[jira] [Comment Edited] (WICKET-5866) Reconsider generics of IConverterLocator#getConverter()

["Sven Meier (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/WICKET-5866?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15385697#comment-15385697 ] 

Sven Meier edited comment on WICKET-5866 at 7/21/16 7:57 AM:
-------------------------------------------------------------

We could ease the pain with a new factory method on Component:

{code}
	/**
	 * Get the converter that should be used by this component, delegates to
	 * {@link #createConverter(Class)} and then to the applications
	 * {@link IConverterLocator}.
	 * 
	 * @param type
	 *            The type to convert to
	 * 
	 * @return The converter that should be used by this component
	 */
	@SuppressWarnings("unchecked")
	@Override
	public <C> IConverter<C> getConverter(Class<C> type) {
		IConverter<?> converter = createConverter(type);
		if (converter != null) {
			return (IConverter<C>) converter;
		}
		return getApplication().getConverterLocator().getConverter(type);
	}

	/**
	 * Factory method for converters to be used by this component.
	 *
	 * parameter - returns {@code null} by default.
	 * 
	 * @param type
	 *            The type to convert to
	 * 
	 * @return a converter to be used by this component
	 */
	protected IConverter<?> createConverter(Class<?> type) {
		return null;
	}
{code}


was (Author: svenmeier):
We could ease the pain with a new method on Component:

{code}
	/**
	 * Gets the converter that should be used by this component.
	 * 
	 * @param type
	 *            The type to convert to
	 * 
	 * @return The converter that should be used by this component
	 * 
	 * @see #getRawConverter(Class)
	 */
	@SuppressWarnings("unchecked")
	@Override
	public <C> IConverter<C> getConverter(Class<C> type) {
		IConverter<?> converter = getRawConverter(type);
		if (converter == null) {
			return (IConverter<C>) converter;
		}
		return getApplication().getConverterLocator().getConverter(type);
	}

	/**
	 * Convenience method to allow usage of converters without generic type
	 * parameter - returns {@code null} by default.
	 * 
	 * @param type
	 *            The type to convert to
	 * 
	 * @return The converter that should be used by this component
	 */
	protected IConverter<?> getRawConverter(Class<?> type) {
		return null;
	}
{code}

> Reconsider generics of IConverterLocator#getConverter()
> -------------------------------------------------------
>
>                 Key: WICKET-5866
>                 URL: https://issues.apache.org/jira/browse/WICKET-5866
>             Project: Wicket
>          Issue Type: Improvement
>          Components: wicket
>    Affects Versions: 7.0.0
>            Reporter: Sven Meier
>            Assignee: Sven Meier
>            Priority: Minor
>             Fix For: 8.0.0-M2
>
>
> IConverterLocator#getConverter() has a generic parameter <C> currently.
> It seems to me that this is not very useful: almost all code calling #getConverter() does not care for the type parameter.
> From the user perspective it's very common to override Component#getConverter(). With the need for a cast and to suppress the generics warning, providing a custom converter is much too hard currently:
> {code}
>     public <C> IConverter<C> getConverter(Class<C> clazz)
>      {
>          if (Date.class.isAssignableFrom(clazz))
>          {
>              @SuppressWarnings("unchecked")
>              return (IConverter<C>)new DateConverter();
>          }
>          else
>          {
>              return super.getConverter(clazz);
>          }
>      }
> {code}
> I propose to remove the generics parameter from the method:
> {code}
>     public IConverter<?> getConverter(Class<?> clazz)
>      {
>          if (Date.class.isAssignableFrom(clazz))
>          {
>              return new DateConverter();
>          }
>          else
>          {
>              return super.getConverter(clazz);
>          }
>      }
> {code}



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