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WebWork2.2新特性之异常映射/全局异常映射(有异常的页面显示)

JSPWebworkXMLHTML 
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在xwork中,package的定义中增加了global-exception-mappings,action的定义中增加了exception-mapping,要想使用这2个特性,必须使用xwork-1.1.dtd才行.
DTD中,global-exception-mappings是这样定义的,
<ELEMENT global-exception-mappings (exception-mapping+)>
也就是说如果要使用,至少包含一个异常映射.
exception-mapping的定义如下:

<!ELEMENT exception-mapping (#PCDATA|param)*>
<!ATTLIST exception-mapping
    name CDATA #IMPLIED
    exception CDATA #REQUIRED
    result CDATA #REQUIRED
>  

可以看到有3个属性:名称,异常类型,和结果.

经过一番查看,发现xwork-default.xml中还没有定义相关的拦截器,搜索了一下,发现了ExceptionMappingInterceptor,看来它是把异常翻译为相应的结果的.
(在最后发行版本中,应该会定义的.目前只好我们自己定义了.)
首先我们虚拟一个程序,假设程序会抛出几种程序
Action定义如下:
package com.jscud.ww2test.exceptionmap;
 
import com.opensymphony.xwork.ActionSupport;
 
/**
  * @author scud http://www.jscud.com
  *
  */
public class ExpMappingAction extends ActionSupport
{
     private int type;
 
     public String execute() throws NoRightException,NotFoundException
     {
         if(type==1)
         {
             throw new NoRightException();
         }
         else if(type ==99)
         {
             throw new NotFoundException();
         }
         else if(type==60) //其他异常
         {
             throw new IllegalArgumentException(); 
         }
         
         return SUCCESS;
     }
     
     public int getType()
     {
         return type;
     }
     
     public void setType(int type)
     {
         this.type = type;
     }
}  

从Action可以看出,程序至少会抛出3种异常,我们如果使用异常映射,就要考虑到抛出的所有异常.
程序中用到的NoRightException,NotFoundException是为了演示而建立的2个简单异常,无任何特殊代码,继承自Exception.
我们的Xwork.xml中的定义如下:

<package name="exceptionmapping" extends="webwork-default" namespace="/exceptionmap">
 
  <interceptors>
   <interceptor name="exceptionmapping" class="com.opensymphony.xwork.interceptor.ExceptionMappingInterceptor"/>
   
   <interceptor-stack name="myDefaultStack">
       <interceptor-ref name="defaultStack"/>
       <interceptor-ref name="exceptionmapping"/>
   </interceptor-stack>
  </interceptors>

  <default-interceptor-ref name="myDefaultStack"/>


  <global-results>
   <result name="noright" type="dispatcher">
    <param name="location">/exceptionmap/noright.jsp</param>
   </result>
   <result name="exception" type="dispatcher">
    <param name="location">/exceptionmap/exception.jsp</param>
   </result>
  </global-results>
 
  <global-exception-mappings>
   <exception-mapping name="noright" exception="com.jscud.ww2test.exceptionmap.NoRightException" result="noright"/>
   <exception-mapping name="exception" exception="java.lang.Exception" result="exception"/>
  </global-exception-mappings>
 
  <action name="index" class="com.jscud.ww2test.exceptionmap.ExpMappingAction">
   <exception-mapping  name="notfound" exception="com.jscud.ww2test.exceptionmap.NotFoundException" result="notfound"/>
   <result name="success" type="dispatcher">
    <param name="location">/exceptionmap/index.jsp</param>
   </result>
   <result name="notfound" type="dispatcher">
    <param name="location">/exceptionmap/notfound.jsp</param>
   </result>
  </action>
  
</package>
首先定义了一个exceptionmapping拦截器,用来指向ExceptionMappingInterceptor.
然后定义一个拦截器Stack,包含defaultStack和exceptionmapping,注意,exceptionmapping是在Stack的最后面,否则会发生不可预期的结果.
可以看到global-exception-mappings段包含了2个异常映射,一个为NoRight的处理,另外一个为对应java.lang.Exception的映射.
在Action的定义中包含了一个exception-mapping,对应NotFound异常.
没有看到IllegalArgumentException的对应结果?? 拦截器对没有定义的异常会依次找这个异常的父类,一级一级向上查找,例如IllegalArgumentException的最终父节点是Exception,就会转向到Exception对应的结果. 如果一个异常有多个层次关系上的父类,那个关系最近就找谁.
演示页面如下:
<%@ page contentType="text/html; charset=GBK" %>
<%@ taglib uri="webwork" prefix="ww" %>
<html>
   <head>
     <title>exception mapping</title>
   </head>
<body>
 
<br>
Exception 1:
<a href="index.jspa?type=1">Exception 1</a>
<br><br>
 
Exception 99:
<a href="index.jspa?type=99">Exception 99</a>
<br><br>
 
Other Exception:
 
<a href="index.jspa?type=60">Exception 60</a>
<br><br>
 
Normal:
<a href="index.jspa">No Exception</a>
<br><br>
 
</body>
</html>
jsp页面的异常显示：其中AddException，DaoException，FindException是自己定义的异常，继承exception
<%@ page language="java" contentType="text/html; charset=GB18030"
    pageEncoding="GB18030"%>
<%@ taglib prefix="ww" uri="/webwork"%>
<%@ page import="com.opensymphony.xwork.util.OgnlValueStack"%>
<%@ page import="com.opensymphony.xwork.ActionContext"%>
<%@ page import="com.opensymphony.xwork.interceptor.ExceptionHolder"%>
<%@ page import="com.mdcl.framework.exception.*"%>
<%@ page import="java.io.*"%>
<%@ page import="com.mdcl.timecard.util.Translate"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GB18030">
<title>Insert title here</title>
</head>
<body>  
异常信息 
<%
String tipMessge = null;//中文提示信息
    OgnlValueStack s = ActionContext.getContext().getValueStack(); 
    ExceptionHolder e;
    String s1 = new String("");;
    String name = new String("");
    for(int i = s.size();i>0;i--){
        Object obj = s.pop();
        if(obj instanceof ExceptionHolder){
            e = (ExceptionHolder)obj;
            Object o = e.getException();
            if(o instanceof AddException){
                AddException we = (AddException)o;
                tipMessge = Translate.translate("ErrorException");
            }else if(o instanceof DaoException){
                DaoException we = (DaoException)o;
                tipMessge = Translate.translate("ErrorException");
            }
            else if(o instanceof FindException){
                FindException we = (FindException)o;
                tipMessge = Translate.translate("ErrorException");
            }
            s1 =e.getExceptionStack();
            System.out.println(tipMessge);
            break;
        }
    } 
    OutputStream b = response.getOutputStream();
%>
<br/>
<%=tipMessge%>
<%=s1%>
</body>
</html>
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