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3 Methods for Monitoring Log File Changes in Java
When studying the rule engine, if the rules are stored in the form of files, it is necessary to monitor the specified directory or file to sense whether the rules have changed, and then load them.
Of course, in other business scenarios, such as dynamic loading of configuration files, monitoring of log files, and monitoring of FTP file changes, similar scenarios will be encountered.
Today I will share three solutions:
Scheme 1: Scheduled task + File lastModified
This solution is the simplest and most straightforward solution that comes to mind. Through timed tasks, the last modification time of the query file is polled and compared with the last time.
If there is a change, it means the file has been modified and needs to be reloaded or processed with corresponding business logic.
In the previous article Digging Through a Bug in the JDK Monitoring File, a specific example has been written, and its shortcomings have also been proposed.
Here’s some sample code:
For scenarios with low-frequency file changes, this solution is simple to implement and basically meets the requirements. However, as mentioned in the previous article, you need to pay attention to the bug of File#lastModified in Java 8 and Java 9.
However, if this scheme is used for file directory changes, the shortcomings are somewhat obvious. For example, the operation is frequent, and the efficiency is lost in traversing, saving the state, and comparing the state, and the functions of the OS cannot be fully utilized.
Scheme 2: WatchService
In Java 7, java.nio.file.WatchService has been added, which enables monitoring of file changes.
WatchService is a file system monitor based on the operating system. It can monitor the changes of all…
