Using the NetBeans Platform on the Server with Wicket on the Client

Now, let's have a look at the NetBeansPlatformUtils class. First, the method to install the Platform class loader:

    private final static URL[] NO_URLS = new URL[0];
    public static ClassLoader installPlatformClassLoader()
      {
        final ClassLoader classLoaderSave = new URLClassLoader(NO_URLS, Thread.currentThread().getContextClassLoader());
        Thread.currentThread().setContextClassLoader(Lookup.getDefault().lookup(ClassLoader.class));

        return classLoaderSave;
      }

The only note worth mentioning is that the Platform class loader is wrapped by a URLClassLoader: I've experienced some ClassCastExceptions by the JSP facility of Tomcat, that expects the relevant class loader to be URL - based. While I'm not interested in JSPs (and I noted that the exceptions were harmless for my application), the less obscure exceptions at runtime, the better.

Then, the boot() method, which just mimics the needed initialization parts performed by the NetBeans launcher:

    private static volatile boolean initialized;
    
    public synchronized static void boot (final ServletContext servletContext)
      throws Exception
      {
        if (!initialized)
          {
            initialized = true;
            final String fallbackNetBeansHome = servletContext.getInitParameter("netBeansHome");
            final String fallbackNetBeansUser = servletContext.getInitParameter("netBeansUserDir");
            final String netBeansHome = resolveProperties(System.getProperty("netbeans.home", fallbackNetBeansHome));
            final String netBeansUser = resolveProperties(System.getProperty("netbeans.user", fallbackNetBeansUser));
            final String netBeansDirs = findClusters(netBeansHome);
        
            System.setProperty("netbeans.osenv.nullsep", "false");
            System.setProperty("netbeans.home", netBeansHome);
            System.setProperty("netbeans.dirs", netBeansDirs);
            System.setProperty("netbeans.logger.console", "true");
            System.setProperty("netbeans.user", netBeansUser);

            new File(netBeansHome + "/config").mkdirs();
            new File(netBeansUser).getParentFile().mkdirs();
            
            org.netbeans.Main.main(new String[] { "--nosplash", "--userdir", netBeansUser });
          }

Worth mentioning is the "--nosplash" argument, that prevents the pop up window showing the initialization process from appearing at startup. The "netbeans.dirs" property must point to all the directories where a cluster (a set of related modules) has been prepared; you could statically configure this property with a property file, while I prefer to have it discovered at runtime (it's a matter of taste - I preferred this approach for blueMarine too, which has got a custom launcher):

    private static String findClusters (final String netBeansHome)
      throws IOException
      {
        final StringBuilder clusters = new StringBuilder();
        final File[] files = new File(netBeansHome).listFiles();

        if (files == null)
          {
            throw new IllegalArgumentException("Platform directory empty: " + netBeansHome);
          }

        for (final File file : files)
          {
            if (file.isDirectory())
              {
                final File updateTrackingFolder = new File(file, "update_tracking");

                if (updateTrackingFolder.exists())
                  {
                    // platform* is already added as the main directory
//                    if (!file.getName().startsWith("platform"))
                      {
                        if (clusters.length() > 0)
                          {
                            clusters.append(File.pathSeparator);
                          }

                        clusters.append(file.getCanonicalPath());
                      }
                  }
              }
          }

        final String buildDir = System.getProperty("netbeans.build.dir");

        if (buildDir != null)
          {
            clusters.append(File.pathSeparator);
            clusters.append(buildDir);
          }

        return clusters.toString();
      }

The boot code also needs to know about two directories, specified as parameters:

1. "netBeansHome": where the Platform runtime is installed (root of all clusters)
2. "netBeansUserDir": where the Platform configuration files will be placed (and, eventually, the application ones too).

For convenience, I've implemented a simple macro-substitution facility for system properties - you'll see later that this is pretty useful for facilitating both development and deployment:

    private static String resolveProperties (final String string)
      {
        String result = string;

        for (final Entry<Object, Object> entry : System.getProperties().entrySet())
          {
            final String propertyName = (String)entry.getKey();
            final String propertyValue = (String)entry.getValue();
            result = result.replace("{" + propertyName +"}", propertyValue);
          }

        return result;
      }