SimpleEntityExample

Simple Example

Example is created using derby as the database engine. This demonstrates basic features like persisting, retrieval, change tracking

Details

Create the entity

@TableInfo(tableName = "simple_entity")
public class SimpleEntity  extends DefaultEntity
{
    @ColumnInfo(columnType = ColumnType.INTEGER,key = true)
    private int id;
    @ColumnInfo(columnType = ColumnType.VARCHAR)
    private String name;

    public SimpleEntity()
    {
    }

    public int getId()
    {
        return id;
    }

    public void setId(int id)
    {
        this.id = id;
    }

    public String getName()
    {
        return name;
    }

    public void setName(String name)
    {
        this.name = name;
    }
}

Base class for examples

public class ExampleBase
{
    protected ITransactionFactory factory;
    protected String dbName = "testdb";

    public void initializeConnector()
    {
        try
        {
            factory = new DefaultTransactionFactory(() -> {
                try {
                    Logger.getLogger(getClass().getName()).info("Starting in-memory database for unit tests");
                    Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
                    return DriverManager.getConnection(String.format("jdbc:derby:memory:%s;create=true", dbName));
                }
                catch (Exception ex){
                    Logger.getLogger(getClass().getName()).severe(String.format("Exception during database %s startup.",dbName));
                    return null;
                }
            }, DefaultTransactionFactory.DB_DERBY);
        }
        catch (Exception ex)
        {
            ex.printStackTrace();
            Logger.getLogger(getClass().getName()).severe("Exception during database startup.");
        }
    }

    public void destroyConnector()
    {
        try
        {
            DriverManager.getConnection(String.format("jdbc:derby:memory:%s;shutdown=true",dbName)).close();
        }
        catch (SQLException ex)
        {
            if (ex.getErrorCode() != 45000)
            {
                ex.printStackTrace();
            }
        }
        try
        {
            VFMemoryStorageFactory.purgeDatabase(new File(dbName).getCanonicalPath());
        }
        catch (IOException iox)
        {
            iox.printStackTrace();
        }
        ((DefaultTransactionFactory)factory).finalize();
        factory = null;
    }
}

Class to do the operation

public class SimpleExample extends ExampleBase
{
    private int id = 43;

    public SimpleExample()
    {
        dbName = "simple_example";
    }

    public SimpleEntity createEntity()
    {
        SimpleEntity entity = new SimpleEntity();
        entity.setId(id);
        entity.setName("Entity");
        return entity;
    }

    public void patch() throws DBPatchingException, SQLException
            ,TransactionCreationFailedException,TransactionCommitFailedException
    {
        ITransaction tx = factory.createTransaction();
        Collection<Class> entityTypes = new ArrayList<Class>();
        entityTypes.add(SimpleEntity.class);
        factory.getDbGate().patchDataBase(tx,entityTypes,false);
        tx.commit();
        DBMgtUtility.close(tx);
    }

    public void persist(SimpleEntity entity) throws PersistException, SQLException
            ,TransactionCreationFailedException,TransactionCommitFailedException
    {
        ITransaction tx = factory.createTransaction();
        entity.persist(tx);
        tx.commit();
        DBMgtUtility.close(tx);
    }

    public SimpleEntity retrieve() throws SQLException,RetrievalException
            ,TransactionCreationFailedException
    {
        ITransaction tx = factory.createTransaction();
        PreparedStatement ps = tx.getConnection().prepareStatement("select * from simple_entity where id = ?");
        ps.setInt(1,id);
        ResultSet rs = ps.executeQuery();
        SimpleEntity entity = null;
        if (rs.next())
        {
            entity = new SimpleEntity();
            entity.retrieve(rs,tx);
        }
        DBMgtUtility.close(rs);
        DBMgtUtility.close(ps);
        DBMgtUtility.close(tx);
        return entity;
    }

    public SimpleEntity retrieveWithQuery() throws SQLException,RetrievalException
            ,TransactionCreationFailedException
    {
        ITransaction tx = factory.createTransaction();
        ISelectionQuery query = new SelectionQuery()
                .from(QueryFrom.type(SimpleEntity.class))
                .select(QuerySelection.type(SimpleEntity.class));

        Collection entities = query.toList(tx);
        DBMgtUtility.close(tx);

        return (SimpleEntity)entities.iterator().next();
    }

    public static void main(String[] args)
    {
        SimpleExample simpleExample = new SimpleExample();
        simpleExample.initializeConnector();
        try
        {
            simpleExample.patch();
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
        try
        {
            SimpleEntity entity = simpleExample.createEntity();
            simpleExample.persist(entity);
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
        try
        {
            SimpleEntity entity = simpleExample.retrieveWithQuery();
            System.out.println("entity.Name = " + entity.getName());

            entity.setName("Updated");
            simpleExample.persist(entity);
            entity = simpleExample.retrieve();
            System.out.println("entity.Name = " + entity.getName());

            entity.setStatus(EntityStatus.DELETED);
            simpleExample.persist(entity);
            entity = simpleExample.retrieve();
            System.out.println("entity = " + entity);
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
        simpleExample.destroyConnector();
    }
}