JSP中c:foreach遍历和s:iterator遍历异同 JSP中c:foreach遍历和s:iterator遍历异同实例分析

时间:2021-03-20 異次元藍客人气:0

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本文实例分析了JSP中c:foreach遍历和s:iterator遍历的异同。分享给大家供大家参考。具体如下：

①jstl c:foreach

首先我们来看一个普通的servlet:

import com.xy.entity.Board;
import com.xy.entity.Topic;
import com.xy.entity.User;
public class ToMainAction extends HttpServlet
{
 private IBoarderDao boardDao = new BoardDaoImpl();
 private ITopicDao topicDao = new TopicDaoImpl();
 private IUserDao userDao = new UserDaoImpl();
 public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException,IOException
 {
 // 板块列表
 List<Board> boards = boardDao.getAllBoard();
 List<Integer> count = new ArrayList<Integer>();
 List<User> users = new ArrayList<User>();
 List<Topic> lastTopic = new ArrayList<Topic>();
 if (null != boards)
 {
  for (Board b : boards)
  {
  // 回帖数
  List<Topic> topic = topicDao.getTopicByBoardId(b.getborderId());
  if(null!=topic)
  {
   int num = topic.size();
   count.add(num);
  }
  else
  {
   count.add(0);
  }
  // 最近更新
  Topic t = topicDao.getLastTopic(b.getborderId());
  lastTopic.add(t);
  // 最近更新的作者
  User u = userDao.getUserByuId(t.getUid());
  users.add(u);
  }
  request.setAttribute("boards", boards);
  request.setAttribute("count", count);
  request.setAttribute("users", users);
  request.setAttribute("lastTopic", lastTopic);
  RequestDispatcher dis = request.getRequestDispatcher("main.jsp");
  dis.forward(request, response);
 }
 }
 public void doPost
    (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
 {
 this.doGet(request, response);
 }
}

main.jsp:

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<c:if test="${requestScope.boards!=null}">
 <c:forEach var="b" items="${requestScope.boards}" varStatus="status">
 <tr>
 <td width="6%" height="68">
 </td>
 <td width="67%">
  <div align="left" class="blueSpan">
  <img src="images/topic.gif" width="18" height="21" />
  <a href="logined/ToListAction?boardId=${b.borderId}">
  ${b.borderName}</a>
  </div>
 </td>
 <td>
  ${requestScope.count[status.index]}
 </td>
 <td>
  <p align="left">
  ${requestScope.lastTopic[status.index].title}
  </p>
  <br />
  <p align="left">
    ${requestScope.users[status.index].userName}
  </p>
  <br />
  <p align="left">
  修改时间：
  <br>
  ${requestScope.lastTopic[status.index].modifyTime}
  </p>
  <br />
 </td>
 </tr>
 </c:forEach>
</c:if>

②s:iterator

package com.xy.action;
action
public class ToMainAction extends ActionSupport implements RequestAware
{
 private IBoarderDao boardDao = new BoardDaoImpl();
 private ITopicDao topicDao = new TopicDaoImpl();
 private IUserDao userDao = new UserDaoImpl();
 private Map<String, Object> request;
 public void setBoardDao(IBoarderDao boardDao)
 {
 this.boardDao = boardDao;
 }
 public void setTopicDao(ITopicDao topicDao)
 {
 this.topicDao = topicDao;
 }
 public void setUserDao(IUserDao userDao)
 {
 this.userDao = userDao;
 }
 public String execute()
 {
 // 板块列表
 List<Board> boards = boardDao.getAllBoard();
 List<Integer> count = new ArrayList<Integer>();
 List<User> users = new ArrayList<User>();
 List<Topic> lastTopic = new ArrayList<Topic>();
 if (null != boards)
 {
  for (Board b : boards)
  {
  // 回帖数
  List<Topic> topic = topicDao.getTopicByBoardId(b.getBorderId());
  if (null != topic)
  {
   int num = topic.size();
   count.add(num);
  } else
  {
   count.add(0);
  }
  // 最近更新
  Topic t = topicDao.getLastTopic(b.getBorderId());
  lastTopic.add(t);
  // 最近更新的作者
  User u = userDao.getUserByuId(t.getUid());
  users.add(u);
  }
  request.put("boards", boards);
  request.put("count", count);
  request.put("users", users);
  request.put("lastTopic", lastTopic);
 }
 return SUCCESS;
 }
 public void setRequest(Map<String, Object> request)
 {
 this.request = request;
 }
}

main.jsp：

<%@ taglib uri="/struts-tags" prefix="s"%>
<s:if test="#request.boards!=null">
 <s:iterator value="#request.boards" id="b" status="st">
 <tr>
 <td width="6%" height="68">
 </td>
 <td width="67%">
   <div align="left" class="blueSpan">
  <img src="images/topic.gif" width="18" height="21" />
  <a href="logined/ToListAction?boardId="+<s:property value="#b.borderId"/>+">
   <s:property value="#b.borderName" />
  </a>
  </div>
 </td>
 <td>
  <s:property value=" #request.count[#st.index]" />
 </td>
 <td>
 <br />
  <p align="left">
  <s:property value="#request.lastTopic[#st.index].title" />
  </p>
 <br />
  <p align="left">
  <s:property value=" #request.lastTopic[#st.index].userName" />
  </p>
 <br />
  <p align="left">
  修改时间：
 <br/>
  <s:property value=" #request.lastTopic[#st.index].modifyTime" />
  </p>
  <br />
 </td>
 </tr>
    </s:iterator>
</s:if>

希望本文所述对大家的JSP程序设计有所帮助。

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