// This example is from _Java Examples in a Nutshell_. (http://www.oreilly.com)
// Copyright (c) 1997 by David Flanagan
// This example is provided WITHOUT ANY WARRANTY either expressed or implied.
// You may study, use, modify, and distribute it for non-commercial purposes.
// For any commercial use, see http://www.davidflanagan.com/javaexamples

import java.sql.*;
import java.util.Properties;

/**
 * This class uses the DatabaseMetaData class to obtain information about
 * the database, the JDBC driver, and the tables in the database, or about
 * the columns of a named table.
 **/
public class GetDBInfo {
  public static void main(String[] args) {
    Connection c = null;  // The JDBC connection to the database server
    try {
      // Look for the properties file DB.props in the same directory as
      // this program.  It will contain default values for the various
      // parameters needed to connect to a database
      Properties p = new Properties();
      try { p.load(GetDBInfo.class.getResourceAsStream("DB.props")); }
      catch (Exception e) {}
      
      // Get default values from the properties file
      String driver = p.getProperty("driver");          // Name of driver class
      String server = p.getProperty("server", "");      // JDBC URL for server
      String user = p.getProperty("user", "");          // db user name
      String password = p.getProperty("password", "");  // db account password

      // These variables don't have defaults
      String database = null;   // The db name (to be appended to server URL)
      String table = null;      // The optional name of a table in the db
      
      // Parse the command-line arguments to override the default values above
      for(int i = 0; i < args.length; i++) {
        if (args[i].equals("-d")) driver = args[++i];        // -d <driver>
        else if (args[i].equals("-s")) server = args[++i];   // -s <server>
        else if (args[i].equals("-u")) user = args[++i];     // -u <user>
        else if (args[i].equals("-p")) password = args[++i]; // -p <password>
        else if (database == null) database = args[i];       // <dbname>
        else if (table == null) table = args[i];             // <tablename>
        else throw new IllegalArgumentException("Unknown argument: "+args[i]);
      }

      // Make sure that at least a server or a database were specified. 
      // If not, we have no idea what to connect to, and cannot continue.
      if ((server.length() == 0) && (database.length() == 0))
        throw new IllegalArgumentException("No database or server specified.");

      // Load the db driver, if any was specified.
      if (driver != null) Class.forName(driver);
      
      // Now attempt to open a connection to the specified database on
      // the specified server, using the specified name and password
      c = DriverManager.getConnection(server+database, user, password);

      // Get the DatabaseMetaData object for the connection.  This is the
      // object that will return us all the data we're interested in here.
      DatabaseMetaData md = c.getMetaData();

      // Display information about the server, the driver, etc.
      System.out.println("DBMS: " + md.getDatabaseProductName() + 
                         " " + md.getDatabaseProductVersion());
      System.out.println("JDBC Driver: " + md.getDriverName() + 
                         " " + md.getDriverVersion());
      System.out.println("Database: " + md.getURL());
      System.out.println("User: " + md.getUserName());

      // Now, if the user did not specify a table, then display a list of
      // all tables defined in the named database.  Note that tables are
      // returned in a ResultSet, just like query results are.
      if (table == null) {
        System.out.println("Tables:");
        ResultSet r = md.getTables("", "", "%", null);
        while(r.next()) System.out.println("\t" + r.getString(3));
      }
      // Otherwise, list all columns of the specified table.
      // Again, information about the columns is returned in a ResultSet
      else {
        System.out.println("Columns of " + table + ": ");
        ResultSet r = md.getColumns("", "", table, "%");
        while(r.next()) 
          System.out.println("\t" + r.getString(4) + " : " + r.getString(6));
      }
    }
    // Print an error message if anything goes wrong.
    catch (Exception e) {
      System.err.println(e);
      if (e instanceof SQLException)
        System.err.println(((SQLException)e).getSQLState());
      System.err.println("Usage: java GetDBInfo [-d <driver] [-s <dbserver>]\n"
                         + "\t[-u <username>] [-p <password>] <dbname>");
    }
    // Always remember to close the Connection object when we're done!
    finally { 
      try { c.close(); } catch (Exception e) {}
    }
  }
}