Обсуждение: No suitable driver found for jdbc:postgresql [error]

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No suitable driver found for jdbc:postgresql [error]

От
Jonathan Camilleri
Дата:
1. Upon logging to SQL shell the following is being displayed:
Server [localhost]:
Database [postgres]:
Port [5432]:
Username [postgres]:
psql (9.0.4)
WARNING: Console code page (437) differs from Windows code page (1252)
         8-bit characters might not work correctly. See psql reference
         page "Notes for Windows users" for details.
Type "help" for help.

Where do I find the mentioned article?

2. When running a test program, sourced from Core Java Volume 2 (7th Edition), the following error is being displayed:
java.sql.SQLException: No suitable driver found for jdbc:postgresql:COREJAVA;cre
ate=true
        at java.sql.DriverManager.getConnection(DriverManager.java:602)
        at java.sql.DriverManager.getConnection(DriverManager.java:185)
        at TestDB.getConnection(TestDB.java:82)
        at TestDB.runTest(TestDB.java:43)
        at TestDB.main(TestDB.java:20)

In order to enable JDK to connect to the library files, I copied over postgresql-8.4-702.jdbc3.jar, and, 
postgresql-8.4-702.jdbc4.jar to C:\Program Files\Java\jre6\lib\ext.

It was assumed that the file naming indicates type 3 and type 4 respectively, and, I was intending to use type 4, since it is more efficient to use a library that translates Java to the database language for Postgre:

postgresql-8.4-702.jdbc3.jar

  • A type 3 driver is a pure Java client library that uses a database-independent protocol to communicate database requests to a server component, which then translates the requests into a database-specific protocol. This can simplify deployment since the database-dependent code is located only on the server.

    postgresql-8.4-702.jdbc4.jar 

  • A type 4 driver is a pure Java library that translates JDBC requests directly to a database-specific protocol.

TestDB.java
/**
   @version 1.01 2004-09-24
   @author Cay Horstmann (all rights reserved)
*/

import java.sql.*;
import java.io.*;
import java.util.*;

/**
   This program tests that the database and the JDBC 
   driver are correctly configured.
*/
class TestDB
{  
   public static void main (String args[])
   {  
      try
      {  
         runTest();
      }
      catch (SQLException ex)
      {  
         while (ex != null)
         {  
            ex.printStackTrace();
            ex = ex.getNextException();
         }
      }
      catch (IOException ex)
      {  
         ex.printStackTrace();
      }
   }

   /**
      Runs a test by creating a table, adding a value, showing the table contents, and 
      removing the table.
   */
   public static void runTest()
      throws SQLException, IOException
   {
      Connection conn = getConnection();
      try
      {
         Statement stat = conn.createStatement();
         
         stat.execute("CREATE TABLE Greetings (Message CHAR(20))");
         stat.execute("INSERT INTO Greetings VALUES ('Hello, World!')");
         
         ResultSet result = stat.executeQuery("SELECT * FROM Greetings");
         result.next();
         System.out.println(result.getString(1));
         stat.execute("DROP TABLE Greetings");      
      }
      finally
      {
         conn.close();
      }
   }

   /**
      Gets a connection from the properties specified
      in the file database.properties
      @return the database connection
   */
   public static Connection getConnection()
      throws SQLException, IOException
   {  
      Properties props = new Properties();
      FileInputStream in = new FileInputStream("database.properties");
      props.load(in);
      in.close();

      String drivers = props.getProperty("jdbc.drivers");
      if (drivers != null)
         System.setProperty("jdbc.drivers", drivers);
      String url = props.getProperty("jdbc.url");
      String username = props.getProperty("jdbc.username");
      String password = props.getProperty("jdbc.password");

      return DriverManager.getConnection(url, username, password);
   }
}

database.properties
dbc.drivers=org.postgresql.Driver
jdbc.url=jdbc:postgresql:COREJAVA;create=true
jdbc.username=postgre
jdbc.password=

command line
Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\Documents and Settings\Jon>echo %CLASSPATH%
.;.;C:\PROGRA~1\JMF21~1.1E\lib\sound.jar;C:\PROGRA~1\JMF21~1.1E\lib\jmf.jar;C:\P
ROGRA~1\JMF21~1.1E\lib;C:\Program Files\Java\external_jars\junit4.9b2\junit4.9b2
\junit-4.9b2.jar;C:\Program Files\PostgreSQL\pgJDBC;

C:\Documents and Settings\Jon>cd c:\Program Files\PostgreSQL\pgJDBC

C:\Program Files\PostgreSQL\pgJDBC>dir
 Volume in drive C has no label.
 Volume Serial Number is D80F-8634

 Directory of C:\Program Files\PostgreSQL\pgJDBC

09/07/2011  15:42    <DIR>          .
09/07/2011  15:42    <DIR>          ..
03/04/2011  23:22           502,118 postgresql-8.4-702.jdbc3.jar
03/04/2011  23:22           539,510 postgresql-8.4-702.jdbc4.jar
09/07/2011  15:42    <DIR>          scripts
09/07/2011  15:42         5,759,102 uninstall-pgjdbc.exe
               3 File(s)      6,800,730 bytes
               3 Dir(s)  37,139,398,656 bytes free

C:\Program Files\PostgreSQL\pgJDBC>




How can I get the program running?


--
Jonathan Camilleri

Mobile (MT): 00356 7982 7113
E-mail: camilleri.jon@gmail.com
Please consider your environmental responsibility before printing this e-mail.
 
I usually reply to e-mails within 2 business days.  If it's urgent, give me a call.

Re: No suitable driver found for jdbc:postgresql [error]

От
Rodrigo Gonzalez
Дата:
On 07/09/2011 12:56 PM, Jonathan Camilleri wrote:
Notes for Windows users
http://www.postgresql.org/docs/9.0/static/app-psql.html

Re: No suitable driver found for jdbc:postgresql [error]

От
Jon80
Дата:
On Jul 9, 6:32 pm, rjgonz...@estrads.com.ar (Rodrigo Gonzalez) wrote:
> On 07/09/2011 12:56 PM, Jonathan Camilleri wrote:> /Notes for Windows users/
>
> http://www.postgresql.org/docs/9.0/static/app-psql.html

How does this link answer my questions?

Re: No suitable driver found for jdbc:postgresql [error]

От
Adrian Klaver
Дата:
On Tuesday, July 12, 2011 6:07:28 am Jon80 wrote:
> On Jul 9, 6:32 pm, rjgonz...@estrads.com.ar (Rodrigo Gonzalez) wrote:
> > On 07/09/2011 12:56 PM, Jonathan Camilleri wrote:> /Notes for Windows
> > users/
> >
> > http://www.postgresql.org/docs/9.0/static/app-psql.html
>
> How does this link answer my questions?

It answers your first question on where the "Notes for Windows users" is located.

Your second question is a little more involved. From the error message it looks
like your jdbc driver is no being found. Not sure if it a cut and paste error
but you have:

*database.properties*
dbc.drivers=org.postgresql.Driver
jdbc.url=jdbc:postgresql:COREJAVA;create=true
jdbc.username=postgre
jdbc.password=

The first line should be jdbc.drivers=org.postgresql.Driver .

You might have more luck with an answer on the jdbc list:
http://mail.postgresql.org/mj/mj_wwwusr/domain=postgresql.org?func=lists-long-
full&extra=pgsql-jdbc
--
Adrian Klaver
adrian.klaver@gmail.com

Re: No suitable driver found for jdbc:postgresql [error]

От
Craig Ringer
Дата:
On 9/07/2011 11:56 PM, Jonathan Camilleri wrote:

In order to enable JDK to connect to the library files, I copied over postgresql-8.4-702.jdbc3.jar, and, 
postgresql-8.4-702.jdbc4.jar to C:\Program Files\Java\jre6\lib\ext.

Argh, don't do that! You're messing with *every* java program on the system, some of which could have their own bundled copies of different versions of the PostgreSQL JDBC drivers. Exciting and messy things can happen.

Just add the JDBC driver to the classpath using the standard "java -classpath" argument, CLASSPATH env var, or Classpath: jar manifest entry. See the Java documentation.

When you bundle your app into a .war or .jar for production use, you typically bundle the JDBC driver within the app jar. See the documentation on the jar file format.


As for why your program doesn't run even when the driver is on the classpath: you don't seem to be loading it. In a Java SE environment you need to force the classloader to find and register a JDBC driver class before the JDBC DriverManager can find it and use it to handle JDBC connection URLs. That's usually done with a manual classloader call, like:


        Thread.currentThread().getContextClassLoader().loadClass("org.postgresql.Driver");

See the PgJDBC documentation for more detail. Note that the docs use the old-style static "Class.forName(...)" call, which is fine in simple J2SE environments but unwise if you start building modular apps, using OSGi or app servers, etc.

It was assumed that the file naming indicates type 3 and type 4 respectively

"Type 3" and "Type 4" sound like inventions of the author of your textbook for the purposes of classifying and describing different approaches to writing drivers - though I could be wrong, of course.

The "3" and "4" in PgJDBC refer to the version of the JDBC spec that driver is for. JDBC4 drivers can only be used on newer JDKs, so a JDBC3 driver has to be available for people who use older JDKs.

and, I was intending to use type 4, since it is more efficient to use a library that translates Java to the database language for Postgre:

"Postgres" or "PostgreSQL".

PgJDBC is a "type 4" driver according to that classification scheme, whether you use the JDBC3 or JDBC4 version.

--
Craig Ringer

POST Newspapers 276 Onslow Rd, Shenton Park Ph: 08 9381 3088 Fax: 08 9388 2258 ABN: 50 008 917 717 http://www.postnewspapers.com.au/