rdfsource.java

这是外国一个开源推理机

		query.append(" AND localname ");
		if (_rdbms.emptyStringIsNull() && lname.length() == 0) {
			query.append("IS NULL");
		}
		else {
			query.append("= '");
			query.append(_rdbms.escapeString(lname));
			query.append("'");
		}

		try {
			Connection connection = _rdbms.getConnection();
			java.sql.Statement statement = connection.createStatement();
			ResultSet resultSet = statement.executeQuery(query.toString());

			if (resultSet.next()) {
				// URI was found
				result = resultSet.getInt(1);
			}

			resultSet.close();
			statement.close();
			connection.close();
		}
		catch (SQLException e) {
			throw new SailInternalException(e);
		}

		if (idURI != null) {
			// Store the fetched ID in the URI object for use in any subsequent requests
			idURI.setInternalId(result);
		}

		return result;

	}

	/**
	 * Gets the ID of the supplied BNode.
	 * 
	 * @return the ID of the supplied BNode, or 0 if the BNode was not found.
	 */
	protected int _getBNodeId(BNode bNode) {
		IdBNode idBNode = null;

		if (_isOwnValue(bNode)) {
			// ID is possibly stored in the BNode object
			idBNode = (IdBNode)bNode;

			int id = idBNode.getInternalId();
			if (id != 0) {
				return id;
			}
		}

		// Retrieve the ID from the database

		int result = 0;
		String nodeId = bNode.getID();

		StringBuffer query = new StringBuffer(150);
		query.append("SELECT id FROM " + RESOURCES_TABLE);
		query.append(" WHERE namespace = 0 AND localname = '");
		query.append(_rdbms.escapeString(nodeId));
		query.append("'");

		try {
			Connection connection = _rdbms.getConnection();
			java.sql.Statement statement = connection.createStatement();
			ResultSet resultSet = statement.executeQuery(query.toString());

			if (resultSet.next()) {
				// bnode was found
				result = resultSet.getInt(1);
			}

			resultSet.close();
			statement.close();
			connection.close();
		}
		catch (SQLException e) {
			throw new SailInternalException(e);
		}

		if (idBNode != null) {
			// Store the fetched ID in the BNode object for use in any subsequent requests
			idBNode.setInternalId(result);
		}

		return result;
	}

	/**
	 * Gets the ID of the supplied literal.
	 * 
	 * @return the ID of the supplied literal, or 0 if the literal was not found.
	 */
	protected int _getLiteralId(Literal literal) {
		IdLiteral idLiteral = null;

		if (_isOwnValue(literal)) {
			// ID is possibly stored in the Literal object
			idLiteral = (IdLiteral)literal;

			int id = idLiteral.getInternalId();
			if (id != 0) {
				return id;
			}
		}

		// Build query to retrieve the ID from the database

		// Note: the retrieved labels are compared to the label of the specified
		// literal because CLOB/BLOB-comparisons are not supported by Oracle and
		// SQL Server (and possibly others). The label's hash code is used to
		// make a first selection of possible matching literals.

		int result = 0;
		int datatypeId = 0;

		String label = literal.getLabel();
		String language = literal.getLanguage();
		URI datatype = literal.getDatatype();

		if (datatype != null) {
			datatypeId = _getURIId(datatype);

			if (datatypeId == 0) {
				// datatype not found so literal does not exist
				return 0;
			}
		}

		StringBuffer query = new StringBuffer(200);
		query.append("SELECT id, label FROM ");
		query.append(LITERALS_TABLE);
		query.append(" WHERE ");

		// labelHash
		query.append("labelHash = ");
		query.append(_getLabelHash(label));

		// datatype
		query.append(" AND datatype = " + datatypeId);

		// language
		query.append(" AND language");
		if (language == null) {
			query.append(" IS NULL");
		}
		else {
			query.append(" = '");
			query.append(_rdbms.escapeString(language));
			query.append("'");
		}

		try {
			Connection connection = _rdbms.getConnection();
			java.sql.Statement statement = connection.createStatement();
			ResultSet resultSet = statement.executeQuery(query.toString());

			while (resultSet.next()) {
				// a possibly matching literal was found, check its label
				String resultLabel = resultSet.getString(2);

				if (resultLabel == null) {
					resultLabel = "";
				}

				if (resultLabel.equals(label)) {
					// Label matches
					result = resultSet.getInt(1);
					break;
				}
			}

			resultSet.close();
			statement.close();
			connection.close();
		}
		catch (SQLException e) {
			throw new SailInternalException(e);
		}

		if (idLiteral != null) {
			// Store the fetched ID in the Literal object for use in any subsequent requests
			idLiteral.setInternalId(result);
		}

		return result;
	}

	protected boolean _isOwnValue(Value value) {
		return value instanceof IdValue &&
			((IdValue)value).getRdfSource() == this;
	}

	/**
	 * Gets the ID of the supplied namespace.
	 * 
	 * @return the ID of the supplied namespace, or 0 if the namespace was not
	 *         found.
	 */
	protected int _getNamespaceId(String namespace) {
		RdbmsNamespace n = (RdbmsNamespace)_namespaceTable.get(namespace);

		if (n != null) {
			return n.getId();
		}

		return 0;
	}

	/**
	 * Calculates a hash code for the supplied label.
	 **/
	protected long _getLabelHash(String label) {
		// Calculate a 128 bit (16 byte) MD5 hash and use
		// the last 8 bytes of this hash for the result.
		try {
			byte[] labelData = label.getBytes("UTF-8");
			byte[] md5hash = null;

			synchronized(_md5Digest) {
				_md5Digest.reset();
				md5hash = _md5Digest.digest(labelData);
			}

			return (new BigInteger(md5hash)).longValue();
		}
		catch (UnsupportedEncodingException e) {
			// Should never happen as UTF-8 should be available on every Java platform
			throw new SailInternalException(
					"UTF-8 encoding not available on this platorm", e);
		}
	}

	/**
	 * Chops a list of IDs (integers) contained in the supplied ResultSet
	 * into one or more chunks. The chunks are returned as string of the
	 * form "(n1,n2,...)", including parentheses.
	 *
	 * @param ResultSet A one-column ResultSet containing integers.
	 * @param maxStringLength The maximum length (in characters) of a chunk.
	 *
	 * @return an array of strings. Each string in the array is a chunk of
	 * the list of integers, surrounded by brackets and seperated by
	 * commas.
	 */
	protected String[] _chunkIdSet(ResultSet rs, int maxStringLength)
		throws SQLException
	{
		ArrayList chunkList = new ArrayList();

		StringBuffer chunk = new StringBuffer(maxStringLength);
		chunk.append("(");

		int count = 0;

		while (rs.next()) {
			String nextId = String.valueOf(rs.getInt(1));

			if (chunk.length() + nextId.length() + 1 > maxStringLength) {
				// Start with a new chunk
				chunk.append(")");
				chunkList.add(chunk.toString());

				chunk.setLength(0);
				chunk.append("(");

				count = 0;
			}

			if (count > 0) {
				chunk.append(",");
			}
			chunk.append(rs.getInt(1));

			count++;
		}

		if (count > 0) {
			chunk.append(")");
			chunkList.add(chunk.toString());
		}

		String[] result = new String[chunkList.size()];
		for (int i = 0; i < chunkList.size(); i++) {
			result[i] = (String)chunkList.get(i);
		}

		return result;
	}

	protected void _updateExportedNamespaces() {
		ThreadLog.trace("Updating exported namespaces information.");

		// First 'reset' all namespaces that are not user-defined to
		// non-exported. This eliminates exporting of namespaces belonging
		// to removed predicates.
		try {
			_rdbms.executeUpdate("UPDATE " + NAMESPACES_TABLE + " SET export = "
					+ _rdbms.FALSE + " WHERE userDefined = " + _rdbms.FALSE);

			// Query for all namespaces that need to be exported: those that
			// are the in predicates of statements.
			Connection con = _rdbms.getConnection();
			java.sql.Statement st = con.createStatement();
			ResultSet rs = st.executeQuery("SELECT DISTINCT r.namespace "
					+ "FROM " + RESOURCES_TABLE + " r, " + TRIPLES_TABLE + " t "
					+ "WHERE t.pred = r.id ");

			String[] idChunks = _chunkIdSet(rs, 3500);
			rs.close();
			st.close();

			con.setAutoCommit(false);
			st = con.createStatement();

			for (int i = 0; i < idChunks.length; i++) {
				st.executeUpdate("UPDATE " + NAMESPACES_TABLE + " SET export = "
						+ _rdbms.TRUE + " WHERE id IN " + idChunks[i]);
			}

			con.commit();
			st.close();
			con.close();

			_setExportStatusUpToDate(true);

			// re-initialize the namespaces to update the cache.
			_initNamespaceCache();
		}
		catch (SQLException e) {
			throw new SailInternalException(e);
		}
	}

/*-----------------------------------------------------------------------+
| Methods for retrieving Resource and Literal objects with a specific ID |
+-----------------------------------------------------------------------*/

	/**
	 * Gets the Value for the supplied ID.
	 * 
	 * @return An IdValue object.
	 */
	public IdValue getValue(int id) {
		if (id > 0) {
			return getResource(id);
		}
		else if (id < 0) {
			return getLiteral(id);
		}
		else { // id == 0
			return null;
		}
	}

	/**
	 * Gets the Resource for the supplied ID.
	 * 
	 * @return Either an IdURI or an IdBNode object
	 */
	public IdResource getResource(int id) {
		try {
			IdResource result = null;

			Connection con = _rdbms.getConnection();
			java.sql.Statement st = con.createStatement();
			ResultSet rs = st.executeQuery(
					"SELECT r.namespace, r.localname " +
					"FROM " + RESOURCES_TABLE + " r " +
					"WHERE r.id = " + id);

			if (rs.next()) {
				int nsId = rs.getInt(1);
				String localName = rs.getString(2);

				if (localName == null) {
					localName = "";
				}

				if (nsId == 0) {
					// bnode
					result = new IdBNode(this, localName, id);
				}
				else {
					// URI
					result = new IdURI(this, _namespaceNames[nsId], localName, id);
				}
			}

			rs.close();
			st.close();
			con.close();

			return result;
		}
		catch (SQLException e) {
			throw new SailInternalException(e);
		}
	}

	/**
	 * Gets the Literal for the supplied ID.
	 * 
	 * @return An IdLiteral object.
	 */
	public IdLiteral getLiteral(int id) {
		try {
			IdLiteral result = null;

			Connection con = _rdbms.getConnection();
			java.sql.Statement st = con.createStatement();
			ResultSet rs = st.executeQuery(
					"SELECT r.id, r.namespace, r.localname, l.language, l.label " +
					"FROM " + LITERALS_TABLE + " l, " + RESOURCES_TABLE + " r " +
					"WHERE l.datatype = r.id AND l.id = " + id);

			if (rs.next()) {
				int dtId = rs.getInt(1); // datatype id
				String label = rs.getString(5);

				if (label == null) {
					label = "";
				}

				if (dtId != 0) {
					// Datatyped literal
					int dtNsId = rs.getInt(2); // datatype namespace id
					String dtLname = rs.getString(3); // datatype localname

					if (dtLname == null) {
						dtLname = "";
					}

					URI datatype = new IdURI(this, _namespaceNames[dtNsId], dtLname, dtId);
					result = new IdLiteral(this, label, datatype, id);
				}
				else {
					String lang = rs.getString(4);

					if (lang != null) {
						// Literal with language attribute
						result = new IdLiteral(this, label, lang, id);
					}
					else {
						// Plain literal
						result = new IdLiteral(this, label, id);
					}
				}
			}

			rs.close();
			st.close();
			con.close();

			return result;
		}
		catch (SQLException e) {
			throw new SailInternalException(e);
		}
	}

	// implements ValueFactory.createURI(String)
	public URI createURI(String uri) {
		return new IdURI(this, uri, 0);
	}

	public URI createURI(String namespace, String localName) {
		return new IdURI(this, namespace, localName, 0);
	}

	// implements ValueFactory.createBNode()
	public BNode createBNode() {
		if (_nextBNodeID == Integer.MAX_VALUE) {
			// Start with a new bnode prefix
			_updateBNodePrefix();
		}

		return createBNode(_bnodePrefix + _nextBNodeID++);
	}

	// implements ValueFactory.createBNode(String)
	public BNode createBNode(String nodeId) {
		return new IdBNode(this, nodeId, 0);
	}

	// implements ValueFactory.createLiteral(String)
	public Literal createLiteral(String value) {
		return new IdLiteral(this, value, 0);
	}

	// implements ValueFactory.createLiteral(String, String)
	public Literal createLiteral(String value, String language) {
		return new IdLiteral(this, value, language, 0);
	}

	// implements ValueFactory.createLiteral(String, URI)
	public Literal createLiteral(String value, URI datatype) {
		return new IdLiteral(this, value, datatype, 0);
	}

	// implements ValueFactory.createStatement(Resource, URI, Value)
	public Statement createStatement(
			Resource subject, URI predicate, Value object)
	{
		return new StatementImpl(subject, predicate, object);
	}
}