Java EE分页实现详解-优快云博客

本文链接：https://blog.youkuaiyun.com/weixin_60659657/article/details/124098562

本文介绍了在Java EE中如何实现通用分页功能，详细讲解了pageBean的组成，包括页码、每页行数、总记录数、分页状态和查询路径。同时，文章提到了Student模型的创建，包含SId、sname、age和remark属性，并阐述了如何编写 Dao 方法进行数据库操作。测试数据方法也在文中进行了说明。

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1.pageeBean

pageBean里面有页码page，还有每页显示多少行数据rows，数据的总记录数total，是否分页pagination，记录查询的路径用于点击分页保存需要查找的内容url，还有存放参数parameterMap用于在隐藏域中的元素

package com.zking.mymvc.util;

import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import com.mysql.jdbc.StringUtils;

public class PageBean {
	
	/**
	 * 页码
	 */
	private int page = 1;

	/**
	 * 每页显示的记录数
	 */
	private int rows = 10;

	/**
	 * 总记录数
	 */
	private int total = 0;

	/**
	 * 是否分页
	 */
	private boolean pagination = true;
	
	/**
	 * 记录查询的url，以便于点击分页时再次使用
	 */
	private String url;
	
	/**
	 * 存放请求参数，用于生成隐藏域中的元素
	 */
	private Map<String,String[]> parameterMap;
	
	/**
	 * 根据传入的Request初始化分页对象
	 * @param request
	 */
	public void setRequest(HttpServletRequest request) {
		
		if(!StringUtils.isNullOrEmpty(request.getParameter("page"))) {
			this.page = Integer.valueOf(request.getParameter("page"));
		}
		if(!StringUtils.isNullOrEmpty(request.getParameter("rows"))) {
			this.rows = Integer.valueOf(request.getParameter("rows"));
		}
		if(!StringUtils.isNullOrEmpty(request.getParameter("pagination"))) {
			this.pagination = Boolean.valueOf(request.getParameter("pagination"));
		}
		
		this.url = request.getRequestURI();
		this.parameterMap = request.getParameterMap();
		
		request.setAttribute("pageBean", this);
	}


	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 boolean isPagination() {
		return pagination;
	}

	public void setPagination(boolean pagination) {
		this.pagination = pagination;
	}
	
	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;
	}

	//计算起始页码
	public int getStartIndex() {
		return (this.page - 1) * this.rows;
	}
	
	//获取总页数
	public int getTotalPage() {
		if (this.getTotal() % this.rows == 0) {
			return this.getTotal() / this.rows;
		} else {
			return this.getTotal() / this.rows + 1;
		}
	}

	//上一页
	public int getPreviousPage() {
		return this.page - 1 > 0 ? this.page - 1 : 1;
	}
	
	//下一页
	public int getNextPage() {
		return this.page + 1 > getTotalPage() ? getTotalPage() : this.page + 1;
	}

}

编写model Student

属性学生编号SId 学生名称sname 学生年龄age 备注 remark

然后封装 toString方法

package com.zking.mymvc.model;

public class Student {
	
	private Integer sid;
	
	private String sname;
	
	private Integer age;
	
	private String remark;

	public Integer getSid() {
		return sid;
	}

	public void setSid(Integer sid) {
		this.sid = sid;
	}

	public String getSname() {
		return sname;
	}

	public void setSname(String sname) {
		this.sname = sname;
	}

	public Integer getAge() {
		return age;
	}

	public void setAge(Integer age) {
		this.age = age;
	}

	public String getRemark() {
		return remark;
	}

	public void setRemark(String remark) {
		this.remark = remark;
	}

	@Override
	public String toString() {
		return "Student [sid=" + sid + ", sname=" + sname + ", age=" + age + ", remark=" + remark + "]";
	}

}

链接数据库 DBUtil.java

我这边用的是sqlyog

package com.zking.mymvc.util;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

/**
 * @author Administrator
 * @create 2020-05-0811:43
 */
public final class DBUtil {
	
    private static String DRIVER_NAME;

    private static String DB_URL;

    private static String DB_USER;

    private static String DB_PASSWORD;


    private DBUtil() {
    }


    static {
        try {
        	InputStream in = DBUtil.class.getResourceAsStream("/jdbc.properties");
        	Properties properties = new Properties();
			properties.load(in);
			
			DRIVER_NAME = properties.getProperty("driver.name");
			DB_URL = properties.getProperty("db.url");
			DB_USER = properties.getProperty("db.user");
			DB_PASSWORD = properties.getProperty("db.password");
			
            Class.forName(DRIVER_NAME);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }  catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
    }


    public static Connection getConection() throws SQLException {
        Connection connection = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
        return connection;
    }


    public static void closeDB(ResultSet rs, Statement ps, Connection con) {

        try {
            if (rs != null && !rs.isClosed()) {
                rs.close();
            }

            if (ps != null && !ps.isClosed()) {
                ps.close();
            }

            if(con != null && !con.isClosed()) {
                con.close();
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    
    public static void closeDB(ResultSet rs, Statement ps) {

        try {
            if (rs != null && !rs.isClosed()) {
                rs.close();
            }

            if (ps != null && !ps.isClosed()) {
                ps.close();
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    
    public static void main(String[] args) throws SQLException {
    	Connection conection = DBUtil.getConection();
    	DBUtil.closeDB(null, null, conection);
    	System.out.println("------- �ɹ� -------------");
    }

}

编写Dao方法

package com.zking.mymvc.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 javax.swing.event.ListSelectionEvent;

import org.junit.Test;

import com.zking.mymvc.model.Student;
import com.zking.mymvc.util.DBUtil;
import com.zking.mymvc.util.PageBean;

public class StudentDao {
	
	public List<Student> getStudents(String sname, PageBean pageBean) {
		
		//差异部分
		//查询语句
		String sql = "select * from t_student t ";
		if(sname != null && !"".equals(sname)) {
			sql += " where t.sname like ?";
		}
		//~~~~~~
		//相同
		//查询之前的准备
		List<Student> students = new ArrayList<>();
		Connection con = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		//~~~~~
		//如果不需要分页，直接查询
		if(pageBean ==null || !pageBean.isPagination()) {
			//获取连接
			try {
				//相同部分~~~~~~~~~~~~~
				con =DBUtil.getConection();
				ps=con.prepareStatement(sql);
				
				
				if(sname !=null && !"".equals(sname)) {
					ps.setObject(1, sname+"%");
				}
				rs= ps.executeQuery();
				//~~~~~~~~~~·
				//~~~~~~~~~~~~~不相同
				while(rs.next()) {
					Student stu=new Student();
					stu.setSid(rs.getInt("sid"));
					stu.setSname(rs.getString("snmae"));
					stu.setAge(rs.getInt("age"));
					stu.setRemark(rs.getString("remark"));
					students.add(stu);
				}
				//~~~~~~~~~
				return students;
			} catch (SQLException e) {
				
				e.printStackTrace();
			}finally {
				DBUtil.closeDB(rs, ps, con);
			}
			
		}else {
			//如果需要分页
			//1、获取总记录数  一样相同~~~~~~~~~~~~~~
			String countSql="select COUNT(*) from ("+sql+") t";
			
			try {
				con =DBUtil.getConection();
				ps=con.prepareStatement(countSql);
				
				//设置查询参数
				if(sname!=null) {
					ps.setObject(1, sname+"%");
				}
				
				rs=ps.executeQuery();
				// 给总记录赋值
				while(rs.next()) {
					pageBean.setTotal(rs.getInt(1));
				}
				//如果总记录为0则直接返回一个空的结果集
				if(pageBean.getTotal()==0) {
					return students;
				}
				//~~~~~~~~~~~
				
				//~~~~~~~~~~~~~~是
				//查询当前页数据
				String pagingSql=sql +"limit" +pageBean.getStartIndex()+","+pageBean.getRows();
				ps=con.prepareStatement(pagingSql);
				
				//设置查询参数
				if(sname!=null) {
					ps.setObject(1, sname+"%");
				}
				
				rs= ps.executeQuery();
				//~~~~~~~
				
				//~~~~~~~~~`不相同
				while(rs.next()) {
					Student stu=new Student();
					stu.setSid(rs.getInt("sid"));
					stu.setSname(rs.getString("snmae"));
					stu.setAge(rs.getInt("age"));
					stu.setRemark(rs.getString("remark"));
					students.add(stu);
				}
				//~~~~~
				return students;
				
			} catch (Exception e) {
				e.printStackTrace();			
			}finally {
				DBUtil.closeDB(rs, ps, con);
			}	
		}
		return students ;
	}
	
}

如果不需要分页就直接运行查询。

最后直接测试

编写一个测试数据方法

@Test
	public void  testStudentDao(){
		StudentDao dao=new StudentDao();
		PageBean pagebean=new PageBean();
		pagebean.setRows(6);
		List<Student> students = dao.getStudents("芊", pagebean);
		students.forEach(t->System.out.println(t));
		System.out.println(pagebean.getTotal());
		System.out.println(pagebean.getTotalPage());
	}

通用分页01

1.pageeBean

编写model Student