java - 如何检测(在 Hibernate 中)数据库何时出现故障？

Question

我们正在使用 Hibernate 连接 MySQL 数据库。需要一种在数据库出现故障时收到警报的方法。正在阅读有关 Hibernate 中的监听器的信息，但不确定其中任何一个是否可用于检测数据库关闭事件。

Answer 1

正如@Bart在上面的评论中所建议的，尝试通过以下代码来实现该功能。请随时提出任何改进或替代方案。

import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import org.apache.log4j.Logger;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.exception.JDBCConnectionException;

public class PollingThread extends Thread {

private static final Logger LOGGER = Logger.getLogger(PollingThread.class);
private long interval;

public PollingThread() {
    // default polling interval set to 5 seconds
    this(TimeUnit.SECONDS.toMillis(5));
}

public PollingThread(final long interval) {
    this.interval = interval;
    this.setDaemon(true);
    LOGGER.debug("Polling thread initialized!");
}

@Override
public void run() {

    while (true) {
        boolean connected = poll();
        LOGGER.debug("Connected - " + connected);

        if (!connected) {
            // TODO connect to fail-over database
        }

        synchronized (this) {
            try {
                wait(interval);
            } catch (InterruptedException ex) {
                LOGGER.warn("Polling thread interrupted", ex);
            }
        }
    }
}

private boolean poll() {

    boolean connected = true;
    try {
        final Session session = HibernateUtil.getSessionFactory().openSession();
        final Transaction tx = session.beginTransaction();
        tx.commit();
        session.close();
    } catch (JDBCConnectionException ex) {
        connected = false;
    }

    return connected;
}

public static void main(String[] args) {

    Executors.newSingleThreadExecutor().execute(new PollingThread());
}
}