RE: [QUESTIONS] Java and Postgres

Make sure the postmaster is running with the -i option enabled. Java
uses TCP/IP to connect.

I'm forwarding you to the INTERFACES list just in case it's something
more.
-DEJ

> -----Original Message-----
> From: Ilhuicatzi Cortes Jose Henry
> [SMTP:ic94006(at)conejo(dot)ingenieria(dot)uatx(dot)mx]
> Sent: Wednesday, May 06, 1998 7:14 PM
> To: pgsql-questions(at)postgreSQL(dot)org
> Subject: [QUESTIONS] Java and Postgres
>
>
>
> Hi:
> I'm trying to make an application with Java and Postgresql. The
> application will be made for Win95 plataform.
>
> I'm makiing tests of connection wiht a postgres program example
> which is Basic.java, in the example url,database,usr and password
> are
> directly into the program. The program is below.
>
> import java.io.*;
> import java.sql.*;
> import java.text.*;
>
> /**
> * This example tests the basic components of the JDBC driver, and
> shows
> * how even the simplest of queries can be implemented.
> *
> * To use this example, you need a database to be in existence. This
> example
> * will create a table called basic.
> *
> */
>
> public class Basic
> {
> Connection db; // The connection to the database
> Statement st; // Our statement to run queries with
>
> public Basic() throws ClassNotFoundException, FileNotFoundException,
> IOException, SQLException
> {
> String url = "jdbc:postgresql://148.219.122.11:5432/ic94006";
> String usr = "ic94006";
> String pwd = "???????";
>
> // Load the driver
> Class.forName("postgresql.Driver");
>
> // Connect to database
> System.out.println("Connecting to Database URL = " + url);
> db = DriverManager.getConnection(url, usr, pwd);
>
> System.out.println("Connected...Now creating a statement");
> st = db.createStatement();
>
> // Clean up the database (in case we failed earlier) then
> initialise
> cleanup();
>
> // Now run tests using JDBC methods
> doexample();
>
> // Clean up the database
> cleanup();
>
> // Finally close the database
> System.out.println("Now closing the connection");
> st.close();
> db.close();
>
> }
>
> /**
> * This drops the table (if it existed). No errors are reported.
> */
> public void cleanup()
> {
> try {
> st.executeUpdate("drop table basic");
> } catch(Exception ex) {
> // We ignore any errors here
> }
> }
>
> /**
> * This performs the example
> */
> public void doexample() throws SQLException
> {
> System.out.println("\nRunning tests:");
>
> // First we need a table to store data in
> st.executeUpdate("create table basic (a int2, b int2)");
>
> // Now insert some data, using the Statement
> st.executeUpdate("insert into basic values (1,1)");
> st.executeUpdate("insert into basic values (2,1)");
> st.executeUpdate("insert into basic values (3,1)");
>
> // For large inserts, a PreparedStatement is more efficient,
> because it
> // supports the idea of precompiling the SQL statement, and to
> store
> // directly, a Java object into any column. PostgreSQL doesnt
> support
> // precompiling, but does support setting a column to the value of
> a
> // Java object (like Date, String, etc).
> //
> // Also, this is the only way of writing dates in a datestyle
> independent
> // manner. (DateStyles are PostgreSQL's way of handling different
> methods
> // of representing dates in the Date data type.)
> PreparedStatement ps = db.prepareStatement("insert into basic
> values (?,?)");
> for(int i=2;i<5;i++) {
> ps.setInt(1,4); // "column a" = 5
> ps.setInt(2,i); // "column b" = i
> ps.executeUpdate(); // executeUpdate because insert returns
> no data
> }
> ps.close(); // Always close when we are done
> with it
>
> // Finally perform a query on the table
> System.out.println("performing a query");
> ResultSet rs = st.executeQuery("select a, b from basic");
> if(rs!=null) {
> // Now we run through the result set, printing out the result.
> // Note, we must call .next() before attempting to read any
> results
> while(rs.next()) {
> int a = rs.getInt("a"); // This shows how to get the value by
> name
> int b = rs.getInt(2); // This shows how to get the value by
> column
> System.out.println(" a="+a+" b="+b);
> }
> rs.close(); // again, you must close the result when done
> }
>
> // Now run the query again, showing a more efficient way of
> getting the
> // result if you don't know what column number a value is in
> System.out.println("performing another query");
> rs = st.executeQuery("select * from basic where b>1");
> if(rs!=null) {
> // First find out the column numbers.
> //
> // It's best to do this here, as calling the methods with the
> column
> // numbers actually performs this call each time they are
> called. This
> // really speeds things up on large queries.
> //
> int col_a = rs.findColumn("a");
> int col_b = rs.findColumn("b");
>
> // Now we run through the result set, printing out the result.
> // Again, we must call .next() before attempting to read any
> results
> while(rs.next()) {
> int a = rs.getInt(col_a); // This shows how to get the value by
> name
> int b = rs.getInt(col_b); // This shows how to get the value by
> column
> System.out.println(" a="+a+" b="+b);
> }
> rs.close(); // again, you must close the result when done
> }
>
> // The last thing to do is to drop the table. This is done in the
> // cleanup() method.
> }
>
> /**
> * Display some instructions on how to run the example
> */
> public static void instructions()
> {
> System.out.println("\nThis example tests the basic components of
> the JDBC driver, demonstrating\nhow to build simple queries in
> java.\n");
> System.out.println("Useage:\n java example.basic
> jdbc:postgresql:database user password [debug]\n\nThe debug field can
> be anything. It's presence will enable DriverManager's\ndebug trace.
> Unless you want to see screens of items, don't put anything in\
> nhere.");
> System.exit(1);
> }
>
> /**
> * This little lot starts the test
> */
> public static void main(String args[])
> {
> System.out.println("PostgreSQL basic test v6.3 rev 1\n");
>
> //if(args.length<3)
> // instructions();
>
> // This line outputs debug information to stderr. To enable this,
> simply
> // add an extra parameter to the command line
>
> DriverManager.setLogStream(System.err);
>
> // Now run the tests
> try {
> Basic test = new Basic();
> } catch(Exception ex) {
> System.err.println("Exception caught.\n"+ex);
> ex.printStackTrace();
> }
> }
> }
>
> The problem occurs when i run this program from Win95 and the Java
> releases
> next exception.
>
> DriverManager.initialize: jdbc.drivers = null
> JDBC DriverManager initialized
> registerDriver: driver [className = postgresql.Driver,context=null,
> postgresql(dot)Driver(at)1cc771
> Connecting to Database URL =
> jdbc:postgresql://148.219.122.11:5432/ic94006
>
> DriverManager.getConnection("jdbc:postgresql://148.219.122.11:5432/ic9
> 4006")
>
> java.sql.SQL.Exception:Connection failed:java.net.ConnectException
> Connection refused
> at postgresql.Connection.<init> (Connection.java:184)
> at postgresql.Driver.connect(Driver.java:87)
>
> getConnection failed: java.sql.SQLException: Connection failed:
> java.net.ConnectException: Connection refused
> Exception caught.
> java.sql.SQLException: Connection failed: java.net.ConnectException:
> Connection refused
> at postgresql.Connection.<init>(Connection.java: 184)
> at postgresql.Driver.connect(Driver.java:87)
>
>
>
> I think that problem is in the port number, i use 5423 in port
> number but
> i don't know if this port number is OK, or can i use other port
> number?
>
> i use Java class that came with Postgresql and i think that run
> correctly,
> but when i run the program, Java releases those exceptions.
>
> If my program have any error i hope that yours notice me.
>
> Thanks.
> J. Henry Ilhuicatzi Cortes.
> Universidad Autonoma de Tlaxcala
>
>
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