空指针产生的输入结果错误

[fx290318458]

此代码运行的结果是：发表是败。我知道是boo为false 所致.我用基本的输出知道是username=null,object=null,notecontent为空所致
代码如下
package myservlet.control;
import mybean.data.*;
import java.sql.*;
import java.io.*;
import java.util.*;
import java.util.Date;
import java.text.* ;
import javax.servlet.*;
import javax.servlet.http.*;
public class HandleNote extends HttpServlet
{ public void init(ServletConfig config) throws ServletException
{ super.init(config);
try { Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
}
catch(Exception e){}
}
public String handleString(String s)
{ try{ byte bb[]=s.getBytes("iso-8859-1");
s=new String(bb);
}
catch(Exception ee){}
return s;
}


public void DoPost(HttpServletRequest request,HttpServletResponse response)
throws ServletException,IOException
{
Connection con;
PreparedStatement sql;
Note note=new Note();
request.setAttribute("note",note);

String backNews="";
String username=request.getParameter("username");
String object=request.getParameter("object");
String notecontent=request.getParameter("notecontent");
String flag="1" ;
Date currTime=new Date();
SimpleDateFormat formatter=new SimpleDateFormat("yyy/MM/dd a hh:mm:ss",Locale.US);
String notetime=formatter.format(currTime);

if(username==null)
username="";
username=username.trim();
if(object==null)
object="";
object=object.trim();
if(notecontent==null)
notecontent="";
notecontent=notecontent.trim();
boolean boo=username.length()>0&&object.length()>0&¬econtent.length()>0;
System.out.println(username.length()) ;
System.out.println(object.length());
System.out.println(notecontent.length());
System.out.println(notetime.length());
// System.out.println
String uri="jdbc:sqlserver://127.0.0.1:1433;DatabaseName=ComeHere";

try{ con=DriverManager.getConnection(uri,"sa","123");
String str="insert into note (username,object,notecontent,notetime,flag) value(?,?,?,?,?)" ;
sql=con.prepareStatement(str);
if(boo){
sql.setString(1,handleString(username));

sql.setString(2,handleString(object));
sql.setString(3,handleString(notecontent));
sql.setString(4,handleString(notetime));
sql.setString(5,flag);
int m=sql.executeUpdate();
if(m!=0)
{ backNews="留言成功";
note.setBackNews(backNews);
note.setUsername(username);
note.setNotemanager(object);
note.setNotecontent(handleString(notecontent));
note.setNotetime(handleString(notetime));
}
}
else
{ backNews="留言失败";
note.setBackNews(backNews);
}
con.close();
}
catch(SQLException exp)
{ note.setBackNews(""+exp);
}
RequestDispatcher dispatcher= request.getRequestDispatcher("/showNote.jsp");
dispatcher.forward(request, response);
}
public void doGet(HttpServletRequest request,HttpServletResponse response)
throws ServletException,IOException
{ continueDoPost(request,response);
}
}