关于JSP的一点疑问小结

希望谁能帮我看一看问题出在哪?谢谢!
register.html部分:

用户名:
密码:

register.jsp部分:

register.java(JavaBean)部分:

package mypack; 
public class register { 
private String username = ""; 
private String pwd = ""; 
public void setUserName(String nm) 
{ 
this.username = nm; 
} 
public String getUserName() 
{ 
return this.username; 
} 
public void setPwd(String pd) 
{ 
this.pwd = pd; 
} 
public String getPwd() 
{ 
return this.pwd; 
} 
public boolean judge() 
{ 
boolean temp = false; 
if(username.equals("teacher") && pwd.equals("teacher")) 
{ 
temp = true; 
} 
return temp; 
} 
} 
sbmt.java(Servlet)部分: 
package mypack; 
import java.io.IOException; 
import java.io.PrintWriter; 
import javax.servlet.ServletException; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
import javax.servlet.http.HttpSession; 
public class sbmt extends HttpServlet { 
private static final long serialVersionUID = 1L; 
public sbmt() { 
super(); 
} 
public void destroy() { 
super.destroy(); 
} 
public void doGet(HttpServletRequest request, HttpServletResponse response) 
throws ServletException, IOException { 
response.setContentType("text/html"); 
PrintWriter out = response.getWriter(); 
out 
.println(""-//W3C//DTD HTML 4.01 Transitional//EN\">"); 
out.println(""); 
out.println(" "); 
out.println(" "); 
out.print(" This is "); 
out.print(this.getClass()); 
out.println(", using the GET method"); 
out.println(" "); 
out.println(""); 
out.flush(); 
out.close(); 
} 
public void doPost(HttpServletRequest request, HttpServletResponse response) 
throws ServletException, IOException { 
HttpSession session = request.getSession(false); 
if(session == null) 
{ 
response.sendRedirect("error.jsp"); 
return; 
} 
String usernameone = (String)session.getAttribute("username"); 
String usernametwo = request.getParameter("username"); 
if(!usernameone.equals(usernametwo)) 
{ 
response.sendRedirect("error.jsp"); 
return; 
} 
response.setContentType("text/html;charset = GBK"); 
request.setAttribute("username", usernametwo); 
if(usernametwo.equals("teacher")) 
{ 
response.sendRedirect("teacher.jsp"); 
return; 
} 
else 
{ 
response.sendRedirect("error.jsp"); 
return; 
} 
} 
} 
}