java：
Properties props = new Properties();
FileInputStream in = new FileInputStream("database.properties");
props.load(in);
in.close();
String drivers = props.getProperty("jdbc.driver");
String url = props.getProperty("jdbc.url");
String username = props.getProperty("jdbc.username");
String password = props.getProperty("jdbc.password");
return DriverManager.getConnection(url, username, password);
database.properties：
jdbc.drivers=org.postgresql.Driver
jdbc.url=jdbc:postgresql:COREJAVA
jdbc.username=dbuser
jdbc.password=secret
ok
