name.didier.david.test4j.utils.ExitCaptor Maven / Gradle / Ivy

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package name.didier.david.test4j.utils;

/**
 * Capture all exit calls. Usage:
 * 
 *  * ExitCaptor captor = new ExitCaptor();
 * try {
 *     captor.startCapturing();
 *     doSomeExiting();
 * } catch (NoExitException e) {
 *     doSomethingWithStatus(e.getStatus());
 * } catch (Exception e) {
 *     propagate(e);
 * } finally {
 *     captor.stopCapturing();
 * }
 * 
 * 
 * @author ddidier
 */
public class ExitCaptor {

    /** The backup {@link SecurityManager}. */
    private SecurityManager oldSecurityManager;
    /** The capturing {@link SecurityManager}. */
    private SecurityManager newSecurityManager;

    /** Default constructor. */
    public ExitCaptor() {
        super();
    }

    /**
     * Start to capture exit calls. The security manager is reassigned so do not forget to restore the previous state
     * with {@link #stopCapturing()}. Use a {@code finally} block!
     * 
     * @throws IllegalStateException if already capturing exit calls.
     */
    public void startCapturing() {
        if (isCapturing()) {
            throw new IllegalStateException("Already capturing exit calls");
        }

        oldSecurityManager = System.getSecurityManager();
        newSecurityManager = new NoExitSecurityManager();
        System.setSecurityManager(newSecurityManager);
    }

    /**
     * Stop to capture exit calls. The previous security manager is restored. Should be used in a {@code finally} block!
     * 
     * @throws IllegalStateException if not capturing exit calls.
     */
    public void stopCapturing() {
        if (!isCapturing()) {
            throw new IllegalStateException("Not capturing exit calls");
        }

        System.setSecurityManager(oldSecurityManager);
        reset();
    }

    /**
     * @return true if capturing exit calls, false otherwise.
     */
    public boolean isCapturing() {
        return newSecurityManager != null;
    }

    /**
     * Reset the capturing state of exit calls.
     */
    private void reset() {
        oldSecurityManager = null;
        newSecurityManager = null;
    }
}