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An example that demystifies pg_notify using PostgreSQL's native connection.
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| import org.postgresql.PGNotification; | |
| import org.postgresql.ds.PGSimpleDataSource; | |
| import org.postgresql.jdbc.PgConnection; | |
| import java.sql.SQLException; | |
| import java.util.concurrent.ScheduledExecutorService; | |
| import java.util.concurrent.ScheduledFuture; | |
| import java.util.concurrent.TimeUnit; | |
| import static java.lang.Thread.ofVirtual; | |
| import static java.util.concurrent.Executors.newSingleThreadScheduledExecutor; | |
| public class PgNotify { | |
| private static final ScheduledExecutorService SCHEDULER = newSingleThreadScheduledExecutor(ofVirtual().factory()); | |
| private final ScheduledFuture<?> handler; | |
| public PgNotify(PgConnection pgConnection) throws SQLException { | |
| this.handler = SCHEDULER.scheduleAtFixedRate(() -> { | |
| try { | |
| // To receive notifications, you may need to run this SQL query | |
| // SELECT pg_notify('<channel-name>', 'your-payload'); | |
| pgConnection.execSQLUpdate("LISTEN <channel-name>"); | |
| PGNotification[] notifications = pgConnection.getNotifications(); | |
| if (notifications.length > 0) { | |
| System.out.printf("Notifications %d received: ", notifications.length); | |
| for (PGNotification notification : notifications) { | |
| System.out.print(notification.getParameter()); | |
| } | |
| System.out.println(); | |
| } | |
| } catch (SQLException e) { | |
| getHandler().cancel(true); | |
| } | |
| }, 0, 10, TimeUnit.MILLISECONDS); | |
| } | |
| public ScheduledFuture<?> getHandler() { | |
| return handler; | |
| } | |
| public static void main(String[] args) throws SQLException { | |
| PGSimpleDataSource ds = new PGSimpleDataSource(); | |
| ds.setURL("jdbc:postgresql://localhost:5432/<your-database-name>"); | |
| PgConnection pgConnection = ds.getConnection().unwrap(PgConnection.class); | |
| new PgNotify(pgConnection); | |
| while (true) ; | |
| } | |
| } |
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