JavaWeb开发中关于分页的实现

1、关于Java分页实现的流程图

    

2、在分页的实现中,关键的几个类，以及代码的实现，QueryInfo,QueryResult,PageBean

QueryInfo的代码实现

public class QueryInfo {
    
    private int currentpage = 1;  //用户当前看的页
    private int pagesize = 5;     //记住用户想看的页面大小
    private int startindex;     //记住用户看的页的数据在数据库的起始位置
    
    
    public int getCurrentpage() {
        return currentpage;
    }
    public void setCurrentpage(int currentpage) {
        this.currentpage = currentpage;
    }
    public int getPagesize() {
        return pagesize;
    }
    public void setPagesize(int pagesize) {
        this.pagesize = pagesize;
    }
    public int getStartindex() {
        this.startindex = (this.currentpage-1)*this.pagesize;
        return startindex;
    }
}

QueryResult的代码实现

public class QueryResult {
    
    private List list;   //记住用户看的页的数据
    private int totalrecord;    //记往总记录数
    public List getList() {
        return list;
    }
    public void setList(List list) {
        this.list = list;
    }
    public int getTotalrecord() {
        return totalrecord;
    }
    public void setTotalrecord(int totalrecord) {
        this.totalrecord = totalrecord;
    }
}

PageBean的代码实现

public class PageBean {

    private List list;
    private int totalrecord;
    private int pagesize;
    private int totalpage;
    private int currentpage;
    private int previouspage;
    private int nextpage;
    private int[] pagebar;
    
    
    public List getList() {
        return list;
    }
    public void setList(List list) {
        this.list = list;
    }
    public int getTotalrecord() {
        return totalrecord;
    }
    public void setTotalrecord(int totalrecord) {
        this.totalrecord = totalrecord;
    }
    public int getPagesize() {
        return pagesize;
    }
    public void setPagesize(int pagesize) {
        this.pagesize = pagesize;
    }
    public int getTotalpage() {
        //100   5   20
        //101   5   21
        //99    5   20
        
        if(this.totalrecord%this.pagesize==0){
            this.totalpage = this.totalrecord/this.pagesize;
        }else{
            this.totalpage = this.totalrecord/this.pagesize+1;
        }
        
        
        return totalpage;
    }
    
    public int getCurrentpage() {
        return currentpage;
    }
    public void setCurrentpage(int currentpage) {
        this.currentpage = currentpage;
    }
    public int getPreviouspage() {
        if(this.currentpage-1<1){
            this.previouspage = 1;
        }else{
            this.previouspage = this.currentpage-1;
        }
        return previouspage;
    }
    
    public int getNextpage() {
        if(this.currentpage+1>=this.totalpage){
            this.nextpage = this.totalpage;
        }else{
            this.nextpage = this.currentpage +1;
        }
        return nextpage;
    }
    
    public int[] getPagebar() {
        int startpage;
        int endpage;
        int pagebar[] = null;
        if(this.totalpage<=10){
            pagebar = new int[this.totalpage];
            startpage = 1;
            endpage = this.totalpage;
        }else{
            pagebar = new int[10];
            startpage = this.currentpage - 4;
            endpage = this.currentpage + 5;
            
            //总页数=30      3    -1
            //总页数=30      29   34   21   30
            if(startpage<1){
                startpage = 1;
                endpage = 10;
            }
            
            if(endpage>this.totalpage){
                endpage = this.totalpage;
                startpage = this.totalpage - 9;
            }
        }
        
        int index = 0;
        for(int i=startpage;i<=endpage;i++){
            pagebar[index++] = i;
        }
        
        this.pagebar = pagebar;
        return this.pagebar;
        /*int pagebar[] = new int[this.totalpage];
        for(int i=1;i<=this.totalpage;i++){
            pagebar[i-1] = i;
        }
        this.pagebar = pagebar;
        return pagebar;*/
    }
    
}

Student实体类的代码

package cn.itcast.domain;

public class Student {
    private String id;
    private String name;
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    
    
}

3、关于dao层StudentDao,serive层StudentSerive,controller层StudentServlet层的实现

关于dao层StudentDao

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

import cn.itcast.domain.QueryResult;
import cn.itcast.domain.Student;
import cn.itcast.utils.JdbcUtils;

public class StudentDao {
    
    
    public QueryResult pageQuery(int startindex,int pagesize){

        Connection conn = null;
        PreparedStatement st = null;
        ResultSet rs = null;
        
        QueryResult qr = new QueryResult();
        try{
            conn = JdbcUtils.getConnection();
            String sql = "select * from student limit ?,?";
            st = conn.prepareStatement(sql);
            
            st.setInt(1, startindex);
            st.setInt(2, pagesize);
            
            rs = st.executeQuery();
            
            List list = new ArrayList();
            while(rs.next()){
                Student s = new Student();
                s.setId(rs.getString("id"));
                s.setName(rs.getString("name"));
                list.add(s);
            }
            qr.setList(list);
            
            sql = "select count(*) from student";
            rs = conn.prepareStatement(sql).executeQuery();
            if(rs.next()){
                qr.setTotalrecord(rs.getInt(1));
            }
            return qr;
        }catch (Exception e) {
            throw new RuntimeException(e);
        }finally{
            JdbcUtils.release(conn, st, rs);
        }
    }
    
}

serive层StudentSerive

import cn.itcast.dao.StudentDao;
import cn.itcast.domain.PageBean;
import cn.itcast.domain.QueryInfo;
import cn.itcast.domain.QueryResult;

public class StudentService {
    
    public PageBean pageQuery(QueryInfo info){
        
        StudentDao dao = new StudentDao();
        QueryResult qr = dao.pageQuery(info.getStartindex(), info.getPagesize());
        
        PageBean bean = new PageBean();
        bean.setCurrentpage(info.getCurrentpage());
        bean.setList(qr.getList());
        bean.setPagesize(info.getPagesize());
        bean.setTotalrecord(qr.getTotalrecord());
        
        
        return bean;
    }
    
}

controller层StudentServlet层的实现

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import cn.itcast.domain.PageBean;
import cn.itcast.domain.QueryInfo;
import cn.itcast.service.BusinessService;
import cn.itcast.utils.WebUtils;

public class ListStudentServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        QueryInfo info = WebUtils.request2Bean(request, QueryInfo.class);
        BusinessService service = new BusinessService();
        PageBean bean = service.pageQuery(info);
        request.setAttribute("pagebean", bean);
        request.getRequestDispatcher("/liststudent.jsp").forward(request, response);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

}

4、用到的工具类JdbcUtils和WebUtils

工具类JdbcUtils

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class JdbcUtils {
    
    private static Properties config = new Properties();
    static{
        try {
            config.load(JdbcUtils.class.getClassLoader().getResourceAsStream("db.properties"));
            Class.forName(config.getProperty("driver"));
        } catch (Exception e) {
            throw new ExceptionInInitializerError(e);
        }
    }

    public static Connection getConnection() throws SQLException{
        return DriverManager.getConnection(config.getProperty("url"), config.getProperty("username"), config.getProperty("password"));
    }
    
    
    public static void release(Connection conn,Statement st,ResultSet rs){
        
        if(rs!=null){
            try{
                rs.close();   //throw new 
            }catch (Exception e) {
                e.printStackTrace();
            }
            rs = null;
        }
        if(st!=null){
            try{
                st.close();
            }catch (Exception e) {
                e.printStackTrace();
            }
            st = null;
        }
        if(conn!=null){
            try{
                conn.close();
            }catch (Exception e) {
                e.printStackTrace();
            }
        }
        
        
    }
}    

db.properties的配置

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/student
username=root
password=root

工具类WebUtils

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Map;
import java.util.UUID;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.beanutils.BeanUtils;
import org.apache.commons.beanutils.ConvertUtils;
import org.apache.commons.beanutils.Converter;

public class WebUtils {
    
    public static <T> T request2Bean(HttpServletRequest request,Class<T>  beanClass){
        try{
            T bean = beanClass.newInstance();
            //得到request里面所有数据
            Map map = request.getParameterMap();
            //map{name=aa,password=bb,birthday=1990-09-09}  bean(name=aa,password=dd,birthday=Date)
            
            ConvertUtils.register(new Converter(){

                public Object convert(Class type, Object value) {
                    if(value==null){
                        return null;
                    }
                    String str = (String) value;
                    if(str.trim().equals("")){
                        return null;
                    }
                    
                    SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
                    try {
                        return df.parse(str);
                    } catch (ParseException e) {
                        throw new RuntimeException(e);
                    }
                }
            }, Date.class);
            BeanUtils.populate(bean, map);   
            return bean;
        }catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
    
    public static String generateID(){
        return UUID.randomUUID().toString();
    }
    
    
}

关于页面的显示,主要利用EL表达式和JSTL来获取数据

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>显示学生分页数据</title>
  </head>
  
  <body>
  
      <c:forEach var="s" items="${pagebean.list}">
          ${s.id } ${s.name } <br/>
      </c:forEach>
  
      
     <script type="text/javascript">
        function gotopage(currentpage){      
            var pagesize = document.getElementById("pagesize").value;
            window.location.href = '${pageContext.request.contextPath}/servlet/ListStudentServlet?currentpage=' + currentpage + '&pagesize=' + pagesize;
        }
    </script>
    
    共[${pagebean.totalrecord }]条记录,
    每页<input type="text" id="pagesize" value="${pagebean.pagesize }" onchange="gotopage(${pagebean.currentpage })" style="width: 30px" maxlength="2">条,
    共[${pagebean.totalpage }]页,
    当前[${pagebean.currentpage }]页
    &nbsp;&nbsp;&nbsp;
    <a href="javascript:void(0)" onclick="gotopage(${pagebean.previouspage })">上一页</a>
        <c:forEach var="pagenum" items="${pagebean.pagebar}">
            <c:if test="${pagenum==pagebean.currentpage}">
                <font color="red">${pagenum }</font>
            </c:if>
            
            <c:if test="${pagenum!=pagebean.currentpage}">
                <a href="javascript:void(0)" onclick="gotopage(${pagenum })">${pagenum }</a>
            </c:if>
        </c:forEach>
    <a href="javascript:void(0)" onclick="gotopage(${pagebean.nextpage })">下一页</a>
    <input type="text" id="pagenum" style="width: 30px">
    <input type="button" value=" GO " onclick="gotopage(document.getElementById('pagenum').value)">
  </body>
</html>