JSF 2:这是处理业务异常的好方法吗？

Question

按照我在JSF转换/验证机制之外的Action FacesMessage in action方法中的上一个问题？,我正在尝试处理从托管bean之外的业务层抛出的异常.

策略是在PhaseListener中搜索和转换业务异常以面对消息.

它按照我的预期工作,但我想知道我是刚刚重新发明轮子,还是以错误的方式做到了？

这是我的代码示例代码段:

public class BusinessExceptionHandler implements PhaseListener {

    @Override
    public void afterPhase(PhaseEvent phaseEvent) {
        ExceptionHandler exceptionHandler = phaseEvent.getFacesContext().getExceptionHandler();

        // just debugging the handled exception, nothing here
        /*
        for (ExceptionQueuedEvent event : exceptionHandler.getHandledExceptionQueuedEvents()) {
            ExceptionQueuedEventContext context = (ExceptionQueuedEventContext) event.getSource();
            System.out.println("handled exception : " + context.getException());
        }*/

        for (Iterator<ExceptionQueuedEvent> it = exceptionHandler.getUnhandledExceptionQueuedEvents().iterator(); 
                it.hasNext();) {

            ExceptionQueuedEvent event = it.next();
            ExceptionQueuedEventContext eventContext = (ExceptionQueuedEventContext) event.getSource();
            Throwable e = eventContext.getException();
            System.out.println("unhandled exception : " + e);

            // get the root cause exception
            while (e.getCause() != null) { 
                e = e.getCause();
            }

            System.out.println("cause exception : " + e + 
                ", cause exception is BE : " + (e instanceof BusinessException));

            // handle BE
            if (e instanceof BusinessException) {
                BusinessException be = (BusinessException) e;
                System.out.println("processing BE " + be);
                FacesMessage message = Messages.getMessage(
                    "com.corejsf.errors", 
                    be.getMessage(), 
                    be.getParamValues()
                );
                FacesContext context = FacesContext.getCurrentInstance();
                context.addMessage(null, message);
                it.remove(); // remove the exception

                // works fine without this block, if BE is thrown, always return to the original page
                /*
                NavigationHandler navigationHandler = context.getApplication().getNavigationHandler();
                System.out.println("navigating to " + context.getViewRoot().getViewId());
                navigationHandler.handleNavigation(context, context.getViewRoot().getViewId(), null);
                */
            }
        }
    }

    @Override
    public void beforePhase(PhaseEvent phaseEvent) {
    }

    @Override
    public PhaseId getPhaseId() {
        return PhaseId.INVOKE_APPLICATION;
    }

}

谢谢 !

此致,Albert Kam

Answer 1

您的方法是 JSF 1.x 和 JSF 2.x 异常处理方法的混合。由于您使用的是 JSF 2.x，因此我建议使用纯 JSF 2.x 方法，而无需PhaseListener使用新ExceptionHandlerAPI的帮助。

您可以在“JSF 2.0：完整参考”ViewExpiredException一书的第 282 页找到一个示例，该书可在此处在线获取（单击第一个结果链接）。