jsp异常处理方式：errorPage

声明式异常，在web.xml中配置
       <error-page>
            <error-code>404</error-code>
           <location>/404.html<!--绝对路径--></location>
      </error-page>
     <error-page>
         <exception-type>Java.lang.RuntimeException</exception-type>
         <location>/error.jsp</location>
    <error-page>