EJB 3.0 Database Persistence with Ajax in the UI - EJB 3.0 Database Persistence with Oracle Fusion Middleware 11g - page 283

Create a PrintWriter from the response object:
PrintWriter out = response.getWriter();
Create the response to be sent to the browser. If the validate() method returns
a Catalog entity instance, the catalog id is not valid, as a Catalog entity instance
for the catalog id is already defined. Create an XML string that has root element
Catalog and a sub-element valid with value set to false , and sub-elements
journal , publisher , edition , title and author with values set to the properties
of the Catalog entity instance. If the validate() method returns null , the catalog is
valid, as a new Catalog entity instance for the catalog id is not defined. Construct an
XML string that has root element valid with value set to true .
if (catalog != null) {
out.println("<catalog>" + "<valid>false</valid>"+"<journal>" +
catalog.getJournal() + "</journal>" + "<publisher>" +
catalog.getPublisher() + "</publisher>" + "<edition>" +
catalog.getEdition() + "</edition>" + "<title>" +
catalog.getTitle() + "</title>" + "<author>" +
catalog.getAuthor() + "</author>" + "</catalog>");
} else {
out.println("<valid>true</valid>");
}
The doPost() method of the servlet is invoked when the input form is submitted
for a valid catalog id. In the doPost() method, create an InitialContext object.
Lookup the remote interface of the session bean using the remote JNDI name.
Retrieve the input form field values and invoke the persist() method of the session
bean to persist a new Catalog entity instance. The doPost() method is not invoked
with an Ajax request; therefore, the method does not return a response, but redirects
to a JSP that displays a message that the database has been updated with a new
catalog entry.
beanRemote.persist(catalogId, journal, publisher, edition, title,
author);
response.sendRedirect("catalog.jsp");
If an error is generated in updating the database, redirect the response to an error JSP
error.jsp . The EJB3ClientServlet class is listed below:
package view;
import model.*;
import java.io.*;
import javax.naming.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class EJB3ClientServlet extends HttpServlet {