jsp04

最新推荐文章于 2020-01-12 09:53:27 发布

yasuoi

最新推荐文章于 2020-01-12 09:53:27 发布

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本文链接：https://blog.youkuaiyun.com/yasuoi/article/details/89932182

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该博客介绍了如何在JSP中利用EL表达式存取session数据，进行条件查询，并通过JSTL实现页面上的流程控制和条件回显。详细讲解了在Servlet中处理查询条件，以及如何实现分页功能，包括上一页和下一页的操作。

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1. 思路分析

1. 代码编写
继续完成第四步骤将查询的结果集存放到session

//存

HttpSession session= request.getSession();

session.setAttribute("books",books);

//转

response.sendRedirect("booklist.jsp");

页面使用EL表达式获取作用域的数据

el表达式的语法：${ } 作用是替代页面的小脚本

String name= (String)session.getAttribute("username");

out.write(name);

eL取出来的: ${username}

在页面中需要完成类似java中的流程控制语句, el实现不了，所以需要jstl表达式

添加jar

使用指令引入

<h1 style="text-align: center;">图书借阅系统</h1>

图书分类<select name="booktypeid">

<c:forEach items="${bookTypes}" var="bookType">

<option value="${bookType.id}">${bookType.type_name }</option>

</c:forEach>

</select> 

图书名称<input type="text" name="bookname"> 

是否借阅<select name="borrow">

</select> 

</form>

<tr>

</tr>

<c:forEach items="${books}" var="book">

<tr>

<td>${book.book_author}</td>

<td>${book.publish_press}</td>

<td>

<c:if test="${book.is_borrow ==0}">未借阅</c:if>

<c:if test="${book.is_borrow ==1}">已借阅</c:if>

</td>

</tr>

</c:forEach>

</table>

</div>

完成带条件查询

条件回显

在servlet中将查询条件存放到session

页面显示条件的数据时从session中取出来做判断显示

分页的实现

完整代码：

index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"

pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<title>Insert title here</title>

</head>

<body>

<jsp:forward page="bookServlet.do?choose=1" />

</body>

</html>

booklist.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"

pageEncoding="UTF-8"%>

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<title>Insert title here</title>

#div {

width: 800px;

height: 600px;

margin: 0px auto;

border: 1px solid red;

}

</style>

function doPage(pageno){

//给查询表单的当前页码数赋值

$("input[name='pageno']").val(pageno);

//提交查询表单

$("#query").submit();

}

</script>

</head>

<body>

<h1 style="text-align: center;">图书借阅系统</h1>

图书分类<select name="booktypeid">

<c:forEach items="${bookTypes}" var="bookType">

<option value="${bookType.id}"

<c:if test="${bookType.id==booktypeid}">selected="selected" </c:if>>${bookType.type_name }</option>

</c:forEach>

</select>  图书名称<input type="text" name="bookname" value="${bookname}" >  是否借阅<select

name="borrow">

<option value="0" <c:if test="${borrow==0}">selected="selected"</c:if> >未借阅</option>

<option value="1" <c:if test="${borrow==1}">selected="selected"</c:if> >已借阅</option>

</select> 

</form>

<tr>

</tr>

<c:forEach items="${books}" var="book">

<tr>

<td>${book.book_author}</td>

<td>${book.publish_press}</td>

<td><c:if test="${book.is_borrow ==0}">未借阅</c:if> <c:if

test="${book.is_borrow ==1}">已借阅</c:if></td>

</tr>

</c:forEach>

<tr>

${pageBean.pageNo}/${pageBean.totalPage}页

</tr>

</table>

</div>

</body>

</html>

Servlet

package com.demo.servlet;

import java.io.IOException;

import java.io.PrintWriter;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.Date;

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 javax.servlet.http.HttpSession;

import com.demo.pojo.Book;

import com.demo.pojo.BookType;

import com.demo.service.BookService;

import com.demo.service.BookTypeService;

import com.demo.service.impl.BookServiceImpl;

import com.demo.service.impl.BookTypeServiceImpl;

import com.demo.utils.PageBean;

/**

* Servlet implementation class BookServlet

@WebServlet("/bookServlet.do")

public class BookServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

BookService bookService = new BookServiceImpl();

BookTypeService bookTypeService = new BookTypeServiceImpl();

/**

* @see HttpServlet#HttpServlet()

public BookServlet() {

super();

// TODO Auto-generated constructor stub

}

/**

* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse

* response)

protected void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doPost(request, response);

}

/**

* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse

* response)

protected void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

// jsp的操作流程4个字取调存转

// 设置request接收客户端中文参数乱码问题

request.setCharacterEncoding("utf-8");

String choose = request.getParameter("choose");

switch (choose) {

case "1":

// 查询

System.out.println("进入了servlet中查询的方法");

// 查询图书类型

queryBookType(request, response);

// 查询图书

queryBook(request, response);

break;

case "2":

addBook(request, response);

break;

default:

break;

}

/**

* 查询图书类型

* @param request

* @param response

* @throws ServletException

* @throws IOException

protected void queryBookType(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

// 调用service层的方法

List<BookType> bookTypes = bookTypeService.queryAll();

// 存

HttpSession session = request.getSession();

session.setAttribute("bookTypes", bookTypes);

}

protected void queryBook(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

// 取调存转

String booktypeid = request.getParameter("booktypeid");

String bookname = request.getParameter("bookname");

String borrow = request.getParameter("borrow");

String pageno = request.getParameter("pageno");

int booktypeid1 = 0;

if (booktypeid != null && !"".equals(booktypeid)) {

booktypeid1 = Integer.parseInt(booktypeid);

}

int borrow1 = -1;//0代表未借阅

if (borrow != null && !"".equals(borrow)) {

borrow1 = Integer.parseInt(borrow);

}

int pageno1 = 1;

if (pageno != null && !"".equals(pageno)) {

pageno1 = Integer.parseInt(pageno);

}

// 查询总行数

int count = bookService.bookCount(booktypeid1, bookname, borrow1);

System.out.println("总行数为"+count);

// 创建分页工具类的对象

PageBean<Book> pageBean = new PageBean<Book>();

pageBean.setPageSize(3);// 每页显示的行数

pageBean.setRows(count);

// null 注意 pageno要检测是否为null 为null 报 NumberFromatException

pageBean.setPageNo(pageno1);

// 获取分页的第一个参数

int first = (pageBean.getPageNo() - 1) * pageBean.getPageSize();

// 调用service层将查询的条件及 limit的2个参数传递过去

List<Book> books = bookService.queryBook(booktypeid1, bookname, borrow1, first, pageBean.getPageSize());

pageBean.setLists(books);

// 存

HttpSession session = request.getSession();

session.setAttribute("books", books);

session.setAttribute("username", "zhuyin");

//将查询的条件存放到作用域用于页面的数据回显

session.setAttribute("booktypeid", booktypeid);

session.setAttribute("bookname", bookname);

session.setAttribute("borrow", borrow);

//将当前页码数和总页数存放到session 2个值都是PageBean的属性直接存 PageBean

session.setAttribute("pageBean", pageBean);

// 转

response.sendRedirect("booklist.jsp");

}

public void addBook(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

// 通过jsp的内置对象 request获取 request.getParameter("标签name属性值")

String code = request.getParameter("code");

String bookname = request.getParameter("bookname");

String booktypeid = request.getParameter("booktypeid");

String press = request.getParameter("press");

String author = request.getParameter("author");

String publishdate = request.getParameter("publishdate");

System.out.println("bookname" + bookname);

// 创建book类的对象将获取的值赋给对象

Book book = new Book();

book.setBook_author(author);

book.setBook_code(code);

book.setBook_name(bookname);

book.setBook_type(Integer.parseInt(booktypeid));

book.setIs_borrow(0);

book.setPublish_press(press);

// 格式需要转换

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

Date date = null;

try {

date = sdf.parse(publishdate);

} catch (ParseException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

book.setPublish_date(date);

// 调用service

int num = bookService.addBook(book);

// 根据受影响的行数打印js提示并跳转页面 PrintWrite 对象

// response 是jsp9大内置对象之一服务器给客户端的回馈 response

// 设置response 响应的类型和编码格式解决提示中文乱码

response.setContentType("text/html; charset=UTF-8");

PrintWriter pWriter = response.getWriter();

if (num > 0) {

pWriter.write("<script type='text/javascript' >alert('新增成功');location.href='success.jsp'</script>");

} else {

pWriter.write("<script type='text/javascript' >alert('新增失败');location.href='error.jsp'</script>");

}