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();
@Overrideprotected 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();
@Overridepublic List<Book> getAllBooks() {return bookDao.getAllBooks();}
@Overridepublic 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());@Overridepublic List<Book> getAllBooks() {try {return qr.query("select * from book", new BeanListHandler<Book>(Book.class));} catch (SQLException e) {throw new RuntimeException(e);}}
@Overridepublic 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();@Overrideprotected 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;}@Overridepublic 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;@Overridepublic 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