DatabaseMetaData class to obtain information about the : Metadata DB Info « Database SQL JDBC « Java






DatabaseMetaData class to obtain information about the

  

/*
 * Copyright (c) 2000 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 2nd Edition.
 * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
 * You may study, use, and modify it for any non-commercial purpose.
 * You may distribute it non-commercially as long as you retain this notice.
 * For a commercial use license, or to purchase the book (recommended),
 * visit http://www.davidflanagan.com/javaexamples2.
 */

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
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"); // Driver class name
      String server = p.getProperty("server", ""); // JDBC URL for server
      String user = p.getProperty("user", ""); // db user name
      String password = p.getProperty("password", ""); // db password

      // These variables don't have defaults
      String database = null; // The db name (appended to server URL)
      String table = null; // The optional name of a table in the db

      // Parse the command-line args 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];
        else if (database == null)
          database = args[i]; // <dbname>
        else if (table == null)
          table = args[i]; // <table>
        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 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) {
      }
    }
  }
}

           
         
    
  








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