初学jsp心得

String str1=new String("我是傻瓜");
String str2=new String("我是傻瓜");
if (str1==str2)
out.print("yes");
else
out.print("no");
结果是"no"。

String str1=new String("我是傻瓜");
String str2=new String("我是傻瓜");
if (str1.compareTo(str2)==0)
out.print("yes");
else
out.print("no");
结果是"yes"。

所以在jsp中判断字符串要使用compareTo方法，用惯传统语言还真一下子适应不过来，熟悉java的朋友应该没这个问题。

6。如何判断数据库为空？
  result = stmt.executeQuery(sql);
  if (result.next())  
   ......
  result执行后游标出于一个未明的状态，不能进行状态判断，也不能取值，一定要next()一下才可以用。


7。在jsp中实现分页。
page是关键字，不能当变量。
conn.jsp
<%
  String sDBDriver = "COM.ibm.db2.jdbc.app.DB2Driver";
  String sConnStr = "jdbc:db2:faq";
  Connection conn = null;
  Statement stmt = null;
  ResultSet rs=null;  
    try {
        Class.forName(sDBDriver);   
  }
    catch(java.lang.ClassNotFoundException e)   {
    out.print("faq(): " + e.getMessage());
  }

  try{
    conn = DriverManager.getConnection(sConnStr,"wsdemo","wsdemo1");     
    stmt = conn.createStatement();
  }catch(SQLException e){
    out.print(e.toString());
  }
%>

query.jsp

<%@ page language="java" import="java.sql.*" %>
<%@ page contentType="text/html; charset=gb2312" %>
<%@ include file="conn.jsp" %>
<%
.......
int pages=0;
int pagesize=10;
ResultSet result = null;
ResultSet rcount = null;

pages = new Integer(request.getParameter("pages")).intValue();

if (pages>0)
{

String sql=" state='我不傻'";
int count=0;
try {
rcount = stmt.executeQuery("SELECT count(id) as id from user where "+sql);
catch(SQLException ex) {
out.print("aq.executeQuery: " + ex.getMessage());
}
if(rcount.next())
count = rcount.getInt("id");
rcount.close();

if (count>0)
{  
sql="select * from user where "+sql;
try {
result = stmt.executeQuery(sql);
  }  
catch(SQLException ex) {
out.print("aq.executeQuery: " + ex.getMessage());