ApplicationContext.java 文件源码

@Override
public <T extends EventListener> void addListener(T t) {
    if (!context.getState().equals(LifecycleState.STARTING_PREP)) {
        throw new IllegalStateException(
                sm.getString("applicationContext.addListener.ise",
                        getContextPath()));
    }

    boolean match = false;
    if (t instanceof ServletContextAttributeListener ||
            t instanceof ServletRequestListener ||
            t instanceof ServletRequestAttributeListener ||
            t instanceof HttpSessionAttributeListener) {
        context.addApplicationEventListener(t);
        match = true;
    }

    if (t instanceof HttpSessionListener
            || (t instanceof ServletContextListener &&
                    newServletContextListenerAllowed)) {
        // Add listener directly to the list of instances rather than to
        // the list of class names.
        context.addApplicationLifecycleListener(t);
        match = true;
    }

    if (match) return;

    if (t instanceof ServletContextListener) {
        throw new IllegalArgumentException(sm.getString(
                "applicationContext.addListener.iae.sclNotAllowed",
                t.getClass().getName()));
    } else {
        throw new IllegalArgumentException(sm.getString(
                "applicationContext.addListener.iae.wrongType",
                t.getClass().getName()));
    }
}