-----急急急!基础问题,各位应该可以解答!------
saper 2001-12-15 09:05:47 在windows2000下 安装了jdk1.3.1,tomcat3.2.3,设置如下:
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path=%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;d:\jdk1.3.1\bin;
java_home=d:\jdk1.3.1
tomcat_home=d:\tomcat3.2.3
classpath=.;d:\jdk1.3.1\lib\dt.jar;d:\jdk1.3.1\lib\tools.jar;d:\tomcat3.2.3\servlet.jar;d:\tomcat3.2.3\webserver.jar;
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test.jsp 放在 d:\tomcat3.2.3\webapps\ROOT\jsp\ 下 (jsp 目录为自己新建)
<HTML>
<head>
<meta http-equiv="Content-Type" conntent="text/html; charset=gb2312">
</head>
<BODY>
<%@ page language="java" import="java.sql.*" %>
<jsp:useBean id="sql_bean" scope="page" class="test.faq" />
<%
ResultSet rs=sql_bean.executeQuery("select * from forum_user");
while(rs.next()){
out.println("<li>"+rs.getString(1)+"</li>");
}
rs.close();
%>
</BODY>
</HTML>
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javabean: faq.java编译后放在d:\tomcat3.2.3\webapps\WEB_INF\classes\test 下面
package test;
import java.io.*;
import java.sql.*;
public class faq {
String sDBDriver="oracle.jdbc.driver.OracleDriver";
String sConnStr="jdbc:oracle:thin:ex_user/ex_user@192.168.0.1:1521:oradb";
Connection conn=null ;
ResultSet rs=null;
public faq(){
try{
Class.forName(sDBDriver);
}
catch(java.lang.ClassNotFoundException e){
System.err.println("faq():"+e.getMessage());
}
}
public ResultSet executeQuery(String sql){
rs=null;
try{
conn=DriverManager.getConnection(sConnStr);
Statement stmt=conn.createStatement();
rs=stmt.executeQuery(sql);
}
catch(SQLException ex){
System.err.println("aq.executeQuery:"+ex.getMessage());
}
return rs;
}
}
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运行 http://localhost:8081/jsp/test.jsp 出现以下错误:
javax.servlet.ServletException
......以下省略(太多了)
Root cause:
java.lang.NullPointerException
..........
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注:以上程序在JDeveloper中可以调试通过的