一. 通用分页核心思路
将上一次查询的请求再发一次，只不过页码发生了变化。
二. 前端通用分页与后端通用分页的区别
1.数据处理位置：后端通用分页在服务器端进行数据处理和分页查询，而前端通用分页在客户端进行数据筛选和展示。
2.数据传输量：后端通用分页只将当前页的数据传输给客户端，减少了数据传输量；前端通用分页将全部数据传输到客户端，可能导致数据量较大。
3.性能和响应时间：后端通用分页可以对大容量数据进行高效的分页查询和处理；前端通用分页在数据量较大时可能导致页面加载缓慢。
4.实现复杂度：后端通用分页需要在服务器端编写查询逻辑和分页逻辑；前端通用分页需要在客户端编写分页逻辑和数据筛选逻辑。
三. PageBean的优化
1.新增一个属性url，保留上一次发送的请求地址
2.新增一个属性paramMap，保留上一次发送请求携带的参数
3.新增一个方法，获取最大页的页码
4.新增一个方法，获取上一页的页码
5.新增一个方法，获取下一页的页码
6.增加一个方法，初始化PageBean
package com.xissl.utils;
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;//上一次查询的url
private Map<String, String[]> paramMap;
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 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;
}
// 最大页
public int maxPage() {
return this.total % this.rows == 0 ?
this.total/this.rows :
this.total/this.rows + 1;
}
// 下一页
public int nextPage() {
return this.page < this.maxPage()?
this.page+1 : this.page;
}
// 上一页
public int prevPage() {
return this.page>1 ? this.page-1 : this.page;
}
public void setRequest(HttpServletRequest req) {
// 初始化默认查询第几页的数据
this.setPage(req.getParameter("page"));
this.setRows(req.getParameter("rows"));
this.setPagination(req.getParameter("pagination"));
// 保留上一次的url
this.setUrl(req.getRequestURL().toString());
// 保留携带的参数
this.setParamMap(req.getParameterMap());
}
public void setPagination(String pagination) {
if(StringUtils.isNotBlank(pagination))
this.setPagination(!"false".equals(pagination));
}
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));
}
/**
* 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 + "]";
}
}
四. 自定义pageBean分页标签
运用之前所分享的自定义jsp标签的知识来自定义一个Page标签，PageTag继承 BodyTagSupport类，用stringbuffer中的append方法来实现页面展示效果。最后我们只要在jsp页面引用PageTag标签就可以了
标签助手类PageTag
package com.xissl.tag;
import com.xissl.utils.PageBean;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyTagSupport;
import java.io.IOException;
import java.util.Map;
import java.util.Set;
/**
*
* @author xissl
*
*/
public class PageTag extends BodyTagSupport {
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) {
e.printStackTrace();
}
return SKIP_BODY;
}
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("<form id='pageBeanForm' action='"+pageBean.getUrl()+"' method='post'>");
sb.append("<input type='hidden' name='methodName' value='list'>");
sb.append("<input type='hidden' name='page'>");
// 重要设置拼接操作，将上一次请求参数携带到下一次
Map<String, String[]> paMap = pageBean.getParamMap();
if(paMap !=null && paMap.size()>0){
Set<Map.Entry<String, String[]>> entrySet = paMap.entrySet();
for (Map.Entry<String, String[]> entry : entrySet) {
for (String val : entry.getValue()) {
if(!"page".equals(entry.getKey())){
sb.append("<input type='hidden' name='"+entry.getKey()+"' value='"+val+"'>");
}
}
}
}
sb.append("</form>");
int page = pageBean.getPage();
int max = pageBean.maxPage();
int before = page > 4 ? 4 : page-1;
int after = 10 - 1 - before;
after = page+after > max ? max-page : after;
// disabled
boolean startFlag = page == 1;
boolean endFlag = max == page;
// 拼接分页条
sb.append("<ul class='pagination'>");
sb.append("<li class='page-item "+(startFlag ? "disabled" : "")+"'><a class='page-link' href='javascript:gotoPage(1)'>首页</a></li>");
sb.append("<li class='page-item "+(startFlag ? "disabled" : "")+"'><a class='page-link' href='javascript:gotoPage("+pageBean.prevPage()+")'><</a></li>");
// 代表了当前页的前4页
for (int i = before; i > 0 ; i--) {
sb.append("<li class='page-item'><a class='page-link' href='javascript:gotoPage("+(page-i)+")'>"+(page-i)+"</a></li>");
}
sb.append("<li class='page-item active'><a class='page-link' href='javascript:gotoPage("+pageBean.getPage()+")'>"+pageBean.getPage()+"</a></li>");
// 代表了当前页的后5页
for (int i = 1; i <= after; i++) {
sb.append("<li class='page-item'><a class='page-link' href='javascript:gotoPage("+(page+i)+")'>"+(page+i)+"</a></li>");
}
sb.append("<li class='page-item "+(endFlag ? "disabled" : "")+"'><a class='page-link' href='javascript:gotoPage("+pageBean.nextPage()+")'>></a></li>");
sb.append("<li class='page-item "+(endFlag ? "disabled" : "")+"'><a class='page-link' href='javascript:gotoPage("+pageBean.maxPage()+")'>尾页</a></li>");
sb.append("<li class='page-item go-input'><b>到第</b><input class='page-link' type='text' id='skipPage' name='' /><b>页</b></li>");
sb.append("<li class='page-item go'><a class='page-link' href='javascript:skipPage()'>确定</a></li>");
sb.append("<li class='page-item'><b>共"+pageBean.getTotal()+"条</b></li>");
sb.append("</ul>");
// 拼接分页的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) > "+max+") {");
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();
}
}
tld配置文件
<tag>
<name>page</name>
<tag-class>com.xissl.tag.PageTag</tag-class>
<!-- 该标签有标签体 -->
<body-content>jsp</body-content>
<attribute>
<name>pageBean</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
五. 案例实现
Jsp界面
<%@ 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="l" uri="/xissl" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<link
href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/4.5.0/css/bootstrap.css"
rel="stylesheet">
<script
src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/4.5.0/js/bootstrap.js"></script>
<title>书籍列表</title>
<style type="text/css">
.page-item input {
padding: 0;
width: 40px;
height: 100%;
text-align: center;
margin: 0 6px;
}
.page-item input, .page-item b {
line-height: 38px;
float: left;
font-weight: 400;
}
.page-item.go-input {
margin: 0 10px;
}
</style>
</head>
<body>
<form class="form-inline"
action="${pageContext.request.contextPath }/book.action" method="post">
<div class="form-group mb-2">
<input type="text" class="form-control-plaintext" name="bname"
placeholder="请输入书籍名称">
</div>
<button type="submit" class="btn btn-primary mb-2">查询</button>
</form>
<table class="table table-striped">
<thead>
<tr>
<th scope="col">书籍ID</th>
<th scope="col">书籍名</th>
<th scope="col">价格</th>
</tr>
</thead>
<tbody>
<c:forEach items="${books }" var="b">
<tr>
<td>${b.bid }</td>
<td>${b.bname }</td>
<td>${b.price }</td>
</tr>
</c:forEach>
</tbody>
</table>
<l:page pageBean="${pageBean }"></l:page>
</body>
</html>
查询的servlet
在servlet中调用分页的方法并转发到jsp界面。
1.实例化dao层，实体类，分页类（PageBean）
2.把req请求传进PageBean进行分页的初始化
3.初始化完成后拿到page和实体
4.存入作用域
5.利用转发进行传值
package com.xissl;
import java.io.IOException;
import java.util.List;
import java.util.Map;
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.xissl.dao.BookDao;
import com.xissl.entity.Book;
import com.xissl.utils.PageBean;
@WebServlet("/book.action")
public class BookServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
@SuppressWarnings("unused")
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// String bname = request.getParameter("bname");
map包含了浏览器传递到后台的所有参数键值对
// Map<String, String[]> map = request.getParameterMap();
浏览器请求的地址
// String url = request.getRequestURL().toString();
PageBean pagebean = new PageBean();
pagebean.setRequest(request);
BookDao bookdao = new BookDao();
Book book = new Book();
book.setBname(request.getParameter("bname"));
List<Book> books = null;
try {
books = bookdao.query2(book, pagebean);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
request.setAttribute("books", books);
request.setAttribute("pageBean", pagebean);
request.getRequestDispatcher("book.jsp").forward(request, response);
}
}
运行结果如下：
中文乱码处理
package com.xissl.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("*.action")
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();
}
}
}
扫一扫
394
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
