java常用公共代码二之分页代码的实现

在项目中，我们经常会写到一些公共的代码，来让开发人员调用，减少代码重复，下面，我就将一些常用到的公共类贴出来和大家分享！！

二、分页代码实现：在项目中，分页是一个项目中必不可少的，它可以防止我们从数据库中进行大量数据查询时速度变慢，提高我们的查询效率

1、定义分页模型：PageModel

package com.common.page;

import java.util.List;

/**
 * 封装分页信息
 * @author Administrator
 *
 */
public class PageModel<E> {

    //结果集
    private List<E> list;

    //查询记录数
    private int totalRecords;

    //每页多少条数据
    private int pageSize;

    //第几页
    private int pageNo;

    /**
     * 总页数
     * @return
     */
    public int getTotalPages() {
        return (totalRecords + pageSize - 1) / pageSize;
    }

    /**
     * 取得首页
     * @return
     */
    public int getTopPageNo() {
        return 1;
    }

    /**
     * 上一页
     * @return
     */
    public int getPreviousPageNo() {
        if (pageNo <= 1) {
            return 1;
        }
        return pageNo - 1;
    }

    /**
     * 下一页
     * @return
     */
    public int getNextPageNo() {
        if (pageNo >= getBottomPageNo()) {
            return getBottomPageNo();
        }
        return pageNo + 1;
    }

    /**
     * 取得尾页
     * @return
     */
    public int getBottomPageNo() {
        return getTotalPages();
    }

    public List<E> getList() {
        return list;
    }

    public void setList(List<E> list) {
        this.list = list;
    }

    public int getTotalRecords() {
        return totalRecords;
    }

    public void setTotalRecords(int totalRecords) {
        this.totalRecords = totalRecords;
    }

    public int getPageSize() {
        return pageSize;
    }

    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }

    public int getPageNo() {
        return pageNo;
    }

    public void setPageNo(int pageNo) {
        this.pageNo = pageNo;
    }
}

2、分页测试：在MySQL中建立admin表，里面有字段id、name、password

3、简历Admin的实体bean类：

package com.common.page;

public class Admin {
    private int id;
    private String name;
    private String password;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }

}

4、测试调用：

package com.common.page;

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.common.db.DbUtil;

public class Client {
    public static PageModel findAdmins(int pageNo,int pageSize){
        Connection conn=DbUtil.getConnection();
        String sql="select * from admin limit ?,?";
        PageModel pageModel=null;
        PreparedStatement pstm=null;
        ResultSet rs=null;
        Admin admin=null;
        List<Admin> list=new ArrayList<Admin>();
        try {
            pstm=conn.prepareStatement(sql);
            pstm.setInt(1, (pageNo-1)*pageSize);
            pstm.setInt(2, pageNo*pageSize);
            rs=pstm.executeQuery();;
            while(rs.next()){
                admin=new Admin();
                admin.setId(rs.getInt("a_id"));
                admin.setName(rs.getString("a_name"));
                admin.setPassword(rs.getString("a_pwd"));
                list.add(admin);
            }
            ResultSet rs2=pstm.executeQuery("select count(*) from admin");
            int total=0;
            if(rs2.next()){
                total=rs2.getInt(1);
            }
            pageModel=new PageModel();
            pageModel.setPageNo(pageNo);
            pageModel.setPageSize(pageSize);
            pageModel.setTotalRecords(total);
            pageModel.setList(list);
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            DbUtil.close(conn);
            DbUtil.close(pstm);
            DbUtil.close(rs);
        }
        return pageModel;
    }

    public static void main(String[] args) {
        PageModel pageModel=Client.findAdmins(2,4);
        List<Admin> list=pageModel.getList();
        for(Admin a:list){
            System.out.print("ID:"+a.getId()+",用户名:"+a.getName()+",密码:"+a.getPassword());
            System.out.println();
        }
        System.out.print("当前页:"+pageModel.getPageNo()+" ");
        System.out.print("共"+pageModel.getTotalPages()+"页  ");
        System.out.print("首页:"+pageModel.getTopPageNo()+" ");
        System.out.print("上一页:"+pageModel.getPreviousPageNo()+" ");
        System.out.print("下一页:"+pageModel.getNextPageNo()+" ");
        System.out.print("尾页:"+pageModel.getBottomPageNo()+" ");
        System.out.print("共"+pageModel.getTotalRecords()+"条记录");
        System.out.println();
    }

}

这样分页效果就实现了，我们要实现分页效果，只要传入相应的参数和相应的数据库执行语句即可实现，希望大家能灵活运用。