通用分页01

于 2022-06-16 11:40:13 发布
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分类专栏： JAVA 文章标签： mariadb sql 数据库
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本文链接：https://blog.youkuaiyun.com/weixin_62356088/article/details/125312151
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先简单介绍一下

基于MySql数据库的通用分页
    
   通用分页核心思路：将上一次查询请求再发一次，只不过页码变了
   实现步骤：
   1）先查询全部数据
    Junit测试
    baseDao<T>、CallBack<K>
   2）通用分页实现
    pagebean
    

分页要素

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

   pagination  是否分页    视图层传递过来

   getStartIndex()        基于MySql数据库分页，获取分页开始标记


2. 后台
  2.1 entity
  2.2 dao
      BaseDao<T>
      1）匿名内部接口
      2）分页查询方法，接口方法传参
        （返回：总记录数+指定页码并满足条件的记录集）
      3）二次查询的条件要一致
    getCountSql()/getPagerSql()


3. junit
   java单元测试/白盒测试

一，后端

1，DBHelper——数据库帮助类

package com.zking.pagination.util;

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

/**
 * 提供了一组获得或关闭数据库对象的方法
 * 
 */
public class DBHelper {
	private static String driver;
	private static String url;
	private static String user;
	private static String password;

	static {// 静态块执行一次，加载 驱动一次
		try {
			InputStream is = DBHelper.class
					.getResourceAsStream("config.properties");

			Properties properties = new Properties();
			properties.load(is);

			driver = properties.getProperty("driver");
			url = properties.getProperty("url");
			user = properties.getProperty("user");
			password = properties.getProperty("pwd");

			Class.forName(driver);
		} catch (Exception e) {
			e.printStackTrace();
			throw new RuntimeException(e);
		}
	}

	/**
	 * 获得数据连接对象
	 * 
	 * @return
	 */
	public static Connection getConnection() {
		try {
			Connection conn = DriverManager.getConnection(url, user, password);
			return conn;
		} catch (SQLException e) {
			e.printStackTrace();
			throw new RuntimeException(e);
		}
	}

	public static void close(ResultSet rs) {
		if (null != rs) {
			try {
				rs.close();
			} catch (SQLException e) {
				e.printStackTrace();
				throw new RuntimeException(e);
			}
		}
	}

	public static void close(Statement stmt) {
		if (null != stmt) {
			try {
				stmt.close();
			} catch (SQLException e) {
				e.printStackTrace();
				throw new RuntimeException(e);
			}
		}
	}

	public static void close(Connection conn) {
		if (null != conn) {
			try {
				conn.close();
			} catch (SQLException e) {
				e.printStackTrace();
				throw new RuntimeException(e);
			}
		}
	}

	public static void close(Connection conn, Statement stmt, ResultSet rs) {
		close(rs);
		close(stmt);
		close(conn);
	}

	public static boolean isOracle() {
		return "oracle.jdbc.driver.OracleDriver".equals(driver);
	}

	public static boolean isSQLServer() {
		return "com.microsoft.sqlserver.jdbc.SQLServerDriver".equals(driver);
	}
	
	public static boolean isMysql() {
		return "com.mysql.jdbc.Driver".equals(driver);
	}

	public static void main(String[] args) {
		Connection conn = DBHelper.getConnection();
		DBHelper.close(conn);
		System.out.println("isOracle：" + isOracle());
		System.out.println("isSQLServer：" + isSQLServer());
		System.out.println("isMysql：" + isMysql());
		System.out.println("数据库连接(关闭)成功");
	}
}

2.对应的config.properties文件

#oracle9i
#driver=oracle.jdbc.driver.OracleDriver
#url=jdbc:oracle:thin:@localhost:1521:orcl
#user=scott
#pwd=123


#sql2005
#driver=com.microsoft.sqlserver.jdbc.SQLServerDriver
#url=jdbc:sqlserver://localhost:1433;DatabaseName=test1
#user=sa
#pwd=123


#sql2000
#driver=com.microsoft.jdbc.sqlserver.SQLServerDriver
#url=jdbc:microsoft:sqlserver://localhost:1433;databaseName=unit6DB
#user=sa
#pwd=888888


#mysql
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/T277?useUnicode=true&characterEncoding=UTF-8
user=root
pwd=1234

3.EncodingFilter——中文乱码处理（编码过滤器）

package com.zking.pagination.util;

import java.io.IOException;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 中文乱码处理
 * 
 */
public class EncodingFilter implements Filter {

	private String encoding = "UTF-8";// 默认字符集

	public EncodingFilter() {
		super();
	}

	public void destroy() {
	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		HttpServletRequest req = (HttpServletRequest) request;
		HttpServletResponse res = (HttpServletResponse) response;

		// 中文处理必须放到 chain.doFilter(request, response)方法前面
		res.setContentType("text/html;charset=" + this.encoding);
		if (req.getMethod().equalsIgnoreCase("post")) {
			req.setCharacterEncoding(this.encoding);
		} else {
			Map map = req.getParameterMap();// 保存所有参数名=参数值(数组)的Map集合
			Set set = map.keySet();// 取出所有参数名
			Iterator it = set.iterator();
			while (it.hasNext()) {
				String name = (String) it.next();
				String[] values = (String[]) map.get(name);// 取出参数值[注：参数值为一个数组]
				for (int i = 0; i < values.length; i++) {
					values[i] = new String(values[i].getBytes("ISO-8859-1"),
							this.encoding);
				}
			}
		}

		chain.doFilter(request, response);
	}

	public void init(FilterConfig filterConfig) throws ServletException {
		String s = filterConfig.getInitParameter("encoding");// 读取web.xml文件中配置的字符集
		if (null != s && !s.trim().equals("")) {
			this.encoding = s.trim();
		}
	}

}

4.BaseDao——通用查询分页父类

package com.zking.pagination.dao;

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

import com.zking.pagination.util.DBHelper;
import com.zking.pagination.util.PageBean;

public class BaseDao<T> {

	public static interface CallBack<k> {
		// 只用于遍历ResultSet结果集
		public List<k> foreachRs(ResultSet rs) throws SQLException;
		//把接口作为参数用到方法里面去
	}
	

	/**
	 * 通用分页方法（即支持分页，也支持不分页）
	 * 
	 * @param sql
	 *            普通的SQL
	 * @param pageBean
	 *            分页对象
	 * @return 查询结果集
	 */
	public List<T> executeQuery(String sql, PageBean pageBean, CallBack<T> callBack) {
		Connection conn = null;
		PreparedStatement stmt = null;
		ResultSet rs = null;
		try {
			// 1.分页
			// 2.不分页
			// 获取连接对象
			conn = DBHelper.getConnection();
			// 根据PageBean分页对象判断是否分页pageBean.isPagination()（分页标记必须是真的）
			if (null != pageBean && pageBean.isPagination()) {
				// 1)根据满足条件查询记录数
				String countSQL = this.getCountSQL(sql);
				// 创建执行对象
				stmt = conn.prepareStatement(countSQL);
				// 执行SQL语句并返回总记录数
				rs = stmt.executeQuery();
				// 获取总记录数
				if (rs.next()) {
					//只要验证有没有结果，rs.getInt(1)是总记录数
					pageBean.setTotal(rs.getInt(1));
				}
				// 2)根据满足条件查询分页结果集，放sql不是countSql
				sql = this.getPagerSQL(sql, pageBean);
			}
			// 创建执行对象 这里sql，不管是哪里的 sql都会放到里面去
			stmt = conn.prepareStatement(sql);
			// 查询结果集
			rs = stmt.executeQuery();

			return callBack.foreachRs(rs);
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			DBHelper.close(conn, stmt, rs);
		}
		return null;
	}

	/**
	 * 将普通的SQL语句转换成查询总记录数的SQL语句
	 * select * from t_book 
	 * select * from t_book where ...
	 * select book_id,book_name from t_book where ... 
	 * select count(0) from t_book where ...
	 * 
	 * @param sql普通的SQL
	 * @return 普通总记录数的SQL
	 */
	private String getCountSQL(String sql) {
		//String sql 不管sql语句是以什么形式出现都当成查询所有
		return "select count(0) from (" + sql + ") temp";
		//要取别名，不然会报错temp
	}

	/**
	 * 将普通的SQL语句转换成查询分页结果集的SQL语句 * 
	 * select * from t_book
	 * select * from t_book where... 
	 * select book_id,book_name from t_book 
	 * select book_id,book_name from t_book where ... 
	 * select * from t_book limit 
	 * select * from t_book where 1=1 limit
	 * 
	 * @param sql
	 *            普通的SQL
	 * @param pageBean
	 *            分页对象（包含当前页码和每页条数，用于计算分页的关键数据）
	 * @return
	 */
	private String getPagerSQL(String sql, PageBean pageBean) {
		//？
		return sql + " limit " + pageBean.getStartIndex() + "," + pageBean.getRows();
	}
}

5.BookDao——书籍Dao层类

package com.zking.pagination.dao;

import java.sql.Connection;

import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import com.zking.pagination.entity.Book;
import com.zking.pagination.util.DBHelper;
import com.zking.pagination.util.PageBean;
import com.zking.pagination.util.StringUtils;

import sun.java2d.pipe.AATextRenderer;


public class BookDao  extends BaseDao<Book>{
	//继承方法
	/**
	 * 书本新增
	 * @param book
	 */
	public void addBook(Book book) {
		Connection conn = null;
		PreparedStatement stmt = null;
		try {
			//获取连接对象
			conn = DBHelper.getConnection();
			//定义SQL语句
			String sql = "insert into t_book(book_name,book_name_pinyin,"
					+"book_price,book_type) values(?,?,?,?)";
			//创建执行对象
			stmt = conn.prepareStatement(sql);
			//参数赋值
			stmt.setString(1, book.getBook_name());
			stmt.setString(2, book.getBook_name_pinyin());
			stmt.setFloat(3, book.getBook_price());
			stmt.setString(4, book.getBook_type());
			//执行SQL并返回影响行数
			int i = stmt.executeUpdate();
			if(i<1)
				throw new RuntimeException("影响行数为0，执行失败！");
			
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			DBHelper.close(conn, stmt, null);
		}
	}
	
	/**
	 * 2.书本分页查询
	 * @param book
	 * @return
	 */
	public List<Book> queryBookPager(Book book,PageBean pageBean){
		
		//定义SQL语句
		String sql = "select book_id,book_name,book_name_pinyin,"
				+ "book_price,book_type from t_book where 1=1";
		//拼接查询条件，按照书本名称模糊查询
		if(StringUtils.isNotBlank(book.getBook_name()))
			sql+=" and book_name like '%"+book.getBook_name()+"%'";
		//按照书本编号降序排序
		sql+=" order by book_id desc";
		System.out.println(sql);
//		Collections .sort(new ArrayList<>(),new Comparator<T>() {
//比较器
//			@Override
//			public int compare(T o1, T o2) {
//				// TODO Auto-generated method stub
//				return 0;
//			}
//		});
		
		//子类调用父类的方法super.executeQuery 分页传pageBean 不分页 传null 
		return super.executeQuery(sql, pageBean, new CallBack<Book>() {
			
			@Override
			public List<Book> foreachRs(ResultSet rs) throws SQLException {
				List<Book> lst = new ArrayList<>();
				//定义BOOK对象
				Book b = null;
				//循环遍历结果集
				while(rs.next()) {
					//创建Book对象
					b = new Book();
					b.setBook_id(rs.getInt("book_id"));
					b.setBook_name(rs.getString("book_name"));
					b.setBook_name_pinyin(rs.getString("book_name_pinyin"));
					b.setBook_price(rs.getFloat("book_price"));
					b.setBook_type(rs.getString("book_type"));
					lst.add(b);
				}
				return lst;
			}
		
		});
		
		/*List<Book> lst = new ArrayList<>();
		Connection conn = null;
		PreparedStatement stmt = null;
		ResultSet rs = null;
		try {
			//获取连接对象
			conn = DBHelper.getConnection();
			//创建执行对象
			stmt = conn.prepareStatement(sql);
			//执行SQL语句并返回查询结果集
			rs = stmt.executeQuery();
			
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			DBHelper.close(conn, stmt, rs);
		}
		return lst;*/
	}
	
	//3.书本编辑
	//4.书本删除
	//5.根据书本ID查询单个书本信息
}

6.PageBean——分页工具类

package com.zking.pagination.util;

import java.io.Serializable;

public class PageBean implements Serializable {

	// 当前页码，默认1
	private int page = 1;

	// 页面显示条数，默认10
	private int rows = 81;

	// 总记录数，默认0
	private int total = 0;

	// 是否分页标记，默认分页
	private boolean pagination = true;

	/**
	 * 基于MySql分页，计算limit(分页)开始位置
	 * 
	 * @return
	 */
	public int getStartIndex() {
		//计算公式
		// page=1 (1-1)*10 limit 0,10
		// page=2 (2-1)*10 limit 10,10
		// ...
		return (this.page - 1) * this.rows;
	}

	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;
	}

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

}

二，前端

1.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>pagination</display-name>

<!-- 配置中文乱码过滤器 -->
<filter>
<filter-name>EncodingFilter</filter-name>
<filter-class>com.zking.pagination.util.EncodingFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>EncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<servlet>
<servlet-name>BookAction</servlet-name>
<servlet-class>com.zking.pagination.action.BookAction</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>BookAction</servlet-name>
<url-pattern>/BookAction.action</url-pattern>
</servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
</web-app>

2.StringUtils——助手类

package com.zking.pagination.util;

public class StringUtils {
	// 私有的构造方法，保护此类不能在外部实例化
	private StringUtils() {
	}

	/**
	 * 如果字符串等于null或去空格后等于""，则返回true，否则返回false
	 * 
	 * @param s
	 * @return
	 */
	public static boolean isBlank(String s) {
		boolean b = false;
		if (null == s || s.trim().equals("")) {
			b = true;
		}
		return b;
	}
	
	/**
	 * 如果字符串不等于null或去空格后不等于""，则返回true，否则返回false
	 * 
	 * @param s
	 * @return
	 */
	public static boolean isNotBlank(String s) {
		return !isBlank(s);
	}

}

3.BookDaoTest——助手类

package com.zking.pagination.dao;

import static org.junit.Assert.*;

import java.util.List;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.zking.bookshop.util.PinYinUtil;
import com.zking.pagination.entity.Book;
import com.zking.pagination.util.PageBean;

public class BookDaoTest {
	//Servlet生命周期：init(运行)/service(执行)/destory(销毁)
		Book book = null;
		BookDao bookdao = new BookDao();

		@Before
		public void setUp() throws Exception {
		book = new Book();
		}

		@After
		public void tearDown() throws Exception {
//			System.out.println("tearDown");
		}

		@Test
		public void testAddBook() {
			for(int i = 0;i < 81; i++) {
				book = new Book();
				book.setBook_name("西游记第"+(i+1)+"章");
				book.setBook_name_pinyin(PinYinUtil.toPinyin("西游记第"+(i+1)+"章"));
				book.setBook_price(88f);
				book.setBook_type("神话");
				bookdao.addBook(book);
				}
		}

		@Test
		public void testQueryBookPager() {
			book.setBook_name("1");
			PageBean pageBean = new PageBean();
			//当前页面默认为2
			//pageBean.setPage(2);
			//页码显示条数 为10 
			//pageBean.setRows(8);
			//设置不分页(只要是写了这一句不管你的page rows  写什么都是没有用的)
		//	pageBean.setPagination(false);
			List<Book> books = bookdao.queryBookPager(book,pageBean);
			System.out.println("总记录数："+pageBean.getTotal());
			books.forEach(System.out::println);
			}
}

4.bookList.jsp——前端界面

<%@ page language="java" contentType="text/html; charset=utf-8"
	pageEncoding="utf-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
	<form action="BookAction.action" method="post">
		<label>书本名称：</label> <input type="text" name="bookname" /> <input
			type="submit" value="查询" />
	</form>
	<table width="100%" border="1" cellpadding="0" cellspacing="0">
		<tr>
			<th>书本编号</th>
			<th>书本名称</th>
			<th>书本拼音</th>
			<th>书本价格</th>
			<th>书本类型</th>
		</tr>
		<c:forEach items="${books }" var="b">
			<tr>
				<td>${b.book_id }</td>
				<td>${b.book_name }</td>
				<td>${b.book_name_pinyin }</td>
				<td>${b.book_price }</td>
				<td>${b.book_type }</td>
			</tr>
		</c:forEach>
	</table>
</body>
</html>

5.Servlet

package com.zking.pagination.action;

import java.io.IOException;

import java.util.List;

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

import com.zking.pagination.dao.BookDao;
import com.zking.pagination.entity.Book;
import com.zking.pagination.util.PageBean;

/**
 * Servlet implementation class BookAction
 */

public class BookAction extends HttpServlet {
//@WebServlet("/BookAction")
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		this.doPost(req, resp);
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
	//获取请求查询参数
		String bookname = req.getParameter("bookname");
		//实例化BookDao
		BookDao bookdao = new BookDao();
		//实例化Book
		Book book = new Book();
		book.setBook_name(bookname);
		//创建PageBean
		PageBean pageBean = new PageBean();
		//实例书本查询
		List<Book> books = bookdao.queryBookPager(book,pageBean);
		//将查询结果books保存到request作用域中
		req.setAttribute("books", books);
		//转发到指定页面并显示查询结果
		req.getRequestDispatcher("/bookList.jsp").forward(req, resp);
	}

	
}
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