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
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
注意：不能将分页表单嵌套到其它表单中，否则不能提交表单！！！
具体思路：
1、补全servlet
2、页面展示
3、分页重要参数（page、rows、是否分页、上一次请求、上一次的表单参数）
4、自定义分页标签
对PageBean进行改造：
首先创两个属性：
// 保留上一次的请求地址
private String url;
// 上一次保留上一次请求所携带的参数
private Map<String, String []> paMap = new HashMap<>();
PageBean分页工具类
代码：
package com.xhh.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
// 保留上一次的请求地址
private String url;
// 上一次保留上一次请求所携带的参数
private Map<String, String []> paMap = new HashMap<>();
/**
* pageBean初始化方法
*
* @param req
*/
public void setRequest(HttpServletRequest req) {
this.setPage(req.getParameter("page"));
this.setRows(req.getParameter("rows"));
this.setPagination(req.getParameter("pagination"));
this.setUrl(req.getRequestURI().toString());
this.setPaMap(req.getParameterMap());
}
public void setPagination(String pagination) {
if("false".equals(pagination)) {
this.setPagination(false);
}
}
public void setRows(String rows) {
if(StringUtils.isNotBlank(rows)) {
this.setRows(Integer.valueOf(rows));
}
}
public 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[]> getPaMap() {
return paMap;
}
public void setPaMap(Map<String, String[]> paMap) {
this.paMap = paMap;
}
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;
}
/**
* 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 + "]";
}
/**
* 最大页码
* @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;
}
/**
* 获取下一页
* @return
*/
public int getPreviousPage() {
return this.page> 1 ? this.page-1 : this.page;
}
}
自定义分页标签 PageTag:
- toHTML() 方法
- 定义了一个pageBean属性
- 将隐藏的form表单写入标签助手类
- 将对应的js代码写入标签助手类
package com.xhh.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.xhh.util.PageBean;
public class PageTag extends BodyTagSupport {
private static final long serialVersionUID = 1693978620241849317L;
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 (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return SKIP_BODY;
}
private String toHTML() {
StringBuilder sb=new StringBuilder();
//拼接下一次发送请求所要提交的隐藏的form 表单
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,但是改参数在前面已经单独赋
//为什么要单独赋值呢? 因为上一次请求不是第一页的数据，下一次可能是第二次
//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 value:entry.getValue()) {
if(!"page".equals(entry.getValue()))
sb.append("<input type='hidden' name='"+entry.getKey()+"' value='"+value+"'> ");
}
}
}
}
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 <a ");
sb.append(" href='javascript:gotoPage(1)'>首页</a> <a");
sb.append(" href='javascript:gotoPage("+pageBean.getPreviousPage()+")'>上一页</a> <a");
sb.append(" href='javascript:gotoPage("+pageBean.getNextPage()+")'>下一页</a> <a");
sb.append(" href='javascript:gotoPage("+pageBean.getMaxPage()+")'>尾页</a> <input type='text'");
sb.append(" id='skipPage'");
sb.append(" style='text-align: center; font-size: 12px; width: 50px;'> <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)>"+pageBean.getMaxPage()+"){");
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();
}
}
配置z.tld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>xhh 1.1 core library</description>
<display-name>xhh core</display-name>
<tlib-version>1.1</tlib-version>
<short-name>z</short-name>
<uri>/xhh</uri>
<tag>
<!--填写是标签库中的签名 -->
<name>page</name>
<!--标签对应后台助手类 -->
<tag-class>com.xhh.tag.PageTag</tag-class>
<!--标签类别 -->
<body-content>JSP</body-content>
<attribute>
<!--自定义标签中属性 -->
<name>pageBean</name>
<!--属性是否必填 -->
<required>true</required>
<!--是否支持表达式EL表达式/ognl表达式 -->
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
补全Servlet, (BookServlet):
package com.xhh.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.xhh.Dao.BookDao;
import com.xhh.Dao.BookDao3;
import com.xhh.entity.Book;
import com.xhh.util.PageBean;
public class BookServlet extends HttpServlet{
private static final long serialVersionUID = 132846827306935380L;
private BookDao3 bookDao=new BookDao3();
@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 {
String bname = req.getParameter("bname");
Book book=new Book();
book.setBname(bname);
PageBean pageBean=new PageBean();
/* Map<String, String[]> parameterMap = req.getParameterMap();
String u = req.getRequestURI().toString();*/
pageBean.setRequest(req);
try {
List<Book> list = bookDao.list(book, pageBean);
req.setAttribute("bookList", list);
req.setAttribute("pageBean", pageBean);
req.getRequestDispatcher("/bookList.jsp").forward(req, resp);
} catch (SQLException | InstantiationException | IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
EncodingFiter 过滤器类（处理中文乱码异常）：
package com.xhh.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();
}
}
}
接下来配置BookServlet,同时配置EncodingFiter ：
<?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>PageBean</display-name>
<!-- BookServlet -->
<servlet>
<servlet-name>bookServlet</servlet-name>
<servlet-class>com.xhh.web.BookServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>bookServlet</servlet-name>
<url-pattern>/bookServlet</url-pattern>
</servlet-mapping>
<!-- EncodingFiter -->
<filter>
<filter-name>encodingFiter</filter-name>
<filter-class>com.xhh.util.EncodingFiter</filter-class>
</filter>
<filter-mapping>
<filter-name>encodingFiter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>
jsp页面（bookList）:
<%@ 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="/xhh" prefix="x" %>
<!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="${pageContext.request.contextPath}/bookServlet"
method="post">
<!-- <input type="h idden" name="rows" value="20"> -->
书名：<input type="text" name="bname">
<input type="submit" value="确定">
</form>
<table border="1" width="100%">
<tr>
<td>编号</td>
<td>名称</td>
<td>价格</td>
</tr>
<c:forEach items="${bookList }" var="b">
<tr>
<td>${b.bid }</td>
<td>${b.bname }</td>
<td>${b.price }</td>
</tr>
</c:forEach>
</table>
<x:page pageBean="${pageBean}"></x:page>
</body>
</html>
最后来测试：
运行结果：
不带条件的：
带条件的：
接下来看分页的效果：
扫一扫
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