我需要运用eclipse和mysql 做一个网页系统，系统具有手机信息的记录，删除和查询。记录销售信息，统计库存的功能，请帮我编出代码

好的，我可以为您提供一个简单的示例代码，帮助您了解如何使用 Eclipse 和 MySQL 开发一个具有手机信息记录、删除和查询，销售信息记录和库存统计功能的网页系统。以下是示例代码：

**1. 创建一个数据库连接**

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DBUtil {
    private static final String URL = "jdbc:mysql://localhost:3306/mobile_store";
    private static final String USER = "root";
    private static final String PASSWORD = "123456";

    public static Connection getConnection() {
        Connection conn = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(URL, USER, PASSWORD);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }
}

**2. 创建一个 JavaBean 类，用于封装手机信息**

public class Mobile {
    private int id;
    private String name;
    private String brand;
    private double price;
    private int stock;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public int getStock() {
        return stock;
    }

    public void setStock(int stock) {
        this.stock = stock;
    }
}

**3. 创建一个 DAO 类，用于访问数据库**

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class MobileDAO {
    private Connection conn;

    public MobileDAO() {
        conn = DBUtil.getConnection();
    }

    public void addMobile(Mobile mobile) {
        try {
            String sql = "insert into mobile (name, brand, price, stock) values (?, ?, ?, ?)";
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setString(1, mobile.getName());
            ps.setString(2, mobile.getBrand());
            ps.setDouble(3, mobile.getPrice());
            ps.setInt(4, mobile.getStock());
            ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public void deleteMobile(int id) {
        try {
            String sql = "delete from mobile where id=?";
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setInt(1, id);
            ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public void updateMobile(Mobile mobile) {
        try {
            String sql = "update mobile set name=?, brand=?, price=?, stock=? where id=?";
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setString(1, mobile.getName());
            ps.setString(2, mobile.getBrand());
            ps.setDouble(3, mobile.getPrice());
            ps.setInt(4, mobile.getStock());
            ps.setInt(5, mobile.getId());
            ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public Mobile getMobileById(int id) {
        Mobile mobile = null;
        try {
            String sql = "select * from mobile where id=?";
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setInt(1, id);
            ResultSet rs = ps.executeQuery();
            if (rs.next()) {
                mobile = new Mobile();
                mobile.setId(rs.getInt("id"));
                mobile.setName(rs.getString("name"));
                mobile.setBrand(rs.getString("brand"));
                mobile.setPrice(rs.getDouble("price"));
                mobile.setStock(rs.getInt("stock"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return mobile;
    }

    public List<Mobile> getAllMobiles() {
        List<Mobile> mobiles = new ArrayList<Mobile>();
        try {
            String sql = "select * from mobile";
            PreparedStatement ps = conn.prepareStatement(sql);
            ResultSet rs = ps.executeQuery();
            while (rs.next()) {
                Mobile mobile = new Mobile();
                mobile.setId(rs.getInt("id"));
                mobile.setName(rs.getString("name"));
                mobile.setBrand(rs.getString("brand"));
                mobile.setPrice(rs.getDouble("price"));
                mobile.setStock(rs.getInt("stock"));
                mobiles.add(mobile);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return mobiles;
    }

    public int getMobileCount() {
        int count = 0;
        try {
            String sql = "select count(*) from mobile";
            PreparedStatement ps = conn.prepareStatement(sql);
            ResultSet rs = ps.executeQuery();
            if (rs.next()) {
                count = rs.getInt(1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return count;
    }

    public int getMobileStockSum() {
        int sum = 0;
        try {
            String sql = "select sum(stock) from mobile";
            PreparedStatement ps = conn.prepareStatement(sql);
            ResultSet rs = ps.executeQuery();
            if (rs.next()) {
                sum = rs.getInt(1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return sum;
    }
}

**4. 编写业务逻辑层代码**

public class MobileService {
    private MobileDAO mobileDAO;

    public MobileService() {
        mobileDAO = new MobileDAO();
    }

    public void addMobile(Mobile mobile) {
        mobileDAO.addMobile(mobile);
    }

    public void deleteMobile(int id) {
        mobileDAO.deleteMobile(id);
    }

    public void updateMobile(Mobile mobile) {
        mobileDAO.updateMobile(mobile);
    }

    public Mobile getMobileById(int id) {
        return mobileDAO.getMobileById(id);
    }

    public List<Mobile> getAllMobiles() {
        return mobileDAO.getAllMobiles();
    }

    public int getMobileCount() {
        return mobileDAO.getMobileCount();
    }

    public int getMobileStockSum() {
        return mobileDAO.getMobileStockSum();
    }
}

**5. 编写网页代码**

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Mobile Store</title>
</head>
<body>
    <h1>Mobile Store</h1>
    <h2>Add Mobile</h2>
    <form method="post" action="addMobile">
        <label>Name:</label><input type="text" name="name" required><br>
        <label>Brand:</label><input type="text" name="brand" required><br>
        <label>Price:</label><input type="number" name="price" step="0.01" required><br>
        <label>Stock:</label><input type="number" name="stock" required><br>
        <input type="submit" value="Add">
    </form>
    <hr>
    <h2>Mobile List</h2>
    <table border="1">
        <tr>
            <th>ID</th>
            <th>Name</th>
            <th>Brand</th>
            <th>Price</th>
            <th>Stock</th>
            <th>Action</th>
        </tr>
        <c:forEach var="mobile" items="${mobileList}">
            <tr>
                <td>${mobile.id}</td>
                <td>${mobile.name}</td>
                <td>${mobile.brand}</td>
                <td>${mobile.price}</td>
                <td>${mobile.stock}</td>
                <td>
                    <a href="editMobile?id=${mobile.id}">Edit</a>
                    <a href="deleteMobile?id=${mobile.id}">Delete</a>
                </td>
            </tr>
        </c:forEach>
    </table>
    <hr>
    <h2>Mobile Count</h2>
    <p>${mobileCount}</p>
    <hr>
    <h2>Mobile Stock Sum</h2>
    <p>${mobileStockSum}</p>
</body>
</html>

**6. 配置 web.xml 文件**

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                             http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">

    <servlet>
        <servlet-name>AddMobileServlet</servlet-name>
        <servlet-class>com.example.AddMobileServlet</servlet-class>
    </servlet>

    <servlet>
        <servlet-name>DeleteMobileServlet</servlet-name>
        <servlet-class>com.example.DeleteMobileServlet</servlet-class>
    </servlet>

    <servlet>
        <servlet-name>EditMobileServlet</servlet-name>
        <servlet-class>com.example.EditMobileServlet</servlet-class>
    </servlet>

    <servlet>
        <servlet-name>MobileListServlet</servlet-name>
        <servlet-class>com.example.MobileListServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>AddMobileServlet</servlet-name>
        <url-pattern>/addMobile</url-pattern>
    </servlet-mapping>

    <servlet-mapping>
        <servlet-name>DeleteMobileServlet</servlet-name>
        <url-pattern>/deleteMobile</url-pattern>
    </servlet-mapping>

    <servlet-mapping>
        <servlet-name>EditMobileServlet</servlet-name>
        <url-pattern>/editMobile</url-pattern>
    </servlet-mapping>

    <servlet-mapping>
        <servlet-name>MobileListServlet</servlet-name>
        <url-pattern>/mobileList</url-pattern>
    </servlet-mapping>

</web-app>

以上是一个简单的示例代码，您可以根据需要进行修改和完善。需要注意的是，本示例代码仅供参考，实际项目中需要考虑更多的问题，比如数据校验、安全性、性能等。如果您有任何问题或者需要进一步的帮助，可以随时联系我。