4.3.1.1 Major Interfaces

4.3.1.1.1 SessionFactory

ClusterJ provides these major interfaces for use by application programs: com.mysql.clusterj.SessionFactory, com.mysql.clusterj.Session, com.mysql.clusterj.Transaction, com.mysql.clusterj.query.QueryBuilder, and com.mysql.clusterj.Query. Bootstrapping The helper class com.mysql.clusterj.ClusterJHelper contains methods for creating the com.mysql.clusterj.SessionFactory. Bootstrapping is the process of identifying an NDB Cluster and obtaining the SessionFactory for use with the cluster. There is one SessionFactory per cluster per Java VM.

4.3.1.1.1 SessionFactory

The com.mysql.clusterj.SessionFactory is configured via properties, which identify the NDB Cluster that the application connects to:

• com.mysql.clusterj.connectstring identifies the ndb_mgmd host name and port

• com.mysql.clusterj.connect.retries is the number of retries when connecting

• com.mysql.clusterj.connect.delay is the delay in seconds between connection retries

• com.mysql.clusterj.connect.verbose tells whether to display a message to System.out while connecting

• com.mysql.clusterj.connect.timeout.before is the number of seconds to wait until the first node responds to a connect request

• com.mysql.clusterj.connect.timeout.after is the number of seconds to wait until the last node responds to a connect request

• com.mysql.clusterj.connect.database is the name of the database to use

    File propsFile = new File("clusterj.properties");
    InputStream inStream = new FileInputStream(propsFile);
    Properties props = new Properties();
    props.load(inStream);
    SessionFactory sessionFactory = ClusterJHelper.getSessionFactory(props);

Session The com.mysql.clusterj.Session represents the user's individual connection to the cluster. It contains methods for:

• finding persistent instances by primary key

• persistent instance factory (newInstance)

• persistent instance life cycle management (persist, remove)

• getting the QueryBuilder

• getting the Transaction (currentTransaction)

    Session session = sessionFactory.getSession();
    Employee existing = session.find(Employee.class, 1);
    if (existing != null) {
        session.remove(existing);
    }
    Employee newemp = session.newInstance(Employee.class);
    newemp.initialize(2, "Craig", 15, 146000.00);
    session.persist(newemp);

Transaction The com.mysql.clusterj.Transaction allows users to combine multiple operations into a single database transaction. It contains methods to:

• begin a unit of work

• commit changes from a unit of work

• roll back all changes made since the unit of work was begun

• mark a unit of work for rollback only

• get the rollback status of the current unit of work

    Transaction tx = session.currentTransaction();
    tx.begin();
    Employee existing = session.find(Employee.class, 1);
    Employee newemp = session.newInstance(Employee.class);
    newemp.initialize(2, "Craig", 146000.00);
    session.persist(newemp);
    tx.commit();

QueryBuilder The com.mysql.clusterj.query.QueryBuilder allows users to build queries. It contains methods to:

• define the Domain Object Model to query

• compare properties with parameters using:

  • equal

  • lessThan

  • greaterThan

  • lessEqual

  • greaterEqual

  • between

  • in

• combine comparisons using "and", "or", and "not" operators

    QueryBuilder builder = session.getQueryBuilder();
    QueryDomainType<Employee> qemp = builder.createQueryDefinition(Employee.class);
    Predicate service = qemp.get("yearsOfService").greaterThan(qemp.param("service"));
    Predicate salary = qemp.get("salary").lessEqual(qemp.param("salaryCap"));
    qemp.where(service.and(salary));
    Query<Employee> query = session.createQuery(qemp);
    query.setParameter("service", 10);
    query.setParameter("salaryCap", 180000.00);
    List<Employee> results = query.getResultList();