插入空值错误

我明明对每个插入的值为空都有判断，但是当我所有的内容都为空的时候也可以插入……为什么？？？？？？？？？
<%@ page contentType="text/html;Charset=GB2312" %>
<%@ page import="java.util.*" %>
<%@ page import="java.sql.*" %>
<HTML>
    <BODY>
        <CENTER>      
        <%
        
        Connection con;
        Statement sql;
        
        
        
        String username=null;
        String password=null;
        String name=null;
        String email=null;
        String sex=null;
        String job=null;
        
         username=request.getParameter("username1");
         password=request.getParameter("password1");
        name=request.getParameter("name1");
         email=request.getParameter("email1");
         sex=request.getParameter("R");
        job=request.getParameter("job1");
        try{
                   Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
           }
            catch(ClassNotFoundException e)
            {
                out.print("出错1"+e);
            }
            try{
                  con=DriverManager.getConnection("jdbc:odbc:messagedb","sa","sa");
                  sql=con.createStatement();
                  if(username!=null&&password!=null&&name!=null&&email!=null&&sex!=null&&job!=null)//对插入的数据非空判断
                  {
                                                      
                      String sqls="insert into user(username,password,name,email,sex,job)values('"+username+"','"+password+"','"+name+"','"+email+"','"+sex+"','"+job+"')";
                      int temp=sql.executeUpdate(sqls);            
                      if(temp>0)
                      { 
                        session.setAttribute("OK","恭喜你注册成功");                        
                        response.sendRedirect("login.jsp"); 
                      }
                      else
                      { 
                        session.setAttribute("error","fail"); 
                        response.sendRedirect("error.jsp");     
                      }
                  } 
                else if(username==null && password==null&&name==null&&email==null&&sex==null&&job==null)
                 {
                 %>
                 <FORM action="register.jsp" method=post name="form">
                  <h1>用户注册页面！</h1>
                  用户名:<input type=text name="username1">
                  <BR>
                  <BR>
                  密码:<input type=password name="password1">
                  <BR>
                  <BR>
                  真实姓名:<input type=text name="name1">
                  <BR>
                  <BR>
                  email:<input  type=text name="email1">
                  <BR>
                  <BR>
                  性别:<input type="radio" name="R" value="男" checked="default">男
                  <input type="radio" name="R" value="女">女
                  <BR>
                  <BR>
                  工作：<textarea name="job1" ROWS="10" COLS=36 wrap="physical"></textarea>
                  <BR>
                  <BR>
                  <input type="submit" value="提交" name="submit">
                  &nbsp;&nbsp;
                  <input type="reset" value="重置">     
                 <%
                 }                
                 else  
                 {
                     session.setAttribute("error","error1");
                     response.sendRedirect("error.jsp");
                 }
               }
                catch(SQLException e)
            {
             out.print("出错2"+e);
            }
        %>
        
</CENTER>
</BODY>
</HTML>

解决方案 »

  1.   

    if(username!=null&&password!=null&&name!=null&&email!=null&&sex!=null&&job!=null)//对插入的数据非空判断
    if(username!=""&&password!=""&&name!=""&&email!=""&&sex!=""&&job!="")
      

  2.   

    if(username!=null&&password!=null&&name!=null&& email!=null&&sex!=null&&job!=null)//对插入的数据非空判断
      {
        ==》
    if(username!=null&&password!=null&&name!=null&& email!=null&&sex!=null&&job!=null &&username!=""&&password!=""&&name!=""&&email!=""&&sex!=""&&job!="")//对插入的数据非空判断
      {
        
      

  3.   

    验了“null”还需要验“空” 比如 
    if(username!=null&&!username.trim().equals("") 
    && password!=null&&password.trim().equals("") 
    && name!=null&&!name.trim().equals("")
    && email!=null&&!email.trim().equals("")
    && sex!=null&&!sex.trim().equals("")
    && job!=null&&job.trim().equals("")){

    }