largeobjectmanager.java

PostgreSQL7.4.6 for Linux

/*-------------------------------------------------------------------------
 *
 * LargeObjectManager.java
 *      This class implements the large object interface to org.postgresql.
 *
 *      It provides methods that allow client code to create, open and delete
 *      large objects from the database. When opening an object, an instance of
 *      org.postgresql.largeobject.LargeObject is returned, and its methods
 *      then allow access to the object.
 *
 * Copyright (c) 2003, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/interfaces/jdbc/org/postgresql/largeobject/Attic/LargeObjectManager.java,v 1.10.4.1 2003/12/17 15:48:39 davec Exp $
 *
 *-------------------------------------------------------------------------
 */
package org.postgresql.largeobject;


import java.sql.ResultSet;
import java.sql.SQLException;
import org.postgresql.Driver;
import org.postgresql.core.BaseConnection;
import org.postgresql.fastpath.Fastpath;
import org.postgresql.fastpath.FastpathArg;
import org.postgresql.util.PSQLException;

/*
 * This class implements the large object interface to org.postgresql.
 *
 * <p>It provides methods that allow client code to create, open and delete
 * large objects from the database. When opening an object, an instance of
 * org.postgresql.largeobject.LargeObject is returned, and its methods then allow
 * access to the object.
 *
 * <p>This class can only be created by org.postgresql.Connection
 *
 * <p>To get access to this class, use the following segment of code:
 * <br><pre>
 * import org.postgresql.largeobject.*;
 *
 * Connection  conn;
 * LargeObjectManager lobj;
 *
 * ... code that opens a connection ...
 *
 * lobj = ((org.postgresql.PGConnection)myconn).getLargeObjectAPI();
 * </pre>
 *
 * <p>Normally, client code would use the getAsciiStream, getBinaryStream,
 * or getUnicodeStream methods in ResultSet, or setAsciiStream,
 * setBinaryStream, or setUnicodeStream methods in PreparedStatement to
 * access Large Objects.
 *
 * <p>However, sometimes lower level access to Large Objects are required,
 * that are not supported by the JDBC specification.
 *
 * <p>Refer to org.postgresql.largeobject.LargeObject on how to manipulate the
 * contents of a Large Object.
 *
 * @see java.sql.ResultSet#getAsciiStream
 * @see java.sql.ResultSet#getBinaryStream
 * @see java.sql.ResultSet#getUnicodeStream
 * @see java.sql.PreparedStatement#setAsciiStream
 * @see java.sql.PreparedStatement#setBinaryStream
 * @see java.sql.PreparedStatement#setUnicodeStream
 */
public class LargeObjectManager
{
	// the fastpath api for this connection
	private Fastpath fp;

	/*
	 * This mode indicates we want to write to an object
	 */
	public static final int WRITE = 0x00020000;

	/*
	 * This mode indicates we want to read an object
	 */
	public static final int READ = 0x00040000;

	/*
	 * This mode is the default. It indicates we want read and write access to
	 * a large object
	 */
	public static final int READWRITE = READ | WRITE;

	/*
	 * This prevents us being created by mere mortals
	 */
	private LargeObjectManager()
	{}

	/*
	 * Constructs the LargeObject API.
	 *
	 * <p><b>Important Notice</b>
	 * <br>This method should only be called by org.postgresql.Connection
	 *
	 * <p>There should only be one LargeObjectManager per Connection. The
	 * org.postgresql.Connection class keeps track of the various extension API's
	 * and it's advised you use those to gain access, and not going direct.
	 */
	public LargeObjectManager(BaseConnection conn) throws SQLException
	{
		// We need Fastpath to do anything
		this.fp = conn.getFastpathAPI();

		// Now get the function oid's for the api
		//
		// This is an example of Fastpath.addFunctions();
		//
		String sql;
		if (conn.getMetaData().supportsSchemasInTableDefinitions()) {
			sql = "SELECT p.proname,p.oid "+
				" FROM pg_catalog.pg_proc p, pg_catalog.pg_namespace n "+
				" WHERE p.pronamespace=n.oid AND n.nspname='pg_catalog' AND (";
		} else {
			sql = "SELECT proname,oid FROM pg_proc WHERE ";
		}
		sql += " proname = 'lo_open'" +
			" or proname = 'lo_close'" +
			" or proname = 'lo_creat'" +
			" or proname = 'lo_unlink'" +
			" or proname = 'lo_lseek'" +
			" or proname = 'lo_tell'" +
			" or proname = 'loread'" +
			" or proname = 'lowrite'";

		if (conn.getMetaData().supportsSchemasInTableDefinitions()) {
			sql += ")";
		}

		ResultSet res = conn.createStatement().executeQuery(sql);

		if (res == null)
			throw new PSQLException("postgresql.lo.init");

		fp.addFunctions(res);
		res.close();
		if (Driver.logDebug)
			Driver.debug("Large Object initialised");
	}

	/*
	 * This opens an existing large object, based on its OID. This method
	 * assumes that READ and WRITE access is required (the default).
	 *
	 * @param oid of large object
	 * @return LargeObject instance providing access to the object
	 * @exception SQLException on error
	 */
	public LargeObject open(int oid) throws SQLException
	{
		return new LargeObject(fp, oid, READWRITE);
	}

	/*
	 * This opens an existing large object, based on its OID
	 *
	 * @param oid of large object
	 * @param mode mode of open
	 * @return LargeObject instance providing access to the object
	 * @exception SQLException on error
	 */
	public LargeObject open(int oid, int mode) throws SQLException
	{
		return new LargeObject(fp, oid, mode);
	}

	/*
	 * This creates a large object, returning its OID.
	 *
	 * <p>It defaults to READWRITE for the new object's attributes.
	 *
	 * @return oid of new object
	 * @exception SQLException on error
	 */
	public int create() throws SQLException
	{
		FastpathArg args[] = new FastpathArg[1];
		args[0] = new FastpathArg(READWRITE);
		return fp.getInteger("lo_creat", args);
	}

	/*
	 * This creates a large object, returning its OID
	 *
	 * @param mode a bitmask describing different attributes of the new object
	 * @return oid of new object
	 * @exception SQLException on error
	 */
	public int create(int mode) throws SQLException
	{
		FastpathArg args[] = new FastpathArg[1];
		args[0] = new FastpathArg(mode);
		return fp.getInteger("lo_creat", args);
	}

	/*
	 * This deletes a large object.
	 *
	 * @param oid describing object to delete
	 * @exception SQLException on error
	 */
	public void delete(int oid) throws SQLException
	{
		FastpathArg args[] = new FastpathArg[1];
		args[0] = new FastpathArg(oid);
		fp.fastpath("lo_unlink", false, args);
	}

	/*
	 * This deletes a large object.
	 *
	 * <p>It is identical to the delete method, and is supplied as the C API uses
	 * unlink.
	 *
	 * @param oid describing object to delete
	 * @exception SQLException on error
	 */
	public void unlink(int oid) throws SQLException
	{
		delete(oid);
	}

}