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JSP自定义标签之自定义分页标签02

2022-07-28 11:41:00 【Champion_me】

这一章将继续上一章的内容，完善自定义分页标签，上一章主要是重构-提取公用方法，这一章主要是封装分页标签

目录

一、首先是JSP页面

student.jsp
这个页面是分页标签封装之前

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>    
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
	<h1>学生信息</h1>
	
	<form action="<%=request.getContextPath()%>/students" method="post">
		<input type="text" name="sname">
		<input type="submit" value="查询">
	</form>
	
	<table border="1" style="width: 98%;">
	
		<tr>
			<td>学号</td>
			<td>姓名</td>
			<td>年龄</td>
			<td>备注</td>
		</tr>
		
		<c:forEach items="${students}" var="student">
			<tr>
				<td>${student.sid}</td>
				<td>${student.sname}</td>
				<td>${student.score}</td>
				<td>${student.clazz}</td>
			</tr>
		</c:forEach>
		
	</table>
	<div style="text-align: right; width:98%;">
		第${pageBean.page}页&nbsp;&nbsp;&nbsp;
		共${pageBean.total}条记录&nbsp;&nbsp;&nbsp;
		<a href="javascript:goPage(1);">首页</a>&nbsp;&nbsp;&nbsp;
		<a href="javascript:goPage(${pageBean.previousPage});">上页</a>&nbsp;&nbsp;&nbsp; 
		<a href="javascript:goPage(${pageBean.nextPage});">下页</a>&nbsp;&nbsp;&nbsp; 
		<a href="javascript:goPage(${pageBean.totalPage});">尾页</a>&nbsp;&nbsp;&nbsp;
		第<input type="text" size="2" id="pageNumber" onkeypress="toPageNumber(event,this.value)"/> 
		<a href="javascript:goPage(document.getElementById('pageNumber').value);">GO</a>
	</div>
	
	<!-- 用于分页的隐藏表单,保存查询参数 -->
	<form action="${pageBean.url}" id="pagingForm" method="post">
		<input type="hidden" name="page" value="${pageBean.page}"/>
		<!-- 先只考虑本功能的查询参数，没有考虑公用性（不同功能的参数不同） -->
		<input type="hidden" name="sname" value="<%=request.getParameter("sname")%>"/>
	</form>
	
	
</body>
<script> function goPage(pageNum){
       let form = document.getElementById("pagingForm"); let lastPage = '${pageBean.totalPage}'; if(pageNum > lastPage){
       pageNum = lastPage; } if(pageNum < 1){
       pageNum = 1; } form.page.value = pageNum; form.submit(); } function toPageNumber(event,pn){
       //debugger; if(event.keyCode == 13){
       let form = document.getElementById("pagingForm"); form.page.value = pn; form.submit(); } } </script>

</html>

二、准备一个Servlet

准备一个servlet用于处理请求，获取数据库中的数据，并转发到结果显示页面。
StudentServlet .class

package com.zking.mymvc.servlet;

import java.io.IOException;
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.zking.mymvc.model.Student;
import com.zking.mymvc.util.PageBean;
import com.zking.mymvc.util.StudentDao;
@WebServlet("/students")
public class StudentServlet extends HttpServlet {
    
	
	private StudentDao dao = new StudentDao();
	
	@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 {
    
		
		PageBean pageBean = new PageBean();
		pageBean.setRequest(req);
		
		//获取查询参数
		String sname = req.getParameter("sname");
		List<Student> students = dao.getStudent02(sname, pageBean);
		
		req.setAttribute("students", students);
		
		System.out.println("dopost .......... ");
		
		req.getRequestDispatcher("/student2.jsp").forward(req, resp);
		
	}
	
}

三、过滤器解决中文乱码问题

EncodingFiter .class

package com.zking.mymvc.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.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/** * 字符编码过滤器 * @author zjjt * */
@WebFilter("/*")
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();
		}
	}
	
}

在web.xml文件里面写出

四、封装分页标签

为了方便代码的复用，及可维护性，我们将分页功能封装了一个自定义标签（其实就是将原来写在页面中的代码，通过移入到自定义标签中去实现），开发自定义标签分成三步：

编写助手类
编写标签描述文件
在页面上引入标签库，并使用
1） 编写助手类

package com.zking.mymvc.tag;

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

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

import com.zking.mymvc.util.PageBean;
/** * 助手类 * @author zjjt * */
public class PagingTag extends BodyTagSupport{
    
	
	private PageBean pageBean;

	public void setPageBean(PageBean pageBean) {
    
		this.pageBean = pageBean;
	}
	
	@Override
	public int doStartTag() {
    
		
		JspWriter out = this.pageContext.getOut();//得到一个写出对象
		
		try {
    
			out.print(buildHtml());//直接写出
		} catch (IOException e) {
    
			e.printStackTrace();
		}
		
		return SKIP_BODY;
	}
	
	//构造分页的页面输出
	private String buildHtml() {
    
		
		String pagingTool="<div style=\"text-align: right; width:98%;\">\r\n"
				+ " 第"+pageBean.getPage()+"页&nbsp;&nbsp;&nbsp;\r\n"
				+ " 共"+pageBean.getTotal()+"条记录&nbsp;&nbsp;&nbsp;\r\n"
				+ " <a href=\"javascript:goPage(1);\">首页</a>&nbsp;&nbsp;&nbsp;\r\n"
				+ " <a href=\"javascript:goPage("+pageBean.getPreviousPage()+");\">上页</a>&nbsp;&nbsp;&nbsp; \r\n"
				+ " <a href=\"javascript:goPage("+pageBean.getNextPage()+");\">下页</a>&nbsp;&nbsp;&nbsp; \r\n"
				+ " <a href=\"javascript:goPage("+pageBean.getTotalPage()+");\">尾页</a>&nbsp;&nbsp;&nbsp;\r\n"
				+ " 第<input type=\"text\" size=\"2\" id=\"pageNumber\" οnkeypress=\"toPageNumber(event,this.value)\"/> \r\n"
				+ " <a href=\"javascript:goPage(document.getElementById('pageNumber').value);\">GO</a>\r\n"
				+ " </div>";
		
		//构建隐藏表单，用于在分页时传递分页参数
		String hiddenForm = "<form action='" + pageBean.getUrl() + "' id=\"pagingForm\" method=\"post\">"
				+ "<input type=\"hidden\" name=\"page\" />";
		Map<String, String[]> parameterMap = pageBean.getParameterMap();//获取所有的参数
		
		//循环所有的参数，并为所有的参数生成隐藏表单
		for(Map.Entry<String, String[]> param: parameterMap.entrySet()) {
    
			String paramName = param.getKey();//获取到一个名称
			if("page".equals(paramName)) continue;//直接跳过
			String[] values = param.getValue();//获取参数值，一个属性可能有多个值所以用数组
			for(String val:  values) {
    //上面是数组
				hiddenForm += "<input type='hidden' name='" + paramName + "' value='" + val + "'>";
			}
		}
		hiddenForm += "</form>";
		
		String js="<script>\r\n"
				+ " function goPage(pageNum){\r\n"
				+ " let form = document.getElementById(\"pagingForm\");\r\n"
				+ " \r\n"
				+ " let lastPage = '"+pageBean.getTotalPage()+"';\r\n"
				+ " if(pageNum > lastPage){\r\n"
				+ " pageNum = lastPage; \r\n"
				+ " }\r\n"
				+ " if(pageNum < 1){\r\n"
				+ " pageNum = 1;\r\n"
				+ " }\r\n"
				+ " form.page.value = pageNum;\r\n"
				+ " form.submit();\r\n"
				+ " }\r\n"
				+ " \r\n"
				+ " function toPageNumber(event,pn){\r\n"
				+ " //debugger;\r\n"
				+ " if(event.keyCode == 13){\r\n"
				+ " let form = document.getElementById(\"pagingForm\");\r\n"
				+ " form.page.value = pn;\r\n"
				+ " form.submit();\r\n"
				+ " }\r\n"
				+ " }\r\n"
				+ " \r\n"
				+ "</script>";
		
		return pagingTool+hiddenForm+js;
	} 
	
}

2） 标签库描述文件中添加paging标签

<tag>
		<name>paging</name>
		<tag-class>com.zking.mymvc.tag.PagingTag</tag-class>
		<body-content>empty</body-content>
		<description>分页标签</description>
		<attribute>
			<name>pageBean</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
		</attribute>
	</tag>

3） 使用分页标签
首先在页面中引入标签

<%@taglib prefix="z" uri="/zking" %>

将原来的分页功能，替换为标签即可

<z:paging pageBean="${pageBean}"/>

4）封装之后的student.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!-- 引入的C标签 -->
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%> 

<!-- 引入自定义标签库 -->   
<%@taglib prefix="z" uri="/zking" %>

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
	<h1>学生信息</h1>
	
	<form action="<%=request.getContextPath()%>/students" method="post">
		<input type="text" name="sname">
		<input type="submit" value="查询">
	</form>
	
	<table border="1" style="width: 98%;">
	
		<tr>
			<td>学号</td>
			<td>姓名</td>
			<td>年龄</td>
			<td>备注</td>
		</tr>
		
		<c:forEach items="${students}" var="student">
			<tr>
				<td>${
    student.sid}</td>
				<td>${
    student.sname}</td>
				<td>${
    student.score}</td>
				<td>${
    student.clazz}</td>
			</tr>
		</c:forEach>
	</table>
	<z:paging pageBean="${pageBean}"/>
</body>
</html>
原网站

版权声明
本文为[Champion_me]所创，转载请带上原文链接，感谢
https://blog.csdn.net/Champion_me/article/details/126018113

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