新手提问：关于struts2.0的数据操作。

Question

刚学习struts2，想做一个连接数据库的用户登录验证，就是输入账号，然后通过该账号去数据库查找密码；如果查找的密码跟输入的密码一样则登陆成功，否则不成功；
action:package com.test.login;
import java.sql.*;import com.opensymphony.xwork2.ActionSupport;public class Login extends ActionSupport 
{
private  String  username;
private  String  password;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
String a="sadad";
 System.out.print(a);
}
public String  DB()
{
    Connection con = null;
   Statement sql=null;
   ResultSet rs=null;
   try{ 
    Class.forName( "sun.jdbc.odbc.JdbcOdbcDriver");
        con=DriverManager.getConnection("jdbc:odbc:sum","","");
       }catch(Exception e){System.out.println("数据库连接错误！"); 
try{      
     String sqle="select pass from student where studentid='"+username+"'";
         rs=con.createStatement().executeQuery(sqle);
         rs.next();
         String a=rs.getString("pass");
        
         if(rs.next())
         {
         if(a==password) 
          {
          return this.SUCCESS;
          }
          else
          {
          this.addFieldError("password", "password input worng");
          return this.INPUT;
          }
         }
         else
         {
          this.addFieldError("username", "username input worng");
          return this.INPUT;
         }        
}catch(Exception e1){System.out.println(e1.toString()); 
}
}
return null;
}
@Override
public String execute() throws Exception {

return "sucess";
}
@Override
public void validate() 
{

if(null==this.getUsername()||"".equals(this.getUsername().trim()))
{
this.addFieldError("username", "username err");
}
if(null==this.getPassword()||"".equals(this.getPassword().trim()))
{
this.addFieldError("password", "password err");
}
}

}


xml；
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd"><struts>
     <package name="struts2" extends="struts-default">
     
       <action name="login" class="com.test.login.Login"  >
            <result name="input">/login.jsp</result>
            <result name="sucess">/index.jsp</result>
       </action> 
    
    
     </package>
</struts>
运行的结果是不输入东西提示username err或password err错误，然后无论是输入对的密码还是输入错的密码显示的是空白页；各位牛人解答下；

Answer 1

<result>/index.jsp</result>这样。

Answer 2

 try{      
                 String sqle="select pass from student where studentid='"+username+"'";
                 rs=con.createStatement().executeQuery(sqle);
                 rs.next();
                 String a=rs.getString("pass");
                
                 if(rs.next())
                 {
                 if(a==password) 
                     {
                         return this.SUCCESS;
                     }
                     else
                     {
                         this.addFieldError("password", "password input worng");
                         return this.INPUT;
                     }
                 }
去掉这一句 if(rs.next())