通用分页三

点我跳转通用分页一.
点我跳转通用分页二.

改造PageBean

1.增强PageBean属性

    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

2.增加两个新的属性Url请求路径和携带条件的查询集合

    //上一次查询的url
	private String url;
	//上一次查询所携带的查询条件map
	private Map<String, String[]> parameter = new HashMap<String, String[]>();

3.创建初始化方法方便`req`调用的时候保存

public void setRequest(HttpServletRequest req) {
		//初始化jsp页面传递过来的当前页
		this.setPage(req.getParameter("page"));
		//初始化jsp页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.setParameter(req.getParameterMap());
		}

4.初始化后分别对属性重载

//重载setpagination
	private void setPagination(String pagination) {
		//只有填写了false才会不分页 ，其他的字符串无效
			this.setPagination(!"false".equals(pagination));
		
	}
	//重载setRows
	private void setRows(String rows) {
		if(StringUtils.isNotBlank(rows))
			this.setRows(Integer.valueOf(rows));
	} 

	//重载setpage
	private void setPage(String page) {
		   if(StringUtils.isNotBlank(page)) 
			   this.setPage(Integer.valueOf(page));
		   
	}

5.对servlet每次请求的参数进行保存

//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;
	}

6.PageBean实体类改造好了

package com.houzhihong.pagebean.util;

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

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
	
	private boolean pagination = true;// 是否分页
	
	//上一次查询的url
	private String url;
	//上一次查询所携带的查询条件map
	private Map<String, String[]> parameter = new HashMap<String, String[]>();
	

	//对pagebean进行初始化
	public void setRequest(HttpServletRequest req) {
		//初始化jsp页面传递过来的当前页
		this.setPage(req.getParameter("page"));
		//初始化jsp页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.setParameter(req.getParameterMap());
		}
	//重载setpagination
	private void setPagination(String pagination) {
		//只有填写了false才会不分页 ，其他的字符串无效
			this.setPagination(!"false".equals(pagination));
		
	}
	//重载setRows
	private void setRows(String rows) {
		if(StringUtils.isNotBlank(rows))
			this.setRows(Integer.valueOf(rows));
	} 

	//重载setpage
	private void setPage(String page) {
		   if(StringUtils.isNotBlank(page)) 
			   this.setPage(Integer.valueOf(page));
		   
	}


	public String getUrl() {
		return url;
	}
	public void setUrl(String url) {
		this.url = url;
	}
	public Map<String, String[]> getParameter() {
		return parameter;
	}
	public void setParameter(Map<String, String[]> parameter) {
		this.parameter = parameter;
	}
	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 + "]";
	}
	
	//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;
	}

}

通用类BaseDao

1.使用泛型定义好方法方便子类调用达成通用性

package com.houzhihong.pagebean.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;

public class BaseDao<T> {
	public List<T> executeQuery(String sql, Class clz, PageBean pagebean)
			throws SQLException, InstantiationException, IllegalAccessException {
		List<T> list = new ArrayList<>();

		// 获取连接
		Connection con = DBAccess.getConnection();
		// 执行sql
		PreparedStatement ps = null;
		ResultSet rs = null;  
		if(pagebean !=null && pagebean.isPagination()) {
				//分页---> 列表需求
				//查询出符合条件的总记录数
			String countSql = getCountSql(sql);
			ps = con.prepareStatement(countSql);
			rs = ps.executeQuery();  
			if(rs.next()) {
				//把数据放入pageBean
				pagebean.setTotal(rs.getObject(1).toString());
			}
			//展示想要看到的数据 ，比如3页的十条数据
			String pageSql = getPageSql(sql,pagebean);
			ps = con.prepareStatement(pageSql);
			rs = ps.executeQuery();  
		}else {
				//不分页 ---> 下拉框需求
			ps = con.prepareStatement(sql);
			rs = ps.executeQuery();  
		}
		
		while (rs.next()) {
			// *实例化对象
			T t = (T) clz.newInstance();
			for (Field f : clz.getDeclaredFields()) {
				f.setAccessible(true);
				// 给这一个空对象的每一个属性赋值
				f.set(t, rs.getObject(f.getName()));
			}
			// 将赋值完的对象添加到list集合中返回
			list.add(t);
		}
		DBAccess.close(con, ps, rs);
		return list;
	}
	private String getPageSql(String sql, PageBean pagebean) {
		
		return sql + " limit "+pagebean.getStartIndex()+","+pagebean.getRows();
	}
	/**
	 * --原生的带条件的查询语句
	 *	sql =SELECT * FROM t_mvc_book WHERE true and bname like '%斗破%'
	 *
	 *
	 *--符合条件的记录数有多少条
	 * countsql= SELECT COUNT(1) from  (SELECT * FROM t_mvc_book WHERE TRUE AND bname LIKE '%圣墟%') t;
	 *
	 *--查询第几页的数据 LIMIT 起始下标，偏移量 展示的记录数
	 * pagesql=	SELECT * FROM t_mvc_book WHERE TRUE AND bname LIKE '%圣墟%' LIMIT 10,10
	 *  
	 *
	 */

	private String getCountSql(String sql) {
		
		return "select count(1) from ("+sql+") t";
	}
	
}

2.bookDao直接继承BaseDao的方法executeQuery，直接反射一波

return super.executeQuery(sql, Book.class, pagebean);

3.使用反射实例化对象属性，实现一步到位，不需要一个一个的去赋值

while (rs.next()) {
			// *实例化对象
			T t = (T) clz.newInstance();
			for (Field f : clz.getDeclaredFields()) {
				f.setAccessible(true);
				// 给这一个空对象的每一个属性赋值
				f.set(t, rs.getObject(f.getName()));
			}
			// 将赋值完的对象添加到list集合中返回
			list.add(t);
		}

补全Servlet

1.action业务层
2.注意初始化PageBean不要写到异常里面去了

package com.houzhihong.pagebean.web;

import java.io.IOException;
import java.sql.SQLException;
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.houzhihong.pagebean.dao.BookDao;
import com.houzhihong.pagebean.entity.Book;
import com.houzhihong.pagebean.util.PageBean;

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

	private static final long serialVersionUID = 4591437219474314661L;
	private BookDao bookDao = 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 {
		// 实例化对象
		Book book = new Book();
		// 获取表单值
		book.setBname(req.getParameter("bname"));

		// 初始化PageBean
		PageBean pageBean = new PageBean();
		pageBean.setRequest(req);
		try {
			List<Book> list = this.bookDao.list(book, pageBean);
			req.setAttribute("bookList", list);
			req.setAttribute("pageBean", pageBean);
			req.getRequestDispatcher("booklist.jsp").forward(req, resp);
		} catch (InstantiationException | IllegalAccessException | SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

}

封装页面标签自定义Tag

1.PageTag助手类，将页面的表单，分页条，js拼接代码

package com.houzhihong.pagebean.tag;

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

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

import com.houzhihong.pagebean.util.PageBean;

public class PageTag extends BodyTagSupport {

	private static final long serialVersionUID = 6584001758518399660L;
	private PageBean pageBean;

	public PageBean getPageBean() {
		return pageBean;
	}

	public void setPageBean(PageBean pageBean) {
		this.pageBean = pageBean;
	}

	@Override
	public int doStartTag() throws JspException {
		// 输出分页条
		JspWriter out = pageContext.getOut();
		try {
			out.println(toHTML());
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return super.doStartTag();
	}

	private String toHTML() {
		StringBuilder sb = new StringBuilder();
		// 上一次查询的form表单的html拼接
		sb.append("
");
		// 查第几页
		sb.append("");

		// 拼接带条件查询
		Map<String, String[]> parameter = pageBean.getParameter();
		if (parameter.size() > 0) {
			Set<Entry<String, String[]>> entrySet = parameter.entrySet();
			for (Entry<String, String[]> entry : entrySet) {
				if (!"page".equals(entry.getKey())) {
					for (String val : entry.getValue()) {
						sb.append("");
					}
				}
			}
		}
		sb.append(""
);
		// 默认展示前面4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 = max - page > after ? after : max - page;
		// 用来控制上一页的点击按钮特效的
		boolean startFlag = page == 1;

		// 用来控制下一页的点击按钮特效的
		boolean endFlag = max == page;

		// 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();
	}
}

2.配置好自己定义tld标签库

<?xml version="1.0" encoding="UTF-8" ?>

<taglib xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
	version="2.0">

	<description>JSTL 1.1 core library</description>
	<display-name>JSTL core</display-name>
	<tlib-version>1.1</tlib-version>
	<short-name>h</short-name>
	<uri>/houzhihong</uri>

	<tag>

		<name>page</name>
		<tag-class>com.houzhihong.pagebean.tag.PageTag</tag-class>
		<body-content>JSP</body-content>
		<attribute>

			<name>pageBean</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
		</attribute>
	</tag>



</taglib>

3.代码贴的差不多了还有些之前有贴，上效果了