通用分页（二）

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

2. 后台
2.1 entity
2.2 dao
第一次查满足条件的总记录数
第二次查指定页码并满足条件的记录
二次查询的条件要一致
2.3 控制层
Servlet

3. 视图层
PageTag

如何将上一次查询请求再发一次
String contextPath = req.getContextPath();//根目录
String url = req.getServletPath();//请求的地址
req.getRequestURL() //获取请求全路径
Map<String, String[]> parameterMap = req.getParameterMap();//获得请求中的所有参数

注1：不能将分页表单嵌套到其它表单中，否则不能提交表单！！！
不能将分页表单嵌套到其它表单中，否则不能提交表单！！！
不能将分页表单嵌套到其它表单中，否则不能提交表单！！！

4. junit
java单元测试/白盒测试
setUp
tearDown
测试用例

  package com.luoxiaogang.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
	
	Map<String, String[]> paMap=new HashMap<>();
	private String url;
    
	public void setRequest(HttpServletRequest req) {
		
//		保存上一次请求所携带的参数
		this.setPaMap(req.getParameterMap());
		this.setUrl(req.getRequestURL().toString());
//		在jsp页面控制是否分页
		this.setPagination(req.getParameter("Pagination"));
//	        在jsp页面控制一页多少条
		this.setRows(req.getParameter("rows"));
//		默认第几页
		this.setPage(req.getParameter("page"));
	}
	
	
	
	public void setPage(String page) {
		// TODO Auto-generated method stub
		this.page=StringUtils.isNotBlank(page)? Integer.valueOf(page):this.page;
	}



	public void setPagination(String parameter) {
		// TODO Auto-generated method stub
		this.pagination=StringUtils.isNotBlank(parameter)? !"false".equals(parameter):this.pagination;
	}



	public void setRows(String rows) {
		// TODO Auto-generated method stub
		this.rows=StringUtils.isNotBlank(rows)?Integer.valueOf(rows):this.rows;
		
	}



	public Map<String, String[]> getPaMap() {
		return paMap;
	}

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

	public String getUrl() {
		return url;
	}

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

	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 + "]";
	}
   
	/**
	 * 获取最大页数
	 * @return
	 */
	public int getMaxPage() {
		return this.total%this.rows==0?this.total/this.rows:this.total/this.rows+1;
	}
	/**
	 * 获取下一页
	 * @return
	 */
	public int getNextPage() {
		return this.page<this.getMaxPage()?this.page+1:this.page;
	}
	/**
	 * 获取上一页
	 * @return
	 */
	public int getpreviousPage() {
		return this.getPage()>1?this.page-1:this.page;
	}
}

**1.2 EncodingFiter.java

package com.luoxiaogang.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 EncodingFiter implements Filter {

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

	public EncodingFiter() {
		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();
		}
	}

}

这段代码放在xml文件的最前面，方便过滤的servlet：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>web_02</display-name>
  <filter>
  <filter-name>encodingFiter</filter-name>
  <filter-class>com.houyitao.util.EncodingFiter</filter-class>
  </filter>
  <filter-mapping>
  <filter-name>encodingFiter</filter-name>
  <url-pattern>/bookservlet</url-pattern>
  </filter-mapping>

</web-app>

2. 后台
PageTag 标签助手类

package com.luoxiaogang.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.houyitao.util.PageBean;

public class PageTag extends BodyTagSupport{

	private static final long serialVersionUID = 2570317524495960725L;
    
	private PageBean pageBean;

	public PageBean getPageBean() {
		return pageBean;
	}

	public void setPageBean(PageBean pageBean) {
		this.pageBean = pageBean;
	}
	
	
	@Override
	public int doStartTag() throws JspException {
		// TODO Auto-generated method stub
		JspWriter out = pageContext.getOut();
		try {
			out.print(toHTML());
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return super.doStartTag();
	}

	private String toHTML() {
		// TODO Auto-generated method stub
		StringBuilder sb=new StringBuilder();
		
//		拼接下一次发送请求所要提交的隐藏form表达
		sb.append("<form id='pageBeanForm' action='"+pageBean.getUrl()+"' method='post'>");
		sb.append("<input type='hidden' name='page'>");
		Map<String, String[]> paMap = pageBean.getPaMap();
		if(paMap!=null && paMap.size()>0) {
			Set<Entry<String, String[]>> entrySet = paMap.entrySet();
		for (Entry<String, String[]> entry : entrySet) {
//			上一次请求可能携带页码name=page的参数，但是该参数在前面已经单独赋值
//			为什么要单独赋值呢？因为上一次请求是第一页的数据，下一次可能是第二页，
//			以为这前后请求page对应的值是不一样的，需要单独赋值
			if(!"page".equals(entry.getKey())) {
				for(String val:entry.getValue()) {
					sb.append("<input type='hidden' name='"+entry.getKey()+"'value='"+val+"'>");
				}
			}
		}
		}
		sb.append("</form>");
		
	
		
		
//		拼接分页条
		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;");
		sb.append(" <a href='javascript:gotoPage(1)'>首页</a>&nbsp;&nbsp;<a");
		sb.append(" href='javascript:gotoPage("+pageBean.getpreviousPage()+")'>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>");
		
//		拼接分页所需要的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();
	}
	
}

2.把PageBean加入tld文件中

<?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>c</short-name>
  <uri>/houyitao</uri>


  <tag>
  <!-- 标签库中的标签（类似c:set   c:out的定义） -->
   
    <name>page</name>
    <!-- 是标签运行具体的代码，也就是助手类，下面填写的是助手类的全路径名 -->
    <tag-class>com.houyitao.tag.PageTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <!-- 该标签的属性 -->
        <name>pageBean</name>
        <!-- 该标签的是否必填 -->
        <required>true</required>
         <!-- 该标签的是否支持表达式 -->
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
</taglib>

2.3导入自定义分页标签

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
 <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
 <!-- 自定义分页标签 -->
<%@ taglib uri="/houyitao" prefix="z"

2.4 控制层

package com.luoxiaogang.web;

import java.io.IOException;
import java.sql.SQLException;
import java.util.List;
import java.util.Map;

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

import com.houyitao.dao.Book;
import com.houyitao.dao.BookDao;
import com.houyitao.util.PageBean;

public class BookServlet extends HttpServlet {
	
	private  BookDao bookDao=new BookDao();

	private static final long serialVersionUID = -4405443018425237315L;

	@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
		
		String bname=req.getParameter("bname");
		Book book=new Book();
		book.setBname(bname);
//		Map<String, String[]> parameterMap = req.getParameterMap();
//		StringBuffer url = req.getRequestURL();
		PageBean pageBean=new PageBean();
		try {
			pageBean.setRequest(req);
			List<Book> list = this.bookDao.list(book, pageBean);
		    req.setAttribute("bookList", list);
		    req.setAttribute("pageBean", pageBean);
		    req.getRequestDispatcher("NewFile.jsp").forward(req, resp);
		} 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();
		}
	}
}

配置 Servlet：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>web_02</display-name>
  <filter>
  <filter-name>encodingFiter</filter-name>
  <filter-class>com.houyitao.util.EncodingFiter</filter-class>
  </filter>
  <filter-mapping>
  <filter-name>encodingFiter</filter-name>
  <url-pattern>/bookservlet</url-pattern>
  </filter-mapping>
  
 <servlet>
 <servlet-name>bookServlet</servlet-name>
 <servlet-class>com.houyitao.web.BookServlet</servlet-class>
 </servlet>
 <servlet-mapping>
 <servlet-name>bookServlet</servlet-name>
 <url-pattern>/bookservlet</url-pattern>
 </servlet-mapping>
</web-app>

3.画页面

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
 <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
 <!-- 自定义分页标签 -->
<%@ taglib uri="/houyitao" 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">
		书名：<input type="text" name="bname"> <input type="submit"
			value="确定">
			<!-- 是否分页 -->
			<input type="hidden" name="pagination" value="false"> 
			
			<!-- 显示多少页 -->
			 <input type="hidden" name="rows" value="20"> 

	</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>

结果：
在这里插入图片描述

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