我有一个要求,如果在db表中插入一条记录,则需要自动执行一个Java进程。实现db侦听器的最简单方法是什么?
我有一个针对Oracle的解决方案。自从甲骨文购买了Java以来,你不需要创建自己的应用程序,因此它发布了一个监听器。据我所知,这在内部不使用轮询,而是将通知推送到Java端(可能基于某些触发器):
public interface oracle.jdbc.dcn.DatabaseChangeListener extends java.util.EventListener { void onDatabaseChangeNotification(oracle.jdbc.dcn.DatabaseChangeEvent arg0); }
你可以像这样实现它(这只是一个示例):
public class DBListener implements DatabaseChangeListener { private DbChangeNotification toNotify; public BNSDBListener(DbChangeNotification toNotify) { this.toNotify = toNotify; } @Override public void onDatabaseChangeNotification(oracle.jdbc.dcn.DatabaseChangeEvent e) { synchronized( toNotify ) { try { toNotify.notifyDBChangeEvent(e); //do sth } catch (Exception ex) { Util.logMessage(CLASSNAME, "onDatabaseChangeNotification", "Errors on the notifying object.", true); Util.printStackTrace(ex); Util.systemExit(); } } } }
编辑: 你可以使用以下类进行注册:oracle.jdbc.OracleConnectionWrapper
oracle.jdbc.OracleConnectionWrapper
public class oracle.jdbc.OracleConnectionWrapper implements oracle.jdbc.OracleConnection {...}
假设你在某处创建方法:
public void registerPushNotification(String sql) { oracle.jdbc.driver.OracleConnection oracleConnection = ...;//connect to db dbProperties.setProperty(OracleConnection.DCN_NOTIFY_ROWIDS, "true"); dbProperties.setProperty(OracleConnection.DCN_QUERY_CHANGE_NOTIFICATION, "true"); //this is what does the actual registering on the db end oracle.jdbc.dcn.DatabaseChangeRegistration dbChangeRegistration= oracleConnection.registerDatabaseChangeNotification(dbProperties); //now you can add the listener created before my EDIT listener = new DBListener(this); dbChangeRegistration.addListener(listener); //now you need to add whatever tables you want to monitor Statement stmt = oracleConnection.createStatement(); //associate the statement with the registration: ((OracleStatement) stmt).setDatabaseChangeRegistration(dbChangeRegistration); //look up the documentation to this method [http://docs.oracle.com/cd/E11882_01/appdev.112/e13995/oracle/jdbc/OracleStatement.html#setDatabaseChangeRegistration_oracle_jdbc_dcn_DatabaseChangeRegistration_] ResultSet rs = stmt.executeQuery(sql); //you have to execute the query to link it to the statement for it to be monitored while (rs.next()) { ...do sth with the results if interested... } //see what tables are being monitored String[] tableNames = dbChangeRegistration.getTables(); for (int i = 0; i < tableNames.length; i++) { System.out.println(tableNames[i] + " has been registered."); } rs.close(); stmt.close(); }
此示例不包括try-catch子句或任何异常处理。