Service for loading resources in the applications

Objectives

Lutece provides a base implementation for internal services to applcations, allowing them to load their resources. For example , the calendar plugin manages agendas and has an AgendaService service which enables it to load resources, in this case from agenda by means of an identfier.

The aims of this base implementation called Resource Service are to provide :

  • An abstraction layer as long as the loading strategy od resources. These resources can be loaded from files, database etc.. Each loading strategy refers to an implementation of a ResourceLoader. It is possible to combine many loading strategies.
  • An integrated cache to optimize resource access. The cache of each service can be administered from the Cache Management feature of Lutece.
  • Configuration facilities of the service (name, cache activation, ... ) based upon property files.

Here is the class diagram of the API :

Implementation of ResourceService

Here is a minimal implementation of a service under a singleton form. 

public class MyResourceService extends ResourceService
{
    private static MyResourceService _singleton = new MyResourceService
    private static final String PROPERTY_NAME = "myplugin.service.name";
    private static final String PROPERTY_CACHE = "myplugin.service.cache";
    private static final String PROPERTY_LOADERS = "myplugin.service.loaders";

    /**
     * Private constructor
     */
    private MyResourceService
    {
        super();
        setCacheKey( PROPERTY_CACHE );
        setNameKey( PROPERTY_NAME );
    }

    /**
     * Returns the instance of the singleton
     *
     * @return The instance of the singleton
     */
    public static MyResourceService getInstance()
    {
        return _singleton;
    }

    /**
     * Returns the property key that contains the loaders list
     * @return A property key
     */
    protected String getLoadersProperty(  )
    {
        return PROPERTY_LOADERS;
    }

    /**
     * Returns the Resource corresponding to the given name
     *
     * @param strResourceName The resource name
     * @return the Resource corresponding to the given name
     */
    public MyResource getMyResource( String strResourceName )
    {
        return  ( MyResource ) getResource( strResourceName );
    }

La configuration du service se fait dans le fichier properties. Les valeurs de base à configurer sont :

Elément de configuration Exemple dans le fichier properties
Nom du service myplugin.service.name=Plugin MyPlugin - MyResources Loading Service
Activation du cache myplugin.service.cache=true
Liste des loaders myplugin.service.loaders=com.mycompany.myapp.service.MyResourceLoader

Implémentation d'un ResourceLoader

L'implémentation minimum d'un ResourceLoader est la suivante : 

import fr.paris.lutece.portal.service.resource.Resource;
import fr.paris.lutece.portal.service.resource.ResourceLoader;

import java.util.ArrayList;

/**
 * MyResourceLoader
 */
public class MyResourceLoader implements ResourceLoader
{

    /**
     * Implementation of the ResourceLoader interface
     * @return A collection of resources
     */
    public Collection getResources(  )
    {
        // Build a collection of all resources available by this loader
        ArrayList listResources = new ArrayList(  );
        ...
        return listResources
    }

    /**
     * Implementation of the ResourceLoader interface
     * @param strId The resource Id
     * @return The Resource
     */
    public Resource getResource( String strId )
    {
        ...
    }
}

Centralized cache management

Here is a centralized view of cache management of the Lutece's Administration module including Resource Services.