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JSP中c:foreach遍历和s:iterator遍历异同实例分析

2017年12月12日  | 移动技术网IT编程  | 我要评论

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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