我在使用javabeans连接数据库时,老是出现500报错.请各位高手指点,小弟万分感激.
我的bean的内容如下;
/**
* 创建日期 2007-4-17
*
* TODO 要更改此生成的文件的模板,请转至
* 窗口 - 首选项 - Java - 代码样式 - 代码模板
*/
package dd;
import java.sql.*;
/**
* @author Administrator* TODO 要更改此生成的类型注释的模板,请转至
* 窗口 - 首选项 - Java - 代码样式 - 代码模板
*/
public class DBContext{
String CLASSFORNAME="com.microsoft.jdbc.sqlserver.SQLServerDrive";
String url="jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=test";
String user="sa";
String password="123";
Connection con=null;
ResultSet rs=null;public DBContext(){
try{
Class.forName(CLASSFORNAME); }
catch(Exception e){
System.err.println("DBContext():"+e.getMessage());
}
} public ResultSet executeQuery(String sql){
rs=null;
try
{
con=DriverManager.getConnection(url,user,password);
Statement stmt=con.createStatement();
rs=stmt.executeQuery(sql);
}catch(SQLException e){
System.err.println("DBContext.executeQuery:"+e.getMessage()); }
return rs;
}
}
jsp页面的内容如下:
<%@ page contentType="text/html;charset=gb2312"%>
<%@ page import="java.sql.*"%>
<html>
<body>
<%@ page import="dd.DBContext"%>
<jsp:useBean id="S" class="dd.DBContext" scope="session" />
<%
String sql="select * from test";
ResultSet tt=S.executeQuery(sql);
while(tt.next()) {
out.println("您的第一个字段内容为:"+tt.getString("name"));
out.println("您的第二个字段内容为:"+tt.getString("password"));
}%>
<%out.print("数据库操作成功,恭喜你");%>
</body>
</html>
报错内容如下:
HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:372)
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)
root cause java.lang.NullPointerException
org.apache.jsp.index_jsp._jspService(index_jsp.java:62)
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)
note The full stack trace of the root cause is available in the Apache Tomcat/5.0.28 logs.
--------------------------------------------------------------------------------Apache Tomcat/5.0.28
我的bean的内容如下;
/**
* 创建日期 2007-4-17
*
* TODO 要更改此生成的文件的模板,请转至
* 窗口 - 首选项 - Java - 代码样式 - 代码模板
*/
package dd;
import java.sql.*;
/**
* @author Administrator* TODO 要更改此生成的类型注释的模板,请转至
* 窗口 - 首选项 - Java - 代码样式 - 代码模板
*/
public class DBContext{
String CLASSFORNAME="com.microsoft.jdbc.sqlserver.SQLServerDrive";
String url="jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=test";
String user="sa";
String password="123";
Connection con=null;
ResultSet rs=null;public DBContext(){
try{
Class.forName(CLASSFORNAME); }
catch(Exception e){
System.err.println("DBContext():"+e.getMessage());
}
} public ResultSet executeQuery(String sql){
rs=null;
try
{
con=DriverManager.getConnection(url,user,password);
Statement stmt=con.createStatement();
rs=stmt.executeQuery(sql);
}catch(SQLException e){
System.err.println("DBContext.executeQuery:"+e.getMessage()); }
return rs;
}
}
jsp页面的内容如下:
<%@ page contentType="text/html;charset=gb2312"%>
<%@ page import="java.sql.*"%>
<html>
<body>
<%@ page import="dd.DBContext"%>
<jsp:useBean id="S" class="dd.DBContext" scope="session" />
<%
String sql="select * from test";
ResultSet tt=S.executeQuery(sql);
while(tt.next()) {
out.println("您的第一个字段内容为:"+tt.getString("name"));
out.println("您的第二个字段内容为:"+tt.getString("password"));
}%>
<%out.print("数据库操作成功,恭喜你");%>
</body>
</html>
报错内容如下:
HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:372)
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)
root cause java.lang.NullPointerException
org.apache.jsp.index_jsp._jspService(index_jsp.java:62)
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)
note The full stack trace of the root cause is available in the Apache Tomcat/5.0.28 logs.
--------------------------------------------------------------------------------Apache Tomcat/5.0.28
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这条语句应该放在Class.forName(CLASSFORNAME);的下面.
空指针错误
看看DBContext打印的信息是什么
String CLASSFORNAME="com.microsoft.jdbc.sqlserver.SQLServerDrive";
少个r
String CLASSFORNAME="com.microsoft.jdbc.sqlserver.SQLServerDriver";