jsp通用分页【一】

1. PageBean

package com.zyp.util;

/**
 *
 * 分页工具类
 */
public class PageBean {

	private int page = 1;// 页码

	private int rows = 10;// 页大小

	private int total = 0;// 总记录数

	private boolean pagination = true;// 是否分页

	public PageBean() {
		super();
	}

	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 void setTotal(String total) {
		this.total = Integer.parseInt(total);
	}

	public boolean isPagination() {
		return pagination;
	}

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

	/**
	 * 获得起始记录的下标
	 * 
	 * @return
	 */
	public int getStartIndex() {
		return (this.page - 1) * this.rows;
	}

	@Override
	public String toString() {
		return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", pagination=" + pagination + "]";
	}

}

2、BaseDao

package com.zyp.util;

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.zyp.entity.Book;

/**
 * T = Book.class
 * T = Student.class
 * @author zhouyanpeng
 *
 * @param <T>
 */
public class BaseDao<T> {
	/**
	 * 
	 * @param sql	决定查询哪张表的数据
	 * @param clz	查询出来的数据封装到哪个实体类中
	 * @param pagebean	决定是否分页
	 * @return
	 * @throws IllegalAccessException 
	 * @throws InstantiationException 
	 * @throws SQLException 
	 */
	public List<T> executeQuery(String sql,Class clz,PageBean pagebean) throws InstantiationException, IllegalAccessException, SQLException{
		List<T> list = new ArrayList<>();
		Connection con = DBAccess.getConnection();
		PreparedStatement pst = null;
		ResultSet rs = null;
		if(pagebean != null && pagebean.isPagination()) {
			//该分页了
			String countSql = getCountSql(sql);
			pst = con.prepareStatement(countSql);
			rs = pst.executeQuery();
			if(rs.next()) {
				pagebean.setTotal(rs.getLong(1)+"");
			}
			
			String pageSql = getpageSql(sql,pagebean);
			pst = con.prepareStatement(pageSql);
			rs = pst.executeQuery();
		}else {
			pst = con.prepareStatement(sql);
			rs = pst.executeQuery();
		}
		try {
			while (rs.next()) {
				//			list.add(new Book(rs.getInt("bid"), rs.getString("bname"), rs.getFloat("price")));
				/**
				 * 这行代码干的事
				 * 1、创建了一个Book对象
				 * 2、从ResultSet结果集中获取值放入Book对象中属性中
				 * 	2.1	获取Book的属性对象
				 * 	2.2	给属性对象赋值
				 * 3、将已经有值的Book对象放入List集合中
				 */
				T t = (T) clz.newInstance();
				Field[] Fields = clz.getDeclaredFields();
				for (Field field : Fields) {
					field.setAccessible(true);
					field.set(t, rs.getObject(field.getName()));//第二步完成
				}	
				list.add(t);
			} 
		} finally {
			//shift+alt+z
			DBAccess.close(con, pst, rs);;
		}
		return list;
	}

	/**
	 * 将原生sql拼接出符合条件的某一页的数据查询sql
	 * @param sql
	 * @param pagebean
	 * @return
	 */
	private String getpageSql(String sql, PageBean pagebean) {
		// TODO Auto-generated method stub
		return sql+" limit" +pagebean.getStartIndex()+","+pagebean.getRows();
	}


	/**
	 * 用原生sql拼接出查询符合条件的记录数。
	 * @param sql
	 * @return
	 */
	private String getCountSql(String sql) {
		// TODO Auto-generated method stub
		return "select count(1) from ("+sql+") t";
	}
}

3、案例演示【book】

实例化Book类

package com.zyp.entity;

public class Book {
	private int bid;
	private String bname;
	private float price;

	@Override
	public String toString() {
		return "Book [bid=" + bid + ", bname=" + bname + ", price=" + price + "]";
	}

	public int getBid() {
		return bid;
	}

	public void setBid(int 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(int bid, String bname, float price) {
		super();
		this.bid = bid;
		this.bname = bname;
		this.price = price;
	}
	
}

BookDao

package com.zyp.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.zyp.entity.Book;
import com.zyp.util.BaseDao;
import com.zyp.util.DBAccess;
import com.zyp.util.PageBean;
import com.zyp.util.StringUtils;

/**
 * 操作数据库中的t_mvc_book表
 * 1、加载驱动
 * 2、建立连接
 * 3、获取预定义处理对象
 * 4、执行sql语句
 * 5、处理结果集
 * 6、关闭连接
 * @author zhouyanpeng
 *
 */
public class BookDao extends BaseDao<Book>{
	
//	/**
//	 * 
//	 * @param book 是从jsp传递过来的参数封装成对象作为参数查询并执行的sql
//	 * @return pageBean  决定是否分页
//	 * @throws SQLException 
//	 */
//	public List<Book> list(Book book,PageBean pagebean) throws SQLException{
//		List<Book> list = new ArrayList<>();
//		String sql = "select * from t_mvc_book where 1 = 1";
//		if(StringUtils.isNotBlank(book.getBname())) {
//			sql += " and bname like '%"+book.getBname()+"%'";
//		}
//		Connection con = DBAccess.getConnection();
//		PreparedStatement pst = con.prepareStatement(sql);
//		ResultSet rs = pst.executeQuery();
//		while(rs.next()) {
//			list.add(new Book(rs.getInt("bid"), rs.getString("bname"), rs.getFloat("price")));
//		}
//		return list;
//	}
//	public static void main(String[] args) throws SQLException {
//		BookDao bookdao = new BookDao();
//		Book b = new Book();
//		List<Book> list = bookdao.list(b, null);
//		for (Book book : list) {
//			System.out.println(book);
//		}
//	}
	
	/**
	 * 
	 * @param book 是从jsp传递过来的参数封装成对象作为参数查询并执行的sql
	 * @return pageBean  决定是否分页
	 * @throws SQLException 
	 * @throws IllegalAccessException 
	 * @throws InstantiationException 
	 */
	public List<Book> list(Book book,PageBean pagebean) throws SQLException, InstantiationException, IllegalAccessException{
		String sql = "select * from t_mvc_book where 1=1";
		if(StringUtils.isNotBlank(book.getBname())) {
			sql += " and bname like '%"+book.getBname()+"%'";
		}
		return super.executeQuery(sql, Book.class, pagebean);
	}
	public static void main(String[] args) {
		BookDao bookdao = new BookDao();
		try {
			Book b = new Book();
			PageBean pageBean = new PageBean();
//			pageBean.setPage(2);
			pageBean.setPagination(false);
			b.setBname("圣墟");
			List<Book> list = bookdao.list(b, pageBean);
			for (Book book : list) {
				System.out.println(book);
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}
	
}

测试结果

public static void main(String[] args) {
		BookDao bookdao = new BookDao();
		try {
			Book b = new Book();
			PageBean pageBean = new PageBean();
			pageBean.setPage(2);//第几页 2
//			pageBean.setPagination(false);//不分页
			b.setBname("圣墟");//模糊查询的参数
			List<Book> list = bookdao.list(b, pageBean);
			for (Book book : list) {//遍历输出
				System.out.println(book);
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}

打印结果

分页三要素
1、 page： 页码 视图层传递过来
2、rows： 页大小 视图层传递过来
3、total ： 总记录数 后台查出来

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