通用分页（二）

一，改造

1.1通用分页核心思路将上一次查询请求再发一次，只不过页码变了

1.2将查询参数保存到pagebean中Map paramMap 存储参数键值对

1.3在pagebean定义一个属性存放上一次的请求

新建一个外包package package在企业级命名不能为Servlet 最好使用web

package com.GeneralPaging.web;

BookServlet

代码：

 1 package com.GeneralPaging.web;
 2 
 3 import java.io.IOException;
 4 import java.sql.SQLException;
 5 import java.util.List;
 6 import java.util.Map;
 7 
 8 import javax.servlet.ServletException;
 9 import javax.servlet.http.HttpServlet;
10 import javax.servlet.http.HttpServletRequest;
11 import javax.servlet.http.HttpServletResponse;
12 
13 import com.GeneralPaging.dao.BookDao;
14 import com.GeneralPaging.entity.Book;
15 import com.GeneralPaging.util.PageBean;
16 
17 public class BookServlet extends HttpServlet {
18 
19     /**
20      * 
21      */
22     private static final long serialVersionUID = -5342105797517938272L;
23 
24     private BookDao bookDao=new BookDao();
25     
26     @Override
27     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
28         // TODO Auto-generated method stub
29         doPost(req, resp);
30     }
31     
32     @Override
33     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
34         // TODO Auto-generated method stub
35         //前台传入banme
36         String bname=req.getParameter("bname");
37         bname=new String(bname.getBytes("ISO-8859-1"),"UTF-8");
38         Book book=new Book();
39         book.setBname(bname);
40     
41         //分页
42         PageBean pagebean=new PageBean();
43         
44         try {
45             pagebean.setRequest(req);
46             List<Book> list = this.bookDao.list(book, pagebean);
47             req.setAttribute("bookList", list);
48             req.setAttribute("pageBean", pagebean);
49             req.getRequestDispatcher("/bookList.jsp").forward(req, resp);
50         } catch (InstantiationException e) {
51             // TODO Auto-generated catch block
52             e.printStackTrace();
53         } catch (IllegalAccessException e) {
54             // TODO Auto-generated catch block
55             e.printStackTrace();
56         } catch (SQLException e) {
57             // TODO Auto-generated catch block
58             e.printStackTrace();
59         }
60         super.doPost(req, resp);
61     }
62     
63 }

配置BookServlet的xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>JavaGeneralPaging</display-name>
   
     <servlet>
   <servlet-name>bookServlet</servlet-name>
   <servlet-class>com.GeneralPaging.web.BookServlet</servlet-class>
   </servlet>
   <servlet-mapping>
   <servlet-name>bookServlet</servlet-name>
   <url-pattern>/bookServlet.action</url-pattern>
   </servlet-mapping>
</web-app>

乱码处理，在EncodingFiter工具类中添加一个@WebFilter(urlPatterns=("/*"))则不需要配置xml

 1 package com.GeneralPaging.util;
 2 
 3 import java.io.IOException;
 4 import java.util.Iterator;
 5 import java.util.Map;
 6 import java.util.Set;
 7 
 8 import javax.servlet.Filter;
 9 import javax.servlet.FilterChain;
10 import javax.servlet.FilterConfig;
11 import javax.servlet.ServletException;
12 import javax.servlet.ServletRequest;
13 import javax.servlet.ServletResponse;
14 import javax.servlet.annotation.WebFilter;
15 import javax.servlet.http.HttpServletRequest;
16 import javax.servlet.http.HttpServletResponse;
17 
18 /**
19  * 中文乱码处理
20  * 
21  */
22 @WebFilter(urlPatterns=("/*"))
23 public class EncodingFiter implements Filter {
24 
25     private String encoding = "UTF-8";// 默认字符集
26 
27     public EncodingFiter() {
28         super();
29     }
30 
31     public void destroy() {
32     }
33 
34     public void doFilter(ServletRequest request, ServletResponse response,
35             FilterChain chain) throws IOException, ServletException {
36         HttpServletRequest req = (HttpServletRequest) request;
37         HttpServletResponse res = (HttpServletResponse) response;
38 
39         // 中文处理必须放到 chain.doFilter(request, response)方法前面
40         res.setContentType("text/html;charset=" + this.encoding);
41         if (req.getMethod().equalsIgnoreCase("post")) {
42             req.setCharacterEncoding(this.encoding);
43         } else {
44             Map map = req.getParameterMap();// 保存所有参数名=参数值(数组)的Map集合
45             Set set = map.keySet();// 取出所有参数名
46             Iterator it = set.iterator();
47             while (it.hasNext()) {
48                 String name = (String) it.next();
49                 String[] values = (String[]) map.get(name);// 取出参数值[注：参数值为一个数组]
50                 for (int i = 0; i < values.length; i++) {
51                     values[i] = new String(values[i].getBytes("ISO-8859-1"),
52                             this.encoding);
53                 }
54             }
55         }
56 
57         chain.doFilter(request, response);
58     }
59 
60     public void init(FilterConfig filterConfig) throws ServletException {
61         String s = filterConfig.getInitParameter("encoding");// 读取web.xml文件中配置的字符集
62         if (null != s && !s.trim().equals("")) {
63             this.encoding = s.trim();
64         }
65     }
66 
67 }

改造PageBean

保存上一次请求携带的参数
控制是否分页
控制一页显示多少条数据
重载
最大页码数
获取下一页码数
获取上一页码数

  1 package com.GeneralPaging.util;
  2 
  3 import java.util.HashMap;
  4 import java.util.Map;
  5 
  6 import javax.servlet.http.HttpServletRequest;
  7 
  8 /**
  9  * 分页工具类
 10  *
 11  */
 12 public class PageBean {
 13 
 14     private int page = 1;// 页码
 15 
 16     private int rows = 10;// 页大小
 17 
 18     private int total = 0;// 总记录数
 19 
 20     private boolean pagination = true;// 是否分页
 21     
 22     private Map<String, String[]> paMap=new HashMap<>();
 23 
 24     private String url;
 25     
 26     public void setRequest(HttpServletRequest req) {
 27         //保存上一次请求携带的参数
 28         this.setPaMap(req.getParameterMap());
 29         this.setUrl(req.getRequestURL().toString());
 30         
 31         //控制是否分页
 32         this.setPagination(req.getParameter("pagination"));
 33 //        控制一页显示多少条数据
 34         this.setRows(req.getParameter("rows"));
 35         this.setPage(req.getParameter("page"));
 36     }
 37     
 38     //重载
 39     private void setPage(String page) {
 40         // TODO Auto-generated method stub
 41         this.page=StringUtils.isNotBlank(page) ? Integer.valueOf(page) : this.page;
 42     }
 43 
 44     private void setPagination(String pagination) {
 45         // TODO Auto-generated method stub
 46         this.pagination=StringUtils.isNotBlank(pagination) ? !"false".equals(pagination) : this.pagination;
 47     }
 48     private void setRows(String rows) {
 49         // TODO Auto-generated method stub
 50         this.rows=StringUtils.isNotBlank(rows) ? Integer.valueOf(rows) : this.rows;
 51     }
 52 
 53 
 54     public Map<String, String[]> getPaMap() {
 55         return paMap;
 56     }
 57 
 58     public void setPaMap(Map<String, String[]> paMap) {
 59         this.paMap = paMap;
 60     }
 61 
 62     public String getUrl() {
 63         return url;
 64     }
 65 
 66     public void setUrl(String url) {
 67         this.url = url;
 68     }
 69 
 70     public PageBean() {
 71         super();
 72     }
 73 
 74     public int getPage() {
 75         return page;
 76     }
 77 
 78     public void setPage(int page) {
 79         this.page = page;
 80     }
 81 
 82     public int getRows() {
 83         return rows;
 84     }
 85 
 86     public void setRows(int rows) {
 87         this.rows = rows;
 88     }
 89 
 90     public int getTotal() {
 91         return total;
 92     }
 93 
 94     public void setTotal(int total) {
 95         this.total = total;
 96     }
 97 
 98     public void setTotal(String total) {
 99         this.total = Integer.parseInt(total);
100     }
101 
102     public boolean isPagination() {
103         return pagination;
104     }
105 
106     public void setPagination(boolean pagination) {
107         this.pagination = pagination;
108     }
109 
110     /**
111      * 获得起始记录的下标
112      * 
113      * @return
114      */
115     public int getStartIndex() {
116         return (this.page - 1) * this.rows;
117     }
118 
119     @Override
120     public String toString() {
121         return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", pagination=" + pagination + "]";
122     }
123 
124     //最大页码数
125     public int getMaxPage() {
126         return this.total % this.rows ==0 ? this.total/this.rows : this.total/this.rows+1;
127     }
128 
129     /**
130      * 获取下一页码数
131      * @return
132      */
133     public int getNextPage() {
134         return this.page< this.getMaxPage() ? this.page+1 : this.page;
135                 
136     }
137     
138     /**
139      * 获取上一页码数
140      * @return
141      */
142     public int getPreviousPage() {
143         return this.page > 1 ? this.page-1 : this.page;
144     }
145     
146 }

2.通用分页标签编写

具体思路：
1、补全servlet
2、页面展示
3、分页重要参数（page、rows、是否分页、上一次请求、上一次的表单参数）

4、自定义分页标签

先写一个自定义分页标签

PageTag（助手类）

拼接下一次发送请求所要提交的form表单

上一次请求可能携带页码name=page的参数，但是该参数在前面已经单独赋值
为什么单独赋值？因为上一次请求时第一页的数据，下一次可能是第二页，意味着前后请求page对应的值是不一样的，需要单独赋值

下一次请求提交到后台的表单html代码拼接
拼接分页所需要调用的js代码

代码：

 1 package com.JavaGeneralPaging.tag;
 2 
 3 import java.io.IOException;
 4 import java.util.Map;
 5 import java.util.Map.Entry;
 6 import java.util.Set;
 7 
 8 import javax.servlet.jsp.JspException;
 9 import javax.servlet.jsp.JspWriter;
10 import javax.servlet.jsp.tagext.BodyTagSupport;
11 
12 import com.GeneralPaging.util.PageBean;
13 
14 public class PageTag extends BodyTagSupport {
15 
16     /**
17      * 
18      */
19     private static final long serialVersionUID = 46803535500945741L;
20 
21     private PageBean pageBean;
22 
23 
24     public PageBean getPageBean() {
25         return pageBean;
26     }
27 
28     public void setPageBean(PageBean pageBean) {
29         this.pageBean = pageBean;
30     }
31     
32     @Override
33     public int doStartTag() throws JspException {
34         // TODO Auto-generated method stub        
35         JspWriter out = pageContext.getOut();
36         try {
37             out.print(toHTML());
38         } catch (IOException e) {
39             // TODO Auto-generated catch block
40             e.printStackTrace();
41         }
42         return super.doStartTag();
43     }
44     private String toHTML() {
45         StringBuilder sb=new StringBuilder();
46         //拼接下一次发送请求所要提交的form表单
47         //下一次请求提交到后台的表单html代码拼接
48                 sb.append("    <form id='pageBeanForm' action='"+pageBean.getUrl()+"' method='post'>");
49                 Map<String, String[]> paramMap = pageBean.getPaMap();
50                 if(paramMap  != null &&paramMap.size() >0) {
51 //                    Set<Entry<String,String[]>> entrySet = paramMap.entrySet();
52                     //上一次请求可能携带页码name=page的参数，但是该参数在前面已经单独赋值
53                     // 为什么单独赋值？
54                     //因为上一次请求时第一页的数据，下一次可能是第二页，意味着前后请求page对应的值是不一样的，需要单独赋值                        
55                     for(Entry<String,String[]> entry :paramMap.entrySet()) {
56                         if(!"page".equals(entry.getKey())) {
57                             for(String val : entry.getValue()) {
58                                 sb.append("    <input type='hidden' name='"+entry.getKey()+"' value='"+val+"'>");
59                             }
60                         }
61                     }
62                 }
63                 sb.append("    <input type='hidden' name='page'>");
64                 sb.append("    </form>");
65             
66                 //分页条html代码拼接
67                 sb.append("    <div style='text-align: right; font-size: 12px;'>");
68                 sb.append("    每页"+pageBean.getRows()+"条，共"+pageBean.getTotal()+"条，第"+pageBean.getPage()+"页，共"+pageBean.getMaxPage()+"页&nbsp;&nbsp;<a ");
69                 sb.append("    href='javascript:gotoPage(1)'>首页</a>&nbsp;&nbsp;<a");
70                 
71                 sb.append("    href='javascript:gotoPage("+pageBean.getPreviousPage()+")'>上一页</a>&nbsp;&nbsp;<a");
72                 sb.append("    href='javascript:gotoPage("+pageBean.getNextPage()+")'>下一页</a>&nbsp;&nbsp;<a");
73                 sb.append("    href='javascript:gotoPage("+pageBean.getMaxPage()+")'>尾页</a>&nbsp;&nbsp;<input type='text'");
74                 sb.append("    id='skipPage'");
75                 sb.append("    style='text-align: center; font-size: 12px;  50px;'>&nbsp;&nbsp;<a");
76                 sb.append("    href='javascript:skipPage()'>Go</a>");
77                 sb.append("    </div>");
78                 
79                 
80                 //拼接分页所需要调用的js代码
81                 sb.append("<script type='text/javascript'>");
82                 sb.append("    function gotoPage(page) {");
83                 sb.append("        document.getElementById('pageBeanForm').page.value = page;");
84                 sb.append("        document.getElementById('pageBeanForm').submit();");
85                 sb.append("    }");
86                 sb.append("    function skipPage() {");
87                 sb.append("        var page = document.getElementById('skipPage').value;");
88                 sb.append("        if(!page || isNaN(page) || parseInt(page)<1 || parseInt(page)>"+pageBean.getMaxPage()+"){");
89                 sb.append("            alert('请输入1~N的数字');");
90                 sb.append("            return;");
91                 sb.append("        }");
92                 sb.append("        gotoPage(page);");
93                 sb.append("    }");
94                 sb.append("</script>");
95                 
96                 return sb.toString();
97 
98     }
99 }

x.tld文件

<?xml version="1.0" encoding="UTF-8"?>
<taglib xmlns="http://java.sun.com/JSP/TagLibraryDescriptor">


<tlib-version>1.0</tlib-version>
<jsp-version>1.2</jsp-version>
  <short-name>Simple Tags</short-name>
  <uri>/XuFanQi</uri>


<tag>
<name>Page</name>
<tag-class>com.JavaGeneralPaging.tag.PageTag</tag-class>
<body-content>JSP</body-content>
<attribute>
<name>pageBean</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>

</tag>

</taglib>

jsp页面调用展示

导入标签

设置hidden隐藏域，放置page分页页码

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3     <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
 4     <%@ taglib uri="/XuFanQi" prefix="x" %>
 5 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 6 <html>
 7 <head>
 8 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 9 <title>Insert title here</title>
10 </head>
11 <body>
12 <h2>小说目录</h2>
13     <br>
14 
15     <form action="${pageContext.request.contextPath}/bookServlet.action"
16         method="post">
17         书名：<input type="text" name="bname"> <input type="submit"
18             value="确定">
19             <input type="hidden" name="bname">
20     </form>
21     <table border="1" width="100%">
22         <tr>
23             <td>编号</td>
24             <td>名称</td>
25             <td>价格</td>
26         </tr>
27         <c:forEach items="${bookList }" var="b">
28             <tr>
29                 <td>${b.bid }</td>
30                 <td>${b.bname }</td>
31                 <td>${b.price }</td>
32             </tr>
33         </c:forEach>
34     </table>
35 
36     <x:Page pageBean="${pageBean }"></x:Page>
37 
38 </body>
39 </html>

测试结果：

搜索框：斗破

尾页

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