请教:struts中<logic:iterate>与Map的使用?

<logic:iterate>的用法，例如下面的例子：
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<%@ page contentType="text/html;charset=GB2312" language="java" %>
<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %>
<%@ taglib uri="/WEB-INF/struts-template.tld" prefix="template" %><html:html>
<head>
<title></title>
<html:base/>
</head>
<body bgcolor="white">
<table width="98%" border="1" bgColor="#E6F2E7" borderColorDark="#FFFFFF" borderColorLight="#008000" cellPadding="3" cellSpacing="0" >
<tr bgcolor='#90C090'>
<td><span CONTENTEDITABLE=true>username</span></td>
<td><span CONTENTEDITABLE=true>password</span></td>
<td><span CONTENTEDITABLE=true>role</span></td>
<td><span CONTENTEDITABLE=true>删除</span></td>
<td><span CONTENTEDITABLE=true>编辑</span></td>
<td><span CONTENTEDITABLE=true>链接</span></td></tr>
<logic:iterate name='lyk' id='lyk' type='emptyprj.lyk' scope='request'>
<logic:notEqual name='lykForm' property='action' value='edit'> 
<tr>
<td><bean:write name='lyk' property='username' /></td>
<td><bean:write name='lyk' property='password' /></td>
<td><bean:write name='lyk' property='role' /></td>
<td><a href="lykAction.do?action=delete&search=search&expression=<bean:write name='lyk' property='username' />">删除</a></td>
<td><a href="lykAction.do?action=edit&search=search&expression=<bean:write name='lyk' property='username' />">编辑</a></td>
<td><a href="lykAction.do?action=link&search=search&expression=<bean:write name='lyk' property='username' />">链接</a></td></tr>
</logic:notEqual> 
<logic:equal name='lykForm' property='action' value='edit'> 
<tr>
<form  method='post' name='lykForm' action="/hib/lykAction.do?action=update&search=search&expression=<bean:write name='lyk' property='username' />">
<td><html:text name='lyk' property='username' /></td>
<td><html:text name='lyk' property='password' /></td>
<td><html:text name='lyk' property='role' /></td>
<td><a href="lykAction.do?action=delete&search=search&expression=<bean:write name='lyk' property='username' />">删除</a></td>
<td><html:submit value='更新'></html:submit></form ><form  method='post' action="lykAction.do?action=reset&search=search&expression=<bean:write name='lyk' property='username' />" ><html:submit value='取消'></html:submit>
</form ></td>
<td><a href="lykAction.do?action=link&search=search&expression=<bean:write name='lyk' property='username' />">链接</a></td></tr>
</logic:equal> 
</logic:iterate><tr><td  align=middle colSpan=7 ><bean:write property='pagestr' name='lykForm' filter='false' /></td></tr></tr>
</table>
</body>
</html:html>