求救，java.lang.NumberFormatException: null

Question

真的快疯了，下面的代码不知道为什么出错，没财富值了，所以给不了分，谢谢好心人
<form name="form1" method="post" action="submit_order.jsp">
<%
Connection con;
Statement sql;
ResultSet rs;
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
}
catch(ClassNotFoundException e){out.print("类找不到!");
out.print(e);
}
try{
con=DriverManager.getConnection("jdbc:sqlserver://localhost:1433; DatabaseName=book","sa","11011");
sql=con.createStatement();
if(request.getParameter("id")==null||(request.getParameter("id").trim()).length()==0)
{ }//如果没有要购买书，只是查看购物车中的商品 }
else{
}
float all=(float)0.0;//总价
out.print("<table border bordercolor=#ccc8888 align=center>");
out.print("<tr><td colspan=8 align=center bgcolor=#0009999>购物车的书有:</td></tr>");
out.print("<tr align=center>");
out.print("<td width=40>"+"序号");
out.print("<td width=400>"+"书名");
out.print("<td width=40>"+"数目");
out.print("<td width=40>"+"单价");
out.print("<td width=80>"+"总价");
out.print("</tr>");
Hashtable list=buycar.listgoods();
Enumeration en=list.keys();
while(en.hasMoreElements()){
String id=(String)en.nextElement();
byte[] b=id.getBytes("ISO-8859-1");
id=new String(b);
out.print("<tr align=center>");
rs=sql.executeQuery("select * from book where id="+id);
out.print("<td>"+id+"</td>");
rs.next();
out.print("<td>"+rs.getString("name")+"</td>");
out.print("<td>"+list.get(id)+"</td>");
out.print("<td>"+rs.getFloat("price")+"</td>");
out.print("<td>"+rs.getFloat("price")*((Integer)list.get(id)).intValue()+"</td>");
all+=rs.getFloat("price")*((Integer)list.get(id)).intValue();
out.print("<input type=hidden name=id value="+id+">");
out.print("</tr>");
}
out.print("<tr td align=center>");
out.print("<td align=center>"+"总价"+"</td>");
out.print("<td>"+all+"元"+"</td><td> </td><td> </td>");
out.print("</tr>");
out.print("</table>");
con.close();
}
catch(Exception ee){
out.println("error!");
out.print(ee.getMessage());
}
%>
</form>

submit_order.jsp:
<%
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Connection con=DriverManager.getConnection("jdbc:sqlserver://localhost:1433;DatabaseName=book","sa", "11011")
Statement stmt=con.createStatement();
int id = Integer.parseInt(request.getParameter("id"));
String book_id=(request.getParameter("id"));
String book_number=(request.getParameter("book_number"));
String price=request.getParameter("price");
String sql="insert into orders(book_id,book_number,status,price)"
+"values('"+id+",'"+book_number+"','"+0+"','"+price+"')";
stmt.executeUpdate(sql);
con.close();
stmt.close();
%>

Answer 1

错误信息很明显，是告诉你数字格式化错误的异常，看看你代码，
int id = Integer.parseInt(request.getParameter("id"));
检查下，看看request.getParameter("id")得到的id是否为null。