Using DatabaseManager

The DatabaseManager class allows creation and control of one or more database instances on a PostgreSQL server.

By default, each PostgreSQL server has two databases:

• the template1 template database from which all other databases are cloned
• the postgres default database.

Additional databases can be created using the standard SQL CREATE DATABASE commands.

DatabaseManager has two operation modes:

• In single database mode, only a single database exists (the postgres database). Every call to DatabaseManager.getDatabaseInfo() returns a DatabaseInfo instance that can be used to connect to the single database.
• In multi database mode, every call to DatabaseManager.getDatabaseInfo() creates a new database on the PostgreSQL server and returns a DatabaseInfo instance that decribes this new database. Each database has a unique name and is cloned from the template1 database, so any operations on the template (creating tables, loading plugins etc.) are also applied to each new database instance.

Each DatabaseManager instance manages an EmbeddedPostgres instance to control the database server. Calling DatabaseManager.close() shuts down the PostgreSQL server instance.

try (DatabaseManager manager = DatabaseManager.singleDatabase()
    // same as EmbeddedPostgres.defaultInstance()
    .withInstancePreparer(EmbeddedPostgres.Builder::withDefaults)
    .build()
    .start()) {
    DatabaseInfo databaseInfo = manager.getDatabaseInfo();
    try (Connection c = databaseInfo.asDataSource().getConnection();
        Statement s = c.createStatement()) {
        try (ResultSet rs = s.executeQuery("SELECT 1")) {
            assertTrue(rs.next());
            assertEquals(1, rs.getInt(1));
            assertFalse(rs.next());
        }
    }
}

A DatabaseManager is created by calling either DatabaseManager.singleDatabase() or DatabaseManager.multiDatabases(). Each call returns a Builder which allows further customization of the PostgreSQL server and the databases. The builder creates the DatabaseManager instance by calling the Builder.build() method.

Every DatabaseManager instance must be explicitly started by calling the start() method.

try (DatabaseManager manager = DatabaseManager.singleDatabase()
    // set the default connection timeout for all DataSources
    .withInstancePreparer(builder -> builder.addConnectionProperty("connectTimeout", "20"))
    .build()
    .start()) {
    ...
}