#_lists_maps_pipes_and_closures"></a>Lists, maps, pipes and closures</h3>
 <div class="ulist">
 <ul>
 <li>
 <p>lists - <code>[]</code></p>
 </li>
 </ul>
 </div>
 <div class="paragraph">
 <p>[source,sh]ell
    g! list = [1 2 a b]
    1
    2
    a
    b</p>
 </div>
 <div class="ulist">
 <ul>
 <li>
 <p>maps - <code>[]</code></p>
 </li>
 </ul>
 </div>
 <div class="paragraph">
 <p>[source,sh]ell
    g! map = [Jan=1 Feb=2 Mar=3]
    Jan                 1
    Feb                 2
    Mar                 3</p>
 </div>
 <div class="ulist">
 <ul>
 <li>
 <p>pipes - <code>|</code></p>
 </li>
 </ul>
 </div>
 <div class="paragraph">
 <p>[source,sh]ell
    g! bundles | grep gogo
        2|Active     |    1|org.apache.felix.gogo.command (0.6.0)
        3|Active     |    1|org.apache.felix.gogo.runtime (0.6.0)
        4|Active     |    1|org.apache.felix.gogo.shell (0.6.0)</p>
 </div>
 <div class="ulist">
 <ul>
 <li>
 <p>closures - <code>{}</code></p>
 </li>
 </ul>
 </div>
 <div class="paragraph">
 <p>[source,sh]ell
    g! echo2 = { echo xxx $args yyy }
    g! echo2 hello world
    xxx hello world yyy</p>
 </div>
 </div>
 <div class="sect2">
 <h3 id="_leverages_existing_java_capabilities_via_reflection"><a class="anchor" href="#_leverages_existing_java_capabilities_via_reflection"></a>Leverages existing Java capabilities, via reflection</h3>
 <div class="ulist">
 <ul>
 <li>
 <p>exception handling - console shows summary, but full context available</p>
 </li>
 </ul>
 </div>
 <div class="paragraph">
 <p>[source,sh]ell
    g! start xxx
    E: Cannot coerce start[xxx] to any of [(Bundle)]
    g! $exception printstacktrace
    java.lang.IllegalArgumentException: Cannot coerce start[xxx] to any of [(Bundle)]
            at org.apache.felix.gogo.runtime.shell.Reflective.method(Reflective.java:162)
            at org.apache.felix.gogo.runtime.shell.Command.execute(Command.java:40)
            at org.apache.felix.gogo.runtime.shell.Closure.execute(Closure.java:211)
            at org.apache.felix.gogo.runtime.shell.Closure.executeStatement(Closure.java:146)
            at org.apache.felix.gogo.runtime.shell.Pipe.run(Pipe.java:91)
    &#8230;&#8203;</p>
 </div>
 <div class="ulist">
 <ul>
 <li>
 <p>add all public methods on <code>java.lang.System</code> as commands:</p>
 </li>
 </ul>
 </div>
 <div class="paragraph">
 <p>[source,sh]ell
    g! addcommand system (loadClass java.lang.System)
    g! system:getproperties
    sun.io.unicode.encodingUnicodeLittle
    java.version        1.5.0_19
    java.class.path     bin/felix.jar
    java.awt.graphicsenvapple.awt.CGraphicsEnvironment
    user.language       en
    sun.os.patch.level  unknown
    os.version          10.6.2
    [snip]</p>
 </div>
 </div>
 <div class="sect2">
 <h3 id="_easy_to_implement_and_test_commands_without_needing_osgi"><a class="anchor" href="#_easy_to_implement_and_test_commands_without_needing_osgi"></a>Easy to implement and test commands without needing OSGi</h3>
 <div class="paragraph">
 <p>Command implementations don&#8217;t need to reference any OSGi interfaces.
 They can use <code>System.in</code>, <code>System.out</code> and <code>System.err</code>, just as you would in a trivial Java application.
 The <code>ThreadIO</code> service transparently manages the singleton <code>System.out</code> etc, so that each thread sees the appropriate stream:</p>
 </div>
 <div class="listingblock">
 <div class="content">
 <pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java"> public void cat(String[] args) throws Exception {
      for (String arg : args) {
          IOUtil.copy(arg, System.out);
      }
  }</code></pre>
 </div>
 </div>
 </div>
 <div class="sect2">
 <h3 id="_normal_commands_can_provide_control_primitives"><a class="anchor" href="#_normal_commands_can_provide_control_primitives"></a>Normal commands can provide control primitives</h3>
 <div class="listingblock">
 <div class="content">
 <pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java"> public void each(CommandSession session, Collection&lt;Object&gt; list, Function closure) throws Exception {
      for (Object x : list) {
          closure.execute(session, null);
      }
  }</code></pre>
 </div>
 </div>
 <div class="paragraph">
 <p>then</p>
 </div>
 <div class="paragraph">
 <p>[source,sh]ell
  g! each [Jan Feb Mar] { echo $it | grep . }
  Jan
  Feb
  Mar</p>
 </div>
 <div class="admonitionblock note">
 <table>
 <tr>
 <td class="icon">
 <i class="fa icon-note" title="Note"></i>
 </td>
 <td class="content">
 The default <em>echo</em> command <em>returns</em> a String and does not write to System.out.
 Also, by default, the console prints the results of each command, so <em>echo</em> appears to behave as you would expect.
 However, the console does not see the <em>each</em> closure above, so the result of echo would not be seen.
 This is why it is piped into <em>grep</em>, as the <em>result</em> of the command as well as its output is written to a pipeline.
 </td>
 </tr>
 </table>
 </div>
 </div>
 </div>
 </div>
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