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First Servlet, Jdbc program :(

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posted 23 years ago

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Hi,
I am trying to write a code that retrieves info from database and show it on the web. I couldn't view it through Tomcat, I don't understand the reason. Can anyone explain it to me?
This is my code:

<fontsize ="+0">
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
public class ShowEmployees extends HttpServlet
{
 Connection conn = null;

public void init() throws ServletException
{
try
{
    DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
         conn = DriverManager.getConnection ("jdbc    [img]http://www.javaranch.com/ubb/redface.gif[/img]racle:thin:@host","userid","password");
}

catch(SQLException e)
{throw new UnavailableException("Unable to connect");
}
catch(Exception e)
{throw new UnavailableException("Error:" + e);
}
}

public void service(HttpServletRequest request, HttpServletResponse response) 
throws ServletException, IOException
{
  response.setContentType("text/html");
  PrintWriter out = response.getWriter();
  
 try
  {
  String sql = "Select E.name from Employees E ";
Statement st = conn.createStatement();
ResultSet rs = st.executeQuery(sql);

out.println("<HTML>");
out.println("<HEAD><title> Show Employees </title></head>");
out.println("Body");
out.println("<table border = \"1\" cellapdding =\"3\">");
out.println("<tr>");
out.println("<th>Name</th>");
out.println("</tr>");

while (rs.next())
{out.println("<tr>");
     out.println("<td>" + rs.getString("Name")+ "</td>");
 out.println("</tr>");
 
}

out.println("</table>");
out.println("</body></html>");
rs.close();
st.close();
 }
  catch(SQLException e)
  {
  out.println("<HE> DATABSE CURRENTLY unavailable.</h2>");
  }
  out.close();
}
}
</font>

I am using correct userid and password. I tried a Jdbc program seperately it works fine. But here it throws Exception.
Just couple of lines of the exception.
javax.servlet.ServletException: Cannot allocate servlet instance for path /examples/servlet/ShowEmployees
root cause
java.lang.NoClassDefFoundError: oracle/jdbc/driver/OracleDriver
Thanks,
Vanitha.

[This message has been edited by Vanitha Sugumaran (edited November 18, 2001).]

Kyle Brown

author

Posts: 3892

posted 23 years ago

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From the exception given it's clear that the oracle drivers aren't on the classpath that Tomcat is using...
Kyle
------------------
Kyle Brown,
Author of Enterprise Java (tm) Programming with IBM Websphere
See my homepage at http://members.aol.com/kgb1001001 for other WebSphere information.

Kyle Brown, Author of Persistence in the Enterprise and Enterprise Java Programming with IBM Websphere, 2nd Edition
See my homepage at http://www.kyle-brown.com/ for other WebSphere information.

Mike Curwen

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posted 23 years ago

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Your stand-alone program will use the System CLASSPATH, and thus find your Oracle drivers.

Tomcat 4.0.x does not use System CLASSPATH, so you must include your Oracle drivers in the library directory <tomcat-home>/common/lib

This makes it available to any application running under Tomcat, or you can alternately place classes.zip (the Oracle drivers) under the <webcontext>/WEB-INF/lib directory of each webapp that needs db connections.

I also seem to recall that Tomcat doesn't like zip'd files, so simply rename classes.zip to classes.jar

Hope that helps.

Vanitha Sugumaran

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Posts: 356

posted 23 years ago

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Thanks Kyle and Mike for your replies.
I copied the classes12.zip, modified to jar file, I kept the classes.jar file in <tomcat home>/common/lib --> didn't work same error.
<tomcat home>/server/lib --> didn't work.
I couldn't find lib dir in the webapps/web-inf directory.
I don't know where else should I keep the classes12.jar file, can anyone give some suggestions please?
Thanks.
Vanitha

Vanitha Sugumaran

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Posts: 356

posted 23 years ago

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Hi,
I have a seperate Jdbc program in the tomcat directory it is working, if I mix it with servlet then it is not working what might be the problem?
this is my code for jdbc program:

<font size="+0">
import java.sql.*;
public class EmployeeI
{
static ResultSet rset;

public static ResultSet getResultSet() throws SQLException 
  {
    // Load the Oracle JDBC driver
    DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
    // Connect to the database             
  // You can use either the fully specified SQL*net syntax or a short cut
    // syntax as <host>:<port>:<sid>.  The example uses the short cut syntax.
    Connection conn =
      DriverManager.getConnection ("jdbc  [img]http://www.javaranch.com/ubb/redface.gif[/img]racle:thin:@host",
                                   "userid", "pass");
    // Create a Statement
    Statement stmt = conn.createStatement ();
    // Select the ENAME column from the EMP table
    ResultSet rset = stmt.executeQuery ("select * from Employees");
    // Iterate through the result and print the employee names
    return rset;
  
  }
  
  
public static void main(String s[]) throws SQLException
{
ResultSet ss = getResultSet();

while(ss.next()) System.out.println(ss.getString(1));
}
  
  
  
}                                  
</font>

After keeping the classess.zip do we have specify any path name?
I have to finish my class project with in a week, so if anyone can solve my problem that would be great.
Vanitha.
[This message has been edited by Vanitha Sugumaran (edited November 19, 2001).]

Vanitha Sugumaran

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posted 23 years ago

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Do I have to change anything in server.xml?
Vanitha.

James Redpath

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Posts: 13

posted 21 years ago

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For Oracle JDBC the key for Apache Jakarta Tomcat 5 is to place the classes111.zip file in the subdirectory common/lib with the jar extension. So rename the Oracle file classes111.zip to classes111.jar and copy to <installed directory>/common/lib/classes111.jar. Then stop and restart the server. It should work.

Harsha Huddar

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Posts: 23

posted 21 years ago

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If you are using JDK 1.4.x you'll need ojdbc.jar(from Oracle) in common\lib