java - 未找到符号

Question

DBHelper.java

package com.control;    
import java.sql.*;    
public class DBHelper 
{
Connection conn;
Statement st;
ResultSet rs;
public DBHelper()throws ClassNotFoundException
{
    Class.forName("oracle.jdbc.driver.OracleDriver");
}

public boolean getConnection()throws SQLException
{
    conn=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe","system","system");
    if(conn!=null)
        return true;
    return false;
}

public void execute(String query)throws SQLException
{
    st=conn.createStatement();
    st.execute(query);

}
public boolean match(String uname,String pwd)throws Exception
{
    st=conn.createStatement();
    rs=st.executeQuery("select * from register");


        while(rs.next())
        {
            String unm=rs.getString(1);
            String pd=rs.getString(2);
            if(uname.equals(unm) && pwd.equals(pd))
            {
                return true;
            }

        }
        return false;


}



}

LoginSevlet.java

package com.control;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
public class LoginServlet extends HttpServlet
{


    public void doPost(HttpServletRequest req,HttpServletResponse res)throws IOException,ServletException
    {
        try{
        DBHelper obj=new DBHelper();
        obj.getConnection();
        PrintWriter out=res.getWriter();
        res.setContentType("text/html");
        String uname=req.getParameter("email");
        String pwd=req.getParameter("password");
        //ResultSet rs=obj.match(uname,pwd);
        //if(uname.equals(rs.getString(1)) && pwd.equals(rs.getString(2)))
        if(obj.match(uname,pwd))
        {
            RequestDispatcher rd=req.getRequestDispatcher("profile.html");
            rd.forward(req,res);

        }
        else
        {

            RequestDispatcher rd=req.getRequestDispatcher("index.html");
            rd.include(req,res);
            out.println("<b>Incorrect Email or password!</b>");
        }

        }catch(Exception e)
        {

        }

    }    
}

I am trying to access DBHelper class in LoginServlet while Compilation i did javac DBHelper.java javac -cp "C:\Users\dell\Desktop\MYServlet\WEB-INF\lib\servlet-api-2.5.jar;" LoginServlet.java LoginServlet.java:13: error: cannot find symbol
DBHelper obj=new DBHelper();
^
symbol: class DBHelper
location: class LoginServlet
LoginServlet.java:13: error: cannot find symbol
DBHelper obj=new DBHelper();
^
symbol: class DBHelper
location: class LoginServlet
2 errors
I have placed .java files in C:\Users\dell\Desktop\MYServlet\WEB-INF\classes\com\control
All the Files are in the same package and that too public then why cant LoginServlet access DBHelper class

Answer 1

因为你的LoginServlet类中没有import com.control.*;。有关套餐的更多信息 Java packages使用包时请尽量使用正确的命令进行编译和执行。