通用分页（全）

pagebean与book

pagebean

package com.rong.util;

import java.util.HashMap;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;

public class PageBean {

	private Integer page=1;
	private Integer rows=3;
	private Integer total=0;
	private boolean pagination=true;
	
	private String url;
	private Map<String, String[]> parametermap=new HashMap<String, String[]>();
	
	public PageBean() {
		super();
	}
	
	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;
	}

	public Integer getPage() {
		return page;
	}
	public void setPage(Integer page) {
		this.page = page;
	}
	public void setPage(String page) {
		if(StringUtils.isNotBlank(page))
			this.setPage(Integer.valueOf(page));
	}

	public Integer getRows() {
		return rows;
	}
	public void setRows(Integer rows) {
		this.rows = rows;
	}
	public void setRows(String rows) {
		if(StringUtils.isNotBlank(rows))
			this.setRows(Integer.valueOf(rows));
	}

	public Integer getTotal() {
		return total;
	}
	public void setTotal(Integer 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;
	}
	public void setPagination(String pagination) {
		this.setPagination(!"false".equals(pagination));
	}
	
	@Override
	public String toString() {
		return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", pagination=" + pagination + "]";
	}
	
	public int getStartIndex() {
		return (this.page-1)*this.rows;
	}
	
	public void SetRequest(HttpServletRequest req) {
		this.setPage(req.getParameter("page"));
		this.setRows(req.getParameter("rows"));
		this.setPagination(req.getParameter("pagination"));
		this.setUrl(req.getRequestURL().toString());
		this.setParametermap(req.getParameterMap());
	}
	
	public int getMaxPage() {
		return this.total%this.rows==0 ? this.total/this.rows : (this.total/this.rows)+1;
	}
	
	
	public int getPerPage() {
		return this.page>1 ? this.page-1 : this.page;
	}
	
	public int getNextPage() {
		return this.page<this.getMaxPage() ? this.page+1 : this.getMaxPage();
	}
	
}

book

package com.rong.entity;

public class Book {

	private Integer bid;
	private String bname;
	private Float price;
	
	public Integer getBid() {
		return bid;
	}
	public void setBid(Integer 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;
	}
	public Book() {
		super();
	}
	public Book(Integer bid, String bname, Float price) {
		super();
		this.bid = bid;
		this.bname = bname;
		this.price = price;
	}
	@Override
	public String toString() {
		return "Book [bid=" + bid + ", bname=" + bname + ", price=" + price + "]";
	}
	
}

后台dao

BaseDao

package com.rong.dao;

import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.rong.entity.Book;
import com.rong.util.DBHelper;
import com.rong.util.PageBean;
import com.rong.util.StringUtils;

public class BaseDao<T> {

	public List<T> executeQuery(String sql,Class clz, PageBean pagebean) throws SQLException, InstantiationException, IllegalAccessException{
		List<T> list=new ArrayList<T>();
		
		Connection con=DBHelper.getConnection();
		PreparedStatement ps=null;
		ResultSet rs=null;
		
		if(pagebean!=null&&pagebean.isPagination()) {
			String countsql=getCountSql(sql);
			ps=con.prepareStatement(countsql);
			rs=ps.executeQuery();
			if(rs.next()) {
				//拿到总记录条数
				pagebean.setTotal(rs.getObject(1).toString());
			}
			//分页
			String pagesql=getPageSql(sql,pagebean);
			ps=con.prepareStatement(pagesql);
			rs=ps.executeQuery();
		}else {//不分页
			ps=con.prepareStatement(sql);
			rs=ps.executeQuery();
		}
		while(rs.next()) {
//			list.add(new Book(rs.getInt("bid"), rs.getString("bnaem"), rs.getFloat("price")));
			T t=(T) clz.newInstance();
			for(Field f:clz.getDeclaredFields()) {
				f.setAccessible(true);
				f.set(t, rs.getObject(f.getName()));
			}
			list.add(t);
		}
		DBHelper.close(con, ps, rs);
		return list;
	}
	
	
	private String getPageSql(String sql, PageBean pagebean) {
		return sql+" limit "+pagebean.getStartIndex()+","+pagebean.getRows();
	}
	public String getCountSql(String sql) {
		return "select count(1) from("+sql+") t";
	}
	
}

BookDao

package com.rong.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.rong.entity.Book;
import com.rong.util.DBHelper;
import com.rong.util.PageBean;
import com.rong.util.StringUtils;

public class BookDao extends BaseDao<Book>{

	public List<Book> getAll(Book book, PageBean pagebean) throws SQLException, InstantiationException, IllegalAccessException{
		List<Book> list=new ArrayList<Book>();
		String sql="select * from book where true";
		if(StringUtils.isBlank(book.getBname())) {
			sql+=" and bname like '%"+book.getBname()+"%'";
		}
		
		return super.executeQuery(sql, Book.class, pagebean);
	}
	
}

action

package com.rong.web;

import java.io.IOException;
import java.sql.SQLException;
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.rong.dao.BookDao;
import com.rong.entity.Book;
import com.rong.util.PageBean;
@WebServlet("*.action")
public class BookAction extends HttpServlet {

	private static final long serialVersionUID = -2170150748234359807L;
	private BookDao bookDao=new BookDao();
	
	@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 {
		Book book=new Book();
		book.setBname(req.getParameter("bname"));
		PageBean pagebean=new PageBean();
		pagebean.SetRequest(req);
		
		try {
			List<Book> list=this.bookDao.getAll(book, pagebean);
			req.setAttribute("booklist", list);
			req.setAttribute("pagebean", pagebean);
			req.getRequestDispatcher("/booklist.jsp").forward(req, resp);
		} catch (InstantiationException | IllegalAccessException | SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
	
}

自定义标签

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

tag助手类

package com.rong.tag;

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.rong.util.PageBean;

public class PageTag extends BodyTagSupport {

	private static final long serialVersionUID = 7207395987868814509L;
	
	private PageBean pagebean;

	public PageBean getPagebean() {
		return pagebean;
	}

	public void setPagebean(PageBean pagebean) {
		this.pagebean = pagebean;
	}
	
	@Override
	public int doStartTag() throws JspException {
		JspWriter out=pageContext.getOut();
		try {
			out.print(toHTML());
		} catch (Exception e) {
			// TODO: handle exception
			e.printStackTrace();
		}
		return super.doStartTag();
	}
	
	private String toHTML() {
        StringBuilder sb = new StringBuilder();

//        这里拼接的是一个上一次发送的请求以及携带的参数，唯一改变的就是页码
        sb.append("
");
        sb.append("");
        sb.append("");
//        重要设置拼接操作，将上一次请求参数携带到下一次
        Map<String, String[]> paMap = pagebean.getParametermap();
        if(paMap !=null && paMap.size()>0){
            Set<Map.Entry<String, String[]>> entrySet = paMap.entrySet();
            for (Map.Entry<String, String[]> entry : entrySet) {
                for (String val : entry.getValue()) {
                    if(!"page".equals(entry.getKey())){
                        sb.append("");
                    }
                }
            }
        }
        sb.append(""
);


        int page = pagebean.getPage();
        int max = pagebean.getMaxPage();
        int before = page > 4 ? 4 : page-1;
        int after = 10 - 1 - before;
        after = page+after > max ? max-page : after;
//        disabled
        boolean startFlag = page == 1;
        boolean endFlag = max == page;

//        拼接分页条
        sb.append("
");
        sb.append("
首页
");
        sb.append("
<
");

//        代表了当前页的前4页
        for (int i = before; i > 0 ; i--) {
            sb.append("
"+(page-i)+"
");
        }

        sb.append("
"+pagebean.getPage()+"
");

//        代表了当前页的后5页
        for (int i = 1; i <= after; i++) {
            sb.append("
"+(page+i)+"
");
        }

        sb.append("
>
");
        sb.append("
尾页
");
        sb.append("
到第页
");
        sb.append("
确定
");
        sb.append("
共"+pagebean.getTotal()+"条
");
        sb.append("
");

//        拼接分页的js代码
        sb.append("");

        return sb.toString();
    }
	
}

jsp页面代码

<%@ 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="/rong" prefix="r" %>
<!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 action="book.action" method="post">
	    <input type="text" name="bname" placeholder="请输入书籍名称"/>
	  	<button type="submit" >查询</button>
	</form>
	<table border="1px" width="100%">
	  <tr>
	  	<td>书籍编号</td>
	  	<td>书籍名称</td>
	  	<td>书籍价格</td>
	  </tr>
	  <c:forEach var="b" items="${booklist }">
	  	<tr>
		  	<td>${b.bid }</td>
		  	<td>${b.bname }</td>
		  	<td>${b.price }</td>
		  </tr>
	  </c:forEach>
	</table>
	<r:page pagebean="${pagebean }"></r:page>
</body>
</html>

总结

这个代码敲的我脑壳疼！不解释了，我自己都脑壳疼，多注意细节。