Java基础入门day60

day60

购物车案例补充

设置欢迎页

打开也系统，就可以直接看到商品列表页面

之前曾经设置过欢迎页，都是针对页面，可以有html页面，也可以有jsp页面

但是今天我们将一个servlet设置成欢迎页

在web.xml文件中设置欢迎页
<welcome-file-list>
 <welcome-file>BookServlet</welcome-file>
</welcome-file-list>
直接访问该项目，会直接访问BookServlet请求所对应的Servlet

实现商品列表功能

BookServlet.java

package com.saas.servlet;

import com.saas.service.IBookService;
import com.saas.service.impl.BookServiceImpl;
import com.saas.entity.Book;

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 java.io.IOException;
import java.util.List;

@WebServlet(name = "BookServlet", value = "/BookServlet")
public class BookServlet extends HttpServlet {

 private IBookService bookService = new BookServiceImpl();

 @Override
 protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     String action = req.getParameter("action");

     if(action == null){
         getAllBooks(req, resp);
     }else if ("detail".equalsIgnoreCase(action)){
         getBookDetail(req, resp);
     }
 }


 protected void getBookDetail(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     String sbid = req.getParameter("bid");

     int bid = sbid == null ? 0 : Integer.parseInt(sbid);

     Book book = bookService.getBookDetail(bid);

     req.setAttribute("book", book);

     req.getRequestDispatcher("book.jsp").forward(req, resp);
 }


 protected void getAllBooks(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     List<Book> list = bookService.getAllBooks();

     req.setAttribute("books", list);

     req.getRequestDispatcher("books.jsp").forward(req, resp);
 }
}

在service方法中，由于没有传递任何的action，所以action为空，则执行getAllBooks()方法

在getAllBooks()方法中，借助service和dao完成查询所有的Book对象列表

IBookService.java

package com.saas.service;

import com.saas.entity.Book;

import java.util.List;

public interface IBookService {
 List<Book> getAllBooks();

 Book getBookDetail(int bid);
}

BookServiceImpl.java

package com.saas.service.impl;

import com.saas.dao.IBookDao;
import com.saas.dao.impl.BookDaoImpl;
import com.saas.entity.Book;
import com.saas.service.IBookService;

import java.util.List;

public class BookServiceImpl implements IBookService {

 private IBookDao bookDao = new BookDaoImpl();

 @Override
 public List<Book> getAllBooks() {
     return bookDao.getAllBooks();
 }

 @Override
 public Book getBookDetail(int bid) {
     return bookDao.getBookDetail(bid);
 }
}

IBookDao.java

package com.saas.dao;

import com.saas.entity.Book;

import java.util.List;

public interface IBookDao {
 List<Book> getAllBooks();

 Book getBookDetail(int bid);
}

BookDaoImpl.java

package com.saas.dao.impl;

import com.saas.dao.IBookDao;
import com.saas.entity.Book;
import com.saas.util.DruidUtil;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;

import java.sql.SQLException;
import java.util.List;

public class BookDaoImpl implements IBookDao {

 private QueryRunner qr = new QueryRunner(DruidUtil.getDataSource());
 @Override
 public List<Book> getAllBooks() {
     try {
         return qr.query("select * from book", new BeanListHandler<Book>(Book.class));
     } catch (SQLException e) {
         throw new RuntimeException(e);
     }
 }

 @Override
 public Book getBookDetail(int bid) {
     try {
         return qr.query("select * from book where bid = ?", new BeanHandler<Book>(Book.class), bid);
     } catch (SQLException e) {
         throw new RuntimeException(e);
     }
 }
}

通过BookService,BookDao与数据库交互后得到Book对象的list集合

在BookServlet的getAllBooks()方法中，将Book对象的list存储到request范围中，key为books

跳转到books.jsp页面

<%--
Created by IntelliJ IDEA.
User: Administrator
Date: 2024/5/27
Time: 8:47
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
 <title>books</title>
 <%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
 <style>
     td：{
         margin: 10px;
         text-align: center;
     }
 </style>
</head>
<body>
<c:if test="${empty books}">
 nothing
</c:if>

<c:if test="${not empty books}">
 <table width="80%" align="center">
     <c:set var="count" value="0" />
     <tr>
         <c:forEach items="${books}" var="book">
             <td>
                 <center>
                     <a href="BookServlet?action=detail&bid=${book.bid}"><img src="imgs/${book.img}" width="100" height="100"/><br /></a><br />

                     ${book.name}<br />
                     <del>${book.nprice}</del><br />
                     ${book.oprice}<br />

                 </center>
             </td>
             <c:set var="count" value="${count+1}" />
             <c:if test="${count%5==0}">
                 </tr>
                 <tr>
             </c:if>
         </c:forEach>
     </tr>
 </table>
</c:if>
</body>
</html>

在books.jsp页面中分别判断books是否为空，为空显示nothing，不为空，把数据遍历到表格中显示

该页面还要进行一个分行处理，每隔五个表格的单元格之后进行换行操作，借助jstl的set属性用count来进行判断处理

在该页面中还设置了图片的超链接，点击图片之后，发送一个请求为以下内容BookServlet?action=detail&bid=${book.bid}

那么该请求继续交给BookServlet进行处理，action目前的值是detail，则在BookServlet中的service方法进行分支处理后会调用getBookDetail（）方法进行进一步的处理

在该getBookDetail（）方法中，由于刚刚的url中还含有bid的值，再该方法中拿到bid之后进行处理，再借助Book的service和dao进行根据bid查找Book对象

在当前servlet中再次将查询出来的book对象存储在key值为book的request作用范围内

最后跳转到book.jsp页面

book.jsp

<%--
Created by IntelliJ IDEA.
User: Administrator
Date: 2024/5/27
Time: 11:29
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
 <title>book</title>
 <style>
     table{
         align: center;
     }
 </style>
</head>
<body>
<h1>this is book detail page</h1>

<form action="CartServlet" method="post">
 <input type="hidden" name="bid" value="${book.bid}">
 <table align="center" width="30%">
     <tr>
         <td rowspan="4"><img src="imgs/${book.img}" /></td>
         <td>
             ${book.bid}
         </td>
     </tr>
     <tr>
         <td>
             ${book.name}
         </td>
     </tr>
     <tr>
         <td>
             <del>${book.nprice}</del>
         </td>
     </tr>
     <tr>
         <td>
             ${book.oprice}
         </td>
     </tr>
     <tr>
         <td>
             <input type="submit" value="加入购物车"/>
         </td>
     </tr>
 </table>
<form>

</body>
</html>

在当前book.jsp页面中，分别显示之前点击书籍商品的详情信息

用户点击加入购物车按钮

由于当前按钮是一个提交按钮，会触发该按钮锁对应的form表的action请求

该action请求的url内容为CartServlet

CartServlet.java

package com.saas.servlet;

import com.saas.entity.Book;
import com.saas.entity.CartItem;
import com.saas.service.IBookService;
import com.saas.service.impl.BookServiceImpl;

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

@WebServlet(urlPatterns = "/CartServlet")
public class CartServlet extends HttpServlet {

 private IBookService iBookService = new BookServiceImpl();

 @Override
 protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     String sbid = req.getParameter("bid");

     int bid = sbid == null ? 0 : Integer.parseInt(sbid);

     Book book = iBookService.getBookDetail(bid);

     HttpSession session = req.getSession();

     Object objCart = session.getAttribute("cart");

     if (objCart == null) {
         Map<Integer, CartItem> cart = new HashMap<>();

         cart.put(bid, new CartItem(1, book));

         session.setAttribute("cart", cart);
     } else{
         if (objCart instanceof Map) {
             Map<Integer, CartItem> cart = (Map<Integer, CartItem>) objCart;

             if (cart.containsKey(bid)) {
                 CartItem item = cart.get(bid);

                 item.setCount(item.getCount() + 1);
             } else {
                 cart.put(bid, new CartItem(1, book));
             }

             session.setAttribute("cart", cart);
         }
     }

     resp.sendRedirect("cart.jsp");
 }
}

CartItem.java

package com.saas.entity;

public class CartItem {

 private int count;

 private Book book;

 public CartItem() {
 }

 public CartItem(int count, Book book) {
     this.count = count;
     this.book = book;
 }

 @Override
 public String toString() {
     return "CartItem{" +
             "count=" + count +
             ", book=" + book +
             '}';
 }

 public int getCount() {
     return count;
 }

 public void setCount(int count) {
     this.count = count;
 }

 public Book getBook() {
     return book;
 }

 public void setBook(Book book) {
     this.book = book;
 }
}

Book.java

package com.saas.entity;

public class Book {
 private int bid;
 private String name;
 private String img;
 private double oprice;
 private double nprice;

 @Override
 public String toString() {
     return "Book{" +
             "bid=" + bid +
             ", name='" + name + '\'' +
             ", img='" + img + '\'' +
             ", oprice=" + oprice +
             ", nprice=" + nprice +
             '}';
 }

 public int getBid() {
     return bid;
 }

 public void setBid(int bid) {
     this.bid = bid;
 }

 public String getName() {
     return name;
 }

 public void setName(String name) {
     this.name = name;
 }

 public String getImg() {
     return img;
 }

 public void setImg(String img) {
     this.img = img;
 }

 public double getOprice() {
     return oprice;
 }

 public void setOprice(double oprice) {
     this.oprice = oprice;
 }

 public double getNprice() {
     return nprice;
 }

 public void setNprice(double nprice) {
     this.nprice = nprice;
 }
}

cart.jsp

<%--
Created by IntelliJ IDEA.
User: Administrator
Date: 2024/5/27
Time: 11:53
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
 <title>cart</title>
 <%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
</head>
<body>
<h1>this is cart page.</h1>
<c:if test="${empty cart}">
 nothing
</c:if>

<c:if test="${not empty cart}">
 <table width="80%" align="center" border="1">
     <tr>
         <th>name</th>
         <th>image</th>
         <th>oprice</th>
         <th>nprice</th>
         <th>count</th>
         <th>summary</th>
     </tr>

     <c:forEach items="${cart}" var="c">
         <tr>
             <td>${c.value.book.name}</td>
             <td><img src="imgs/${c.value.book.img}" width="100" height="100"/></td>
             <td>${c.value.book.oprice}</td>
             <td>${c.value.book.nprice}</td>
             <td>${c.value.count}</td>
             <td>${c.value.count * c.value.book.nprice}</td>
         </tr>
     </c:forEach>
 </table>
</c:if>
</body>
</html>

该页面使用jstl进行数据的展示，以及各种运算