JAVA语言实现大量信息的分页显示功能及对象反射（通过参数找到对应的函数）
1.对象的反射：通过对象找出该类中所有的方法
Class cla=this.getClass();
Method method=cla.getDeclaredMethod(methodName,HttpServletRequest.class,HttpServletResponse.class );
例子：通过参数能调用该类中参数所对应的方法
超链接请求，参数method对应的是要调用的方法，pageNo对应的是分页显示的要显示第几页
<h3><a href="${pageContext.request.contextPath}/FunctionServlet?method=getUserList&pageNo=1">查询所有用户信息。</a></h3>反射处理：
1.首先建立一个父类BaseServlet
@WebServlet("/BaseServlet")
public class BaseServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected static int pageNo=1;//设置默认显示的页码
protected static int pageSize = 1;//每页有多少条记录
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try{
pageNo=Integer.parseInt(request.getParameter("pageNo"));
}catch(Exception e){
e.getMessage();
}
//获取用户传递的请求参数
String methodName = request.getParameter("method");
//通过方法名获取到方法的对象
//获取当前类的Class对象
Class cla = this.getClass();
//获取cla的的方法（Method对象）
//getDeclaredMethod需要两个参数，方法名和参数名
//因为在java需要通过方法名和参数列表来确定一个方法
try {
//获取方法对象
Method method = cla.getDeclaredMethod(methodName, HttpServletRequest.class , HttpServletResponse.class);
//设置方法的访问权限
method.setAccessible(true);
//调用方法
//invoke用于调用一个方法，第一个参数时要调用方法的对象，剩下是调用方法需要的参数
method.invoke(this, request , response);
} catch (Exception e) {
e.printStackTrace();
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf8");
doGet(request, response);
}
}
2. 建立一个子类继承BaseServlet父类，定义每个参数对应的要调用的方法
@WebServlet("/FunctionServlet")
public class FunctionServlet extends BaseServlet {
private static final long serialVersionUID = 1L;
private Userservice userservice=new UserserviceImp();
public void loginByNameAndPwd(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
String username=request.getParameter("username");
String password=request.getParameter("password");
request.setAttribute("username", username);
int resule=userservice.findByNameAndPwd(username, password);
if(resule==1){
response.sendRedirect(request.getContextPath()+"/login-success.jsp?username="+username+"");
//request.getRequestDispatcher("/login-success.jsp").forward(request, response);
}else{
response.sendRedirect(request.getContextPath()+"/login-error.html");
}
}
public void getUserList(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
String url=WEBUtils.getPath(request);
Page<User> page=userservice.getUserList(pageNo, pageSize);
page.setPath(url);
request.setAttribute("page", page);
request.getRequestDispatcher("/WEB-INF/pages/list.jsp").forward(request, response);
}
} 以后在参数中写上要调用的方法名即可调用
二、信息分页处理
1.建立page实体类，用到泛型
public class Page<T> {
private List<T> data; //后台数据库查询出来
private int totalRecord; //表示总共有多少记录，从数据库中查询出来
// private int totalPage; // 表示总共有多少页，计算得到！
// private int index; //表示当前索引值，计算出来的！
private int pageNumber; //表示的是当前页码，这个参数是从页面传递过来的！
private int pageSize; //表示的是每页显示多少条数据 ，在servlet中设置的！
private String path;//表示超链接地址URL
public Page() {
super();
}
public Page(int totalRecord, int pageNumber, int pageSize) {
super();
this.totalRecord = totalRecord;
this.pageNumber = pageNumber;
this.pageSize = pageSize;
}
public String getPath() {
return path;
}
public void setPath(String path) {
this.path = path;
}
public List<T> getData() {
return data;
}
public void setData(List<T> data) {
this.data = data;
}
public int getTotalRecord() {
return totalRecord;
}
public void setTotalRecord(int totalRecord) {
this.totalRecord = totalRecord;
}
public int getTotalPage() {
/**
* totalPage:表示总共有几页！
*
* 总页数 totalRecord[总记录数] pageSize
* 5 10 2
* 5 9 2
* 4 8 2
*/
if(totalRecord % pageSize ==0){
return totalRecord / pageSize;
}
return (totalRecord / pageSize + 1);
}
public int getIndex() {
/**
* index表示的是当前索引值，是计算得到的！
* 当前索引值 每页显示几条数据 当前页是第几页
* 0 3 1
* 3 3 2
*
index = (pageNumber -1)*pageSize;
*/
return (getPageNumber() -1)*pageSize;
}
public int getPageNumber() {
if(pageNumber < 1){
return 1;
}else if(pageNumber > getTotalPage()){
return getTotalPage();
}
return pageNumber;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
}
2.怎么获取URL？
String url=WEBUtils.getPath(request);WEBUtils类中的getPath方法
public static String getPath(HttpServletRequest request){
String requestURI = request.getRequestURI();
String queryString = request.getQueryString();
String url = requestURI+"?"+queryString;
if(url.contains("&pageNo")){
url = url.substring(0, url.indexOf("&pageNo"));
}
return url;
}3.显示列表的Servlet中的方法
protected void getStuList(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String url = WEBUtils.getPath(request);
Page<Student> page=stuService.getStudentList(pageNo,pageSize);
page.setPath(url);
request.setAttribute("page",page );
request.getRequestDispatcher("/WEB-INF/view/list.jsp").forward(request, response);
}业务层Service中的函数
public Page<Student> getStudentList(int pageNo, int pageSize){
//第一步：查询当前表的所有记录数
int totalRecord= stuDao.getTotalRecord();
//第二步：创建page对象
Page<Student> page = new Page<Student>(totalRecord,pageNo,pageSize);
//第三步：查询分页列表数据并设置到page对象中！
List<Student> list = stuDao.getLimitStuList(page.getIndex(),page.getPageSize());
page.setData(list);
return page;
}持有层Dao中要有1.获取所有记录的方法2.分页显示的方法
视图层页面显示代码：将页表显示分离到另一个页面，通过静态引入
总体显示页面 list.jsp
<%@ 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 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>
<c:choose>
<c:when test="${empty page.data }">
<h1 align="center">没有学生数据</h1>
</c:when>
<c:otherwise>
<h1 align="center">学生列表</h1>
<table border="1" align="center" width="50%">
<tr>
<th>姓名</th>
<th>密码</th>
<th>邮箱</th>
<th colspan="2">操作</th>
</tr>
<c:forEach items="${page.data}" var="stu">
<tr>
<td>${stu.username }</td>
<td>${stu.password }</td>
<td>${stu.mail }</td>
<td><a href="${pageContext.request.contextPath}/StudentServlet?method=toUpdatePage&id=${stu.id}" >修改</a></td>
<td><a href="#?${stu.id}">删除</a></td>
</tr>
</c:forEach>
<tr><td colspan="5" align="center"><a href="#">添加</a></td></tr>
</table>
<br/>
<%@ include file="/WEB-INF/pages/paging.jsp" %>
</c:otherwise>
</c:choose>
</body>
</html>页表显示页面 paging.jsp 显示5页的数据
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<div id="page_nav" align="center">
<a href="${page.path}&pageNo=1">首页</a>
<a href="${page.path}&pageNo=${page.pageNumber -1 }">上一页</a>
<c:choose>
<c:when test="${page.totalPage <= 5 }" >
<c:set var="begin" value="1"></c:set>
<c:set var="end" value="${page.totalPage}"></c:set>
</c:when>
<c:when test="${page.pageNumber <= 3 }">
<c:set var="begin" value="1"></c:set>
<c:set var="end" value="5"></c:set>
</c:when>
<c:otherwise>
<c:set var="begin" value="${page.pageNumber-2}"></c:set>
<c:set var="end" value="${page.pageNumber+2}"></c:set>
<c:if test="${end > page.totalPage }">
<c:set var="begin" value="${page.totalPage-4}"></c:set>
<c:set var="end" value="${page.totalPage}"></c:set>
</c:if>
</c:otherwise>
</c:choose>
<c:forEach begin="${begin }" end="${end}" var="num">
<c:if test="${page.pageNumber == num }">
【${num}】
</c:if>
<c:if test="${page.pageNumber != num }">
<a href="${page.path}&pageNo=${num}">${num }</a>
</c:if>
</c:forEach>
<a href="${page.path}&pageNo=${page.pageNumber +1}">下一页</a>
<a href="${page.path}&pageNo=${page.totalPage}">末页</a>
共${page.totalPage }页，${page.totalRecord }条记录到,去第<input value="${page.totalPage }" name = "pn" id ="pn_input"/>页
<input type="button" value="确定" id="btn_id"/>
<script type="text/javascript">
$("#btn_id").click(function(){
var value= $("#pn_input").val();
window.location="${page.path}&pageNo="+value;
});
</script>
</div>