Database db;
Product product;
ProductGroup group;
ProductDetail detail;
Computer computer;
OQLQuery productOql;
OQLQuery groupOql;
OQLQuery computerOql;
QueryResults results;
db = _jdo.getDatabase();
db.begin();
writer.println( "Begin transaction" );
// Look up the product and if found in the database,
// delete this object from the database
productOql = db.getOQLQuery( "SELECT p FROM myapp.Product p WHERE id = $1" );
productOql.bind( 4 );
results = productOql.execute();
while ( results.hasMore() ) {
product = (Product) results.next();
writer.println( "Deleting existing product: " + product );
db.remove( product );
}
// Look up the computer and if found in the database,
// delete ethis object from the database
computerOql = db.getOQLQuery( "SELECT c FROM myapp.Computer c WHERE id = $1" );
computerOql.bind( 6 );
results = computerOql.execute();
while ( results.hasMore() ) {
computer = (Computer) results.next();
writer.println( "Deleting existing computer: " + computer );
db.remove( computer );
}
// Look up the group and if found in the database,
// delete this object from the database
groupOql = db.getOQLQuery( "SELECT g FROM myapp.ProductGroup g WHERE id = $1" );
groupOql.bind( 3 );
results = groupOql.execute();
while ( results.hasMore() ) {
group = (ProductGroup) results.next();
writer.println( "Deleting existing group: " + group );
db.remove( group );
}
// Checkpoint commits all the updates to the database
// but leaves the transaction (and locks) open
writer.println( "Transaction checkpoint" );
db.commit();
db.begin();
// If no such group exists in the database, create a new
// object and persist it
groupOql.bind( 3 );
results = groupOql.execute();
if ( ! results.hasMore() ) {
group = new ProductGroup();
group.setId( 3 );
group.setName( "a group" );
db.create( group );
writer.println( "Creating new group: " + group );
} else {
group = (ProductGroup) results.next();
writer.println( "Query result: " + group );
}
// If no such product exists in the database, create a new
// object and persist it
// Note: product uses group, so group object has to be
// created first, but can be persisted later
productOql.bind( 4 );
results = productOql.execute();
if ( ! results.hasMore() ) {
product = new Product();
product.setId( 4 );
product.setName( "some product" );
product.setPrice( 55 );
product.setGroup( group );
detail = new ProductDetail();
detail.setId( 1 );
detail.setName( "one" );
product.addDetail( detail );
detail = new ProductDetail();
detail.setId( 2 );
detail.setName( "two" );
product.addDetail( detail );
writer.println( "Creating new product: " + product );
db.create( product );
} else {
writer.println( "Query result: " + results.next() );
}
// If no such computer exists in the database, create a new
// object and persist it
// Note: computer uses group, so group object has to be
// created first, but can be persisted later
computerOql.bind( 6 );
results = computerOql.execute();
if ( ! results.hasMore() ) {
computer = new Computer();
computer.setId( 6 );
computer.setCpu( "Pentium" );
computer.setName( "MyPC" );
computer.setPrice( 300 );
computer.setGroup( group );
detail = new ProductDetail();
detail.setId( 4 );
detail.setName( "mouse" );
computer.addDetail( detail );
detail = new ProductDetail();
detail.setId( 5 );
detail.setName( "screen" );
computer.addDetail( detail );
writer.println( "Creating new computer: " + computer );
db.create( computer );
} else {
writer.println( "Query result: " + results.next() );
}
writer.println( "Commit transaction" );
db.commit();
Marshaller marshaller;
marshaller = new Marshaller( writer );
marshaller.setMapping( _mapping );
db.begin();
marshaller.marshal( db.load( Product.class, new Integer( 4 ) ) );
computerOql = db.getOQLQuery( "SELECT c FROM myapp.Computer c" );
results = computerOql.execute();
while( results.hasMore() )
marshaller.marshal( results.next() );
db.commit();
db.close();