纯Servlet简单分页代码

素颜马尾好姑娘i 2022-04-05 06:08 280阅读 0赞

### 运行方式： ###

1）直接复制代码，可以直接拉到底下复制

2）启动Tomcat

3）跳转请求/top10

### 分页功能主要注意点： ###

1）<a href='?city=london'>London</a>：只有一个？表示在当前页传值，主要是为了完成分页功能

2）<a href='top10'>Select City</a>：当前页不传值跳转的超链接格式

3）List如何赋值给另一个List

List<String> londonAttractions= new ArrayList<String>(3){
       {
        add("b1");
        add("b2");
        add("b3");
    }};
    List<String> attractions = null;
    attractions = londonAttractions;

注意点1、2相关内容，[点击跳转][Link 1]

注意点3相关内容，[点击跳转][Link 2]

### 分页主要代码： ###

判断当前第几页Page

int page = 1;
    String pageParameter = req.getParameter("page");
    if (pageParameter != null){
       try{
          page = Integer.parseInt(pageParameter);
       }catch (NumberFormatException e){
          e.printStackTrace();
       }
       if (page > 2){
           page = 1;
       }
    }

根据page的值来决定显示哪一页消息

int start = page * 5 - 5;
    for (int i = start; i < start + 5; i++) {
         writer.println(attractions.get(i) + "<br/>");
    }

完整Servlet代码：

package com.fxy.servlet;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.io.PrintWriter;
    import java.util.ArrayList;
    import java.util.List;
    
    @WebServlet(name = "Top10Servlet",urlPatterns = {"/top10"})
    public class Top10Servlet extends HttpServlet{
        private static final long serialVersionUID = 987654321L;
    
        private List<String> londonAttractions;
        private List<String> parisAttractions;
        public void init() throws ServletException{
            londonAttractions = new ArrayList<String>(10);
            londonAttractions.add("a1");
            londonAttractions.add("a2");
            londonAttractions.add("a3");
            londonAttractions.add("a4");
            londonAttractions.add("a5");
            londonAttractions.add("a6");
            londonAttractions.add("a7");
            londonAttractions.add("a8");
            londonAttractions.add("a9");
            londonAttractions.add("a10");
    
            parisAttractions = new ArrayList<String>(10){
       {
                add("b1");
                add("b2");
                add("b3");
                add("b4");
                add("b5");
                add("b6");
                add("b7");
                add("b8");
                add("b9");
                add("b10");
            }};
    
        }
    
        /**
         * urlPatterns = {"/top10"}拦截请求第一次进入这个servlet调用的方法
         * 快捷键：Ctrl+O 重写方法
         */
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            String city = req.getParameter("city");
            if (city != null && ( city.equals("london") || city.equals("paris") )) {
                showAttractions(req,resp,city);
            }else {
                showMainPage(req,resp);
            }
        }
    
        /**
         * 首页，注意超链接格式
         * <a href='?city=london'>London</a>
         * 只有一个？表示在当前页传值，主要是为了完成分页功能
         */
        private void showMainPage(HttpServletRequest req, HttpServletResponse resp) throws IOException {
            resp.setContentType("text/html");
            PrintWriter writer = resp.getWriter();
            writer.print("<html><head>"+"<title>Top10Tourist Attractions</title>"+
                "</head><body>"+
                "Please select a city:"+
                "<br/><a href='?city=london'>London</a>"+
                "<a href='?city=paris'>Paris</a><br/>"
            );
        }
    
        /**
         * 显示数据页面，注意：
         * 1）List如何赋值给另一个List
         * 2）当前页不传值跳转的超链接格式<a href='top10'>Select City</a>
         */
        private void showAttractions(HttpServletRequest req, HttpServletResponse resp, String city) throws IOException {
            int page = 1;
            String pageParameter = req.getParameter("page");
            if (pageParameter != null){
                try{
                    page = Integer.parseInt(pageParameter);
                }catch (NumberFormatException e){
                    e.printStackTrace();
                }
                if (page > 2){
                    page = 1;
                }
            }
    
            List<String> attractions = null;
            if (city.equals("london")){
                attractions = londonAttractions;
            }else if (city.equals("paris")){
                attractions = parisAttractions;
            }
            resp.setContentType("text/html");
    
            PrintWriter writer = resp.getWriter();
            writer.println("<html><head>"+
                "<title>Top 10 Tourist Attractions</title>"+
                "</head><body>");
            writer.println("<a href='top10'>Select City</a>");
            writer.println("<hr/>Page"+ page + "<hr/>");
    
            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'/>"+
                "<a href='?city=" + city +
                "&page=1'>Page 1</a>"
            );
            writer.print("<hr style='color:blue'/>"+
                    "<a href='?city=" + city +
                    "&page=2'>Page 2</a>"
            );
            writer.println("</body></html>");
    
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            super.doPost(req, resp);
        }
    }

[Link 1]: https://blog.csdn.net/qq_36688143/article/details/84950336
[Link 2]: https://blog.csdn.net/qq_36688143/article/details/84949893