Question

我创建了一个登录页面并将登录信息处理到数据库。该类将检查用户并返回其ID。一切顺利，直到我通过初始化变量UID的点。之后我有一个SQL查询打破了程序。我的错是什么？
错误

HTTP Status 500 - Internal Server Error

type Exception report

messageInternal Server Error

descriptionThe server encountered an internal error that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: java.lang.NullPointerException
root cause

java.lang.NullPointerException

的login.jsp

</head>
<body>
    <%
    if(request.getParameter("submit")!=null)
    {
        String ime = request.getParameter("name");
        String pass = request.getParameter("pass");
        int uid = DbBroker.checkUser(name,pass);

        if (uid>0)
        {
            session.setAttribute("uid", name);
            response.sendRedirect("prodaja.jsp");
        }
        else if (uid==0)
        {
            session.setAttribute("uid", ime);
            response.sendRedirect("administrator.jsp");
        }       
        else  out.print("Korisnik nepostoji");

    }
    %>

</body>

dbBroker.java

public class DbBroker {

    public static Connection conn;

    public  static void conn()
    {
        try
        {
                Class.forName("com.mysql.jdbc.Driver").newInstance();
                conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/prodavnica", "root", "");
        }
        catch(Exception e)
        {
            System.out.println(e);
        }
    }

    private void close()
    {
        try
        {
            conn.close();
        }
        catch(Exception e)
        {
            System.out.println(e);
        }
    }  

    public static int checkUser(String name, String pass) throws SQLException
    {
        conn();
        name=name.trim().replace("'", "");
        pass=pass.trim().replace("'","");
        int uid = -1;
        Statement st=conn.createStatement();
        ResultSet rs=st.executeQuery("SELECT id from user WHERE name='"+name+
                                     "' and pass='"+pass+"';");
        if (rs.next())
        {
            uid=rs.getInt("id");
        }
        conn.close();
        return uid;
    }
}

Answer 1

我认为你需要添加你的＆＃34; DbBroker＆＃34;类在JSP页面中的类：

＆lt;％@ page import =＆＃34; packagename.DbBroker＆＃34; ％GT;

<html> <%@ page import="packagename.DbBroker" %> <head> </head> <body> <% if(request.getParameter("submit")!=null) { String ime = request.getParameter("name"); String pass = request.getParameter("pass"); int uid = DbBroker.checkUser(name,pass); if (uid>0) { session.setAttribute("uid", name); response.sendRedirect("prodaja.jsp"); } else if (uid==0) { session.setAttribute("uid", ime); response.sendRedirect("administrator.jsp"); } else out.print("Korisnik nepostoji"); } %> </body> </html>

Java Web编程

1 个答案: