Test connection to a Database using Java (Simple main class)

TestConnection.java

package com.example.jdbc_postgres;

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

/**
 * Test connection to a Database using Java
 * 
 * @author Fernando Lozano
 *
 */
public class TestConnection {

	/**
	 * JDBC URL
	 * 
	 * Examples:
	 * 
	 * Oracle Thin: jdbc:oracle:thin:@//localhost:1521/XE DB2:
	 * jdbc:db2://127.0.0.1:50000/SAMPLE PostgreSQL:
	 * jdbc:postgresql://127.0.0.1:5432/test HSQLDB:
	 * jdbc:hsqldb:hsql://127.0.0.1:1476 HSQLDB Embedded: jdbc:hsqldb:file:filepath
	 * MySQL: jdbc:mysql://127.0.0.1:3306/test
	 * 
	 */
	private final static String DB_URL = "jdbc:postgresql://localhost/example";
	private final static String USER = "admin";
	private final static String PASS = "admin";
	private final static String CREATE_TABLE = "CREATE TABLE EXAMPLE_TABLE (id INTEGER not NULL, text_field VARCHAR(255), PRIMARY KEY ( id ))";
	private final static String INSERT = "INSERT INTO EXAMPLE_TABLE VALUES (1, 'hello')";
	private final static String SELECT = "SELECT * FROM EXAMPLE_TABLE";
	private final static String DROP = "DROP TABLE EXAMPLE_TABLE";

	/**
	 * Driver class
	 * 
	 * Examples:
	 * 
	 * Oracle Thin: oracle.jdbc.driver.OracleDriver DB2: com.ibm.db2.jcc.DB2Driver
	 * PostgreSQL: org.postgresql.Driver HSQLDB: org.hsqldb.jdbcDriver HSQLDB
	 * Embedded: org.hsqldb.jdbcDriver MySQL: com.mysql.jdbc.Driver
	 * 
	 */
	private final static String DRIVER = "org.postgresql.Driver";

	private final static boolean autosave = false;

	public static void main(String[] args) {
		Connection conn = null;
		Statement stmt = null;

		try {

			Class.forName(DRIVER);

			System.out.println("Connecting to database…");
			Properties props = new Properties();
			props.setProperty("user", USER);
			props.setProperty("password", PASS);
			if (autosave) {
				props.setProperty("autosave", "ALWAYS");
			}
			conn = DriverManager.getConnection(DB_URL, props);
			conn.setAutoCommit(false);
			System.out.println("Connected.");

			stmt = conn.createStatement();
			try {
				stmt.executeUpdate(CREATE_TABLE);
				System.out.println("Created table.");
			} catch (SQLException e) {
				if (e.toString().contains("already exists")) {
					System.out.println("Table already exists, omiting...");
				} else {
					e.printStackTrace();
					throw e;
				}
			}

			try {
				stmt.executeUpdate(INSERT);
				System.out.println("Inserted row.");
				try {
					stmt.executeUpdate(INSERT);
				} catch (SQLException e) {
					System.err.println("Error inserting.");
				}

			} catch (SQLException e) {
				if (e.toString().contains("duplicate key value violates unique constraint")) {
					System.err.println("Failed inserting row.");
				} else {
					e.printStackTrace();
					throw e;
				}
			}

			ResultSet rs = stmt.executeQuery(SELECT);
			while (rs.next()) {
				System.out.println("ID: " + rs.getString("id") + ", TEXT_FIELD: " + rs.getString("text_field"));
			}

			stmt.executeUpdate(DROP);
			System.out.println("Dropped table.");

		} catch (SQLException se) {
			System.err.println("SQLException:");
			se.printStackTrace();

		} catch (Exception e) {
			e.printStackTrace();

		} finally {
			try {
				if (stmt != null)
					conn.close();
			} catch (SQLException se) {
			} // do nothing
			try {
				if (conn != null)
					conn.close();
			} catch (SQLException se) {
				se.printStackTrace();
			}
		}
	}
}