我用jsp 连接 sql server 2000 老是提示出错，下面是 tomcat 的log文件信息

Question

2006-11-02 09:48:49 StandardWrapperValve[jsp]: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
at org.apache.jsp.login_005fin_jsp._jspService(login_005fin_jsp.java:75)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:133)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:311)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:284)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:204)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:257)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:564)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:245)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:199)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:564)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:195)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:164)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:149)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:564)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:156)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:564)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:972)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:206)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:828)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:700)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:584)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
at java.lang.Thread.run(Thread.java:595)

Answer 1

是不是象数据库连接字符串为空，或者页面接收变量时为NULL

Answer 2

package ConnectSql;
import java.sql.*;
public class db_conn
{
//变量
private Connection conn = null;
//连接数据库
private void BulidConnection()
{
try
{
Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
conn = DriverManager.getConnection("jdbc:microsoft:sqlserver://192.168.0.110:1433;DatabaseName=BugDB","zzx","zzx");

}catch(Exception ex)
{
System.out.println(" -BulidConnection- error!  ");
System.out.println(ex.toString());
}
}
// 构造函数
public db_conn()
{
BulidConnection();
}
//方法
public Connection getConnection()
{
if(conn==null)
{
BulidConnection();
}
return conn;
}
//方法
public void close()
{
try
{
conn.close();
conn = null;
}catch(SQLException ex)
{
}
}
}

Answer 3

java.lang.NullPointerException  出现这个异常一般是你代码字母输入错误,你好好检查一下

Answer 4

找到原因了！   原因是，在XP上装了 SQLSERVER2000， 系统没有打开 1433 端口， 必须去微软的网站上下载一个补丁，补丁装好后，系统打开1433端口后，就OK了，代码没有问题！
   注： 不打补丁，手动更改别的端口号也不行，必须要打补丁。