Class SingletonUtil


  • public final class SingletonUtil
    extends java.lang.Object
    Creates and maintains a unique instance of a given type for the given scope. The scope is either a UI session or an application context. Within the context of this scope, getUniqueInstance(...) will always return the same object, but for different scopes the returned instances will be different.

    This utility class can be used to adjust classic singletons to the appropriate scope in RAP. Example:

     public class FooSingleton {
    
       private FooSingleton() {
       }
    
       public static FooSingleton getInstance() {
         return SingletonUtil.getUniqueInstance( FooSingleton.class, RWT.getUISession() );
       }
     }
     
    Since:
    2.0
    • Constructor Summary

      Constructors 
      Constructor Description
      SingletonUtil()  
    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static <T> T getSessionInstance​(java.lang.Class<T> type)
      Returns an instance of the specified type that is unique within the current UI session.
      static <T> T getUniqueInstance​(java.lang.Class<T> type, ApplicationContext applicationContext)
      Returns an instance of the specified type that is unique within the given UI session.
      static <T> T getUniqueInstance​(java.lang.Class<T> type, UISession uiSession)
      Returns an instance of the specified type that is unique within the given UI session.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Constructor Detail

      • SingletonUtil

        public SingletonUtil()
    • Method Detail

      • getSessionInstance

        public static <T> T getSessionInstance​(java.lang.Class<T> type)
        Returns an instance of the specified type that is unique within the current UI session. If no such instance exists yet, a new one will be created. The specified type must have a parameterless constructor.

        This method is a shortcut for getUniqueInstance( type, RWT.getUISession() ).

        Parameters:
        type - the type to obtain a singleton instance for
        Returns:
        the unique instance of the specified type that is associated with the current UI session
      • getUniqueInstance

        public static <T> T getUniqueInstance​(java.lang.Class<T> type,
                                              UISession uiSession)
        Returns an instance of the specified type that is unique within the given UI session. If no such instance exists yet, a new one will be created. The specified type must have a parameterless constructor.
        Parameters:
        type - the type to obtain a singleton instance for
        uiSession - the UI session to store the singleton instance in
        Returns:
        the unique instance of the specified type that is associated with the given UI session
        Since:
        2.3
      • getUniqueInstance

        public static <T> T getUniqueInstance​(java.lang.Class<T> type,
                                              ApplicationContext applicationContext)
        Returns an instance of the specified type that is unique within the given UI session. If no such instance exists yet, a new one will be created. The specified type must have a parameterless constructor.
        Parameters:
        type - the type to obtain a singleton instance for
        applicationContext - the application context to store the singleton instance in
        Returns:
        the unique instance of the specified type that is associated with the given application context
        Since:
        2.3