PrintWriter可以写入“打开”文本文件（Java）

Question

I'm required to create a part of a java program that logs all activity "secretly" that the user is doing with the program. purely to catch people trying to "cheat" the system. The thing is, multiple people will be using the same program on multiple computers

All the information needs to be written using PrintWriter to a single text file that will, later on, be used by an administrative part of the program.

 PrintWriter printer = new PrintWriter(new FileWriter(serverFolderLocation + "\\LogUserInfo.txt", true));

It's expected that 50+- computers will be using this program, every few seconds an array of 7+ lines of text is expected to be written to that file every time a specific button is pressed on a computer

I know that writing text to a text file is extremely quick and this is unlikely to happen, but If 2 or more computers happens to write to the text file at the same time, while append is set to true, will data go missing? or will it append normally?

Is this even possible? 2+ devices writing data to a text file at different times?

Do note that it is important that all the data from all 50+ computers arrive at the destinated file.

If problems are likely to occur, what other methods can be used of doing something like this, other than setting up a dedicated database?

Answer 1

Setting append to true in the FileWriter :

append - boolean if true, then data will be written to the end of the file rather than the beginning.

If you've got 50 machines doing this all at the same time, there's going to be conflicts. Your computer complains when you try to modify a file that's being used by another process, don't go throwing in 50 more contenders.

You could try using Sockets .

Whichever machine holds that file, designate that as the 'server' and make the other machines 'clients'. Your clients send messages to the server, your server appends those messages to the file in a synchronised manner.

You could then prevent your ~50 clients from directly changing the logs file with some network & server security.

Answer 2

You are simply re-inventing the wheel here, but in a very wrong way. The other answer is correct: using a simple file, and having multiple distributed users write to the same file just screams for failure.

But I disagree with the idea to use sockets instead. That is really low level, and requires you to implement a lot of (complicated) things yourself. You will have to think about network issues, multi threading, locking, buffering, ...

Sure, if this is for education, then building something like that is a challenge. But if you the goal here is to come to a robust solution that just works, you should rather think about using some 3rd party off-the-shelf solution.

You could start reading here . And then pick a framework such as logback. Alternatively, you could look into messaging services , such as ActiveMQ, or RabbitMQ.

Again: creating and collection logs in distributed environments is A) hard to get right but B) a solved problem.