谁来帮我看看这个异常到底是什么错啊！！！谢谢了，急啊
<html:form action="startExam.do?action=submitTestPaper" method="post"><table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td>
<table id="single" width="90%" border="0" cellspacing="0" cellpadding="0" align=center>
<tr>
<td colspan="4" height=23 style="font-size:11pt;">一、单选题（<font color=red>每题<%=s %>分，答错不得分</font>）</td>
</tr>
<logic:iterate id="questions" name="singleQue" type="com.exam.struts.form.QuestionForm" scope="request" indexId="ind">
<tr>
<td height=23 colspan="4" align=center nowrap>
<table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td width="8%" align=right height=23>[ ${ind+1} ]</td>
<td width="2%"> </td>
<td width="90%" align=left nowrap style="font-size:11pt;"><bean:write name="questions" property="subject" filter="true"/>
<html:hidden property="idArrS[${ind}]" name="questions"/>
</td>
</tr>
</table>
</td>
</tr>
<tr>
<td width="8%" height=23 nowrap> </td>
<td width="3%" align=center nowrap><html:radio property="answerArrS[${ind}]" styleClass="noborder" value="A"/></td>
<td width="3%" align=center nowrap>A.</td>
<td width="86%" align=left nowrap><bean:write name="questions" property="optionA" filter="true"/></td>
</tr>
<tr>
<td width="8%" height=23 nowrap> </td>
<td width="3%" align=center nowrap><html:radio property="answerArrS[${ind}]" styleClass="noborder" value="B"/></td>
<td width="3%" align=center nowrap>B.</td>
<td width="86%" align=left nowrap><bean:write name="questions" property="optionB" filter="true"/></td>
</tr>
<tr>
<td width="8%" height=23 nowrap> </td>
<td width="3%" align=center nowrap><html:radio property="answerArrS[${ind}]" styleClass="noborder" value="C"/></td>
<td width="3%" align=center nowrap>C.</td>
<td width="86%" align=left nowrap><bean:write name="questions" property="optionC" filter="true"/></td>
</tr>
<tr>
<td width="8%" height=23 nowrap> </td>
<td width="3%" align=center nowrap><html:radio property="answerArrS[${ind}]" styleClass="noborder" value="D"/></td>
<td width="3%" align=center nowrap>D.</td>
<td width="86%" align=left nowrap><bean:write name="questions" property="optionD" filter="true"/></td>
</tr>
</logic:iterate>
</table>
<table id="single" width="90%" border="0" cellspacing="0" cellpadding="0" align=center>
<tr>
<td colspan="4" height=23 style="font-size:11pt;">二、多选题（<font color=red>每题<%=m%>分，答错不得分</font>）</td>
</tr>
<logic:iterate id="questions" name="moreQue" type="com.exam.struts.form.QuestionForm" scope="request" indexId="ind">
<tr>
<td height=23 colspan="4" align=center nowrap>
<table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td width="8%" align=right height=23>[ ${ind+1} ]</td>
<td width="2%"> </td>
<td width="90%" align=left nowrap style="font-size:11pt;"><bean:write name="questions" property="subject" filter="true"/>
<html:hidden property="idArrM[${ind}]" name="questions"/>
</td>
</tr>
</table>
</td>
</tr>
<tr>
<td width="8%" height=23 nowrap> </td>
<td width="3%" align=center nowrap><html:multibox property="moreSelect[${ind}].answerArr" styleClass="noborder" value="A"/></td>
<td width="3%" align=center nowrap>A.</td>
<td width="86%" align=left nowrap><bean:write name="questions" property="optionA" filter="true"/></td>
</tr>
<tr>
<td width="8%" height=23 nowrap> </td>
<td width="3%" align=center nowrap><html:multibox property="moreSelect[${ind}].answerArr" styleClass="noborder" value="B"/></td>
<td width="3%" align=center nowrap>B.</td>
<td width="86%" align=left nowrap><bean:write name="questions" property="optionB" filter="true"/></td>
</tr>
<tr>
<td width="8%" height=23 nowrap> </td>
<td width="3%" align=center nowrap><html:multibox property="moreSelect[${ind}].answerArr" styleClass="noborder" value="C"/></td>
<td width="3%" align=center nowrap>C.</td>
<td width="86%" align=left nowrap><bean:write name="questions" property="optionC" filter="true"/></td>
</tr>
<tr>
<td width="8%" height=23 nowrap> </td>
<td width="3%" align=center nowrap><html:multibox property="moreSelect[${ind}].answerArr" styleClass="noborder" value="D"/></td>
<td width="3%" align=center nowrap>D.</td>
<td width="86%" align=left nowrap><bean:write name="questions" property="optionD" filter="true"/></td>
</tr>
</logic:iterate>
</table>
</td>
</tr>
<tr>
<td align="center"><html:submit property="submit" styleClass="btn_grey" value="交卷"/> </td>
</tr>
</table>
</html:form>
这提交后出现下面异常
Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
javax.servlet.ServletException: BeanUtils.populate
org.apache.struts.util.RequestUtils.populate(RequestUtils.java:495)
org.apache.struts.action.RequestProcessor.processPopulate(RequestProcessor.java:805)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:203)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
com.exam.struts.form.CharFilter.doFilter(CharFilter.java:28)
root cause
java.lang.NullPointerException
org.(PropertyUtils.java:1458)
org.(BeanUtils.java:1013)
org.(BeanUtils.java:808)
org.apache.struts.util.RequestUtils.populate(RequestUtils.java:493)
org.apache.struts.action.RequestProcessor.processPopulate(RequestProcessor.java:805)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:203)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
com.exam.struts.form.CharFilter.doFilter(CharFilter.java:28)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.25 logs.
这是form里的
public class QuestionForm extends ActionForm {
private int id;
private int taotiID;
private int lessonID;
private String lessonName;
private String taotiName;
private String type;
private String subject;
private String optionA;
private String optionB;
private String optionC;
private String optionD;
private String answer;
private String[] answerArray;
private String[] answerArrS;
private MoreSelect[] moreSelect;
private int[] dellArray;
private String note;
private int[] idArrS;
private int[] idArrM;
有谁能帮看下啊 ，找了很久了，急啊！！！！
