Struts 1.x 异常处理方式(jsp生成形式，非ajax)

　基本原理:　

　如果有异常，把异常存入request里，然后转发到指定的jsp页面，然后可以用struts的error标签取出来　

ActionErrors errors = new ActionErrors();

errors.add( ActionErrors.GLOBAL_ERROR,new ActionError("error.application.exception"));

saveErrors(request, errors);

return (new ActionForward(mapping.getInput()));

方式1 用一个BaseAction 继承DispatchAction改写perform方法
详细参见http://www.cnblogs.com/kapok/archive/2005/10/15/255395.html

public class BaseDispatchAction extends DispatchAction {

      public ActionForward perform(ActionMapping mapping,ActionForm form,HttpServletRequest request,HttpServletResponse response)throws IOException, ServletException {        
 　　// 获取方法名的key参数
　　String parameter = mapping.getParameter();
　　String name = request.getParameter(parameter);        
　　Method method = null;
　　method = getMethod(name);

　　ActionForward forward = null;
　　try {
         Object args[] = { mapping, form, request, response };
　　　　 forward = (ActionForward) method.invoke(this, args);
　　}catch (InvocationTargetException e) {
  　if (e.getTargetException() instanceof BaseException) {
 　　 forward = processExceptions(request, mapping, e);
　　 }if (e.getTargetException() instanceof ApplicationException) {
　　　forward = processExceptions(request, mapping, e);
 　　} else if (e.getTargetException() instanceof SystemException) {
　　　　request.setAttribute("EXCEPTION_KEY", e);   
　　　　//直接跳到错误页面去
　　　　forward = mapping.findForward("systemerror");
     } 
　　}
       return (forward);

     }

　　protected ActionForward processExceptions( HttpServletRequest request, ActionMapping mapping,Throwable throwable) {
　　ActionErrors errors = new ActionErrors();
　　ActionForward forward = null;
　　if (mapping.getInput() != null) {
　　forward = new ActionForward(mapping.getInput());
　　　　} else if (mapping.findForward("FAILURE_KEY") != null) {
　　forward = mapping.findForward("FAILURE_KEY");
　　　　}
　　saveErrors(request, errors);
　　return forward;

     }

 }

方式2 使用 ExceptionHandler 
配置
　　<global-exceptions>
　　<exception key="todo" type="org.chage.exception.BaseException"        handler="org.chage.exception.MyExceptionHandler" />
　　</global-exceptions>

public class MyExceptionHandler  extends ExceptionHandler {
　　public ActionForward execute( Exception exception,ExceptionConfig config, ActionMapping mapping,ActionForm form, HttpServletRequest request,
HttpServletResponse response)throws ServletException {       
　　　　request.setAttribute("exception", exception);
　　　　return mapping.getInputForward();
　　}
　}  

在页面上：

<logic:present name="exception">

<bean:write name="exception"/>

</logic:present>