package DBconn; import java.sql.*; /** * @author Administrator * * To change this generated comment edit the template variable "typecomment": * Window>Preferences>Java>Templates. * To enable and disable the creation of type comments go to * Window>Preferences>Java>Code Generation. */ public class DBconn { String strDBDriver = "sun.jdbc.odbc.JdbcOdbcDriver"; String strConn = "jdbc:odbc:flower"; Connection connect = null; ResultSet rs = null; Statement stmt=null;
可能性: 1、你的类放在class 目录下了吗? 2、WEB-INF目录下的web.xml文件为:<?xml version="1.0" encoding="ISO-8859-1"?> <!-- Copyright 2004 The Apache Software Foundation Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. --><web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" version="2.4"> <display-name>Welcome to Tomcat</display-name> <description> Welcome to Tomcat </description> <!-- JSPC servlet mappings start --> <servlet> <servlet-name>org.apache.jsp.index_jsp</servlet-name> <servlet-class>org.apache.jsp.index_jsp</servlet-class> </servlet> <servlet-mapping> <servlet-name>org.apache.jsp.index_jsp</servlet-name> <url-pattern>/index.jsp</url-pattern> </servlet-mapping><!-- JSPC servlet mappings end --></web-app>
别的没看出来什么问题,你也可以把查询语句写在bean
中,然后写个输出语句看下System.out.println();
odbc也配制了
在学校机房上的机子上我配制了可以运行
在我的机子就没有配制出来,
不过我很多同学也出现了一样的错误
import java.sql.*;
/**
* @author Administrator
*
* To change this generated comment edit the template variable "typecomment":
* Window>Preferences>Java>Templates.
* To enable and disable the creation of type comments go to
* Window>Preferences>Java>Code Generation.
*/
public class DBconn { String strDBDriver = "sun.jdbc.odbc.JdbcOdbcDriver";
String strConn = "jdbc:odbc:flower";
Connection connect = null;
ResultSet rs = null;
Statement stmt=null;
public DBconn() {
try {
Class.forName(strDBDriver);
} catch(java.lang.ClassNotFoundException e) {
System.err.print(e.getMessage());
}
}
public ResultSet executeQuery (String sql) {
try {
connect = DriverManager.getConnection(strConn);
stmt = connect.createStatement();
rs = stmt.executeQuery(sql);
} catch (SQLException ex) {
System.err.println(ex.getMessage());
}
return rs;
} }
后台的错误是:
java.lang.NullPointerException
org.apache.jsp.DBconn_jsp._jspService(DBconn_jsp.java:85)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
这是怎么回事?
1、你的类放在class 目录下了吗?
2、WEB-INF目录下的web.xml文件为:<?xml version="1.0" encoding="ISO-8859-1"?>
<!--
Copyright 2004 The Apache Software Foundation Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
--><web-app xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
version="2.4"> <display-name>Welcome to Tomcat</display-name>
<description>
Welcome to Tomcat
</description>
<!-- JSPC servlet mappings start --> <servlet>
<servlet-name>org.apache.jsp.index_jsp</servlet-name>
<servlet-class>org.apache.jsp.index_jsp</servlet-class>
</servlet> <servlet-mapping>
<servlet-name>org.apache.jsp.index_jsp</servlet-name>
<url-pattern>/index.jsp</url-pattern>
</servlet-mapping><!-- JSPC servlet mappings end --></web-app>