Oracle Enterprise Pack for Eclipse allows you to view, create, and manage JPA entity relationships. The Entity Editor provides a centralized view of all entity relationships, allows you to modify entity properties, and allows you to navigate between the object model, mapping associations, and database schema layers.

The tasks you will complete in this step are:

• View an entity relationship diagram, using the Entity Editor
• View the properties of JPA persistent entities, using the Entity Editor and the JPA Details View
• Manage JPA entity mappings

View an Entity Relationship Diagram, Using the Entity Editor
As described previously, the Entity Editor displays relationship diagrams for entities defined in the project.

1. In the Project Explorer view, expand oepe-jpa-tutorial > JPA >Show in Entity Editor. Oracle Enterprise Pack for Eclipse provides a list of entities under the Entities branch based on the entities defined in the Persistence configurations file.

The JPA Persistence Entity Editor displays all entity relationships defined in the Web application. Each box displays a specific entity, its properties, and an icon denoting the nature of the relationship.

2. The JPA Persistence Entity Editor displays and selects property types for an entity by using tool tip popups. You can work with entity relationship diagrams by selecting operations such as Zoom In, Zoom Out, Export to Image, and Print. To view a tool tip, hover your cursor over the respective entity. To view and edit the details, use the JPA Details View.

The JPA Persistence Entity Editor also allows you to filter relationships between entities. This feature helps you simplify your view of the diagram when it is large and complex.

3. Click Filters and select the options Many to One and One to Many to filter which entity relationships are noted in the diagram.

4. Reset both filters.

View and Edit JPA Persistent Entities, Using the Entity Editor
Using the JPA Details View, you can easily edit entity properties.

1. Select the Contact entity in the JPA Entity Editor.
2. Click the Properties tab to view the JPA Details view. The JPA Details View displays the properties for the Contact entity.

3. With the JPA Details view, you can edit the associated Java Bean class, strategy for persistence, and the database access information for the selected entity. To edit, either enter text in the text box or click on the dropdown lists for the schema binding, Primary Key Generation, Sequence Generators, Queries, etc.
4. In the JPA Persistence Entity Editor, select the phone property of the Contact entity. The JPA Details view displays properties of the phone property. Observe the properties.



5. Use the JPA Details view to modify the Length of phone property. For example:
   • Set Nullable to false
   • Update the Length value from 20 to 25
   • Press CTRL+S to save the changes.

6. Within the JPA Entity Editor, right-click the entity Contact to view its source code or see the associated configuration in persistence.xml.

Manage JPA Entity Mappings
The following describes how the annotations are translated into what the JPA Details view displays. When the JPA Details view displays an underlined label, you can click the label to view the corresponding Java source code or item in the Data Source Explorer.

1. In the JPA Entity Editor, review the many-to-one association between OrderData and Customer. Select the customer property OrderData entity to view its properties in the JPA Details view.
   

2. Within the JPA Details view, examine the Join Columns. Select the association and click Edit to edit the mapping association.
   Click Cancel.
   

3. Next, locate the one-to-many association between OrderData and Lineitems.
   Click on the lineitems property in the OrderData entity and view Target Entity and Mapped By properties in the JPA Details View.
   
4. Clicking Target Entity in the JPA Details View will take you to the class for the related entity type Lineitem.
   
5. Close the LineItem.java file.
6. Clicking Mapped By under the Join Properties will allow you to change the field by which the many-to-one association of OrderData to Lineitem is mapped. Do not make any changes at this time.
   

7. Close the LineItem.java file.

In Part 5 I will explore persistence settings.

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