jsp mysql 实现客户端简单分页查询

jsp mysql 实现客户端简单分页查询

 

dao.impl

import com.mchange.v2.c3p0.ComboPooledDataSource;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import sim.dao.StudentDao;
import sim.entity.Student;

import javax.sql.DataSource;
import java.sql.SQLException;
import java.util.List;

public class StudentDaoImpl implements StudentDao {
    private DataSource ds = new ComboPooledDataSource();
    private QueryRunner qr = new QueryRunner(ds);  // 必有的两句

    @Override
    public List selectAll(Integer currentPageNo, Integer pageSize) {
        List  studentList = null;
        try {
            String sql  ="select *  from  user  limit ?,?";
            Object[] objects={(currentPageNo-1)*pageSize,pageSize};  //页面数量，页面大小
            studentList = qr.query(sql,new BeanListHandler(Student.class),objects);  //很多地方少写了 r currentPageNo
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return studentList;
    }


    @Override
    public Integer selectCount() {
        Long count = null;
        try {
            String sql ="select count(1) from  user";   //把 Long 写成 long
            count = (Long) qr.query(sql,new ScalarHandler());  //总页数
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return Integer.parseInt(count+"");
    }
}

 

StudentServiceImpl

import sim.dao.StudentDao;
import sim.dao.StudentDaoImpl.StudentDaoImpl;
import sim.entity.Student;
import sim.service.StudentService;

import java.util.List;

public class StudentServiceImpl implements StudentService {
    private StudentDao studentDao  = new StudentDaoImpl();  //必有的实例
    @Override
    public List selectAll(Integer currentPageNo, Integer pageSize) {   //
        return studentDao.selectAll(currentPageNo,pageSize);
    }

    @Override
    public Integer selectCount() {
        return studentDao.selectCount();
    }
}

 

servlet

import sim.Utils.PageUtils;
import sim.entity.Student;
import sim.service.StudentService;
import sim.service.StudentServiceImpl.StudentServiceImpl;

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 java.io.IOException;
import java.util.List;

@WebServlet(name = "studentServlet" ,urlPatterns = "/studentServlet")
public class StudentServlet extends HttpServlet {
    private StudentService studentService;  //一定有的一句

    @Override
    public void init() throws ServletException {
        studentService = new StudentServiceImpl();   //一定有的一句
    }

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String currentPageNoStr = req.getParameter("currentPageNo");  //本页的当前页量
        Integer currentPageNo = null;
        if(currentPageNoStr ==null || currentPageNoStr==""){
            currentPageNo = 1;
        }else{
            currentPageNo =Integer.parseInt(currentPageNoStr);
        }

        String pageSizeStr = req.getParameter("pageSize");  //当前页量数
        Integer pageSize=null;
        if(pageSizeStr ==null || pageSizeStr==""){
            pageSize = 2;  //无页量，则为2
        }else{
            pageSize =Integer.parseInt(pageSizeStr);  //有页量，则传递
        }

        Integer totalPageCount = studentService.selectCount();
        Integer totalPageSize =  totalPageCount  % pageSize ==0 ? totalPageCount / pageSize  //为什么等于0————因为把 % 打成了 /
                : totalPageCount / pageSize +1;
        List studentList = studentService.selectAll(currentPageNo,pageSize);
        PageUtils pageUtils = new PageUtils<>();  //数据库的名字和实体类不同，导致错误。
        pageUtils.setCurrentPageNo(currentPageNo);
        pageUtils.setPageSize(pageSize);
        pageUtils.setTotalPageCount(totalPageCount);
        pageUtils.setTotalPageSize(totalPageSize);
        pageUtils.setList(studentList);
        req.setAttribute("pageUtils",pageUtils);
        req.getRequestDispatcher("index.jsp").forward(req,resp);
    }
}

 

index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>

  
    
    
  
  

<%--  重定向，加载两次页面（跳过第一次无数据）--%>
<%      Object object = request.getAttribute("pageUtils");
        if (object==null){
          request.getRequestDispatcher("studentServlet").forward(request,response);
        }
%>


  
      

    

      
编号
      
名字
      
年龄
    
    

        
${student.uid}
        
${student.uname}
        
${student.uage}
      
    

    

  

    首页

    上一页

  <%--中间的小于，是在大括号内--%>
    下一页

    末页
    共有${pageUtils.totalPageCount}条
    ${pageUtils.currentPageNo}页/${pageUtils.totalPageSize}页
    
  
  
  

 

StudentDao (实现；定义)

 

Student （实现；三个变量；两构造；set get；toString）

 

PageUtils （五个变量；两构造；set get；toString）

 

结果展示：

首页

第四页

跳转成功