Re: How to load .page files at runtime...

[Eduardo Lobo]

Originally I had a problem to load specification files(.page) at runtime 
located in external JAR files.

Finally I found a solution by myself, if somebody is interested in it 
here is.

First, you must extends the ApplicationServlet class overloading the 
createResourceResolver() method to return your own IResourceResolver 
implementation.
(Of course you must use this new servlet class for your Tapestry 
application).
<!-- Sample -->
<servlet>
       <servlet-name>app</servlet-name>
       <servlet-class>com.project.web.SiteManagerServlet</servlet-class>
 </servlet>

Here is my IResourceResolver implementation:
public class MyResourceResolver extends DefaultResourceResolver {
   private ClassLoader currentLoader;
   private ClassLoader parentLoader;
  
   public MyResourceResolver () {
       currentLoader = Thread.currentThread().getContextClassLoader();
       parentLoader = 
Thread.currentThread().getContextClassLoader().getParent();
   }
  
   public MyResourceResolver (ClassLoader loader) {
       currentLoader = loader;
       parentLoader = loader.getParent();
   }
  
   public URL getResource(String name){
      
       String stripped = removeLeadingSlash(name);
      
       URL result = currentLoader.getResource(stripped);
       if(result == null){
           result = parentLoader.getResource(stripped);
       }
        
       return result;
   }

   private String removeLeadingSlash(String name){
      
       while (name.startsWith("/")) {
           return name.substring(1);
       }

       return name;
   }
  
   public Class findClass(String name)
   {
       try
       {
           Class clazz = Class.forName(name, true, currentLoader);
           if(clazz == null){
               clazz = Class.forName(name, true, parentLoader);
           }
          
           return clazz;
       }
       catch (Throwable t)
       {
           throw new ApplicationRuntimeException(
               Tapestry.format("ResourceResolver.unable-to-load-class", 
name, currentLoader, t.getMessage()),
               t);
       }
   }

   public Class classForName(String name, Map map) throws 
ClassNotFoundException
   {
       return findClass(name);
   }
  
   public ClassLoader getClassLoader()
   {
       return currentLoader;
   }

}
Library file sample (external JAR):
   <library-specification>  
       <page name="SamplePage" specification-path="SamplePage.page"/>
         .....
   <library-specification>

Loader:
       ISpecificationSource spec = getEngine().getSpecificationSource();
       IApplicationSpecification app = getEngine().getSpecification();
      
       IResourceLocation location =
           new 
ClasspathResourceLocation(getEngine().getResourceResolver(),
                   "com/project/sample.library");
      
       ILibrarySpecification ls = 
getEngine().getSpecificationSource().getLibrarySpecification(location);
       INamespace namespace = spec.getApplicationNamespace();
      
       Iterator it = ls.getPageNames().iterator();
      
       while(it.hasNext()){
           String name = (String) it.next();
           String path = ls.getPageSpecificationPath(name);
          
           try{
              
               IResourceLocation loc =
                   new 
ClasspathResourceLocation(getEngine().getResourceResolver(),
                           "com/project/" + path); // the .page files 
are located in the same package of the .library file
              
               IComponentSpecification component = 
getEngine().getSpecificationSource().getPageSpecification(loc);
              
               namespace.installPageSpecification(name, component);
              
           } catch(Exception e){
               logger.debug("installing exception: " + e.getMessage());
           }
       }


Eduardo Lobo wrote:
Hi,
I'm making an application that needs to load war files as plugins for 
the tapestry application to load them without making a new deploy or 
restarting the application server

Does anybody knows how to load pages at runtime, or another way to do 
this?

Thanks in advance.

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