package com.zhulinjun.util;
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
//  增加一个最大页的方法
  public int maxPage() {
    return this.total % this.rows ==0?
        this.total / this.rows:
          this.total / this.rows+1;
  }
//  增加一个下一页的方法
  public int nextPage() {
      return this.page < this.maxPage() ?
          this.page+1 : this.page;
    }
//  增加一个上一页的方法
    public int prevPage() {
      return this.page > 1 ? this.page -1 : this.page;
    } 
    public void setRequest(HttpServletRequest req) {
//      初始化默认查询第几页的数据(初始化pageBean的方法)
      this.setPage(req.getParameter("page"));
      this.setRows(req.getParameter("rows"));
      this.setPagination(req.getParameter("pagination")); 
//      保留上一次的url(增加一个属性url，保留上一次发送的请求地址)
      this.setUrl(req.getRequestURL().toString());
//      保留携带的参数(增加一个属性paramMap，保留上一次发送的请求携带的参数)
      this.setParamMap(req.getParameterMap());
    }
  public void setPage(String page) {
      if(StringUtils.isNotBlank(page)) {
        this.setPage(Integer.valueOf(page));
      }
    }
    public void setRows(String rows) {
      if(StringUtils.isNotBlank(rows))
        this.setRows(Integer.valueOf(rows));
    }
    public void setPagination(String pagination) {
    if(StringUtils.isBlank(pagination)) {
      this.setPagination(!"false".equals(pagination));
    }
  }
  private String url;
  private Map<String, String[]> paramMap;
  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 PageBean() {
    super();
  }
  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 + "]";
  }
}

<?xml version="1.0" encoding="UTF-8" ?>
<taglib xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"
    version="2.1">
  <description>JSTL 1.1 core library</description>
  <display-name>JSTL core</display-name>
  <tlib-version>1.1</tlib-version>
  <short-name>z</short-name>
  <uri>http://jsp.veryedu.cn</uri>
  <tag>
    <name>page</name>
    <tag-class>com.zhulinjun.tag.tag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <name>pageBean</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
</taglib>

package com.zking.servlet;
import java.io.IOException;
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;
import com.zhulinjun.dao.BookDao;
import com.zhulinjun.entity.Book;
import com.zhulinjun.util.PageBean;
@WebServlet("/book.action")
public class BookServlet extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req, resp);
}
@SuppressWarnings("unused")
@Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//  String bname = req.getParameter("bname");
  map包含了浏览器传递到后台的所有参数键值对
//  Map<String, String[]> parameterMap = req.getParameterMap();
  浏览器请求的地址
//  String url = req.getRequestURI().toString();
  PageBean pageBean=new PageBean();
  pageBean.setRequest(req);
  BookDao bookDao=new BookDao();
  Book book = new Book();
  book.setBname(req.getParameter("bname"));
  try {
    List<Book> books = bookDao.list(book, pageBean);
    req.setAttribute("books", books);
//    System.out.println(books);
  } catch (Exception e) {
    e.printStackTrace();
  }
  req.setAttribute("pageBean", pageBean);
  System.out.println(pageBean);
    req.getRequestDispatcher("bookList.jsp").forward(req, resp);
}
}

<%@ page language="java" contentType="text/html; charset=UTF-8"
  pageEncoding="UTF-8"%>
  <%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
  <%@taglib prefix="z" uri="http://jsp.veryedu.cn"%>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<link
  href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/4.5.0/css/bootstrap.css"
  rel="stylesheet">
<script
  src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/4.5.0/js/bootstrap.js"></script>
<title>书籍列表</title>
<style type="text/css">
.page-item input {
  padding: 0;
  width: 40px;
  height: 100%;
  text-align: center;
  margin: 0 6px;
}
.page-item input, .page-item b {
  line-height: 38px;
  float: left;
  font-weight: 400;
}
.page-item.go-input {
  margin: 0 10px;
}
</style>
</head>
<body>
   <form class="form-inline"
    action="${pageContext.request.contextPath }/book.action" method="post">
    <div class="form-group mb-2">
      <input type="text" class="form-control-plaintext" name="bname"
        placeholder="请输入书籍名称">
    </div>
    <button type="submit" class="btn btn-primary mb-2">查询</button>
  </form>
  <table class="table table-striped">
    <thead>
      <tr>
        <th scope="col">书籍ID</th>
        <th scope="col">书籍名</th>
        <th scope="col">价格</th>
      </tr>
    </thead>
    <tbody>
        <c:forEach items="${books }" var="b">
      <tr>
        <td>${b.bid }</td>
        <td>${b.bname }</td>
        <td>${b.price }</td>
      </tr>
      </c:forEach>
    </tbody>
  </table>
<z:page pageBean="${pageBean }"></z:page> 
  </script> 
</body>
</html>

package com.zhulinjun.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.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * 中文乱码处理
 * 
 */
@WebFilter("*.action")
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();
    }
  }
}