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;
}
}
答案 0 :(得分：0)
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>