Frank Nimphius>, Oracle Corporation
The sample workspace built for this how-to document shows a table that updates a declarative component whenever the row currency changes. The declarative component shows the first name, last name and mail information of the current user. Following this how-to document and downloading the sample workspace you learn how to create and deploy declarative components, how to use attribute bindings to reference the current row of a table and how to enable PPR for declarative components.
You create a declarative component as described in Shay Shmeltzer's online tutorial. To reuse a declarative component, it needs to be deployed in an ADF Library that is created from its own project in this example. The technology scope of this project is set to "ADF Faces".
On the project root, choose New from the context menu to access the Oracle Jdeveloper New Gallery. Under the JSF node, select the JSF Declarative Component option to start the wizard that leads you through the initial component creation.
Fill in the component template to provide a name for the component, UserInfo in this example, a file name and package structure. The custom component is added as a tag library after deployment, which is why you need to use the Add Tag Library button to define the library's name, namespace and prefix.
For the declarative component you can create attributes, facets and methods as needed. This can be done later on as well using the property palette. Use attributes to pass data in from the outside to the declarative components, which is what we use within this example. Use a facet for the application developer to be able to add other components as child components to your declarative component. This option is useful if your declarative component is a composite layout container you created to enforce a consistent layout for a specific functionality in a JSF page. Similar, you use methods to map action command contained in the declarative component to a method accessible through Expression Language on the containing page.
Once the declarative component is configured and shows in the visual editor of Oracle JDeveloper 11, you can use the property palette to further edit or add facet definitions, attributes and methods. The screenshot below shows the property palette as it is current in Oracle JDeveloper 11 TP4. The property palette's look and feel will change in releases after TP4, though the exposed information remains.
For this example, I created a panel box with 3 text fields to show the user information. I could have added a submit button to perform updates to the data as well. Selecting a text field in the visual editor - or the structure window - allows you to use the Expression Builder from the property palette to map the component's value property with one of the defined attributes. Any change to the attribute's value from then on shows in the text field as its value.
As you see, the defined attributes show under the attrs node of the JSP Object node for easy access. Select an attribute and press the Insert button or double click onto the attribute to build the Expression Language reference to it.
Once the declarative component is done, double click onto the project node, or choose Properties from the context menu, to open the project's properties. Choose the Deployment node to create a new deployment profile, which you set to be of type ADF Library JAR file.
After deploying the library, you'll find the generated JAR in the deploy directory of the declarative component project. At least for Oracle JDeveloper 11 TP4, make sure that the deploy directory is within a path that does not contain a blank character or copy the generated JAR file to a directory that doesn't contain one. This restriction will be addressed in a later version of Oracle JDeveloper 11.
That is all what it takes to build a new declarative JavaServer Faces component, ready to be used in a web application project. The really nice to say about declarative components is that it allows you to create reusable building blocks for your personal application development the easy way without copy and pasting code snippets between projects.
To add a declarative component to the Oracle JDeveloper web project, you need to import the created ADF Library jar file and the contained tag library. While this can be done through the Manage Libraries option of the Tools menu, there is an even more elegant option, which is to build a new IDE connection to a directory on the file system. Using an IDE connection you create a resource catalog reference that allows you to easily browse and search for existing declarative components to add them to the project.
Following the instructions shown in the image above (Use View | Resource Palette to open the resource catalog window), you create a new File System connection by clicking onto the Create folder icon and choosing New Connection from the context menu.
Create a new IDE connection and point the directory path to the directory that contains the ADF library file for the declarative component you just created. You can test the connection to ensure no typo prevents accessing the resources.
Select the web application project and expand the File System node. It shows a sub node with the name of the create IDE connection name. Below this node you find the deployed declarative component JAr file entry. Select it and choose Add to Active Project from the context menu to add the library to the current web application project.
Soon after the ADF library gets imported in Oracle JDeveloper, a new node shows in the Component Palette for you to add the contained declarative components to the web application project.
Note that in this example, the user info panel appears read only, which means that no additional ADF Faces components can be added to it. This is because the example uses attributes to pass data in, but no facets to add nested components. If you want to allow developers to add ADF Faces components to your declarative component, in which case your declarative component becomes the parent of the added component, you need to add a facet to the declarative component.
The really cool feature of declarative components is that selecting the declarative component in Oracle JDeveloper, using the visual editor or the Structure window, the property inspector (ctrl+shift+P) exposes the defined attributes and methods as properties. In above image the FirstName, LastName and Mail attributes are exposed in the property inspector.
While you could have added hard coded values to the exposed attribute properties of the declarative component, using a Expression Language string to look up the ADF binding layer is closer to what your requirements would be in a production environment.
In the example provided with this document, the web page consists of a splitter component, with an ADF bound table added to the first splitter area. A page definition file exists and we navigate to this fie to add additional attribute bindings that are then referenced by the declarative component.
Note that the table binding uses a single node tree binding, which is bound to the EmployesView1 iterator. Selecting a row in the table always sets this row as the current row in the underlying iterator. The action performed for this uses partial page rendering (its doing the Ajax thing if you want to see it this way), which means that no page reload is required for this. All that we need to wire up the declarative component properties to the current row in the iterator is to create a "window" to the current row. This " window" is built through attribute bindings that expose a single attribute to the binding layer.
After creating attribute bindings for the the FirstName, LastName and Email attribute or the ViewObject, you are good to bind the declarative component's exposed properties to ADF. For this you use the property palette and choose Expression Builder from the context menu (click onto the black triangle icon).
It is important to node that you bind the attributes to the attribute binding's inputValue property. To use the attribute binding itself is a frequent error among application developers that use ADF. Data is accessed through the inputValue property of the attribute binding.
Once all of the declarative component's attribute are bound to attribute bindings in ADF, your are done with this part of the job. All that is missing is to ensure the declarative component gets refreshed as soon as the row currency of the table changes.
Declarative components themselves don't provide a partial page refresh property that you can set to the ID value of a triggering component. However, you can wrap the declarative component with a component that does support PPR. In this example I surrounded the declarative component with a PanelGroupLayout component to then reference the table's ID property form the Partial Trigger property.
You can choose any layout container as a wrapper for the declarative component.
You can use the Edit option of the wrapper component's Partial Trigger Property to browse the page's component tree for the component that triggers the refresh. Note that this approach is less error prone than typing the ID reference in directly because chances are that the triggering component itself is wrapped in a container, like panelCollection in the table case.
While you can define the ID property for the table component within this working step, note that because of a refresh problem in Oracle JDeveloper 11 TP4, you will have to run the dialog twice to get the EL reference created. In this case it is better to define the table's ID property before opening the Expression Language builder on the partial trigger property of the panelGroupLayout.
This is it then. At runtime, changing the row selection in the table now will update the declarative component.
Running the provided example against the HR sample schema shows the following screen.
The example workspace used in this how-to document is provided below. Edit the connection property to meet your HR data schema configuration.
|Shay Shmeltzer's Declarative Component demo|
|Chapter 17 of the Web Developer Guide|