后台页面的查看分类
- 在超链接上，绑定处理请求的Servlet
else if (method.equals("look")) {
List<Category> list = service.getAllCategory();
request.setAttribute("list", list);
request.getRequestDispatcher("/background/lookCategory.jsp").forward(request, response);
}
- 显示分类页面的JSP
<c:if test="${empty(list)}">
暂时还没有分类数据哦，请你添加把
</c:if>
<c:if test="${!empty(list)}">
<table border="1px">
<tr>
<td>分类名字</td>
<td>分类描述</td>
<td>操作</td>
</tr>
<c:forEach items="${list}" var="category">
<tr>
<td>${category.name}</td>
<td>${category.description}</td>
<td>
<a href="#">删除</a>
<a href="#">修改</a>
</td>
</tr>
</c:forEach>
</table>
</c:if>
- 效果：
图书模块
分析
在设计图书管理的时候，我们应该想到：图书和分类是有关系的。一个分类可以对应多本图书。
为什么要这样设计？这样更加人性化，用户在购买书籍的时候，用户能够查看相关分类后的图书，而不是全部图书都显示给用户，让用户一个一个去找。
设计实体
private String id;
private String name;
private String author;
private String description;
private double price;
//记住图片的名称
private String image;
//记住分类的id
private String category_id;
//各种setter和getter
设计数据库表
CREATE TABLE book (
id VARCHAR(40) PRIMARY KEY,
name VARCHAR(10) NOT NULL UNIQUE,
description VARCHAR(255),
author VARCHAR(10),
price FLOAT,
image VARCHAR(100),
category_id VARCHAR(40),
CONSTRAINT category_id_FK FOREIGN KEY (category_id) REFERENCES category (id)
);
编写DAO
/**
* 图书模块
* 1：添加图书
* 2：查看图书
* 3：查找图书的分页数据【图书一般来说有很多，所以要分页】
*/
public class BookDaoImpl {
public void addBook(Book book) {
QueryRunner queryRunner = new QueryRunner(Utils2DB.getDataSource());
String sql = "INSERT INTO book (id,name,description,author,price,image,category_id) VALUES(?,?,?,?,?,?,?)";
try {
queryRunner.update(sql, new Object[]{book.getId(), book.getName(), book.getDescription(), book.getAuthor(), book.getPrice(),book.getImage(), book.getCategory_id()});
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
public Book findBook(String id) {
QueryRunner queryRunner = new QueryRunner(Utils2DB.getDataSource());
String sql = "SELECT * FROM book WHERE id=?";
try {
return (Book) queryRunner.query(sql, id, new BeanHandler(Book.class));
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
/**得到图书的分页数据*/
public List<Book> getPageData(int start, int end) {
QueryRunner queryRunner = new QueryRunner(Utils2DB.getDataSource());
String sql = "SELECT * FROM book limit ?,?";
try {
return (List<Book>) queryRunner.query(sql, new BeanListHandler(Book.class), new Object[]{start, end});
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
/**得到按照分类图书的分页数据*/
public List<Book> getPageData(int start, int end,String category_id) {
QueryRunner queryRunner = new QueryRunner(Utils2DB.getDataSource());
//WHERE字句在limit字句的前边，注意Object[]的参数位置！
String sql = "SELECT * FROM book WHERE category_id=? limit ?,?";
try {
return (List<Book>) queryRunner.query(sql, new BeanListHandler(Book.class), new Object[]{ category_id,start, end});
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
/**
* 得到图书的总记录数
*/
public int getTotalRecord() {
QueryRunner queryRunner = new QueryRunner(Utils2DB.getDataSource());
String sql = "SELECT COUNT(*) FROM book";
try {
return (int) queryRunner.query(sql, new ScalarHandler());
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
/**
* 得到分类后图书的总记录数
* getCategoryTotalRecord
*/
public long getCategoryTotalRecord(String category_id) {
try {
QueryRunner queryRunner = new QueryRunner(Utils2DB.getDataSource());
String sql = "SELECT COUNT(*) FROM book WHERE category_id=?";
return (long) queryRunner.query(sql, category_id, new ScalarHandler());
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
}
测试DAO
public class BookDemo {
BookDaoImpl bookDao = new BookDaoImpl();
@Test
public void add() {
Book book = new Book();
book.setId("5");
book.setName("SQLServer");
book.setAuthor("我也不知道");
book.setImage("33333332432");
book.setPrice(33.22);
book.setDescription("这是一本好书");
book.setCategory_id("2");
bookDao.addBook(book);
}
@Test
public void look() {
List<Book> bookList = bookDao.getPageData(3, 3);
for (Book book : bookList) {
System.out.println(book.getName());
}
List<Book> books = bookDao.getPageData(0,2,"2");
for (Book book : books) {
System.out.println(book.getName());
}
}
@Test
public void find() {
String id = "2";
Book book = bookDao.findBook(id);
System.out.println(book.getName());
}
}
抽取成DAO接口
public interface BookDao {
void addBook(Book book);
Book findBook(String id);
List<Book> getPageData(int start, int end);
List<Book> getPageData(int start, int end, String category_id);
long getTotalRecord();
long getCategoryTotalRecord(String category_id);
}
编写Service层
/*添加图书*/
public void addBook(Book book) {
bookDao.addBook(book);
}
/*查找图书*/
public Book findBook(String id) {
return bookDao.findBook(id);
}
/*查找图书*/
public Book findBook(String id) {
return bookDao.findBook(id);
}
/*获取图书的分页数据*/
public Page getPageData(String pageNum) {
Page page=null;
if (pageNum == null) {
page = new Page(1, bookDao.getTotalRecord());
} else {
page = new Page(Integer.valueOf(pageNum), bookDao.getTotalRecord());
}
List<Book> books = bookDao.getPageData(page.getStartIndex(), page.getLinesize());
page.setList(books);
return page;
}
/*获取图书分类后的分页数据*/
public Page getPageData(String currentPageCount,String category_id) {
Page page=null;
if (currentPageCount == null) {
page = new Page(1, bookDao.getCategoryTotalRecord(category_id));
} else {
page = new Page(Integer.valueOf(currentPageCount), bookDao.getCategoryTotalRecord(category_id));
}
List<Book> books = bookDao.getPageData(page.getStartIndex(), page.getLinesize(), category_id);
page.setList(books);
return page;
}