README.md

🧠 10.2 Introducing the Interfaces of JDBC

• There are 4 kkey interfaces in JDBC which are implemented in JDBC driver

• Different vendors of databases provided different implementations. E.g. the jar for PostgreSQL is postgresql-9.4-1201.jdbc4.jar

• Here are interfaces of JDBC:

  1. Driver - knows how to get a connection to DB
  2. Connection - knows how to communicatte with DB
  3. Statement - knows how to run SQL
  4. ResultSet - knows whhat is returned from select statement

• The implementing classes of these interfaces all have the name of vendor name + name of interface , e.g. FooDriver

• Here is an example of using JDBC akin to what you would see in the exam:

public static void main(String[] args) throws SQLException {
    String url = "jdbc:derby:zoo";
    try (Connection conn = DriverManager.getConnection(url);
        Statement stmt = conn.createStatement();
        ResultSet rs = stmt.executeQuery("select name from animal")) {
        
        while(rs.next()) {
            System.out.println(rs.getString(1));
        }
    }
}

• This program will print the following:

Elsa
Zelda
Ester
Eddie
Zoe

• If the URL was using FooDriver, the DriverManager would return an instance of FooConnection
• The conn.createStatement() returns an instance of FooStatement
• The stmt.executeQuery() returns an instance of FooResultSet