// ObjectDB for Java Demo - JDO Directory - A Brief JDO Tutorial
// Copyright (C) 2001-2003, ObjectDB Software. All rights reserved.
package directory.step2;
import java.util.*;
import javax.jdo.*;
import directory.pc.*;
/**
* The Update class shows how to update and delete persistent objects, and
* how to retrieve objects using queries and object IDs.
*/
public class Update {
/**
* Runs the example.
*/
public void run() {
// Obtain a PersistenceManager instance:
PersistenceManager pm =
directory.Utilities.getPersistenceManager(false);
// Do some operations:
try {
Object oid = addNewBook(pm);
updateBook(pm, oid);
deleteBook(pm, oid);
System.out.println("Operations have been completed...");
}
catch (RuntimeException x) {
System.out.println("Error: " + x.getMessage());
}
// Close the PersistenceManager instance:
finally {
if (pm.currentTransaction().isActive())
pm.currentTransaction().rollback();
if (!pm.isClosed())
pm.close();
}
}
/**
* Adds a new book.
*
* @return the persistent object ID.
*/
private static Object addNewBook(PersistenceManager pm) {
// Retrieve the Books category:
Query query = pm.newQuery(Category.class, "this.name == name");
query.declareParameters("String name");
Iterator itr = ((Collection)query.execute("Books")).iterator();
if (!itr.hasNext())
throw new RuntimeException("Category 'Books' cannot be found.");
Category books = (Category)itr.next();
query.closeAll();
// Add a new book:
pm.currentTransaction().begin();
Book newBook = new Book("JDO in a Nutshell", 992,
"http://www.oreilly.com/catalog/javanut4", "David Flanagan",
"0596002831", "O'Reilly & Associates", 2002, 3);
books.add(newBook);
pm.currentTransaction().commit();
// Return the new object ID:
return JDOHelper.getObjectId(newBook);
}
/**
* Updates the name field in a specified persistent object.
*/
private static void updateBook(PersistenceManager pm, Object oid) {
pm.currentTransaction().begin();
Book book = (Book)pm.getObjectById(oid, true);
book.setName("Java in a Nutshell");
pm.currentTransaction().commit();
}
/**
* Deletes a specified persistent object.
*/
private static void deleteBook(PersistenceManager pm, Object oid) {
pm.currentTransaction().begin();
Book book = (Book)pm.getObjectById(oid, true);
pm.deletePersistent(book);
pm.currentTransaction().commit();
}
}
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