postgres/src/interfaces/jdbc/example/metadata.java

package example;

import java.io.*;
import java.sql.*;

/*
 * This example application is not really an example. It actually performs
 * some tests on various methods in the DatabaseMetaData and ResultSetMetaData
 * classes.
 *
 * To use it, simply have a database created. It will create some work tables
 * and run tests on them.
 */

public class metadata
{
	Connection	db;		// The connection to the database
	Statement	st;		// Our statement to run queries with
	DatabaseMetaData dbmd;	// This defines the structure of the database

	/*
	 * These are the available tests on DatabaseMetaData
	 */
	public void doDatabaseMetaData() throws SQLException
	{
		if (doTest("getProcedures() - should show all available procedures"))
			displayResult(dbmd.getProcedures(null, null, null));

		if (doTest("getProcedures() with pattern - should show all circle procedures"))
			displayResult(dbmd.getProcedures(null, null, "circle%"));

		if (doTest("getProcedureColumns() on circle procedures"))
			displayResult(dbmd.getProcedureColumns(null, null, "circle%", null));

		if (doTest("getTables()"))
			displayResult(dbmd.getTables(null, null, null, null));

		if (doTest("getColumns() - should show all tables, can take a while to run"))
			displayResult(dbmd.getColumns(null, null, null, null));

		if (doTest("getColumns() - should show the test_b table"))
			displayResult(dbmd.getColumns(null, null, "test_b", null));

		if (doTest("getColumnPrivileges() - should show all tables"))
			displayResult(dbmd.getColumnPrivileges(null, null, null, null));

		if (doTest("getPrimaryKeys()"))
			displayResult(dbmd.getPrimaryKeys(null, null, null));

		if (doTest("getTypeInfo()"))
			displayResult(dbmd.getTypeInfo());

	}

	/*
	 * These are the available tests on ResultSetMetaData
	 */
	public void doResultSetMetaData() throws SQLException
	{

		String sql = "select imagename,descr,source,cost from test_a,test_b,test_c where test_a.id=test_b.imageid and test_a.id=test_c.imageid";

		System.out.println("Executing query for tests");
		ResultSet rs = st.executeQuery(sql);
		ResultSetMetaData rsmd = rs.getMetaData();

		if (doTest("isCurrency()"))
			System.out.println("isCurrency on col 1 = " + rsmd.isCurrency(1) + " should be false\nisCurrency on col 4 = " + rsmd.isCurrency(4) + " should be true");

		// Finally close the query. Now give the user a chance to display the
		// ResultSet.
		//
		// NB: displayResult() actually closes the ResultSet.
		if (doTest("Display query result"))
		{
			System.out.println("Query: " + sql);
			displayResult(rs);
		}
		else
			rs.close();
	}

	/*
	 * This creates some test data
	 */
	public void init() throws SQLException
	{
		System.out.println("Creating some tables");
		cleanup();
		st.executeUpdate("create table test_a (imagename name,image oid,id int4)");
		st.executeUpdate("create table test_b (descr text,imageid int4,id int4)");
		st.executeUpdate("create table test_c (source text,cost money,imageid int4)");

		System.out.println("Adding some data");
		st.executeUpdate("insert into test_a values ('test1',0,1)");
		st.executeUpdate("insert into test_b values ('A test description',1,2)");
		st.executeUpdate("insert into test_c values ('nowhere particular','$10.99',1)");
	}

	/*
	 * This removes the test data
	 */
	public void cleanup() throws SQLException
	{
		try
		{
			st.executeUpdate("drop table test_a");
			st.executeUpdate("drop table test_b");
			st.executeUpdate("drop table test_c");
		}
		catch (Exception ex)
		{
			// We ignore any errors here
		}
	}

	public metadata(String args[]) throws ClassNotFoundException, FileNotFoundException, IOException, SQLException
	{
		String url = args[0];
		String usr = args[1];
		String pwd = args[2];

		// Load the driver
		Class.forName("org.postgresql.Driver");

		// Connect to database
		System.out.println("Connecting to Database URL = " + url);
		db = DriverManager.getConnection(url, usr, pwd);

		dbmd = db.getMetaData();
		st = db.createStatement();

		// This prints the backend's version
		System.out.println("Connected to " + dbmd.getDatabaseProductName() + " " + dbmd.getDatabaseProductVersion());

		init();

		System.out.println();

		// Now the tests
		if (doTest("Test DatabaseMetaData"))
			doDatabaseMetaData();

		if (doTest("Test ResultSetMetaData"))
			doResultSetMetaData();

		System.out.println("\nNow closing the connection");
		st.close();
		db.close();

		cleanup();
	}

	/*
	 * This asks if the user requires to run a test.
	 */
	public boolean doTest(String s)
	{
		System.out.println();
		System.out.print(s);
		System.out.print(" Perform test? Y or N:");
		System.out.flush();
		char c = ' ';
		try
		{
			while (!(c == 'n' || c == 'y' || c == 'N' || c == 'Y'))
			{
				c = (char)System.in.read();
			}
		}
		catch (IOException ioe)
		{
			return false;
		}

		return c == 'y' || c == 'Y';
	}

	/*
	 * This displays a result set.
	 * Note: it closes the result once complete.
	 */
	public void displayResult(ResultSet rs) throws SQLException
	{
		ResultSetMetaData rsmd = rs.getMetaData();
		int count = 0;

		// Print the result column names
		int cols = rsmd.getColumnCount();
		for (int i = 1;i <= cols;i++)
			System.out.print(rsmd.getColumnLabel(i) + (i < cols ? "\t" : "\n"));

		// now the results
		while (rs.next())
		{
			count++;
			for (int i = 1;i <= cols;i++)
			{
				Object o = rs.getObject(i);
				if (rs.wasNull())
					System.out.print("{null}" + (i < cols ? "\t" : "\n"));
				else
					System.out.print(o.toString() + (i < cols ? "\t" : "\n"));
			}
		}

		System.out.println("Result returned " + count + " rows.");

		// finally close the result set
		rs.close();
	}

	/*
	 * This process / commands (for now just /d)
	 */
	public void processSlashCommand(String line) throws SQLException
	{
		if (line.startsWith("\\d"))
		{
			if (line.startsWith("\\d "))
			{
				// Display details about a table
				String table = line.substring(3);
				displayResult(dbmd.getColumns(null, null, table, "%"));
			}
			else
			{
				String types[] = null;
				if (line.equals("\\d"))
					types = allUserTables;
				else if (line.equals("\\di"))
					types = usrIndices;
				else if (line.equals("\\dt"))
					types = usrTables;
				else if (line.equals("\\ds"))
					types = usrSequences;
				else if (line.equals("\\dS"))
					types = sysTables;
				else
					throw new SQLException("Unsupported \\d command: " + line);

				// Display details about all system tables
				//
				// Note: the first two arguments are ignored. To keep to the spec,
				//		 you must put null here
				//
				displayResult(dbmd.getTables(null, null, "%", types));
			}
		}
		else
			throw new SQLException("Unsupported \\ command: " + line);
	}

	private static final String allUserTables[] = {"TABLE", "INDEX", "SEQUENCE"};
	private static final String usrIndices[] = {"INDEX"};
	private static final String usrTables[] = {"TABLE"};
	private static final String usrSequences[] = {"SEQUENCE"};
	private static final String sysTables[] = {"SYSTEM TABLE", "SYSTEM INDEX"};

	/*
	 * Display some instructions on how to run the example
	 */
	public static void instructions()
	{
		System.out.println("\nThis is not really an example, but is used to test the various methods in\nthe DatabaseMetaData and ResultSetMetaData classes.\n");
		System.out.println("Useage:\n java example.metadata jdbc:postgresql:database user password [debug]\n\nThe debug field can be anything. It's presence will enable DriverManager's\ndebug trace. Unless you want to see screens of debug items, don't put anything in\nhere.");
		System.exit(1);
	}

	/*
	 * This little lot starts the test
	 */
	public static void main(String args[])
	{
		System.out.println("PostgreSQL metdata tester v6.4 rev 1\n");

		if (args.length < 3)
			instructions();

		// This line outputs debug information to stderr. To enable this, simply
		// add an extra parameter to the command line
		if (args.length > 3)
			DriverManager.setLogStream(System.err);

		// Now run the tests
		try
		{
			metadata test = new metadata(args);
		}
		catch (Exception ex)
		{
			System.err.println("Exception caught.\n" + ex);
			ex.printStackTrace();
		}
	}
}