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	package foo;

import javax.faces.event.PhaseId;
import javax.faces.event.PhaseEvent;
import javax.faces.event.PhaseListener;

public class MyPhaseListener implements PhaseListener {

    // Class-level immutable (final) variables are thread-safe since they are read-only
    // and are initialized at about the same time as the constructor. The Java compiler
    // will also permit you to initialize final variables within the body of the constructor.
    private final String classLevelImmutableVariable1 = "cannot-change-me-1";
    private final String classLevelImmutableVariable2; // initialized in constructor

    // Class-level mutable (non-final) variables are NOT thread-safe. Don't use these
    // without synchronization!
    private String classLevelMutableVariable = "can-change-me-but-dont-do-it!";

    // Static final constants (like loggers) are typically thread-safe.
    private static final Logger logger = LoggerFactory.getLogger(MyPhaseListener.class);

    /**
     * PhaseListener constructors execute when Mojarra/MyFaces initializes.
     */
    public MyPhaseListener() {
        // It's OK to initialize final class-level variables here.
        this.classLevelImmutableVariable2 = "cannot-change-me-2";
    }

    public void afterPhase(PhaseEvent phaseEvent) {

        // Accessing method parameters is thread-safe.
        PhaseId phaseId = phaseEvent.getPhaseId();

        // Accessing FacesContext is thread-safe since it is a ThreadLocal singleton.
        FacesContext facesContext = phaseEvent.getFacesContext();
    }

    public void beforePhase(PhaseEvent phaseEvent) {

        // Creating local method variables is thread-safe, since the JVM will create an
        // instance (copy) on the stack for each Thread.
        String mutableLocalMethodVariable = "ok-to-change-me-in-the-scope-of-this-method";

        // Writing to a logger is thread-safe, providing the underlying logger
        // implementation is thread-safe!
        logger.debug("inside beforePhase method");
    }
}