新手求教JSP怎么使用javabean

我有个B.JSP文件接受A.JSP文件传递来的值，想用javabean判断是否和数据库里有重复，java文件已经试过没问题（我具体在JAVA文件里赋值测试没问题）。但是在JSP里无论接受什么值都说已经重复。怎么办？
JSP:
   <%String username="1223";%>   //假设1223是传递来的值
   <jsp:useBean id="ID" class="count.Username" scope="page"/>
   <%String end = ID.namecheck();%>  
   <%=end%>JAVA:public String namecheck(){

        Connection conn = null;
        Statement stmt=null;
        ResultSet rs = null;
        String username=null;

String end = "you can use the username!";
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
                           conn = DriverManager.getConnection("jdbc:odbc:register");
                           stmt = conn.createStatement();
                           String sql = "select * from register where username='"+username+"'";
                           rs = stmt.executeQuery(sql);
            
                          while(rs.next()){
                            String username2 = rs.getString("username");
                           if(username==username2 || username2.equals(username)){
                          end = "username is being!";
                
              }
            }
   
            
         }
         catch(SQLException ex){
System.out.println("database.executeQuery:"+ex.getMessage());
     }
         catch(java.lang.ClassNotFoundException e){
//打印错误信息
System.out.print("mydb():"+e.getMessage());
     }
     
     System.out.print(end);
     return end;
}