How do I properly close a HikariCP Connection Pool

Question

I'm using HikariDataSource to connect to a MariaDB database. The following class returns a Connection.

public class DataSource { private HikariDataSource ds; // The constructor takes db name as an argument and creates a new datasource for the connection accordingly. public DataSource(String dbString) { HikariConfig config = new HikariConfig(); Map map = DbConfigParser.configKeyValue(dbString); config.setJdbcUrl(String.valueOf(map.get("uri"))); config.setUsername(String.valueOf(map.get("uname"))); config.setPassword(String.valueOf(map.get("pwd"))); config.addDataSourceProperty("cachePrepStmts", "true"); config.addDataSourceProperty("prepStmtCacheSize", "250"); config.addDataSourceProperty("prepStmtCacheSqlLimit", "2048"); ds = new HikariDataSource(config); } // Returns a Connection to the database public Connection getConnection() throws SQLException { return ds.getConnection(); } // Close the datasource public void close(){ if (ds != null) { ds.close(); } } }

This is the method that executes the select query. The class also contains a close method

public List<DataFile> getAllFiles() throws SQLException { try (Connection connection = dataSource.getConnection(); DSLContext ctx = DSL.using(connection, SQLDialect.MARIADB)) { List<DataFile> dataFileList = new DataFileQueries().selectQuery(ctx) .fetchInto(DataFile.class); if (dataFileList == null || dataFileList.isEmpty()) { throw new IllegalStateException("The List is Empty!"); } return dataFileList; } } public void close() { try { dataSource.close(); } catch (Exception e) { LOG.error("A SQLException was caught", e); } }

The try-with-block closes the Connection object automatically, but how do I close the connection pool? Should I call the call the close method after the database operation, for example

public static void main(String[] args) throws SQLException { DataFileDaoImpl service = new DataFileDaoImpl("testi"); List<DataFile> list = service.getAllFiles(); list.stream().forEach( e -> System.out.println(e.toString()) ); service.close(); }

When I don't call the close() method, I don't see any console output regarding shutdown initiation. Is this the right way to close HikariDataSource and Connection Pool?

informatik01 · Accepted Answer · 2019-06-01 22:50:54Z

19

You don't need to call DataSource's close() for every connection:

Shutdown the DataSource and its associated pool.

It's defined only for application termination:

close() is essential at application termination

You should continue working with the pool, notice you are closing (correctly) the connection with try with resources

try (Connection connection = dataSource.getConnection()

edited Jun 1, 2019 at 22:50

informatik01

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answered Feb 17, 2019 at 11:11

Ori Marko

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3 Comments

Roshan Upreti Over a year ago

Thank you very much for your explanation. So, it's okay to call close() only during the application termination and not after every Connection is closed?

Ori Marko Over a year ago

@RoshanUpreti yes

Mark Rotteveel Over a year ago

@RoshanUpreti If you close the data source after each connection, you throw away any benefit a connection pool has (not to mention that you might break concurrent use of connections checked out of the pool).

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