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struts2 异常处理

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关键字: struts 2 在学习struts2的过程中,想到了struts1的错误处理机制,转载一篇 Callan (javaeye)的文章。

利用struts2的异常处理机制可以很方便的实现异常处理,你不再需要在Action中捕获异常,并抛出相关的异常了,这些都交给拦截器来帮你做了。在struts-default.xml中己经设置了拦截器,因此我们可以直接使用声明式异常.struts2-default-xml声明的拦截器如下:



Xml代码
<interceptors>  
<interceptor name="exception"    
class="com.opensymphony.xwork.interceptor.ExceptionMappingInterceptor"/>  
</interceptors>  

<interceptors>
<interceptor name="exception"
class="com.opensymphony.xwork.interceptor.ExceptionMappingInterceptor"/>
</interceptors>





异常的类型可以分为两种:局部异常映射和全局异常映射



当Action抛出异常时,会在局部中和全局中查找与之相匹配的异常,如果局部和全局中都有满足的异常映射,以局部的为准. 例子说明:



action:



Java代码
public class LogonAction {  
     private String userName;  
     private String userPwd;  
     public String getUserName() {  
         return userName;  
     }  
     public void setUserName(String userName) {  
         this.userName = userName;  
     }  
     public String getUserPwd() {  
         return userPwd;  
     }  
     public void setUserPwd(String userPwd) {  
         this.userPwd = userPwd;  
     }  
     public String execute() throws Exception{  
         if(userName.equals("callan") && userPwd.equals("fjf")){  
             ActionContext.getContext().getSession().put("userName", "callan");  
             return "succee";  
         } else {  
             throw new SQLException(“用户名密码不正确”);  
         }  
     }  
}  

public class LogonAction {
private String userName;
private String userPwd;
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getUserPwd() {
return userPwd;
}
public void setUserPwd(String userPwd) {
this.userPwd = userPwd;
}
public String execute() throws Exception{
if(userName.equals("callan") && userPwd.equals("fjf")){
ActionContext.getContext().getSession().put("userName", "callan");
return "succee";
} else {
throw new SQLException(“用户名密码不正确”);
}
}
}

配置文件:

Xml代码
<package name="logon" extends="struts-default">  
       <!-- global-exception-mappings必需在action的上面 -->  
       <global-exception-mappings>  
             <exception-mapping result="all" exception="java.lang.Exception">  
                 </exception-mapping>  
         </global-exception-mappings>  
         <action name="logon" class="com.LogonAction">  
             <result name="succee">/logon/welcome.jsp</result>  
             <result name="error">/logon/error.jsp</result>  
             <exception-mapping result="sql" exception="java.sql.SQLException"/></exception-mapping>  
             <exception-mapping result="nullPoint" exception="java.lang.NullPointerException"></exception-mapping>  
             <result name="nullPoint">/logon/nullpoint.jsp</result>  
             <result name="sql">/logon/sql.jsp</result>  
             <result name="all">/logon/all.jsp</result>  
         </action>  
     </package>  

<package name="logon" extends="struts-default">
       <!-- global-exception-mappings必需在action的上面 -->
       <global-exception-mappings>
         <exception-mapping result="all" exception="java.lang.Exception">
                 </exception-mapping>
         </global-exception-mappings>
         <action name="logon" class="com.LogonAction">
             <result name="succee">/logon/welcome.jsp</result>
             <result name="error">/logon/error.jsp</result>
             <exception-mapping result="sql" exception="java.sql.SQLException"/></exception-mapping>
             <exception-mapping result="nullPoint" exception="java.lang.NullPointerException"></exception-mapping>
             <result name="nullPoint">/logon/nullpoint.jsp</result>
             <result name="sql">/logon/sql.jsp</result>
             <result name="all">/logon/all.jsp</result>
         </action>
     </package>


上面是个用户登陆的action及配置,定义了两个局部异常和一个全局异常
当输入的用户名和密码不为callan和fjf时,会抛出SQLException异常,局部异常配置起作用,会定向到sql.jsp,如果注释局部sql异常,全局异常起作用,定向到all.jsp





可以使用Struts2的标签来输出异常信息
<s:property value="exception.message"/>
<s:property value="exceptionStack"/>

例如sql.jsp页面

<body>
   <s:property value="exception.message"/>
</body>
可以输出 用户名密码不正确
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