[jira] [Commented] (WICKET-4802) Standard IDataColumn

["Jesse Long (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/WICKET-4802?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13473108#comment-13473108 ] 

Jesse Long commented on WICKET-4802:
------------------------------------

There are actually 2 use cases for a standard exportable column type:

1. Allows libraries to provide columns that can be exported by all Wicket apps.
2. Allows libraries to provide exporting code that can export columns in all Wicket apps (Think export to Microsoft Excel library).

I have started implementing this idea here: https://github.com/jesselong/wicket/tree/datatable-export

Its untested, not nicely formatted, undocumented etc, I'll update more when I have time.
                
> Standard IDataColumn
> --------------------
>
>                 Key: WICKET-4802
>                 URL: https://issues.apache.org/jira/browse/WICKET-4802
>             Project: Wicket
>          Issue Type: New Feature
>          Components: wicket-extensions
>    Affects Versions: 6.1.0
>            Reporter: Jesse Long
>            Priority: Minor
>
> In Igor's book he describes a way of exporting a data table to CSV. It requires tagging exportable columns with a interface, which allows retrieving of the data for the column by passing it the row model.
> I, and I'm sure many others, have implemented this functionality, and we all have our own CSVExportToolbar, or something similar. The problem is that each export implementation is checking for instances of their own hand-crafted IDataColumn interface. This makes it difficult for people to write libraries that provide columns that will be exportable across the board.
> I propose that we add a standard IDataColumn that can be used to tagging exportable columns, and which every CSVExportToolbar and ExcelExportToolbar etc can check for when determining which columns to use to export.
> Something like:
> /** does not need sort parameter, does not need to extend IColumn */
> public interface IDataColumn<R, T>
> {
>     /** get data for row by passing row model, in imodel format to allow this method to be used for rendering in an abstract implementation. */
>     IModel<T> getDataModel(IModel<R> rowModel);
>     /** get column header, useful in exporting. same signature as AbstractColumn method */
>     IModel<String> getDisplayModel();
> }
> Then an abstract implementation, where the user only needs to implement getDataModel()
> public abstract class AbstractDataColumn<R, S, T>
> extends AbstractColumn<R, S>
> implements IDataColumn<R, T>
> {
>     // normal AbstractColumn constructors.
>     protected Component createNewDisplayComponent(String componentId, IModel<T> dataModel)
>     {
>         return new Label(componentId, dataModel);
>     }
>     @Override
>     public void populateItem(Item<ICellPopulator<R>> cellItem, String componentId, IModel<R> rowModel)
>     {
>         cellItem.add(createNewDisplayComponent(componentId, getDataModel(rowModel)));
>     }
> }

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