In-Memory Databases in Composition Environment

Some times in java programming, It is a big pain deal with Collections and Arrays, it’s not so easy getting the flexibility presented in our sql engine.
Using hsqldb open source database engine you can manage your in-memory data the same way that your persistent databases.
I prepared a small example to show this funcionality.

Create a java project.

Add hsqldb.jar in your java build path.

Try this example.

import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement;  import org.hsqldb.Server;   public class Customers {            private Server server;                 public void start() throws Exception {                                        String serverProps = “database.0=mem:customers;”;                  server = new Server();         server.putPropertiesFromString(serverProps);            server.start();                              try {             Class.forName(“org.hsqldb.jdbcDriver”);         } catch (Exception e) {             e.printStackTrace();             System.out.println(“.setUp() error: ” + e.getMessage());         }                  try {                       Connection c = DriverManager.getConnection(“jdbc:hsqldb:mem:customers”);                        Statement s = (Statement) c.createStatement();                                   s.execute(“CREATE TABLE customers ( id INTEGER PRIMARY KEY, name CHAR(100), address CHAR(100) )”);                                       c.close();         }         catch(Exception e) {                       }                 }            public void insert(int id, String name, String address) throws Exception {                      Connection c = DriverManager.getConnection(“jdbc:hsqldb:mem:customers”);                     Statement s = (Statement) c.createStatement();                      s.execute(“INSERT INTO customers VALUES (” + String.valueOf(id) + “,'” + name + “‘,'” + address + “‘)”);            c.close();      }            public ResultSet read(String condition) throws Exception {           Connection c = DriverManager.getConnection(“jdbc:hsqldb:mem:customers”);                     Statement s = (Statement) c.createStatement();                     ResultSet rs = s.executeQuery(“SELECT * FROM customers ” + condition);                c.close();           return rs;      }            public void stop() {                      server.stop();                 }            public Customers() {                            }       public static void main(String[] args) throws Exception {           Customers customers = new Customers();                     customers.start();           customers.insert(1, “Alvaro Tejada”,”Perú”);           customers.insert(2, “Craig Cmehil”,”Germany”);           customers.insert(3, “Jim Spath”,”US”);           customers.insert(4, “Mark Yolton”,”US”);           customers.insert(5, “Mark Finnern”,”US”);           ResultSet rs = customers.read(“WHERE name like ‘%Mark%'”);                     while (rs.next()) {                System.out.println(rs.getString(“id”) + “-” + rs.getString(“name”) + “-” + rs.getString(“address”));                          }                customers.stop();      }  } 

See, you can select from your in-memory table using like condition:

  customers.insert(1, “Alvaro Tejada”,”Perú”);
  customers.insert(2, “Craig Cmehil”,”Germany”);
  customers.insert(3, “Jim Spath”,”US”);
  customers.insert(4, “Mark Yolton”,”US”);
  customers.insert(5, “Mark Finnern”,”US”);
  ResultSet rs = customers.read(“WHERE name like ‘%Mark%’“);  
  while (rs.next()) {
   System.out.println(rs.getString(“id”) + “-” + rs.getString(“name”) + “-” + rs.getString(“address”));   
  }

Console output:
4-Mark Yolton-US
5-Mark Finnern-US

Your comments are welcome,
Thanks and Regards,
Ignacio.