Cayenne User Documentation
DataViews in Action

Here we illustrate the discussion of DataViews with configuration samples and code snippets. Cayenne project DTD file supports references to data view configuration files. This information is loaded into the Cayenne Configuration instance along with the DataDomain, DataNode, and DataMap entries. Since the DataView functionality is optional and would not be very useful in some deployment scenarios (server-side applications) the DataView configiuration itself is not loaded at the time of initialization. Neither DataView instances are created by the configuration process. A DataView can be created in a Swing application with the code similar to the following:

    //Assume, this is your Cayenne Configuration instance.
    Configuration cayenneConfiguration = ...;

    //You will need to setup a Cayenne EntityResolver in your DataView
    //For example you can retrieve it from the DataContext in use
    //with dataContext.getEntityResolver();
    //or construct your own composite one, spanning several Data Domains.
    EntityResolver entityResolver = ...;

    //Create new DataView instance, and set its entityResolver
    //*before* loading the actual configuration
    DataView dataView = new DataView();
    dataView.setEntityResolver(entityResolver);

    //Load the configuration
    cayenneConfiguration.loadDataView(dataView);

    //Here we go. Our Data View is ready to be used in the application
    //This way you can create several of them, completely separated if needed.

It is worth mentioning one instance of DataView serves to incorporate several Data View configurations saved in different files. Therefore it defines single namespace and easily resolves inter-configuration references among the ObjEntityViews

Next, let us see how a Swing table model and JTable can be configured with our Data View to display and edit a list of data objects.

    DataView dataView = ...;

    JTable featureTable = ...;
    ObjEntityView featureView = dataView.getObjEntityView("ProductFeatureView");

    // This is a descendant of javax.swing.table.AbstractTableModel
    DOTableModel tableModel = new DOTableModel();
    tableModel.setView(featureView);

    // Retrieve a list of data objects (with SelectQuery, say)
    // and initialize the model with it
    DataObjectList featureDataObjects = ...;
    tableModel.setDataObjects(matrixEntries);

    featureTable.setModel(tableModel);

    // set the apropriate TableCellRenderers and Editors
    new CellRenderers().installRenderers(featureTable);
    new CellEditors().installEditors(featureTable);

In fact, there is many more cool things you could do with DataViews to build your Cayenne enabled Swing rich client faster and cleaner, and separate the GUI related stuff from your domain logic defining the clear declarative rules telling the framework how to interprete, render, and edit the ObjEntities and DataObjects your application relies upon.

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