How to prevent concurrency in web service API?

Question

We have three web service ( /a, /b, /c), where each service maps the method ( go()) in a separate Java class ( ClassA, ClassB, ClassC).

Only one service is started at a time (i.e., /bit cannot work while it is running /a). However, since this is a REST API, nothing prevents clients from simultaneously requesting services.

What is the best and easiest way on the server to ensure that services do not start simultaneously?

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Update . This is an internal application, we will not have a large load and there will be only one application server.

Update . This is a subjective question, since you can make different arguments in the overall design of the application, which affects the final answer. Accepted an excessive answer, as I found that the most interesting and useful.

Answer 1

Assuming it's not that simple to get the web server to have only one auditory stream serving requests ... I suppose I just used a static lock ( ReentrantLock , perhaps for clarity, although you could synchronize any common object):

public class Global {
  public static final Lock webLock = new ReentrantLock();
}

public class ClassA {
    public void go() {
        Global.webLock.lock()
        try {
            // do A stuff
        } finally {
            Global.webLock.unlock()
        }
    }
}

public class ClassB {
    public void go() {
        Global.webLock.lock()
        try {
            // do B stuff
        } finally {
            Global.webLock.unlock()
        }
    }
}

public class ClassC {
    public void go() {
        Global.webLock.lock()
        try {
            // do C stuff
        } finally {
            Global.webLock.unlock()
        }
    }
}

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