通用分页（二）

最新推荐文章于 2023-06-27 17:27:12 发布

CJQ余小C

最新推荐文章于 2023-06-27 17:27:12 发布

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CC 4.0 BY-SA版权

本文链接：https://blog.youkuaiyun.com/CJQYQX/article/details/96783605

本文介绍了如何在Java中创建一个通用分页解决方案，包括分页工具类PageBean的创建、自定义分页标签PageTag的实现、Servlet的处理以及JSP页面的展示。强调了分页参数的重要性，并提醒注意分页表单不能嵌套在其他表单中以避免提交问题。

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一、通用分页
将上一次查询请求再发一次，只不过改变了页码。

二、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

创建一个通用分页：

1.创建分页工具类PageBean类：

package com.cjq.util;
import java.util.HashMap;
import java.util.Map;import javax.servlet.http.HttpServletRequest;/**
 * 分页工具类
 *
 */
public class PageBean { private int page = 1;// 页码 
private int rows = 10;// 页大小 
private int total = 0;// 总记录数 
private boolean pagination = true;// 是否分页 private String url;
 private Map<String, String[]> paramMap = new HashMap<>();
  public void setRequest(HttpServletRequest req) {
  this.setPage(req.getParameter("page"));
  this.setRows(req.getParameter("rows"));
  this.setPagination(req.getParameter("pagination"));
  // getRequestURL获取到浏览器请求的全路径
  this.setUrl(req.getRequestURL().toString());
  // getParameterMap可以获取到一次url请求所携带的所有参数
  this.setParamMap(req.getParameterMap()); 
  } 
  public void setPagination(String pagination) {
  if (StringUtils.isNotBlank(pagination)) {
   this.setPagination(!"false".equals(pagination));//是否分页
  }
 } 
 public void setRows(String rows) {
  if (StringUtils.isNotBlank(rows))
   this.setRows(Integer.valueOf(rows));//每页多少天数据 
   }
   public void setPage(String page) {
  if (StringUtils.isNotBlank(page)) {
   this.setPage(Integer.valueOf(page));//多少页
  }
 } public PageBean() {
  super();
 } public String getUrl() {
  return url;
 } public void setUrl(String url) {
  this.url = url;
 } public Map<String, String[]> getParamMap() {
  return paramMap;
 } public void setParamMap(Map<String, String[]> paramMap) {
  this.paramMap = paramMap;
 } public int getPage() {
  return page;
 } public void setPage(int page) {
  this.page = page;
 } public int getRows() {
  return rows;
 } public void setRows(int rows) {
  this.rows = rows;
 } public int getTotal() {
  return total;
 } public void setTotal(int total) {
  this.total = total;
 } public void setTotal(String total) {
  this.total = Integer.parseInt(total);
 } public boolean isPagination() {
  return pagination;
 } public void setPagination(boolean pagination) {
  this.pagination = pagination;
 } /**
  * 获得起始记录的下标
  * 
  * @return
  */
 public int getStartIndex() {
  return (this.page - 1) * this.rows;
 } @Override
 public String toString() {
  return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", pagination=" + pagination + "]";
 } /**
  * 获取到总页数
  * @return
  */
 public int getMaxPage() {
  return this.total % this.rows == 0 ? 
    this.total / this.rows : 
     (this.total / this.rows) + 1;
 }
 
 /**
  * 获取下一页页码
  * @return
  */
 public int getNextPage() {
  return this.page < this.getMaxPage() ? this.page+1 : this.page;
 }
 
 /**
  * 获取上一页页码
  * @return
  */
 public int getPreviousPage() {
  return this.page > 1 ? this.page-1 : this.page;
 }}

2.创建PageTag类：
注1：不能将分页表单嵌套到其它表单中，否则不能提交表单！！！

package com.cjq.tag;
import java.io.IOException;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyTagSupport;import com.cjq.util.PageBean;public class PageTag extends BodyTagSupport{ private static final long serialVersionUID = -3016912383168058950L;
 private PageBean pageBean;
 
 @Override
 public int doStartTag() throws JspException {
  JspWriter out = pageContext.getOut();
  try {
   out.write(toHTML());
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  return super.doStartTag();
 }
 
 public String toHTML() {
  StringBuffer sb = new StringBuffer();
  //下一次请求提交到后台的表单html代码拼接
  sb.append("<form id='pageBeanForm' action='"+pageBean.getUrl()+"' method='post'>");
  Map<String, String[]> paramMap = pageBean.getParamMap();
  if(paramMap !=null && paramMap.size()>0) {
   Set<Entry<String, String[]>> entrySet = paramMap.entrySet();
   for(Entry<String, String[]> entry:paramMap.entrySet()) {
    if(!"page".equals(entry.getKey())) {
     sb.append("<input type='hidden' name='"+entry.getKey()+"' value='"+entry.getValue()+"'>");
    }
   }
  }
  sb.append("<input type='hidden' name='page'>");
  sb.append("</form>");
  
  //分页条html代码拼接
  sb.append("<div style='text-align: right; font-size: 12px;'>");
  sb.append("每页"+pageBean.getRows()+"条，共"+pageBean.getTotal()+"条，第"+pageBean.getPage()+"页，共"+pageBean.getMaxPage()+"页&nbsp;&nbsp;<a href='javascript:gotoPage("+pageBean.getPreviousPage()+")'>首页</a>&nbsp;&nbsp;<a");
  sb.append(" href='javascript:gotoPage(1)'>上一页</a>&nbsp;&nbsp;<a");
  sb.append(" href='javascript:gotoPage("+pageBean.getNextPage()+")'>下一页</a>&nbsp;&nbsp;<a");
  sb.append(" href='javascript:gotoPage("+pageBean.getMaxPage()+")'>尾页</a>&nbsp;&nbsp;<input type='text'");
  sb.append(" id='skipPage'");
  sb.append(" style='text-align: center; font-size: 12px; width: 50px;'>&nbsp;&nbsp;<a");
  sb.append(" href='javascript:skipPage()'>Go</a>");
  sb.append("</div>");
  //分页所需要调用的js代码
  sb.append("<script type='text/javascript'>");
  sb.append("function gotoPage(page) {");
  sb.append("  document.getElementById('pageBeanForm').page.value = page;");
  sb.append("  document.getElementById('pageBeanForm').submit();");
  sb.append("}");
  sb.append("function skipPage() {");
  sb.append("  var page = document.getElementById('skipPage').value;");
  sb.append("  if(!page || isNaN(page) || parseInt(page)<1 || parseInt(page)>maxPage){");
  sb.append("   alert('请输入1~N的数字');");
  sb.append("   return;");
  sb.append("  }");
  sb.append("  gotoPage(page);");
  sb.append("}");
  sb.append("</script>");
  return sb.toString();
 } public PageBean getPageBean() {
  return pageBean;
 }
 public void setPageBean(PageBean pageBean) {
  this.pageBean = pageBean;
 }
 
}

3.创建BookServlet类：

package com.cjq.web;
import java.io.IOException;
import java.sql.SQLException;
import java.util.List;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import com.cjq.dao.BookDao;
import com.cjq.entity.Book;
import com.cjq.util.PageBean;public class BookServlet extends HttpServlet{
// 调用数据层访问数据库
 private BookDao bookDao = new BookDao(); private static final long serialVersionUID = -7654671804738498584L;
 
 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  doPost(req, resp);
 }
 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//  拿到前台的dname
  String bname = req.getParameter("bname");
//  将前台传过来的值封装到实体类中
  Book book = new Book();
  //把bname放进去
  book.setBname(bname);//有可能查询维度不止这个bname，有可能还会有别的。这里的话以bname为例
  PageBean pagebean = new PageBean();
  try {
//   list 查出符合条件的某一页的记录数 默认是第一页
   List<Book> list = bookDao.list(book, pagebean);
//   转发的同时转到req的作用域中
   req.setAttribute("bookList", list);
   req.setAttribute("pagebean", pagebean);//pagebean传过去了，最大页数，当前页数，是否分页，第几页都传过去了。
   req.getRequestDispatcher("bookList.jsp").forward(req, resp);//转发
  } catch (InstantiationException e) {
   e.printStackTrace();
  } catch (IllegalAccessException e) {
   e.printStackTrace();
  } catch (SQLException e) {
   e.printStackTrace();
  }
 }
}

4.创建z.tld属性文件:

<?xml version="1.0" encoding="UTF-8" ?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
    version="2.0">
    
  <description>cjq 1.1 core library</description>
  <display-name>cjq core</display-name>
  <tlib-version>1.1</tlib-version>
  <short-name>c</short-name>
  <uri>/cjq</uri>  <tag>
   <!-- 标签库中的标签名 -->
    <name>page</name>
    <!-- 标签对应的助手类的全路径名 -->
    <tag-class>com.cjq.tags.PageTag</tag-class>
    <!-- JSP -->
    <body-content>JSP</body-content>
    <attribute>
     <!-- 属性名 -->
        <name>pageBean</name>
        <!-- 属性值是否必填 -->
        <required>true</required>
        <!-- 是否支持表达式 -->
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
  
</taglib>

5.配置web.xml文件：

 <?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>cjq_pagebean2</display-name>
      <filter>
       <filter-name>encodingFiter</filter-name>
       <filter-class>com.cjq.util.EncodingFiter</filter-class>
      </filter>
      <filter-mapping>
       <filter-name>encodingFiter</filter-name>
       <url-pattern>/*</url-pattern>
      </filter-mapping>
      <servlet>
       <servlet-name>bookServlet</servlet-name>
       <servlet-class>com.cjq.web.BookServlet</servlet-class>
      </servlet>
      <servlet-mapping>
       <servlet-name>bookServlet</servlet-name>
     <url-pattern>/bookServlet</url-pattern>   
      </servlet-mapping>
    </web-app>

6.用EncodingFiter类处理中文乱码：

package com.cjq.util;
import java.io.IOException;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;/**
 * 中文乱码处理
 */
public class EncodingFiter implements Filter { private String encoding = "UTF-8";// 默认字符集 public EncodingFiter() {
  super();
 } public void destroy() {
 } public void doFilter(ServletRequest request, ServletResponse response,
   FilterChain chain) throws IOException, ServletException {
  HttpServletRequest req = (HttpServletRequest) request;
  HttpServletResponse res = (HttpServletResponse) response;  // 中文处理必须放到 chain.doFilter(request, response)方法前面
  res.setContentType("text/html;charset=" + this.encoding);
  if (req.getMethod().equalsIgnoreCase("post")) {
   req.setCharacterEncoding(this.encoding);
  } else {
   Map map = req.getParameterMap();// 保存所有参数名=参数值(数组)的Map集合
   Set set = map.keySet();// 取出所有参数名
   Iterator it = set.iterator();
   while (it.hasNext()) {
    String name = (String) it.next();
    String[] values = (String[]) map.get(name);// 取出参数值[注：参数值为一个数组]
    for (int i = 0; i < values.length; i++) {
     values[i] = new String(values[i].getBytes("ISO-8859-1"),
       this.encoding);
    }
   }
  }  chain.doFilter(request, response);
 } public void init(FilterConfig filterConfig) throws ServletException {
  String s = filterConfig.getInitParameter("encoding");// 读取web.xml文件中配置的字符集
  if (null != s && !s.trim().equals("")) {
   this.encoding = s.trim();
  }
 }}

7.bookList.jsp动态网页：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
    <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
    <%@ taglib uri="/cjq"  prefix="z" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h2>小说目录</h2>
 <br>
 <form action="${pageContext.request.contextPath}/bookServlet"
  method="post">
<!--   <input type="hidden" name="rows" value="20"> -->
  <input type="hidden" name="pagination" value="false">
  书名：<input type="text" name="bname"> <input type="submit"
   value="确定">
 </form>
 <table border="1" width="100%">
  <tr>
   <td>编号</td>
   <td>名称</td>
   <td>价格</td>
  </tr>
  <c:forEach items="${bookList }" var="b">
   <tr>
    <td>${b.bid }</td>
    <td>${b.bname }</td>
    <td>${b.price }</td>
   </tr>
  </c:forEach>
 </table>
 
 <z:page pageBean="${pagebean }"></z:page>
 
</body>
</html>

运行结果如下：

在这里插入图片描述