| Pedro n/a 2005-04-09, 8:26 pm |
| Hello,
I'm quite new at java and I was just following a tutorial when I bumped
with a horrible exception. The program compiled smoothly, but when I runned
it I got an error message and I wasn't able to found any track through the
internet. So I would like to know if any of you could help me. Here is the
error track spilled from my VM:
org.postgresql.util.PSQLException: The connection attempt failed.
org.postgresql.util.PSQLException: The connection attempt failed.
at
org.postgresql.core.v3. ConnectionFactoryImp
l. openConnectionImpl(C
onnectionFactoryImpl
.java:136)
at
org.postgresql.core.ConnectionFactory. openConnection(Conne
ctionFactory.java:65)
at
org.postgresql.jdbc2. AbstractJdbc2Connect
ion.<init> (AbstractJdbc2Connec
tion.java:117)
at
org.postgresql.jdbc3. AbstractJdbc3Connect
ion.<init> (AbstractJdbc3Connec
tion.java:30)
at
org.postgresql.jdbc3.Jdbc3Connection.<init>(Jdbc3Connection.java:24)
at org.postgresql.Driver.connect(Driver.java:235)
at java.sql.DriverManager. getConnection(Driver
Manager.java:512)
at java.sql.DriverManager. getConnection(Driver
Manager.java:171)
at HelloPostgresql.<init>(HelloPostgresql.java:34)
at HelloPostgresql. main(HelloPostgresql
.java:118)
Caused by: java.net. UnknownHostException
: localhost
at java.net.PlainSocketImpl. connect(PlainSocketI
mpl.java:153)
at java.net.Socket.connect(Socket.java:452)
at java.net.Socket.connect(Socket.java:402)
at java.net.Socket.<init>(Socket.java:309)
at java.net.Socket.<init>(Socket.java:124)
at org.postgresql.core.PGStream.<init>(PGStream.java:58)
at
org.postgresql.core.v3. ConnectionFactoryImp
l. openConnectionImpl(C
onnectionFactoryImpl
.java:77)
... 9 more
A little note: I think that attempt to connect wasn't completed because it
didn't generate any entry in the postgresql log files.
Here's the code I compiled...
/**
* A demo program to show how jdbc works with postgresql
* Nick Fankhauser 10/25/01
* nickf@ontko.com or nick@fankhausers.com
* This program may be freely copied and modified
* Please keep this header intact on unmodified versions
* The rest of the documentation that came with this demo program
* may be found at http://www.fankhausers.com/postgresql/jdbc
*/
import java.sql.*; // All we need for JDBC
import java.text.*;
import java.io.*;
public class HelloPostgresql
{
Connection db; // A connection to the database
Statement sql; // Our statement to run queries with
DatabaseMetaData dbmd; // This is basically info the driver delivers
// about the DB it just connected to. I use
// it to get the DB version to confirm the
// connection in this example.
//CONSTRUCTOR
public HelloPostgresql(Stri
ng argv[]) throws ClassNotFoundExcepti
on,
SQLException
{
String database = argv[0];
String username = argv[1];
String password = argv[2];
Class.forName("org.postgresql.Driver"); //load the driver
db = DriverManager.getConnection("jdbc:postgresql:"+database,
username,
password); //connect to the db
dbmd = db.getMetaData(); //get MetaData to confirm connection
System.out.println("Connection to "+dbmd. getDatabaseProductNa
me()+" "+
dbmd. getDatabaseProductVe
rsion()+" successful.\n");
sql = db.createStatement(); //create a statement that we can use later
String sqlText = "create table jdbc_demo (code int, text varchar(20))";
System.out.println("Executing this command: "+sqlText+"\n");
sql. executeUpdate(sqlTex
t);
sqlText = "insert into jdbc_demo values (1,'One')";
System.out.println("Executing this command: "+sqlText+"\n");
sql. executeUpdate(sqlTex
t);
sqlText = "insert into jdbc_demo values (3,'Four')";
System.out.println("Executing this command twice: "+sqlText+"\n");
sql. executeUpdate(sqlTex
t);
sql. executeUpdate(sqlTex
t);
sqlText = "update jdbc_demo set text = 'Three' where code = 3";
System.out.println("Executing this command: "+sqlText+"\n");
sql. executeUpdate(sqlTex
t);
System.out.println (sql.getUpdateCount()+
" rows were update by this statement\n");
System.out.println("\n\nNow demostrating a prepared statement...");
sqlText = "insert into jdbc_demo values (?,?)";
System.out.println("The Statement looks like this: "+sqlText+"\n");
System.out.println("Looping three times filling in the fields...\n");
PreparedStatement ps = db. prepareStatement(sql
Text);
for (int i=10;i<13;i++)
{
System.out.println(i+"...\n");
ps.setInt(1,i); //set column one (code) to i
ps.setString(2,"HiHo"); //Column two gets a string
ps.executeUpdate();
}
ps.close();
System.out.println("Now executing the command: "+
"select * from jdbc_demo");
ResultSet results = sql.executeQuery("select * from jdbc_demo");
if (results != null)
{
while (results.next())
{
System.out.println("code = "+results.getInt("code")+
"; text = "+results.getString(2)+"\n");
}
}
results.close();
sqlText = "drop table jdbc_demo";
System.out.println("Executing this command: "+sqlText+"\n");
sql. executeUpdate(sqlTex
t);
db.close();
}
public static void correctUsage()
{
System.out.println("\nIncorrect number of arguments.\nUsage:\n "+
"java \n");
System.exit(1);
}
public static void main (String args[])
{
if (args.length != 3) correctUsage();
try
{
HelloPostgresql demo = new HelloPostgresql(args
);
}
catch (Exception ex)
{
System.out.println("***Exception:\n"+ex);
ex.printStackTrace();
}
}
}
Thanks In Advance,
Pedro
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