Connect with Java

This example connects to PostgreSQL® service from Java, making use of JDBC Driver.

Variables

These are the placeholders you will need to replace in the code sample:

Variable	Description
HOSTNAME	Hostname for PostgreSQL connection, from the service overview page
PORT	Port for PostgreSQL connection, from the service overview page
DATABASE	Database Name for PostgreSQL connection, from the service overview page
PASSWORD	avnadmin password, from the service overview page

Prerequisites

For this example you will need the PostgreSQL Driver:

1. If you have maven version >= 2+, run the code:

   mvn org.apache.maven.plugins:maven-dependency-plugin:2.8:get -Dartifact=org.postgresql:postgresql:42.3.2:jar -Ddest=postgresql-42.3.2.jar

2. Manually the jar could be downloaded from https://jdbc.postgresql.org/download/

Code

Add the following to PostgresqlExample.java and replace the placeholder with the PostgreSQL URI:

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Locale;

public class PostgresqlExample {
  public static void main(String[] args) throws ClassNotFoundException {
    String host, port, databaseName, userName, password;
    host = port = databaseName = userName = password = null;
    for (int i = 0; i < args.length - 1; i++) {
      switch (args[i].toLowerCase(Locale.ROOT)) {
        case "-host": host = args[++i]; break;
        case "-username": userName = args[++i]; break;
        case "-password": password = args[++i]; break;
        case "-database": databaseName = args[++i]; break;
        case "-port": port = args[++i]; break;
      }
    }
    // JDBC allows to have nullable username and password
    if (host == null || port == null || databaseName == null) {
      System.out.println("Host, port, database information is required");
      return;
    }
    Class.forName("org.postgresql.Driver");
    try (final Connection connection =
                 DriverManager.getConnection("jdbc:postgresql://" + host + ":" + port + "/" + databaseName + "?sslmode=require", userName, password);
         final Statement statement = connection.createStatement();
         final ResultSet resultSet = statement.executeQuery("SELECT version()")) {

      while (resultSet.next()) {
        System.out.println("Version: " + resultSet.getString("version"));
      }
    } catch (SQLException e) {
      System.out.println("Connection failure.");
      e.printStackTrace();
    }
  }
}

This code creates a PostgreSQL client and opens a connection to the database. Then runs a query checking the database version and prints the response

Before running the code, change:

• HOST to HOSTNAME
• PORT: to PORT
• DATABASE to DATABASE
• PASSWORD to PASSWORD

To run the code:

javac PostgresqlExample.java && java -cp postgresql-42.2.24.jar:. PostgresqlExample -host HOST -port PORT -database DATABASE -username avnadmin -password PASSWORD

If the script runs successfully, the outputs should be the PostgreSQL version running in your service like:

Version: PostgreSQL 13.4 on x86_64-pc-linux-gnu, compiled by gcc, a cdda7373b4 p 9751fce1e6, 64-bit