如何在JDBC中检测Oracle数据库关闭？

Question

In an application, we have used JDBC to connect to Oracle database. We have attached. The issue is to identify through a callback/listener, that the database was shutdown.

Currently, we have the the following listener attached:

Connection eventListener = new ConnectionEventListener() {
    @Override
    public void connectionErrorOccurred(ConnectionEvent event){
        // log - connection error
    }

    @Override
    public void connectionClosed(ConnectionEvent event) {
        // log - connection closed
    }
}

None of this events are triggered when the database is shutdown.

The idea is to detect the database shutdown and then the database start , and have a mechanism to inform the users, and to either poll for the database (configurable) or suspend the service (the application).

Answer 1

I'm afraid your request is not fully defined. For example in case of RAC cluster you might configure the application to respond to ONS messages, and your application can safely migrate all the connections to another database node. So even if one database node is down, your application can still work smoothly.

For brief overview look at JBOSS source code, there is a class called exception sorter, which lists various useful Oracle errors codes. For example , but I think the current JBOSS'es code base has even longer list.

Here is a list of error codes, I collected. All of the error codes express a situation, where connection to the database is not possible (for some reason).

PS: the DCD (dead connection detection) is a different topic.

Answer 2

You can not properly specify the problem. You could only get connection or fail to get connection, the reason (unable to connect, db shutdown etc) could not be specified, you gonna get same exceptions with all these cases.

Answer 3

您可能需要事务，因此如果查询失败，它将给您一个错误，您可以随后检查连接。