<logic:present name="result">
        <logic:iterate id="book" name="result">
             <logic:present name="book">
                 <tr>
                     <td><bean:write name="book" property="name" /></td>
                     <td><bean:write name="book" property="author" /></td>
                     <td><bean:write name="book" property="price" /></td>
                  </tr>
              </logic:present>
         </logic:iterate>
</logic:present>

<logic:present name="result" scope="session">这里有个scope属性可能是request,session等,name指的是一个对象,可能是javaBean,也可能是集合的对象,整个意思就是就是在scope(session,request)范围里面查找name(一个对象)是否存在,相当于一个if()语句.