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分享非常奇怪的问题
我编写了一个数据库连接类，使用test.java文件,在jdk编译,全部正常。
可是我把.class移到tomcat中，使用jsp访问，抛出
java.lang.NullPointerException
at test.test.testDBOperator.executeQueryInt(testDBOperator.java:110)
at org.apache.jsp.test2$jsp._jspService(test2$jsp.java:94)
错误。
全部代码如下，非常简单。
大虾们，帮帮我吧，我快被折磨完蛋了。
可是我把.class移到tomcat中，使用jsp访问，抛出
java.lang.NullPointerException
at test.test.testDBOperator.executeQueryInt(testDBOperator.java:110)
at org.apache.jsp.test2$jsp._jspService(test2$jsp.java:94)
错误。
全部代码如下，非常简单。
大虾们，帮帮我吧，我快被折磨完蛋了。
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bigglacier 2004-01-06
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====================================
既然报
NoClassDefFoundError: oracle/jdbc/driver/OracleDriver
这个错，说明没有找到Oracle的驱动啊。
估计还是你没把驱动放到Tomcat 的lib/extend目录下
==========================================
问题解决了，我把class12.zip放在jdk的lib/extend目录下就可以了，看来是没有找到类包。
可他没报import错误。
可我通过电脑属性classpath已经指定了，
在tomcat中的lib目录下装了oracle的驱动文件，
而且在tomcat的catalina.bat也已经制定了，
也通过web-inf目录下的lib文件夹也放了，
看来对于类包的一些知识我还不够了解，
谁能详细的解释一下关于类包的指定，以及这几个方法那个优先权最高等，
在线等待，结贴，给分（我已经快没分了）55555555555555。。。
既然报
NoClassDefFoundError: oracle/jdbc/driver/OracleDriver
这个错，说明没有找到Oracle的驱动啊。
估计还是你没把驱动放到Tomcat 的lib/extend目录下
==========================================
问题解决了，我把class12.zip放在jdk的lib/extend目录下就可以了，看来是没有找到类包。
可他没报import错误。
可我通过电脑属性classpath已经指定了，
在tomcat中的lib目录下装了oracle的驱动文件，
而且在tomcat的catalina.bat也已经制定了，
也通过web-inf目录下的lib文件夹也放了，
看来对于类包的一些知识我还不够了解，
谁能详细的解释一下关于类包的指定，以及这几个方法那个优先权最高等，
在线等待，结贴，给分（我已经快没分了）55555555555555。。。
chenyongcsdn 2004-01-05
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不是已经报NullPointerException了吗！
你的testDBOperator.java ，110行出错，你去看一下就知道了！
你的testDBOperator.java ，110行出错，你去看一下就知道了！
dropship 2004-01-05
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还有了，你要定位编译后生成的servlet文件，位于work/standalone下面，看看那一行出的异常
wangnanwn 2004-01-05
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上面那位仁兄提到的空格是不能有的？
还有你在tomcat中的lib目录下装了oracle的驱动文件吧？
还有你在tomcat中的lib目录下装了oracle的驱动文件吧？
寒冬 2004-01-05
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你先按照楼上说的，改改试试
stonecsdn 2004-01-05
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url= "jdbc:oracle:thin:@192.9.200.36:1521:123 ";//123后面根了一个空格
private static String user= "system ";
private static String password= "manager ";
是不是这几行结尾中空格的问题？
private static String user= "system ";
private static String password= "manager ";
是不是这几行结尾中空格的问题？
bigglacier 2004-01-05
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全部代码如下，非常简单，就是数据库访问：
testDBOperator.java
------------------------------
package test.test;
import java.io.*;
import java.sql.*;
import java.util.*;
import oracle.jdbc.driver.*;
final public class testDBOperator{
private final static boolean FLAG_CHECKIN = true; // wether use checkIn sql convert
private final static boolean FLAG_CHECKOUT = true; // wether use checkOut sql convert
private final static int SUCCEED = 0; // Operation succeed
private final static int FAILURE = -1; // Operation failure
private static String url= "jdbc:oracle:thin:@192.9.200.36:1521:123 ";
private static String user= "system ";
private static String password= "manager ";
// private java.sql.Connection conn = null;
//private java.sql.Statement stmt = null;
//private java.sql.ResultSet rs = null;
private ResultSetMetaData meta = null;
private int columnCount;
/**
/* construct function
*/
public testDBOperator() {
}
final public static String checkIn(String a_strInput) throws Exception
{
if (a_strInput == null) return " ";
try{
if (FLAG_CHECKIN)
return new String(a_strInput.getBytes(), "GB2312 ");
else
return a_strInput;
} catch(Exception e) {
throw new Exception( "Error Occur in checkIn. "+ e.getMessage());
}
}
/**
* Convert db string to page string
* @param string : input string
* @return string converted
*/
final public static String checkOut(String a_strInput) throws Exception
{
if (a_strInput == null) return " ";
try{
if (FLAG_CHECKOUT)
return new String(a_strInput.getBytes( "GB2312 "));
else
return a_strInput;
}catch(Exception e){
throw new Exception( "Error Occur in checkOut. "+ e.getMessage());
}
}
final public static int executeQueryInt (String sql)
throws SQLException,Exception
{
int rtn = FAILURE;
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
conn=DriverManager.getConnection(url,user,password);
//mps use
//conn = DbConnectionManager.getConnection();
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
if (rs.next()) rtn = rs.getInt(1);
//Logged program for debug
//Mpslog.record (SystemProperty.INFO,sql);
//System.out.println(rtn);
//rtn = stmt.executeUpdate(sql);
// stmt.close();
// conn.close();
} catch (SQLException sqle) {
conn.rollback();
throw new SQLException ( "Error Occur in executeUpdate. " + sqle.getMessage());
} catch (Exception ex) {
conn.rollback();
throw new Exception ( "Error Occur in executeUpdate. " + ex.getMessage());
} finally {
if (stmt != null) stmt.close();
//stmt.close();
//if (!conn.isClosed() ) conn.close();
if (conn != null && !conn.isClosed()) conn.close();
//conn.close();
}
return rtn;
}
}
-----------------------
test.jsp
----------------------
<html >
<head >
<%@ page language = "java " % >
<%@ page import= " java.io.* " % >
<%@ page import = " java.sql.* " % >
<%@ page import = "test.test.* " % >
<%@ page import = "java.util.* " % >
<title >Untitled Document </title >
<meta http-equiv= "Content-Type " content= "text/html; charset=gb2312 " >
<style type= "text/css " >
<!--
font {
font-size: 9pt;
}
p {
font-size: 9pt;
}
td {
font-size: 9pt;
}
-- >
</style >
</head >
<body bgcolor= "#FFFFFF " text= "#000000 " leftmargin= "0 " topmargin= "0 " marginwidth= "0 " marginheight= "0 " >
<%
try {
//String sql = " ";
//String sqlcount = " ";
//sql = "select sysdate from dual ";
String sql= "select count(a1) from test ";
testDBOperator op = new testDBOperator();
int tmp = op.executeQueryInt(sql);
out.println( " Testing executeQueryString -- sysdate : " + tmp);
} catch (SQLException sqle){
sqle.printStackTrace();
} catch (Exception ex) {
ex.printStackTrace();
}
% >
</body >
</html >
----------------------------
testDBOperator.java
------------------------------
package test.test;
import java.io.*;
import java.sql.*;
import java.util.*;
import oracle.jdbc.driver.*;
final public class testDBOperator{
private final static boolean FLAG_CHECKIN = true; // wether use checkIn sql convert
private final static boolean FLAG_CHECKOUT = true; // wether use checkOut sql convert
private final static int SUCCEED = 0; // Operation succeed
private final static int FAILURE = -1; // Operation failure
private static String url= "jdbc:oracle:thin:@192.9.200.36:1521:123 ";
private static String user= "system ";
private static String password= "manager ";
// private java.sql.Connection conn = null;
//private java.sql.Statement stmt = null;
//private java.sql.ResultSet rs = null;
private ResultSetMetaData meta = null;
private int columnCount;
/**
/* construct function
*/
public testDBOperator() {
}
final public static String checkIn(String a_strInput) throws Exception
{
if (a_strInput == null) return " ";
try{
if (FLAG_CHECKIN)
return new String(a_strInput.getBytes(), "GB2312 ");
else
return a_strInput;
} catch(Exception e) {
throw new Exception( "Error Occur in checkIn. "+ e.getMessage());
}
}
/**
* Convert db string to page string
* @param string : input string
* @return string converted
*/
final public static String checkOut(String a_strInput) throws Exception
{
if (a_strInput == null) return " ";
try{
if (FLAG_CHECKOUT)
return new String(a_strInput.getBytes( "GB2312 "));
else
return a_strInput;
}catch(Exception e){
throw new Exception( "Error Occur in checkOut. "+ e.getMessage());
}
}
final public static int executeQueryInt (String sql)
throws SQLException,Exception
{
int rtn = FAILURE;
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
conn=DriverManager.getConnection(url,user,password);
//mps use
//conn = DbConnectionManager.getConnection();
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
if (rs.next()) rtn = rs.getInt(1);
//Logged program for debug
//Mpslog.record (SystemProperty.INFO,sql);
//System.out.println(rtn);
//rtn = stmt.executeUpdate(sql);
// stmt.close();
// conn.close();
} catch (SQLException sqle) {
conn.rollback();
throw new SQLException ( "Error Occur in executeUpdate. " + sqle.getMessage());
} catch (Exception ex) {
conn.rollback();
throw new Exception ( "Error Occur in executeUpdate. " + ex.getMessage());
} finally {
if (stmt != null) stmt.close();
//stmt.close();
//if (!conn.isClosed() ) conn.close();
if (conn != null && !conn.isClosed()) conn.close();
//conn.close();
}
return rtn;
}
}
-----------------------
test.jsp
----------------------
<html >
<head >
<%@ page language = "java " % >
<%@ page import= " java.io.* " % >
<%@ page import = " java.sql.* " % >
<%@ page import = "test.test.* " % >
<%@ page import = "java.util.* " % >
<title >Untitled Document </title >
<meta http-equiv= "Content-Type " content= "text/html; charset=gb2312 " >
<style type= "text/css " >
<!--
font {
font-size: 9pt;
}
p {
font-size: 9pt;
}
td {
font-size: 9pt;
}
-- >
</style >
</head >
<body bgcolor= "#FFFFFF " text= "#000000 " leftmargin= "0 " topmargin= "0 " marginwidth= "0 " marginheight= "0 " >
<%
try {
//String sql = " ";
//String sqlcount = " ";
//sql = "select sysdate from dual ";
String sql= "select count(a1) from test ";
testDBOperator op = new testDBOperator();
int tmp = op.executeQueryInt(sql);
out.println( " Testing executeQueryString -- sysdate : " + tmp);
} catch (SQLException sqle){
sqle.printStackTrace();
} catch (Exception ex) {
ex.printStackTrace();
}
% >
</body >
</html >
----------------------------
