Changing boolean value from another servlet to stop the loop

Question

I have a for loop which runs based on value of boolean variable.

public class LoopClass{
..
private boolean[] toInterrupt = new boolean[];
public boolean getValue() {
        
        return toInterrupt[0];
    }

    public void setValue(boolean newValue) {
        toInterrupt[0] = newValue;
    }
}
public method abc{

for loop{

if (getValue()){
   break:
}}}

I want to interrupt this loop through servlet:

public class interruptServlet exetnds HttpServlet {

LoopClass = lp = new LoopClass();
lp.setValue(true)
}

Even after executing servlet, boolean toInterrupt[0] always remain false. How can i change boolean value through servlet to stop the loop ?

If interruptServlet is running in another thread (as I assume it is), you need to properly manage the multi-threaded access to the variable to avoid data consistency issues. BTW, please, post the code as close as possible to what you're actually doing, so volunteers can help you better; the one you posted doesn't compile. — lealceldeiro
– lealceldeiro, Commented Sep 29, 2023 at 7:28
If you create a new instance of LoopClass, it won’t affect the value in some other existing instance. — Tim Moore
– Tim Moore, Commented Sep 29, 2023 at 7:36
@TimMoore: Thanks for your comment. how can i change the value in existing instance ? — Stephan
– Stephan, Commented Sep 29, 2023 at 7:51
You need a reference to that instance. I think the question would benefit from a lot more context about what your use case is overall. — Tim Moore
– Tim Moore, Commented Sep 29, 2023 at 8:05

Rob Spoor · Accepted Answer · 2023-09-29 08:35:12Z

1

As said before, the new LoopClass instance does not share any state with the actual servlet.

There is a pretty easy way to share state between servlets: the ServletContext. For instance:

LoopClass:

private static final String INTERRUPTED_ATTRIBUTE = LoopClass.class.getName() + ".interrupted";

public static void setInterrupt(ServletContext context, boolean interrupt) {
    context.setAttribute(INTERRUPTED_ATTRIBUTE, interrupt);
}

private boolean interrupted() {
    return Boolean.TRUE.equals(getServletContext().getAttribute(INTERRUPTED_ATTRIBUTE);
}

InterruptServlet:

LoopClass.setInterrupt(getServletContext(), true);

Note that I kept all of the actual code for interrupting in LoopClass. That way you can easily rename the attribute name without having to change other code.

answered Sep 29, 2023 at 8:35

Rob Spoor

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