Messages: No result defined for action com.xxx.action.SomeAction and result input
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症状: action中无法正常进行跳转.

原因: 验证值时验证报错.

解决办法:
1) 给 Action 加入 input 的结果;
2) 去除所有证验相关的拦截器,包括默认的validation
     调试方法:在 input 中加入调试
                      <s:fielderror/>
                      <s:debug />
                      <a href="javascript:void(0);" onclick="toggleDebug('debug');return false;">[调试信息]</a>
                      可显示下列信息:
                      Invalid field value for field "attachment". 
                      fieldErrors {attachment=[Invalid field value for field "attachment".]} 
3) Action 不再继承自 ActionSupport(里面有 ValidationAware 接口), 而转而只实现 Action 接口即可.