JSP通用分页【二】

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最新推荐文章于 2023-06-28 10:08:04 发布

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分类专栏： JAVA 文章标签：通用分页【二】简化分页

本文链接：https://blog.youkuaiyun.com/zyp_baoku/article/details/90814330

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本文详细介绍了分页工具类PageBean的实现原理及应用，包括如何设置页码、页大小、总记录数等属性，以及如何通过PageBean进行分页操作。同时，文章还提供了PageTag类的使用方法，展示了如何在JSP页面上实现分页显示。

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1、需要的资源

DBAccess类：提供了一组获得或关闭数据库对象的方法
config.properties：连接数据库
EncodingFiter类：中文乱码处理
StringUtils类：判断是否存在
Book类：它是一个实体类
PageTag类：自定义标签的助手类
BookDao类：所用到的dao方法
PageBean类：分页的工具类【核心类】
在这里插入图片描述

2、分页的实现

分页工具类【核心代码】PageBean类

package com.zyp.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

	private String url;
	private Map<String, String[]> paramMap = new HashMap<>();

	public void setRequest(HttpServletRequest req) {
		this.setPage(req.getParameter("page"));
		this.setRows(req.getParameter("rows"));
		this.setPagination(req.getParameter("pagination"));
		// getRequestURL获取到浏览器请求的全路径
		this.setUrl(req.getRequestURL().toString());
		// getParameterMap可以获取到一次url请求所携带的所有参数
		this.setParamMap(req.getParameterMap());

	}

	public void setPagination(String pagination) {
		if (StringUtils.isNotBlank(pagination)) {
			this.setPagination(!"false".equals(pagination));//是否分页
		}
	}

	public void setRows(String rows) {
		if (StringUtils.isNotBlank(rows))
			this.setRows(Integer.valueOf(rows));//每页多少天数据

	}

	public void setPage(String page) {
		if (StringUtils.isNotBlank(page)) {
			this.setPage(Integer.valueOf(page));//多少页
		}
	}

	public PageBean() {
		super();
	}

	public String getUrl() {
		return url;
	}

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

	public Map<String, String[]> getParamMap() {
		return paramMap;
	}

	public void setParamMap(Map<String, String[]> paramMap) {
		this.paramMap = paramMap;
	}

	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 + "]";
	}

	/**
	 * 获取到总页数
	 * @return
	 */
	public int getMaxPage() {
		return this.total % this.rows == 0 ? 
				this.total / this.rows : 
					(this.total / this.rows) + 1;
	}
	
	/**
	 * 获取下一页页码
	 * @return
	 */
	public int getNextPage() {
		return this.page < this.getMaxPage() ? this.page+1 : this.page;
	}
	
	/**
	 * 获取上一页页码
	 * @return
	 */
	public int getPreviousPage() {
		return this.page > 1 ? this.page-1 : this.page;
	}

}

PageTag类

package com.zyp.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.zyp.util.PageBean;

public class PageTag extends BodyTagSupport{

	private static final long serialVersionUID = -3609493782238830873L;
	private PageBean pageBean;
	
	@Override
	public int doStartTag() throws JspException {
		JspWriter out = pageContext.getOut();
		try {
			out.write(toHTML());
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return super.doStartTag();
	}
	
	public String toHTML() {
		StringBuffer sb = new StringBuffer();
		//下一次请求提交到后台的表单html代码拼接
		sb.append("<form id='pageBeanForm' action='"+pageBean.getUrl()+"' method='post'>");
		Map<String, String[]> paramMap = pageBean.getParamMap();
		if(paramMap !=null && paramMap.size()>0) {
			Set<Entry<String, String[]>> entrySet = paramMap.entrySet();
			for(Entry<String, String[]> entry:paramMap.entrySet()) {
				if(!"page".equals(entry.getKey())) {
					sb.append("<input type='hidden' name='"+entry.getKey()+"' value='"+entry.getValue()+"'>");
				}
			}
		}
		sb.append("<input type='hidden' name='page'>");
		sb.append("</form>");
		
		//分页条html代码拼接
		sb.append("<div style='text-align: right; font-size: 12px;'>");
		sb.append("每页"+pageBean.getRows()+"条，共"+pageBean.getTotal()+"条，第"+pageBean.getPage()+"页，共"+pageBean.getMaxPage()+"页&nbsp;&nbsp;<a href='javascript:gotoPage("+pageBean.getPreviousPage()+")'>首页</a>&nbsp;&nbsp;<a");
		sb.append(" href='javascript:gotoPage(1)'>上一页</a>&nbsp;&nbsp;<a");
		sb.append(" href='javascript:gotoPage("+pageBean.getNextPage()+")'>下一页</a>&nbsp;&nbsp;<a");
		sb.append(" href='javascript:gotoPage("+pageBean.getMaxPage()+")'>尾页</a>&nbsp;&nbsp;<input type='text'");
		sb.append(" id='skipPage'");
		sb.append(" style='text-align: center; font-size: 12px; width: 50px;'>&nbsp;&nbsp;<a");
		sb.append(" href='javascript:skipPage()'>Go</a>");
		sb.append("</div>");
		//分页所需要调用的js代码
		sb.append("<script type='text/javascript'>");
		sb.append("function gotoPage(page) {");
		sb.append("		document.getElementById('pageBeanForm').page.value = page;");
		sb.append("		document.getElementById('pageBeanForm').submit();");
		sb.append("}");
		sb.append("function skipPage() {");
		sb.append("		var page = document.getElementById('skipPage').value;");
		sb.append("		if(!page || isNaN(page) || parseInt(page)<1 || parseInt(page)>maxPage){");
		sb.append("			alert('请输入1~N的数字');");
		sb.append("			return;");
		sb.append("		}");
		sb.append("		gotoPage(page);");
		sb.append("}");
		sb.append("</script>");
		return sb.toString();
	}

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

BookServlet类

package com.zyp.web;

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

public class BookServlet extends HttpServlet{
//	调用数据层访问数据库
	private BookDao bookDao = new BookDao();

	private static final long serialVersionUID = -7654671804738498584L;
	
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doPost(req, resp);
	}
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//		拿到前台的dname
		String bname = req.getParameter("bname");
//		将前台传过来的值封装到实体类中
		Book book = new Book();
		//把bname放进去
		book.setBname(bname);//有可能查询维度不止这个bname，有可能还会有别的。这里的话以bname为例
		PageBean pagebean = new PageBean();
		try {
//			list 查出符合条件的某一页的记录数 默认是第一页
			List<Book> list = bookDao.list(book, pagebean);
//			转发的同时转到req的作用域中
			req.setAttribute("bookList", list);
			req.setAttribute("pagebean", pagebean);//pagebean传过去了，最大页数，当前页数，是否分页，第几页都传过去了。
			req.getRequestDispatcher("bookList.jsp").forward(req, resp);//转发
		} catch (InstantiationException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
}

z.tld属性文件

<?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>zking 1.1 core library</description>
  <display-name>zking core</display-name>
  <tlib-version>1.1</tlib-version>
  <short-name>c</short-name>
  <uri>/zking</uri>

  <tag>
  	<!-- 标签库中的标签名 -->
    <name>page</name>
    <!-- 标签对应的助手类的全路径名 -->
    <tag-class>com.zking.tags.PageTag</tag-class>
    <!-- JSP -->
    <body-content>JSP</body-content>
    <attribute>
    	<!-- 属性名 -->
        <name>pageBean</name>
        <!-- 属性值是否必填 -->
        <required>true</required>
        <!-- 是否支持表达式 -->
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
  
</taglib>

web.xml配置文件

<?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>T224_Z</display-name>
  <filter>
  	<filter-name>encodingFiter</filter-name>
  	<filter-class>com.zking.util.EncodingFiter</filter-class>
  </filter>
  <filter-mapping>
  	<filter-name>encodingFiter</filter-name>
  	<url-pattern>/*</url-pattern>
  </filter-mapping>
  <servlet>
  	<servlet-name>bookServlet</servlet-name>
  	<servlet-class>com.zking.web.BookServlet</servlet-class>
  </servlet>
  <servlet-mapping>
  	<servlet-name>bookServlet</servlet-name>
	<url-pattern>/bookServlet</url-pattern>  	
  </servlet-mapping>
</web-app>

这里利用了上面所提到的EncodingFiter类处理中文乱码。

bookList.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
    <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
    <%@ taglib uri="/zking"  prefix="z" %>
<!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>
<h2>小说目录</h2>
	<br>

	<form action="${pageContext.request.contextPath}/bookServlet"
		method="post">
<!-- 		<input type="hidden" name="rows" value="20"> -->
		<input type="hidden" name="pagination" value="false">
		书名：<input type="text" name="bname"> <input type="submit"
			value="确定">
	</form>
	<table border="1" width="100%">
		<tr>
			<td>编号</td>
			<td>名称</td>
			<td>价格</td>
		</tr>
		<c:forEach items="${bookList }" var="b">
			<tr>
				<td>${b.bid }</td>
				<td>${b.bname }</td>
				<td>${b.price }</td>
			</tr>
		</c:forEach>
	</table>
	
	<z:page pageBean="${pagebean }"></z:page>
	
</body>
</html>