package transactions;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.List;
import java.util.SimpleTimeZone;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityManager;
import javax.persistence.EntityTransaction;
import javax.persistence.Query;
import javax.servlet.http.*;
import com.google.appengine.api.datastore.Key;
import com.google.appengine.api.datastore.KeyFactory;
import com.google.appengine.api.datastore.KeyFactory.Builder;
import transactions.Book;
import transactions.BookReview;
import transactions.EMF;
@SuppressWarnings("serial")
public class JPATransactionsServlet extends HttpServlet {
public void doGet(HttpServletRequest req,
HttpServletResponse resp)
throws IOException {
resp.setContentType("text/html");
PrintWriter out = resp.getWriter();
EntityManagerFactory emf = EMF.get();
EntityManager em = null;
try {
em = emf.createEntityManager();
Book book = new Book("978-0596522728");
book.setTitle("Programming Google App Engine");
book.setAuthor("Dan Sanderson");
book.setCopyrightYear(2010);
Date authorBirthdate =
new GregorianCalendar(1978, Calendar.JANUARY, 11).getTime();
book.setAuthorBirthdate(authorBirthdate);
em.persist(book);
} finally {
em.close();
}
try {
em = emf.createEntityManager();
EntityTransaction txn = em.getTransaction();
txn.begin();
try {
Book book = em.find(Book.class, "978-0596522728");
BookReview bookReview = new BookReview();
bookReview.setRating(5);
book.getBookReviews().add(bookReview);
// No need to explicitly persist() the BookReview
// because it is a field of Book.
// Persist all updates and commit.
txn.commit();
} finally {
if (txn.isActive()) {
txn.rollback();
}
}
} finally {
em.close();
}
try {
em = emf.createEntityManager();
Book book = em.find(Book.class, "978-0596522728");
if (book != null) {
out.println("<p>Ratings for <i>" + book.getTitle() + "</i>: ");
for (BookReview review : book.getBookReviews()) {
out.println("[" + review.getRating() + "]");
}
out.println("</ul>");
} else {
out.println("Could not find that book I was looking for...");
}
} finally {
em.close();
}
out.println("<p>Objects saved. See <a href=\"/_ah/admin\">the datastore viewer</a>.</p>");
SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss.SSSSSS");
fmt.setTimeZone(new SimpleTimeZone(0, ""));
out.println("<p>The time is: " + fmt.format(new Date()) + "</p>");
}
}