The exception indicates a typical case of application code which leaks database connections. You need to ensure that you acquire and close all of them (Connection, Statement and ResultSet) in a try-with-resources block in the very same method block according the normal JDBC idiom.
public void create(Entity entity) throws SQLException {
try (
Connection connection = dataSource.getConnection();
PreparedStatement statement = connection.prepareStatement(SQL_CREATE);
) {
statement.setSomeObject(1, entity.getSomeProperty());
// ...
statement.executeUpdate();
}
}
Or when you’re not on Java 7, in a try-finally block. Closing them in finally will guarantee that they are also closed in case of exceptions.
public void create(Entity entity) throws SQLException {
Connection connection = null;
PreparedStatement statement = null;
try {
connection = dataSource.getConnection();
statement = connection.prepareStatement(SQL_CREATE);
statement.setSomeObject(1, entity.getSomeProperty());
// ...
statement.executeUpdate();
} finally {
if (statement != null) try { statement.close(); } catch (SQLException logOrIgnore) {}
if (connection != null) try { connection.close(); } catch (SQLException logOrIgnore) {}
}
}
Yes, you still need to close connections yourself, even when using connection pooling. It’s a common mistake among starters that they think that it will then automatically handle the close. This is not true. The connection pool namely returns a wrapped connection which does something like the following in the close():
public void close() throws SQLException {
if (this.connection is still eligible for reuse) {
do not close this.connection, but just return it to pool for reuse;
} else {
actually invoke this.connection.close();
}
}
Not closing them would cause the connection not being released back to the pool for reuse and thus it will acquire a new one again and again until the DB runs out of connections which will cause your application to crash.