Question

为什么在运行时出现此异常？我在libraries文件夹中添加了ojdbc.jar 之后抛出异常。

是ojdbc.jar引起的问题吗？

这是我的代码：

public class DBManager {

private Connection connection=null;
private PreparedStatement preparedStatement=null;
private ResultSet resultSet = null;
private String URL;
private String userName;
private String pass;

public DBManager(String URL,String userName,String pass){
    try{
    Class.forName("oracle.jdbc.driver.OracleDriver");
    }catch(ClassNotFoundException e){
        e.printStackTrace();
    }
    try{
    connection = DriverManager.getConnection(URL, userName, pass);
    }catch(SQLException e){
        e.printStackTrace();
    }
}

public ResultSet validate(Users user,String sql){

    try{
    preparedStatement = connection.prepareStatement(sql);
    preparedStatement.setString(1,user.getEmail());
    preparedStatement.setString(2,user.getPassword());
    resultSet = preparedStatement.executeQuery();
    }catch(SQLException e){
        e.printStackTrace();
    }

    return resultSet;
}

}

public class MyServlet extends HttpServlet {

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    Users user = new Users();
    user.setEmail(request.getParameter("email"));
    user.setPassword(request.getParameter("password"));
    try {
        DBManager manager = new DBManager("jdbc:oracle:thin:@localhost:1521:XE", "databaseName", "Password");
        String sql = "SELECT FIRSTNAME,LASTNAME FROM USERS WHERE EMAIL=? and PASSWORD=?";
        ResultSet resultSet = manager.validate(user, sql);
        while (resultSet.next()) {
            user.setFname(resultSet.getString("FIRSTNAME"));
            user.setLname(resultSet.getString("LASTNAME"));
        }
        request.setAttribute("user", user);
        response.sendRedirect("welcome.jsp");
    } catch (Exception e) {
        e.printStackTrace();
    }
}

和index.html：

<html>
<head>
    <title>Login</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<body>
    <div id = "main"> 
        <form action="MyServlet" method="POST">
            <table>

                <tr>
                    <th>
                        Your Email: 
                    </th>
                    <td>
                        <input type = "email" name="emial">
                    </td>
                </tr>

                <tr>
                    <th>
                        Your Password: 
                    </th>
                    <td>
                        <input type = "password" name="password">
                    </td>
                </tr>

                <tr>
                    <th>

                    </th>
                    <td>
                        <input type = "submit">
                    </td>
                </tr>

            </table>
        </form>
    </div>
</body>

欢迎jsp页面是

<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>Welcome</title>
</head>
<body>
    <h1> Welcome 
    <%
        Users user = (Users)request.getAttribute("user");
        out.print(user.getFname()+" "+user.getLname());   
    %>
    </h1>
</body>

StandardWrapperValve [jsp]：servlet jsp的Servlet.service（）抛出异常java.lang.NullPointerException

0 个答案: