maven实现登录修改删除转账

Maven 是一个项目管理工具，它可以帮助我们自动化构建、测试和部署 Java 项目。而实现登录、修改、删除和转账等功能需要编写 Java 代码和操作数据库。

下面是一个使用 Maven 实现登录、修改、删除和转账功能的示例项目：

1. 创建 Maven 项目

首先，我们需要创建一个 Maven 项目。可以使用 Eclipse 或者 IntelliJ IDEA 等 Java IDE 工具创建 Maven 项目。

2. 添加依赖

我们需要添加如下依赖到 pom.xml 文件中：

<dependencies>
  <dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.23</version>
  </dependency>
  <dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>4.0.1</version>
  </dependency>
</dependencies>

其中，mysql-connector-java 是操作 MySQL 数据库的 JDBC 驱动，javax.servlet-api 是操作 Servlet 的 API。

3. 编写代码

接下来，我们需要编写 Java 代码实现登录、修改、删除和转账等功能。下面是示例代码：

// 登录
public boolean login(String username, String password) {
  Connection conn = null;
  PreparedStatement stmt = null;
  ResultSet rs = null;
  try {
    conn = getConnection();
    String sql = "select * from user where username=? and password=?";
    stmt = conn.prepareStatement(sql);
    stmt.setString(1, username);
    stmt.setString(2, password);
    rs = stmt.executeQuery();
    return rs.next();
  } catch (SQLException e) {
    e.printStackTrace();
  } finally {
    close(conn, stmt, rs);
  }
  return false;
}

// 修改密码
public boolean changePassword(String username, String oldPassword, String newPassword) {
  Connection conn = null;
  PreparedStatement stmt = null;
  try {
    conn = getConnection();
    String sql = "update user set password=? where username=? and password=?";
    stmt = conn.prepareStatement(sql);
    stmt.setString(1, newPassword);
    stmt.setString(2, username);
    stmt.setString(3, oldPassword);
    int rows = stmt.executeUpdate();
    return rows > 0;
  } catch (SQLException e) {
    e.printStackTrace();
  } finally {
    close(conn, stmt, null);
  }
  return false;
}

// 删除用户
public boolean deleteUser(String username) {
  Connection conn = null;
  PreparedStatement stmt = null;
  try {
    conn = getConnection();
    String sql = "delete from user where username=?";
    stmt = conn.prepareStatement(sql);
    stmt.setString(1, username);
    int rows = stmt.executeUpdate();
    return rows > 0;
  } catch (SQLException e) {
    e.printStackTrace();
  } finally {
    close(conn, stmt, null);
  }
  return false;
}

// 转账
public boolean transfer(String fromAccount, String toAccount, double amount) {
  Connection conn = null;
  PreparedStatement stmt = null;
  try {
    conn = getConnection();
    conn.setAutoCommit(false);
    String sql1 = "update account set balance=balance-? where account=?";
    stmt = conn.prepareStatement(sql1);
    stmt.setDouble(1, amount);
    stmt.setString(2, fromAccount);
    int rows1 = stmt.executeUpdate();
    if (rows1 <= 0) {
      conn.rollback();
      return false;
    }
    String sql2 = "update account set balance=balance+? where account=?";
    stmt = conn.prepareStatement(sql2);
    stmt.setDouble(1, amount);
    stmt.setString(2, toAccount);
    int rows2 = stmt.executeUpdate();
    if (rows2 <= 0) {
      conn.rollback();
      return false;
    }
    conn.commit();
    return true;
  } catch (SQLException e) {
    try {
      conn.rollback();
    } catch (SQLException ex) {
      ex.printStackTrace();
    }
    e.printStackTrace();
  } finally {
    close(conn, stmt, null);
  }
  return false;
}

// 获取数据库连接
private Connection getConnection() throws SQLException {
  String url = "jdbc:mysql://localhost:3306/test?useSSL=false&serverTimezone=UTC";
  String username = "root";
  String password = "root";
  return DriverManager.getConnection(url, username, password);
}

// 关闭资源
private void close(Connection conn, Statement stmt, ResultSet rs) {
  try {
    if (rs != null) rs.close();
    if (stmt != null) stmt.close();
    if (conn != null) conn.close();
  } catch (SQLException e) {
    e.printStackTrace();
  }
}

这段代码定义了一个 UserDao 类，其中包含了 login、changePassword、deleteUser 和 transfer 四个方法，分别用于实现登录、修改密码、删除用户和转账功能。getConnection 方法用于获取数据库连接，close 方法用于关闭资源。

4. 编写 Servlet

最后，我们需要编写 Servlet，将前端请求与 Java 代码联系起来。下面是示例代码：

@WebServlet("/login")
public class LoginServlet extends HttpServlet {

  private UserDao userDao = new UserDao();

  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    boolean result = userDao.login(username, password);
    if (result) {
      response.sendRedirect("index.jsp");
    } else {
      response.sendRedirect("login.jsp");
    }
  }
}

@WebServlet("/changePassword")
public class ChangePasswordServlet extends HttpServlet {

  private UserDao userDao = new UserDao();

  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String username = request.getParameter("username");
    String oldPassword = request.getParameter("oldPassword");
    String newPassword = request.getParameter("newPassword");
    boolean result = userDao.changePassword(username, oldPassword, newPassword);
    if (result) {
      response.sendRedirect("index.jsp");
    } else {
      response.sendRedirect("changePassword.jsp");
    }
  }
}

@WebServlet("/deleteUser")
public class DeleteUserServlet extends HttpServlet {

  private UserDao userDao = new UserDao();

  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String username = request.getParameter("username");
    boolean result = userDao.deleteUser(username);
    if (result) {
      response.sendRedirect("index.jsp");
    } else {
      response.sendRedirect("deleteUser.jsp");
    }
  }
}

@WebServlet("/transfer")
public class TransferServlet extends HttpServlet {

  private UserDao userDao = new UserDao();

  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String fromAccount = request.getParameter("fromAccount");
    String toAccount = request.getParameter("toAccount");
    double amount = Double.parseDouble(request.getParameter("amount"));
    boolean result = userDao.transfer(fromAccount, toAccount, amount);
    if (result) {
      response.sendRedirect("index.jsp");
    } else {
      response.sendRedirect("transfer.jsp");
    }
  }
}

这段代码定义了四个 Servlet，分别对应登录、修改密码、删除用户和转账四个功能。每个 Servlet 通过 UserDao 类中的方法实现相应的功能。

5. 编译打包

最后，我们需要使用 Maven 编译打包项目。在项目根目录下执行以下命令：

mvn clean package

执行完成后，会在 target 目录下生成一个 war 包。将这个 war 包部署到 Tomcat 等 Java Web 服务器上即可使用。