通用分页（全）

通用分页
一、核心思想：将上一次查询请求再发一次，只不过页码变了
二、分页三要素：（PageBean）
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
三、后台
entity
dao
四、视图层：（PageTag）

1、准备工作：
导入jar包：

2、建包建类：

3、utils包里的各个类，都有各自不同的作用：
连接数据库—DBAccess

package com.xieying.utils;

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 DBAccess {
	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 = DBAccess.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 = DBAccess.getConnection();
		DBAccess.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");
	}
}

中文乱码处理—EncodingFilter

package com.xieying.utils;

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.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 中文乱码处理
 * 
 */
@WebFilter(filterName="encodingFilter",urlPatterns="*.action")
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();
		}
	}

}

分页工具类—PageBean

package com.xieying.utils;

import java.util.HashMap;
import java.util.Map;

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

/**
 * 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
	
	//上一次查询的URL
	private String url;
	
	//上一次查询所携带的查询条件
	private Map parameterMap=new HashMap();
	
	//对pagebean进行初始化
	public void setRequest(HttpServletRequest req) {
		//初始化jsp界面传递过来的当前页
		this.setPage(req.getParameter("page"));
		//初始化jsp界面传递过来的页大小
		this.setRows(req.getParameter("rows"));
		//初始化jsp页面传递过来是否分页
		this.setPagination(req.getParameter("pagination"));
		//保留上一次的查询请求
		this.setUrl(req.getRequestURL().toString());
		//保留上一次的查询条件
		this.setParameterMap(req.getParameterMap());
		
	}
	
	private void setPagination(String pagination) {
		//
	}
	
	private void setRows(String rows) {
		if(StringUtils.isNotBlank(rows)) {
			this.setRows(Integer.valueOf(rows));
		}
	}
	
	private void setPage(String page) {
		if(StringUtils.isNotBlank(page)) {
			this.setPage(Integer.valueOf(page));
		}
	}
	
	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;
	}

	
	public String getUrl() {
		return url;
	}

	public void setUrl(String url) {
		this.url = url;
	}

	public Map getParameterMap() {
		return parameterMap;
	}

	public void setParameterMap(Map parameterMap) {
		this.parameterMap = parameterMap;
	}

	/**
	 * 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 + "]";
	}

	//上一页
	public int getPrevPage() {
		return this.page > 1 ? this.page -1 : this.page;
	}
	//下一页
	public int getNextPage() {
		return this.page < this.getMaxPage() ? this.page + 1 : this.page;
	}
	
	//最大页
	public int getMaxPage() {
		return this.total % this.rows == 0 ? this.total / this.rows : (this.total / this.rows) + 1;
		
	}
	
}

4、写实体类—Book

package com.xieying.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(int bid, String bname, float price) {
		super();
		this.bid = bid;
		this.bname = bname;
		this.price = price;
	}

	public Book() {
		
	}
	
}

dao方法—BookDao

package com.xieying.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.xieying.entity.Book;
import com.xieying.utils.BaseDao;
import com.xieying.utils.DBAccess;
import com.xieying.utils.PageBean;
import com.xieying.utils.StringUtils;

public class BookDao extends BaseDao{
	
	//通过反射改装后的通过分页的写法
	public List list(Book b,PageBean pagebean) throws SQLException, InstantiationException, IllegalAccessException{
		String sql="select * from t_mvc_book where true";
		String bname=b.getBname();
		if(StringUtils.isNotBlank(bname)) {
			sql +=" and bname like '%"+bname+"%'";
		}
		return super.executeQuery(Book.class,sql, pagebean);
	}
	
	public static void main(String[] args) throws SQLException, InstantiationException, IllegalAccessException {
		BookDao bd=new BookDao();
		Book b=new Book();
		b.setBname("绝望教室");
		PageBean pb=new PageBean();
		pb.setPage(2);
		pb.setPagination(false);
		
		List list = bd.list(b, pb);
		for (Book book : list) {
			System.out.println(book);
		}
		System.out.println(pb);
	}
	
	
}

BaseDao

package com.xieying.utils;

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.xieying.entity.Book;

public class BaseDao {

	public List executeQuery(Class clz, String sql,PageBean pagebean) throws SQLException, InstantiationException, IllegalAccessException{
		List list=new ArrayList();
		Connection con = DBAccess.getConnection();
		PreparedStatement ps=con.prepareStatement(sql);
		ResultSet rs=ps.executeQuery();
		
		if(pagebean !=null &&pagebean.isPagination()) {
			//想要分页-->列表需求
			//查询出符合分页的总记录数
			String countSql=getCountSql(sql);
			ps=con.prepareStatement(countSql);
			rs=ps.executeQuery();
			if(rs.next()) {
				pagebean.setTotal(rs.getObject(1).toString());
			}
			//展示想要看到的数据，就比如说第三页的第十条数据
			String pageSql=getPageSql(sql,pagebean);
			ps=con.prepareStatement(pageSql);
			rs=ps.executeQuery();
		}else {
			//不想分页-->下拉需求
			ps=con.prepareStatement(sql);
			rs=ps.executeQuery();
		}
		
		
		
		while(rs.next()) {
			//list.add(new Book(rs.getInt("bid"), rs.getString("bname"), rs.getFloat("price")));
			/**
			 * Book b=new Book();
			 * b.setBid(rs.getInt("bid"));
			 * b.setBname(rs.getString("bname"));
			 * b.setPrice(rs.getFloat("price"));
			 * list.add(b);
			 * 
			 * 实例化了一个对象
			 * 给这一个空对象的每一个属性赋值
			 * 将赋值完的对象添加到list集合中返回
			 */
				T t=(T)clz.newInstance();
				Field[] declaredFields = clz.getDeclaredFields();//拿到所有属性对象
				for (Field f : declaredFields) {
					f.setAccessible(true);
					f.set(t, rs.getObject(f.getName()));
				}
				list.add(t);
		}
		DBAccess.close(con, ps, rs);
		return list;
	}

	private String getPageSql(String sql, PageBean pagebean) {

		return sql + " limit "+pagebean.getStartIndex()+","+pagebean.getRows();
	}

	private String getCountSql(String sql) {
		
		return "select count(1) form ("+sql+") t";
	}
	
	/**
	 * sql=select * from t_mvc_book where true and bname like '"绝望"'
	 * countSql=select count(1) form (select * from t_mvc_book where true and bname like '"绝望"')
	 * pageSql=select * from t_mvc_book where true and bname like '"绝望"' limit 10,10
	 * 
	 */
	
	
	
	
}

拼接展示—PageTag

package com.xieying.tag;

import java.util.Map;
import java.util.Set;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyTagSupport;

import com.xieying.utils.PageBean;

public class PageTag extends BodyTagSupport{

	private static final long serialVersionUID = 5173138912016761869L;

	private PageBean pagebean;

	public PageBean getPagebean() {
		return pagebean;
	}

	public void setPagebean(PageBean pagebean) {
		this.pagebean = pagebean;
	}
	
	@Override
	public int doStartTag() throws JspException {
		JspWriter out=pageContext.getOut();
		try {
			out.print(toHTML());
		} catch (Exception e) {
			// TODO: handle exception
			e.printStackTrace();
		}
		return super.doStartTag();
	}

	private String toHTML() {
        StringBuilder sb = new StringBuilder();

//        这里拼接的是一个上一次发送的请求以及携带的参数，唯一改变的就是页码
        sb.append("
");
        sb.append("");
        sb.append("");
//        重要设置拼接操作，将上一次请求参数携带到下一次
        Map paMap = pagebean.getParameterMap();
        if(paMap !=null && paMap.size()>0){
            Set> entrySet = paMap.entrySet();
            for (Map.Entry entry : entrySet) {
                if (!"page".equals(entry.getKey()) ) {
                    for(String val : entry.getValue()){
                        sb.append("");
                    }
                }
            }
        }
        sb.append("");

        //默认展示前四页，当前页，后面5页
        int page = pagebean.getPage();
        int max = pagebean.getMaxPage();
        int before = page > 4 ? 4 : page-1;
        int after = 10 - 1 - before;
        after = page+after > max ? max-page : after;
        //用来控制下一页的点击控制特效的
        boolean afterFlag = page > 1;
        //用来控制上一页的点击控制特效的
        boolean startFlag = page < max;
       

        //拼接分页条
        sb.append("
");
        sb.append("
首页
");
        sb.append("
<
");

//        代表了当前页的前4页
        for (int i = before; i > 0 ; i--) {
            sb.append("
"+(page-i)+"
");
        }

        sb.append("
"+pagebean.getPage()+"
");

//        代表了当前页的后5页
        for (int i = 1; i <= after; i++) {
            sb.append("
"+(page+i)+"
");
        }

        sb.append("
>
");
        sb.append("
尾页
");
        sb.append("
到第页
");
        sb.append("
确定
");
        sb.append("
共"+pagebean.getTotal()+"条
");
        sb.append("
");

//        拼接分页的js代码
        sb.append("");

        return sb.toString();
    }
}

BookAction

package com.xieying.web;

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

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 com.xieying.dao.BookDao;
import com.xieying.entity.Book;
import com.xieying.utils.PageBean;

@WebServlet(name="book",urlPatterns="/book.action")
public class BookAction extends HttpServlet{

	private static final long serialVersionUID = 7857580259883137815L;
	private BookDao bd=new BookDao();
	
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doPost(req, resp);
	}
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		// TODO Auto-generated method stub
		Book b=new Book();
		b.setBname(req.getParameter("bname"));
		PageBean pagebean =new PageBean();
		pagebean.setRequest(req);
		try {
			List list=this.bd.list(b, pagebean);
			req.setAttribute("booklist", list);
			req.setAttribute("pagebean", pagebean);
			req.getRequestDispatcher("/booklist.jsp").forward(req, resp);
		} catch (Exception e) {
			// TODO: handle exception
			e.printStackTrace();
		}
		
	}
			
	
}

jsp界面—booklist

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












  

    
  
  查询

	
  	

  

    

      
书籍
      
书名 
      
价格
    
  
  
  
  

  

      
${b.bid }
      
${b.bname }
      
${b.price }
    
  
   
    
  



	

结果展示：