Connecting with Java

This guide shows how to connect your Java app to a TimescaleDB database using the PostgreSQL JDBC driver , parse command-line arguments, and run a basic query. 
 Variables 
 To connect to a TimescaleDB database, the following parameters are required. You can find these details in the Elestio service overview page of your TimescaleDB service. 
 
 
 
 
 Variable 
 
 
 Description 
 
 
 Purpose 
 
 
 
 
 
 
 USER 
 
 
 TimescaleDB (PostgreSQL) username 
 
 
 Identifies the database user with access privileges 
 
 
 
 
 PASSWORD 
 
 
 TimescaleDB password 
 
 
 Authenticates the user against the TimescaleDB database 
 
 
 
 
 HOST 
 
 
 Hostname of the TimescaleDB instance 
 
 
 Specifies the server address of the database 
 
 
 
 
 PORT 
 
 
 Port for TimescaleDB (usually 5432) 
 
 
 Specifies the network port for connections 
 
 
 
 
 DATABASE 
 
 
 Name of the TimescaleDB database 
 
 
 Specifies which database to access 
 
 
 
 
 These values can usually be found in the Elestio service overview details as shown in the image below, make sure to take a copy of these details and add it to the code moving ahead. 
 
 Prerequisites 
 Install Java & JDBC driver 
 Check if Java is installed by running: 
 java -version 
 If not installed, install it first and then download and install  JDBC  driver from  https://jdbc.postgresql.org/download/ or if you have Maven installed, run the following command with updated version of the driver: 
 mvn org.apache.maven.plugins:maven-dependency-plugin:2.8:get \ 
 -Dartifact=org.postgresql:postgresql:42.7.5:jar \
 -Ddest=postgresql-42.7.5.jar 
 Code 
 Once all prerequisites are set up, create a new file named  TDB.java and add the following code: 
 import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.HashMap;
import java.util.Map;

public class TDB {

 static class Config {
 String host, port, database, username, password;

 Config(String host, String port, String database, String username, String password) {
 this.host = host;
 this.port = port;
 this.database = database;
 this.username = username;
 this.password = password;
 }

 String getJdbcUrl() {
 return String.format("jdbc:postgresql://%s:%s/%s?sslmode=require", host, port, database);
 }

 boolean isComplete() {
 return host != null && port != null && database != null && username != null && password != null;
 }
 }

 static Map<String, String> parseArgs(String[] args) {
 Map<String, String> map = new HashMap<>();
 for (int i = 0; i < args.length - 1; i += 2) {
 map.put(args[i], args[i + 1]);
 }
 return map;
 }

 public static void main(String[] args) {
 try {
 Class.forName("org.postgresql.Driver");

 Map<String, String> argMap = parseArgs(args);
 Config cfg = new Config(
 argMap.get("-host"),
 argMap.get("-port"),
 argMap.get("-database"),
 argMap.get("-username"),
 argMap.get("-password")
 );

 if (!cfg.isComplete()) {
 System.err.println("Missing required arguments. Example usage:");
 System.err.println("java -cp postgresql-42.7.5.jar:. TDB -host <HOST> -port <PORT> -database <DB> -username <USER> -password <PASS>");
 return;
 }

 try (Connection conn = DriverManager.getConnection(cfg.getJdbcUrl(), cfg.username, cfg.password)) {
 System.out.println("Connected to TimescaleDB database successfully.");

 Statement stmt = conn.createStatement();
 ResultSet rs = stmt.executeQuery("SELECT current_database(), current_user, version()");

 while (rs.next()) {
 System.out.println("Database: " + rs.getString(1));
 System.out.println("User: " + rs.getString(2));
 System.out.println("Version: " + rs.getString(3));
 }

 rs.close();
 stmt.close();
 }

 } catch (ClassNotFoundException e) {
 System.err.println("PostgreSQL JDBC driver not found.");
 e.printStackTrace();
 } catch (SQLException e) {
 System.err.println("Connection or query error:");
 e.printStackTrace();
 }
 }
} 
 To execute the script, open the terminal or command prompt and navigate to the directory where  TDB.java . Once in the correct directory, run the script with the command (Update the variables with actual values acquired from previous steps). 
 javac TDB.java 
 java -cp postgresql-42.7.5.jar:. TDB -host HOST -port PORT -database DATABASE -username USERNAME -password PASSWORD 
 If the connection is successful, the terminal will display output similar to: 
 Connected to TimescaleDB database successfully.
Database: elestio
User: postgres
Version: PostgreSQL 14.13 (Debian 14.13-1.pgdg120+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 12.2.0-14) 12.2.0, 64-bit