jstl标签库示例二

package app05b;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
* 城市控制类
*/
@WebServlet( name = "BigCitiesServlet", urlPatterns = "/bigCities")
public class BigCitiesServlet extends HttpServlet {
   private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public BigCitiesServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

   /**
   *
   */
   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       // 创建map集合
       Map<String, String> capitals = new HashMap<String, String>();
       // 放入键值对
       capitals.put("Indonesia", "Jakarta");
        capitals.put("Malaysia", "Kuala Lumpur");
        capitals.put("Thailand", "Bangkok");
        // 向页面传递参数
        request.setAttribute("capitals", capitals);
        // 创建map集合,值是数组
        Map<String, String[]> bigCities = new HashMap<String,String[]>();
        // 放入值
        bigCities.put("Australia", new String[] {"Sydney",
                "Melbourne", "Perth"});
        bigCities.put("New Zealand", new String[] {"Auckland",
                "Christchurch", "Wellington"});
        bigCities.put("Indonesia", new String[] {"Jakarta",
                "Surabaya", "Medan"});

        request.setAttribute("capitals", capitals);
        request.setAttribute("bigCities", bigCities);
        /*Set s = bigCities.keySet();
        Iterator it = s.iterator();
        while(it.hasNext()){
           System.out.println(it.next());
        }*/
        // 重定向
        RequestDispatcher rd = request.getRequestDispatcher("/Cities.jsp");
        rd.forward(request, response);
   }

   /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
   */
   protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       // TODO Auto-generated method stub
       doGet(request, response);
   }

}

jsp页面(需要引入jstl的两个jar包)

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix = "c" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Big Cities</title>
<style>
   table,tr,td{
       border: 1px solid #ae7;
       padding: 3px;
   }
</style>
</head>
<body>
Capitals
<table>
   <tr style="background:#448755;color:white;font-weight:bold;">
       <td>Country</td>
       <td>Capital</td>
   </tr>
   
   <c:forEach items="${ requestScope.capitals}" var="mapItem">
       <tr>
           <td>${mapItem.key }</td>
           <td>${mapItem.value }</td>
       </tr>
   </c:forEach>
</table>
<br>
Big Cities
<table>
   <tr style="background:#448755;color:white;font-weight:bold;">
       <td>Country</td>
       <td>Cities</td>
   </tr>
   
   <c:forEach items="${ requestScope.bigCities }" var= "mapItem">
       <tr>
           <td>${mapItem.key }</td>
           <td>
               
               <c:forEach items="${mapItem.value }" var="city" varStatus="status">
                   ${city}<c:if test="${!status.last }">,</c:if>
               </c:forEach>
           </td>
       </tr>
   </c:forEach>
</table>

</body>
</html>