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- ---
- title: Getting Started with SQLContainer
- order: 2
- layout: page
- ---
-
- [[sqlcontainer.getting-started]]
- = Getting Started with SQLContainer
-
- Getting development going with the SQLContainer is easy and quite
- straight-forward. The purpose of this section is to describe how to create the
- required resources and how to fetch data from and write data to a database table
- attached to the container.
-
- [[sqlcontainer.getting-started.connection-pool]]
- == Creating a connection pool
-
- First, we need to create a connection pool to allow the SQLContainer to connect
- to a database. Here we will use the [classname]#SimpleJDBCConnectionPool#, which
- is a basic implementation of connection pooling with JDBC data sources. In the
- following code, we create a connection pool that uses the HSQLDB driver together
- with an in-memory database. The initial amount of connections is 2 and the
- maximum amount is set at 5. Note that the database driver, connection url,
- username, and password parameters will vary depending on the database you are
- using.
-
-
- ----
- JDBCConnectionPool pool = new SimpleJDBCConnectionPool(
- "org.hsqldb.jdbc.JDBCDriver",
- "jdbc:hsqldb:mem:sqlcontainer", "SA", "", 2, 5);
- ----
-
-
- [[sqlcontainer.getting-started.query-delegate]]
- == Creating the [classname]#TableQuery# Query Delegate
-
- After the connection pool is created, we'll need a query delegate for the
- SQLContainer. The simplest way to create one is by using the built-in
- [classname]#TableQuery# class. The [classname]#TableQuery# delegate provides
- access to a defined database table and supports reading and writing data
- out-of-the-box. The primary key(s) of the table may be anything that the
- database engine supports, and are found automatically by querying the database
- when a new [classname]#TableQuery# is instantiated. We create the
- [classname]#TableQuery# with the following statement:
-
-
- ----
- TableQuery tq = new TableQuery("tablename", connectionPool);
- ----
-
- In order to allow writes from several user sessions concurrently, we must set a
- version column to the [classname]#TableQuery# as well. The version column is an
- integer- or timestamp-typed column which will either be incremented or set to
- the current time on each modification of the row. [classname]#TableQuery#
- assumes that the database will take care of updating the version column; it just
- makes sure the column value is correct before updating a row. If another user
- has changed the row and the version number in the database does not match the
- version number in memory, an [classname]#OptimisticLockException# is thrown and
- you can recover by refreshing the container and allow the user to merge the
- data. The following code will set the version column:
-
-
- ----
- tq.setVersionColumn("OPTLOCK");
- ----
-
-
- [[sqlcontainer.getting-started.container-creation]]
- == Creating the Container
-
- Finally, we may create the container itself. This is as simple as stating:
-
-
- ----
- SQLContainer container = new SQLContainer(tq);
- ----
-
- After this statement, the [classname]#SQLContainer# is connected to the table
- tablename and is ready to use for example as a data source for a Vaadin
- [classname]#Table# or a Vaadin [classname]#Form#.
-
-
-
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