HikariCP not closing connections on close() (Connection Leak)

Question

I'm using HikariCP 3.3.1 and PostgreSQL. But I've a problem with closing my connections, in Hikari config I set maximum pool size to 15 and minimum idle connection to 5, but after a few minutes of work with database I've found out connections don't closes, they stack more and more (almost 100 Idle connections right now).

My Connector class:

Connector.java

public class Connector implements IConnector {
private static HikariConfig config = new HikariConfig();
private static HikariDataSource ds;

static {
    config.setDriverClassName(org.postgresql.Driver.class.getName());
    config.setJdbcUrl("jdbc:postgresql://localhost:5432/vskDB");
    config.setUsername("postgres");
    config.setPassword("root");
    config.setMinimumIdle(5);
    config.setMaximumPoolSize(15);
    config.setConnectionTimeout(20000);
    config.setIdleTimeout(300000);
    ds = new HikariDataSource(config);
}

public Connection getConnection() {
    log.info("getConnection() invoked");
    try {
        return ds.getConnection();
    } catch (SQLException e) {
        log.error("Can't get connection from DataSource.");
        log.error(e.getMessage());
        System.out.println(e.getMessage());
    }
    return null;
}

Connector() {
}
}

And here's my DAO class (simplified): UserDAO.java

public class UserDatabaseDAO implements UserDAO {
    private Connector connector = new Connector();
    private Connection dbConnection;

    @Override
    public void removeUser(Long id) {
        try {
            dbConnection = connector.getConnection();
            if (dbConnection == null)
                throw new ConnectException();

            PreparedStatement preparedStatement = dbConnection.prepareStatement("DELETE FROM users WHERE user_id = ?");
            preparedStatement.setLong(1, id);
            preparedStatement.execute();

        } catch (SQLException | ConnectException e) {
            log.error("Can't remove user from database");
            log.error(e.getMessage());
            System.out.print(e.getMessage());
        } finally {
            try {
                dbConnection.close();
            } catch (SQLException e) {
                log.error("Can't close connection");
                log.error(e.getMessage());
                System.out.print(e.getMessage());
            }
        }
    }
}

在这里，我发现了有关 Hikari 的一些事实的问题：
您必须在 HikariCP 为您提供的连接实例上调用 close()

也许我的方法dbConnection.close()不起作用，因为它只是 Hikari 在方法中给我的 Connection 的副本getConnection()。

Answer 1

你还忘记关闭PreparedStatement

try {
       if (preparedStatement != null) {
            preparedStatement.close();
       }
       if (dbConnection != null) {
            dbConnection.close();
       }

立即释放此Statement对象的数据库和JDBC资源，而不是等待它自动关闭时发生。通常，好的做法是在使用完资源后立即释放资源，以避免占用数据库资源。