通用分页详解-阿里云开发者社区

1.封装工具类：

1.1分析数据：

1.首先我们要根据需求拿到要分页展示的数据（如：Mysql）

2.定义需要的mysql语句

3.找到共同特点简化代码

1.2数据配置文件

这里封装了一个管理数据库连接类，可根据自生电脑情况来修改内容

#oracle9i
#driver=oracle.jdbc.driver.OracleDriver
#url=jdbc:oracle:thin:@localhost:1521:orcl
#user=scott
#pwd=123
#sql2005
#driver=com.microsoft.sqlserver.jdbc.SQLServerDriver
#url=jdbc:sqlserver://localhost:1433;DatabaseName=test1
#user=sa
#pwd=123
#sql2000
#driver=com.microsoft.jdbc.sqlserver.SQLServerDriver
#url=jdbc:microsoft:sqlserver://localhost:1433;databaseName=unit6DB
#user=sa
#pwd=888888
#mysql
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis_ssm?useUnicode=true&characterEncoding=UTF-8&useSSL=false
user=root
pwd=123456

1.3数据库帮助类

提供了一组获得或关闭数据库对象的方法

package com.xzs.util;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
/**
 * 提供了一组获得或关闭数据库对象的方法
 * 
 */
public class DBAccess {
  private static String driver;
  private static String url;
  private static String user;
  private static String password;
  static {// 静态块执行一次，加载 驱动一次
    try {
      InputStream is = DBAccess.class
          .getResourceAsStream("config.properties");
      Properties properties = new Properties();
      properties.load(is);
      driver = properties.getProperty("driver");
      url = properties.getProperty("url");
      user = properties.getProperty("user");
      password = properties.getProperty("pwd");
      Class.forName(driver);
    } catch (Exception e) {
      e.printStackTrace();
      throw new RuntimeException(e);
    }
  }
  /**
   * 获得数据连接对象
   * 
   * @return
   */
  public static Connection getConnection() {
    try {
      Connection conn = DriverManager.getConnection(url, user, password);
      return conn;
    } catch (SQLException e) {
      e.printStackTrace();
      throw new RuntimeException(e);
    }
  }
  public static void close(ResultSet rs) {
    if (null != rs) {
      try {
        rs.close();
      } catch (SQLException e) {
        e.printStackTrace();
        throw new RuntimeException(e);
      }
    }
  }
  public static void close(Statement stmt) {
    if (null != stmt) {
      try {
        stmt.close();
      } catch (SQLException e) {
        e.printStackTrace();
        throw new RuntimeException(e);
      }
    }
  }
  public static void close(Connection conn) {
    if (null != conn) {
      try {
        conn.close();
      } catch (SQLException e) {
        e.printStackTrace();
        throw new RuntimeException(e);
      }
    }
  }
  public static void close(Connection conn, Statement stmt, ResultSet rs) {
    close(rs);
    close(stmt);
    close(conn);
  }
  public static boolean isOracle() {
    return "oracle.jdbc.driver.OracleDriver".equals(driver);
  }
  public static boolean isSQLServer() {
    return "com.microsoft.sqlserver.jdbc.SQLServerDriver".equals(driver);
  }
  public static boolean isMysql() {
    return "com.mysql.cj.jdbc.Driver".equals(driver);
  }
  public static void main(String[] args) {
    Connection conn = DBAccess.getConnection();
    System.out.println(conn);
    DBAccess.close(conn);
    System.out.println("isOracle：" + isOracle());
    System.out.println("isSQLServer：" + isSQLServer());
    System.out.println("isMysql：" + isMysql());
    System.out.println("数据库连接(关闭)成功");
  }
}

1.4字节码过滤器

将不是utf-8的文件给过滤出来，中文乱码处理

package com.xzs.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();
    }
  }
}

1.5字符串判空类

package com.xzs.util;
public class StringUtils {
  // 私有的构造方法，保护此类不能在外部实例化
  private StringUtils() {
  }
  /**
   * 如果字符串等于null或去空格后等于""，则返回true，否则返回false
   * 
   * @param s
   * @return
   */
  public static boolean isBlank(String s) {
    boolean b = false;
    if (null == s || s.trim().equals("")) {
      b = true;
    }
    return b;
  }
  /**
   * 如果字符串不等于null或去空格后不等于""，则返回true，否则返回false
   * 
   * @param s
   * @return
   */
  public static boolean isNotBlank(String s) {
    return !isBlank(s);
  }
}

1.6分页工具类（pagebean）

package com.xzs.util;
/**
 * 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
  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 + "]";
  }
}

2.通用分页（后端）

2.1数据变量

package com.xzs.entity;
public class Book {
  private int bid;
  private String bname;
  private float price;
  @Override
  public String toString() {
    return "Book [bid=" + bid + ", bname=" + bname + ", price=" + price + "]";
  }
  public int getBid() {
    return bid;
  }
  public void setBid(int bid) {
    this.bid = bid;
  }
  public String getBname() {
    return bname;
  }
  public void setBname(String bname) {
    this.bname = bname;
  }
  public float getPrice() {
    return price;
  }
  public void setPrice(float price) {
    this.price = price;
  }
}

2.2原生dao层（该方法拿到所有的数据）

package com.xzs.dao;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import com.xzs.entity.Book;
import com.xzs.util.DBAccess;
import com.xzs.util.PageBean;
import com.xzs.util.StringUtils;
public class Bookdao {
  public List<Book> list(Book book,PageBean pageBean) throws Exception{
    List<Book> list  = new ArrayList<Book>();
    Connection con = DBAccess.getConnection();
    String sql = "select * from t_mvc_book where 1=1 ";
    String bname = book.getBname();
    if(StringUtils.isNotBlank(bname)) {
      sql += "and bname like '%"+bname+"%' ";
    }
    PreparedStatement pst = con.prepareStatement(sql);
    ResultSet rs = pst.executeQuery();
    while(rs.next()) {
      list.add(new Book(rs.getInt("bid"), rs.getString("bname"), rs.getFloat("price")));
    }
    return list;
  }
}

2.3BaseDao分页方法

package com.xzs.dao;
import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import com.xzs.util.DBAccess;
import com.xzs.util.PageBean;
public class BaseDao<T> {
  public List<T> executeQuery(String sql,PageBean pageBean,Class<T> clz) throws Exception{
    List<T> list  = new ArrayList<T>();
    Connection con = DBAccess.getConnection();
    PreparedStatement pst = null;
    ResultSet rs = null;
    String countSQL = getCountSQL(sql);
    String pageSQL = getPageSQL(sql,pageBean);
    if(pageBean != null && pageBean.isPagination()) {
      pst = con.prepareStatement(countSQL);
      rs = pst.executeQuery();
      if(rs.next()) {
        pageBean.setTotal(String.valueOf(rs.getObject(1)));
      }
      pst = con.prepareStatement(pageSQL);
      rs = pst.executeQuery();
    }else {
      pst = con.prepareStatement(sql);
      rs = pst.executeQuery();
    }
    while(rs.next()) {
//      list.add(new Book(rs.getInt("bid"), rs.getString("bname"), rs.getFloat("price")));
      T t = clz.newInstance();
      Field[] fields = clz.getDeclaredFields();
      for (Field f : fields) {
        f.setAccessible(true);
        f.set(t, rs.getObject(f.getName()));
      }
      list.add(t);
    }
    return list;
  }
  private String getPageSQL(String sql, PageBean pageBean) {
    return sql + " limit "+pageBean.getStartIndex()+","+pageBean.getRows();
  }
  private String getCountSQL(String sql) {
    return "select count(1) FROM ("+sql+") t";
  }
}

2.4BookDao的分页方法

package com.xzs.dao;
import java.sql.Connection;
import java.util.ArrayList;
import java.util.List;
import com.xzs.entity.Book;
import com.xzs.util.DBAccess;
import com.xzs.util.PageBean;
import com.xzs.util.StringUtils;
public class BookDao1 extends BaseDao {
  public List<Book> list(Book book,PageBean pageBean) throws Exception{
    List<Book> list  = new ArrayList<Book>();
    Connection con = DBAccess.getConnection();
    String sql = "select * from t_mvc_book where 1=1 ";
    String bname = book.getBname();
    if(StringUtils.isNotBlank(bname)) {
      sql += "and bname like '%"+bname+"%' ";
    }
    return super.executeQuery(sql, pageBean, book.getClass());
  }
}

运行结果为：

3.分页通用（前端）

3.1分页的核心思想

3.2优化pagebean

package com.xzs.util;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
/**
 * 分页工具类
 *
 */
public class PageBean1 {
  private int page = 1;// 页码
  private int rows = 10;// 页大小
  private int total = 0;// 总记录数
  // 上一次查询的url
  private String url;
  // 上一次查询所携带的查询条件
  private Map<String, String[]> parameterMap = new HashMap<String, String[]>();
  // 对pagebean进行初始化
  public void setRequest(HttpServletRequest req) {
    // 初始化jsp页面传递过来的当前页
    this.setPage(req.getParameter("page"));
    // 初始化jsp页面传递过来的页大小
    this.setRows(req.getParameter("rows"));
    // 初始化jsp页面传递过来是否分页
    this.setPagination(req.getParameter("pagination"));
    // 保留上一次的查询请求
    this.setUrl(req.getRequestURL().toString());
    // 保留上一次的查询条件
    this.setParameterMap(req.getParameterMap());
  }
  public String getUrl() {
    return url;
  }
  public void setUrl(String url) {
    this.url = url;
  }
  public Map<String, String[]> getParameterMap() {
    return parameterMap;
  }
  public void setParameterMap(Map<String, String[]> parameterMap) {
    this.parameterMap = parameterMap;
  }
  private void setPagination(String pagination) {
    // 只有填写了false字符串，才代表不分页
    this.setPagination(!"false".equals(pagination));
  }
  private void setRows(String rows) {
    if (StringUtils.isNotBlank(rows))
      this.setRows(Integer.valueOf(rows));
  }
  private void setPage(String page) {
    if (StringUtils.isNotBlank(page))
      this.setPage(Integer.valueOf(page));
  }
  private boolean pagination = true;// 是否分页
  public PageBean1() {
    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 + "]";
  }
  // 上一页
  public int getPrevPage() {
    return this.page > 1 ? this.page - 1 : this.page;
  }
  // 下一页
  public int getNextPage() {
    return this.page < this.getMaxPage() ? this.page + 1 : this.page;
  }
  // 最大页
  public int getMaxPage() {
    return this.total % this.rows == 0 ? this.total / this.rows : (this.total / this.rows) + 1;
  }
}

3.3自定义page描述文件

<?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>zking 1.1 core library</description>
  <display-name>zking core</display-name>
  <tlib-version>1.1</tlib-version>
  <short-name>zking</short-name>
  <uri>/zking</uri>
  <tag>
        <name>page</name>
        <tag-class>com.zking.tag.PageTag</tag-class>
        <body-content>JSP</body-content>
        <attribute>
            <name>pageBean</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
</taglib>

3.4page助手类

package com.xzs.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.xzs.util.PageBean;
import com.xzs.util.PageBean1;
public class PageTag extends BodyTagSupport {
  private PageBean1 pageBean;
  public PageBean1 getPageBean() {
    return pageBean;
  }
  public void setPageBean(PageBean1 pageBean) {
    this.pageBean = pageBean;
  }
  @Override
  public int doStartTag() throws JspException {
    JspWriter out = pageContext.getOut();
    try {
      out.print(toHTML());
    } catch (Exception e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
    return super.doStartTag();
  }
  private String toHTML() {
    StringBuffer sb = new StringBuffer();
//    form
    sb.append("<form action=\""+pageBean.getUrl()+"\" id=\"pageBeanForm\" method=\"post\">");
    sb.append(" <input type=\"hidden\" name=\"page\">");
    Map<String, String[]> paramMap = pageBean.getParameterMap();
    if(paramMap != null && paramMap.size() > 0) {
      Set<Entry<String, String[]>> entrySet = paramMap.entrySet();
      for (Entry<String, String[]> entry : entrySet) {
        String name = entry.getKey();
        String[] value = entry.getValue();
        if(value != null && value.length > 0) {
          for (String val : value) {
             if(!"page".equals(entry.getKey())){
               sb.append(" <input type=\"hidden\" name=\""+name+"\" value=\""+val+"\">");
             }
          }
        }
      }
    }
    sb.append("</form>");
//    分页条
    sb.append("<ul class=\"pagination justify-content-center\">");
    sb.append(" <li class=\"page-item "+(pageBean.getPage() == 1 ? "disabled" : "")+"\"><a class=\"page-link\"");
    sb.append(" href='javascript:gotoPage(1)'>首页</a></li>");
    sb.append(" <li class=\"page-item "+(pageBean.getPage() == 1 ? "disabled" : "")+"\"><a class=\"page-link\"");
    sb.append(" href='javascript:gotoPage("+pageBean.getPrevPage()+")'>&lt;</a></li>");
    sb.append(" <li class=\"page-item\"><a class=\"page-link\" href=\"#\">"+pageBean.getPage()+"</a></li>");
//    sb.append(" <li class=\"page-item\"><a class=\"page-link\" href=\"#\">2</a></li>");
//    sb.append(" <li class=\"page-item active\"><a class=\"page-link\" href=\"#\">3</a></li>");
    sb.append(" <li class=\"page-item "+(pageBean.getPage() == pageBean.getMaxPage() ? "disabled" : "")+"\"><a class=\"page-link\" href=\"javascript:gotoPage("+pageBean.getNextPage()+")\">&gt;</a></li>");
    sb.append(" <li class=\"page-item "+(pageBean.getPage() == pageBean.getMaxPage() ? "disabled" : "")+"\"><a class=\"page-link\" href=\"javascript:gotoPage("+pageBean.getMaxPage()+")\">尾页</a></li>");
    sb.append(" <li class=\"page-item go-input\"><b>到第</b><input class=\"page-link\"");
    sb.append(" type=\"text\" id=\"skipPage\" name=\"\" /><b>页</b></li>");
    sb.append(" <li class=\"page-item go\"><a class=\"page-link\"");
    sb.append(" href=\"javascript:skipPage()\">确定</a></li>");
    sb.append(" <li class=\"page-item\"><b>共"+pageBean.getTotal()+"条</b></li>");
    sb.append(" </ul>");
//    分页功能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");
    sb.append("   || parseInt(page) > 1122) {");
    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();
  }
}

3.5Bookservlet

package com.xzs.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.xzs.dao.BookDao1;
import com.xzs.dao.Bookdao;
import com.xzs.entity.Book;
import com.xzs.util.PageBean;
import com.xzs.util.PageBean1;
@WebServlet("/book.search")
public class BookServlet extends HttpServlet {
  @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 {
    BookDao1 bookdao = new BookDao1();
    PageBean pageBean = new PageBean();
    pageBean.setRequest(req);
    Book book = new Book();
    book.setBname(req.getParameter("bname"));
    try {
      List<Book> list = bookdao.list(book, pageBean);
      req.setAttribute("books", list);
      req.setAttribute("pageBean", pageBean);
      req.getRequestDispatcher("/index.jsp").forward(req, resp);
    } catch (Exception e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
  }
}

3.6Jsp界面编写

<%@ page language="java" contentType="text/html; charset=UTF-8"
  pageEncoding="UTF-8"%>
<%@ taglib uri="http://tag.veryedu.cn" prefix="z" %>  
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>  
<!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">
<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="${pageContext.request.contextPath }/book/search" method="post">
    <div class="form-group mb-2">
      <input type="text" class="form-control-plaintext" name="bname"
        placeholder="请输入书籍名称">
    </div>
    <button type="submit" class="btn btn-primary mb-2">查询</button>
  </form>
  <table class="table table-striped bg-success">
    <thead>
      <tr>
        <th scope="col">书籍ID</th>
        <th scope="col">书籍名</th>
        <th scope="col">价格</th>
      </tr>
    </thead>
    <tbody>
      <c:forEach items="${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>
</body>
</html>

3.7测试结果

总结：通用分页就是方便我们简化代码的，所以我们需要将它们共同的代码进行差个分装。但在我们还不熟悉的时候应该先不考虑封装，先将分页写出来，然后提取公共构造，封装继承。通用分页步骤就是先分析分页条属性，然后封装属性实体，然后编写dao层方法提取公共部分，接着编写分页助手类，为了避免出现乱码问题，在编写一个字符过滤器，过滤所有请求，最后在标签库描述文件中添加分页标签，就可以按自己需求来使用了。通用分页的思想就是将能提取的部分给提取出来然后拼接，供以后调用。

通用分页详解