Deploying Java Applets

As an alternative, you can also dynamically load the JNLP classes using reflection as shown in this code excerpt from classJnlpProxyin packagecom.croftsoft.core.jnlp.

  private static Object getBasicServiceObject ( )
  //////////////////////////////////////////////////////////////////////
  {
    try
    {
      Class  serviceManagerClass
        = Class.forName ( "javax.jnlp.ServiceManager" );

      Method  lookupMethod = serviceManagerClass.getMethod (
        "lookup", new Class [ ] { String.class } );

      return lookupMethod.invoke (
        null, new Object [ ] { "javax.jnlp.BasicService" } );
    }
    catch ( Exception ex )
    {
      return null;
    }
  }

ClassMethodis from core packagejava.lang.reflect.

  public static boolean showDocument ( URL url )
  //////////////////////////////////////////////////////////////////////
  {
    if ( basicServiceObject == null )
    {
      return false;
    }

    try
    {
      Method  method = basicServiceClass.getMethod (
        "showDocument", new Class [ ] { URL.class } );

      Boolean  resultBoolean = ( Boolean ) method.invoke (
        basicServiceObject, new Object [ ] { url } );

      return resultBoolean.booleanValue ( );
    }
    catch ( Exception ex )
    {
      ex.printStackTrace ( );

      throw new RuntimeException ( ex.getMessage ( ) );
    }
  }

By saving a singleton static reference to theBasicServiceinstance retrieved, we can then use it within our own staticshowDocument()method. The example method returnsfalseif the client platform does not support JNLP, allowing the calling code to respond with a substitute behavior.

In my opinion, dynamic linking using custom interfaces instead of reflection makes for more comprehensible code. I have found that you almost never need reflection techniques if you keep this in mind.

Please check back next week for the conclusion to this article.