Top
首页 > 老文章 > 正文

JSF和Struts框架的错误控制与封装处理

JSF和Struts框架的错误控制

JSF和Struts框架的错误控制与封装处理
发布时间:2007-07-26 06:45        来源:        作者:dxaw
在struts中,通常采用的全局错误控制模式是构建一个baseAction,在其execute方法中完成前台传回方法的dispatch操作,并由 try……catch……捕获程序错误,实现错误的控制和展示。一个典型的BaseAction例子如下: 代码
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) {

……

    ActionForward forwardPage = null;

    try { 

        String parameter = mapping.getParameter();

        if (parameter == null) { 

        String message = messages.getMessage("dispatch.handler",mapping.getPath());

            response.sendError(500, message);

            return null;

        }

    String name = processReqCode(request.getParameter(parameter));

    forwardPage = dispatchMethod(mapping, form, request, response, name);

    } catch (BaseException ex) { 

        if (log.isDebugEnabled())

            log.debug("发生错误:", ex);

        forwardPage = processBaseException(request, mapping, ex);

        } catch (Throwable ex) { 

            log.error("发生错误:", ex);

        ActionMessages errors = new ActionMessages();

        ByteArrayOutputStream ostr = new ByteArrayOutputStream();

        ex.printStackTrace(new PrintStream(ostr));

        errors.add("org.apache.struts.action.GLOBAL_MESSAGE", new ActionMessage
(ostr.toString()));

        saveErrors(request, errors);

        forwardPage = mapping.findForward("syserror");

        output.setStatus("fail");

        output.setError(ex.getMessage());

    }

    ……

    }
由于JSF采用了managed bean,JSP页面直接通过调用managed bean中的方法完成数据交互,不能像struts一样通过捕获dispatch操作过程抛出的异常来完成错误的处理(因为根本就没有dispatch方法),似乎jsf根本就不支持全局的错误处理。 如果在managed bean中throw 一个exception(这里是AppException),观察一下控制台的日志,可以看到其实错误是从一个ActionListener的实现中抛出的(针对myfaces,这里是ActionListenerImpl),参考jsf的生命周期过程,方法出来了: 代码
public class GlobalActionListener extends ActionListenerImpl {

    public void processAction(ActionEvent event) throws AbortProcessingException { 

        FacesContext facesContext = FacesContext.getCurrentInstance();

        Application application = facesContext.getApplication();

        ActionSource actionSource = (ActionSource) event.getComponent();

        MethodBinding methodBinding = actionSource.getAction();

        String fromAction = null;String outcome = null;

        if (methodBinding != null) {

             fromAction = methodBinding.getExpressionString();

            try { 

                outcome = (String) methodBinding.invoke(facesContext, null);

        } catch (EvaluationException e) { 

            Throwable cause = e.getCause();

            if (cause != null && cause instanceof AppException) { 

        //这里需要根据框架的不同,判断实例是否是程序中手动抛出的错误        

        FacesUtils.addErrorMessage(event.getComponent().getClientId(facesContext),
cause.getMessage());}

         else { 

            throw (AbortProcessingException) cause;

        } 

    } catch (RuntimeException e) { 

        throw new FacesException("Error calling action method of component with id " + 
event.getComponent().getClientId(facesContext), e);

    }

    NavigationHandler navigationHandler = application.getNavigationHandler();

    navigationHandler.handleNavigation(facesContext, fromAction, outcome);

    // Render Response if needed 

      facesContext.renderResponse();

        }

    }
监听器配置,faces-config-application.xml: 代码
<application>
        <variable-resolver>
           org.springframework.web.jsf.DelegatingVariableResolver
        </variable-resolver> 
<message-bundle>resources.application</message-bundle> 
<locale-config> 
<default-locale>en</default-locale> 
</locale-config> 
<action-listener>
org.snailportal.webframework.listener.GlobalActionListener
</action-listener> 
</application>
这样,开发人员只需要在action和managed bean里面根据业务的需要抛出指定基础类型的Exception实例,由BaseAction和ActionListener完成错误的封装处理,再传递给前台进行显示,从而减少开发的代码量,提高框架的可维护性。 (责任编辑:龚勋)
加载更多

专题访谈

合作站点
stat