servlet之重写

2022-11-11 15:30:11

package app02a;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;

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

/**
* url重写
*/
@WebServlet( name = "Top10Servlet", urlPatterns = "/top10")
public class Top10Servlet extends HttpServlet {
   private static final long serialVersionUID = 1L;

   private List<String> londonAttractions;
   private List<String> parisAttractions;

    /**
     * Default constructor.
     */
    public Top10Servlet() {
        // TODO Auto-generated constructor stub
    }

    /**
     * 初始化两个列表存放信息(正常开发存于数据库中)
     */
    @Override
    public void init() throws ServletException {
       londonAttractions = new ArrayList<String>(10);
        londonAttractions.add("Buckingham Palace");
        londonAttractions.add("London Eye");
        londonAttractions.add("British Museum");
        londonAttractions.add("National Gallery");
        londonAttractions.add("Big Ben");
        londonAttractions.add("Tower of London");
        londonAttractions.add("Natural History Museum");
        londonAttractions.add("Canary Wharf");
        londonAttractions.add("2012 Olympic Park");
        londonAttractions.add("St Paul's Cathedral");

        parisAttractions = new ArrayList<String>(10);
        parisAttractions.add("Eiffel Tower");
        parisAttractions.add("Notre Dame");
        parisAttractions.add("The Louvre");
        parisAttractions.add("Champs Elysees");
        parisAttractions.add("Arc de Triomphe");
        parisAttractions.add("Sainte Chapelle Church");
        parisAttractions.add("Les Invalides");
        parisAttractions.add("Musee d'Orsay");
        parisAttractions.add("Montmarte");
        parisAttractions.add("Sacre Couer Basilica");
    }

   /**
   * get请求,判断选择的城市
   */
   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       String city = request.getParameter("city");
       if(city != null && (city.equals("london") || city.equals("paris"))){
           // 选择后
           showAttractions(request, response, city);
       } else{
           // 第一次执行
           showMainPage(request, response);
       }
   }

   /**
   * 显示主页
   * @param request
   * @param response
   * @throws ServletException
   * @throws IOException
   */
   private void showMainPage(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException {
        response.setContentType("text/html");
        PrintWriter writer = response.getWriter();
        writer.print("<html><head>" +
                "<title>Top 10 Tourist Attractions</title>" +
                "</head><body>" +
                "Please select a city:" +
                // 重定向体现(使用a标签的href属性)
                "<br/><a href='?city=london'>London</a>" +
                "<br/><a href='?city=paris'>Paris</a>" +
                "</body></html>");
    }

   /**
   * 显示主要信息
   * @param request
   * @param response
   * @param city 选择的城市
   * @throws ServletException
   * @throws IOException
   */
   private void showAttractions(HttpServletRequest request,
            HttpServletResponse response, String city)
            throws ServletException, IOException {

        int page = 1;
        String pageParameter = request.getParameter("page");
        if (pageParameter != null) {
            try {
                page = Integer.parseInt(pageParameter);
            } catch (NumberFormatException e) {
                // do nothing and retain default value for page
            }
            if (page > 2) {
                page = 1;
            }
        }
        List<String> attractions = null;
        if (city.equals("london")) {
            attractions = londonAttractions;
        } else if (city.equals("paris")) {
            attractions = parisAttractions;
        }
        response.setContentType("text/html");
        PrintWriter writer = response.getWriter();
        writer.println("<html><head>" +
                "<title>Top 10 Tourist Attractions</title>" +
                "</head><body>");
        // 返回主页(href='top10')
        writer.println("<a href='top10'>Select City</a> ");
        writer.println("<hr/>Page " + page + "<hr/>");
        // 总共10条数据,两页,每页显示五条数据(简单的分页实现)
        int start = page * 5 - 5;
        for (int i = start; i < start + 5; i++) {
            writer.println(attractions.get(i) + "<br/>");
        }
        writer.print("<hr style='color:blue'/>" +
               // 重定向体现(使用a标签的href属性)
                "<a href='?city=" + city +
                "&page=1'>Page 1</a>");
        writer.println("  <a href='?city=" + city +
                "&page=2'>Page 2</a>");
        writer.println("</body></html>");
    }


   /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
   */
   protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

   }

}

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