Jruby, JDBC, Netezza

Question

So anyways I have a java program like this and it totally works.

1 import java.sql.*;
2 import org.netezza.*;

class Conn {
 public static void main (String args []) throws SQLException {
  6         try{Class.forName ("org.netezza.Driver");
  7         }
  8         catch (ClassNotFoundException e) {
  9             System.out.println("You made it to here");
 10             e.printStackTrace();
 11         }
 12
 13         Connection conn = DriverManager.getConnection("jdbc:netezza://server/dbname", "user", "pass");
 14
 15         Statement stmt = conn.createStatement();
 16         ResultSet rset = stmt.executeQuery("SELECT 'foo'");
 17         while (rset.next()){
 18             System.out.println(rset.getString(1));
 19         }
 20         stmt.close();
 21         conn.close();
 22     }
 23 }

However, when I attempt to follow what seems like every vanilla JDBC + Jruby tutorial on the internet I get the ubiquitous error "NativeException: java.sql.SQLException: No suitable driver" with this code.

  1 require 'java'
  2 require 'jruby'
  3 require 'nzjdbc.jar'
  4 #F = java.io.File
  5 #class_loader = JRuby.runtime.jruby_class_loader
  6 #class_loader.add_url(F.new('path').to_url)
  7 #class_loader.add_url(F.new('nzjdbc.jar').to_url)
  8
  9 include_class "java.sql.DriverManager"
 10 include_class "org.netezza.Driver"
 11
 12 p $CLASSPATH
 13 p $LOAD_PATH
 14
 15 server = 'server'
 16 databaseName = 'dbname'
 17 user = 'user'
 18 pass = 'pass'
 19
 20 p DRVRMAN = org.netezza.Driver.new
 21
 22 begin
 23     #clazz = Java::JavaClass.for_name("org.netezza.Driver")
 24     clazz = java.lang.Class.for_name("org.netezza.Driver", true, JRuby.runtime.jruby_class_loader)
 25     #java.lang.Thread.currentThread.setContextClassLoader(JRuby.runtime.jruby_class_loader)
 26     #java.sql.DriverManager.registerDriver(Java::OrgNetezza::Driver.new)
 27     url = "jdbc:netezza://" + server + "/" + databaseName
 28     p url
 29     conn = DriverManager.getConnection(url, user, pass)
 30     stmt = conn.create_statement
 31     rs = stmt.execute_query("SELECT 2 + 2")
 32
 33     while rs.next
 34         p [rs.get_int(1)]
 35     end
 36 ensure
 37     rs.close rescue nil
 38     stmt.close rescue nil
 39     conn.close rescue nil
 40 end

and I have tried what seems like everything I could find to fix this issue including checking out the activerecord-jdbc and dbi-jdbc implementations. Its very frustrating and I guess I don't really understand whats going on besides having an issue with teh classloader, load path and the Classpath. Anyways, I was hoping someone could explain step by step how the DriverManager registers drivers in Java and why the java code totally succeeds while the ruby code (which seems equivalent) does not as well as help me mitigate these errors.

(Also any "install X gem" won't work in this instance as a large deal of bureaucracy must be overcome for anything new to be allowed into this system)

Answer 1

I have run into this scenario with Apache CXF. My favorite solution is to

not waste time making jruby code work and simply have a java class do that for you

, which is 100% guaranteed to work. In your case, you can compile/jar your Conn class and call it from jruby like

Java::Conn.main()

Your jar can be placed in jruby/lib.

PS: I see you have tried numerous ways to make it work. Probably Nick Sieger can provide some insight into these class loading issues.

Answer 2

While it doesn't address the specific issue of using your nzjdbc.jar, I can tell you that the code you have will work with postgresql.jar, so your issue must be specific to some quirk of your driver. I'm not sure what netezza is trying to do, but with the postgresql driver, org.postgresql.Driver has a static initialization block that simply calls javax.sql.DriverManager.registerDriver(new org.postgresql.Driver()), so simply loading that class is enough to get the driver registered.

Answer 3

When all else fails with classpath issues, I've found that putting jars in $JRUBY_HOME/lib always works.