e1084. 捕获错误和异常

Posted 2021-01-03 borter

All errors and exceptions extend from Throwable. By catching Throwable, it is possible to handle all unexpected conditions.

There are several scenarios where it is good practice to catch Throwable. For example, in a server application, the threads that handle requests should catch Throwable and relay any errors or exceptions to the client. Another scenario is a long-running thread that performs some background activity. Such threads should catch Throwable, log any errors or exceptions, and then continue functioning.

It is rarely good practice for a method in a library to catch Throwable. In general, errors and exceptions should not be masked from the caller.

This example demonstrates a long-running thread that catches Throwable and logs the exception.

    class BgThread extends Thread {
        // Create a logger. For more information on the logging api‘s,
        // see e385 一个精简的日志记录程序
        Logger logger = Logger.getLogger("com.mycompany.mypackage");
    
        BgThread() {
            // As a daemon thread, this thread won‘t prevent the application from exiting
            setDaemon(true);
        }
    
        // Set to true to shut down this thread
        boolean stop = false;
    
        public void run() {
            while (!stop) {
                try {
                    // Perform work here
                } catch (Throwable t) {
                    // Log the exception and continue
                    logger.log(Level.SEVERE, "Unexception exception", t);
                }
            }
        }
    }