wicket-user-guide/src/docs/guide/resources/resources_13.gdoc

Wicket loads application's resources delegating this task to a resource locator represented by interface @org.apache.wicket.core.util.resource.locator.IResourceStreamLocator@. To retrieve or modify the current resource locator we can use the getter and setter methods defined by setting class @ResourceSettings@:

{code}
  //init application's method
  @Override
  public void init(){   
    //get the resource locator 
    getResourceSettings().getResourceStreamLocator();
    //set the resource locator    
    getResourceSettings().setResourceStreamLocator(myLocator);
  }
{code}

The default locator used by Wicket is class @ResourceStreamLocator@ which in turn tries to load a requested resource using a set of implementations of interface @IResourceFinder@. This interface defines method @find(Class class, String pathname)@ which tries to resolve a resource corresponding to the given class and path.

The default implementation of @IResourceFinder@ used by Wicket is @ClassPathResourceFinder@ which searches for resources into the application class path. This is the implementation we have used so far in our examples. However some developers may prefer storing markup files and other resources in a separate folder rather than placing them side by side with Java classes. 

To customize resource loading we can add further resource finders to our application in order to extend the resource-lookup algorithm to different locations. Wicket already comes with two other implementations of IResourceFinder designed to search for resources into a specific folder on the file system. The first is class @Path@ and it's defined in package @org.apache.wicket.util.file@. The constructor of this class takes in input an arbitrary folder that can be expressed as a string path or as an instance of Wicket utility class @Folder@ (in package @org.apache.wicket.util.file@). The second implementation of interface @IResourceFinder@ is class @WebApplicationPath@ which looks into a folder placed inside webapp's root path (but not inside folder WEB-INF).

Project CustomFolder4MarkupExample uses @WebApplicationPath@ to load the markup file and the resource bundle for its home page from a custom folder. The folder is called markupFolder and it is placed in the root path of the webapp. The following picture illustrates the file structure of the project:

!package-structure-custom-folder.png!

As we can see in the picture above, we must preserve the package structure also in the custom folder used as resource container. The code used inside application class to configure  WebApplicationPath is the following:

{code}
@Override
public void init()
{
	getResourceSettings().getResourceFinders().add(
			new WebApplicationPath(getServletContext(), "markupFolder"));
}
{code}

Method getResourceFinders() defined by setting class ResourceSettings returns the list of  resource finders defined in our application. The constructor of WebApplicationPath takes in input also an instance of standard interface javax.servlet.ServletContext which can be retrieved with WebApplication's method getServletContext().

{note}
By default, if resource files can not be found inside application classpath, Wicket will search for them inside “resources” folder. You may have noted this folder in the previous picture. It is placed next to the folder “java” containing our source files:

!package-structure-resource-folder.png!

This folder can be used to store resource files without writing any configuration code.
{note}