Best web hosting - Chapter 14 Using the DataExpress for EJB components
Chapter 14 Using the DataExpress for EJB components JBuilder has several components that allow you to retrieve data from entity beans into DataExpress DataSets (providing), and to save data from DataExpress DataSets back to entity beans (resolving). These DataExpress for EJB components make it easy to implement a Session Bean wrap Entity Bean or Session Facade design pattern. Using this design pattern, clients usually don t access entity beans directly, but instead they access them using session beans. The session beans, which are co-located with the entity beans, make all the calls to the entity beans within a single transaction and then return all the data at once. DataSets provide a way of transporting the data from the session bean to the client and back. Because data is sent over the wire just once to provide the data to the client, and then just once again to resolve changes to the entity beans on the server, performance improves. These components also make it easier for you to build client applications using DataExpress-aware visual components such as dbSwing or InternetBeans Express. For a full description of DataExpress, see the Developing Database Applications book. This chapter explains how to use these components to transfer data from entity beans deployed on a server to your client application and back again. The data the sample accesses is stored in an Employee data store. The sample creates an entity bean to hold Employee data. It also creates a Personnel session bean that retrieves data from Employee and then sends it to the client. The client sends the data back to the Personnel, which resolves the data to the Employee entity bean instances. Note If you are using JDK 1.4, you won t be able to view live data with the DataExpress for EJB components in the UI designer using the Borland Enterprise Server 5.2.1. The DataExpress EJB components Six of the DataExpress EJB components are on the EJB page of the component palette. You can work with these components in the UI designer, setting properties and events using the Inspector. There are additional classes that your code can call that you don t work with visually. For information about all of the classes, see the API Reference. Chapter 14: Using the DataExpress for EJB components 141
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