Step 5. Exploring Persistence Settings

Time to complete this step: 15 minutes

The persistence.xml file defines the context for JPA persistence. In this step, you will use the JPA Persistence Configuration Editor to explore the persistence.xml file for your JPA web project.

The tasks in this step are:

• To Use the JPA Persistence Configuration Editor to View the Persistence Configuration File
• To View the Connection Properties
• To View JPA Mapping Files
• To View Configuration Properties
• To Understand Validation and Code Completion

To Use the JPA Persistence Configuration Editor to View the Persistence Configuration File

The JPA Persistence Configuration Editor provides a graphical interface that allows you to modify connection information, mapped classes, and JPA properties that are managed by your persistence.xml file. Optionally, you can also use the editor to edit the persistence.xml source file.

• On the AppXplorer view, right-click JPA Configuration and select Open.
  This will open the persistence.xml configuration file in the JPA Persistence Configuration Editor.



• You can also open the persistence.xml file by double-clicking it in the AppXplorer view. The persistence.xml file is located at this path:
  
  <project>/web/WEB-INF/src/java/META-INF



• The JPA Persistence Configuration Editor is organized in four category tabs:
• Connection — Edit the database connection information.
• Mappings — Edit information about mapped classes.
• Properties — Edit vendor-specific properties.
• Source — Edit the persistence.xml source directly.

To View the Connection Properties (Optional)

The Connection tab displays the current connection properties and allows you to modify the existing connection.

• To update the BEA Kodo connection information, click Edit Connection Properties.





• By clicking Populate from existing connection, you can use a connection that you've already set up using DbXplorer. Optionally, you can copy the database driver library and add it to your classpath, where it will be available to your persistence code.



 

To View JPA Mapping Files (Optional)

You can use the Mappings tab to view and modify mapped classes.

• Click the Mappings tab in the JPA Configuration Editor. The editor displays the list of Mapped Classes.
• To edit the JPA entity beans, select a mapped class from the list and the editor displays the corresponding Mapped Class Properties. Click Class Name to view the source code for the selected mapped class.
• The editor also allows you to add a new mapped class by clicking New Mapped Class and browsing to the class.

To View Configuration Properties (Optional)

In the JPA Configurations Editor, the Properties tab displays the current JPA configuration properties and their values through the form editor.

• Click the Properties tab in the JPA Configurations Editor.
• Selecting a configuration property will display the Configuration Property name and value, allowing you to edit them.



• To add additional properties, click the New Property button and specify the Name and Value or click the button to browse through a list of properties. The Select Property dialog displays all the list of Kodo properties with a description.

To Understand Validation and Code Completion (Optional)

The AppXRay provides validation and code completion in the JPA Configurations Editor. When you're editing in the Source tab, you're helped by code completion.

• Switch to the Source tab of the JPA Configurations Editor.
• Edit the line
  
  <class>com.bea.beans.Customer</class>
  
  to
  
  <class>com.bea.beans.Customer_New</class>
• As we have specified an invalid mapping file which does not exist either in the project or at the specified location, the Editor shows a warning. Reset the class to com.bea.beans.Customer. Save persistence.xml.
• When you're editing in the Source tab, you're helped by code completion when you press CTRL+SPACE.
• You can create a new child element of <persistence-unit> by typing a open angle bracket and seleting from the code completion drop down that appears, as shown below.

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