Java(TM) Boutique - XML-to-Database Mapping with Hibernate 3.1

Tutorials : XML-to-Database Mapping with Hibernate 3.1 :

Retrieving an XML Document from Database

Next, retrieve the data you've stored in the database table as an XML document. As in the previous section, create a Configuration object and add the mapping file catalog.hbm.xml to the Configuration object:

Configuration config = new Configuration();
config.addFile("catalog.hbm.xml");

Create a SessionFactory object from the Configuration object and open a Session object from the SessionFactory:

SessionFactory sessionFactory = config.buildSessionFactory();
session = sessionFactory.openSession();

Start a new session in DOM4J entity mode:

Session dom4jSession = session.getSession(EntityMode.DOM4J);

Begin a new transaction:

tx = session.beginTransaction();

Next, construct an XML document with data from Catalog. First, create a Document object using the static method createDocument() (of the DocumentHelper class). Add the root element catalogs to the Document object:

Document document = DocumentHelper.createDocument();
Element rootElement = document.addElement("catalogs");

Create a Hibernate Query Language (HQL) query to select data from the table. HQL syntax is similar to SQL. The SELECT clause is not required for a query. The FROM clause in HQL is specified with the entity name instead of the database table:

String hqlQuery ="FROM  Catalog";

Create a Query object with the createQuery(hqlQuery) method of the Session object and subsequently obtain the query results as a List using the list() method. The HQL query is run using the Session object in DOM4J entity mode:

List results = dom4jSession.createQuery(hqlQuery).list();

Iterate over the List and obtain the Element objects corresponding to the catalog node. A row in Catalog corresponds to a catalog element node in the XML document which is in turn mapped to the database table. Add the catalog nodes to the root element of the Document object:

for (int i = 0; i < results.size(); i++) {
                Element catalog = (Element) results.get(i);
                rootElement.add(catalog);
            }

Output the Document object using an XMLWriter object:

XMLWriter output = new XMLWriter(new FileWriter(
                        new File("c:/catalog/catalog.xml")));
output.write(document);

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