dialect.java

hibernate-3.1.3-all-src.zip 面向对象的访问数据库工具

		return null;
	}

	/**
	 * The keyword used to insert a row without specifying any column values.
	 * This is not possible on some databases.
	 */
	public String getNoColumnsInsertString() {
		return "values ( )";
	}

	/**
	 * Generate the appropriate select statement to to retreive the next value
	 * of a sequence, if sequences are supported.
	 * <p/>
	 * This should be a "stand alone" select statement.
	 *
	 * @param sequenceName the name of the sequence
	 * @return String The "nextval" select string.
	 * @throws MappingException if no sequences
	 */
	public String getSequenceNextValString(String sequenceName) throws MappingException {
		throw new MappingException( "Dialect does not support sequences" );
	}

	/**
	 * Generate the select expression fragment that will retreive the next
	 * value of a sequence, if sequences are supported.
	 * <p/>
	 * This differs from {@link #getSequenceNextValString(String)} in that this
	 * should return an expression usable within another select statement.
	 *
	 * @param sequenceName the name of the sequence
	 * @return String
	 * @throws MappingException if no sequences
	 */
	public String getSelectSequenceNextValString(String sequenceName) throws MappingException {
		throw new MappingException( "Dialect does not support sequences" );
	}

	/**
	 * The syntax used to create a sequence, if sequences are supported.
	 *
	 * @param sequenceName the name of the sequence
	 * @return String
	 * @throws MappingException if no sequences
	 */
	protected String getCreateSequenceString(String sequenceName) throws MappingException {
		throw new MappingException( "Dialect does not support sequences" );
	}

	/**
	 * The multiline script used to create a sequence, if sequences are supported.
	 *
	 * @param sequenceName the name of the sequence
	 * @return String[]
	 * @throws MappingException if no sequences
	 */
	public String[] getCreateSequenceStrings(String sequenceName) throws MappingException {
		return new String[]{getCreateSequenceString( sequenceName )};
	}

	/**
	 * The syntax used to drop a sequence, if sequences are supported.
	 *
	 * @param sequenceName the name of the sequence
	 * @return String
	 * @throws MappingException if no sequences
	 */
	protected String getDropSequenceString(String sequenceName) throws MappingException {
		throw new MappingException( "Dialect does not support sequences" );
	}

	/**
	 * The multiline script used to drop a sequence, if sequences are supported.
	 *
	 * @param sequenceName the name of the sequence
	 * @return String[]
	 * @throws MappingException if no sequences
	 */
	public String[] getDropSequenceStrings(String sequenceName) throws MappingException {
		return new String[]{getDropSequenceString( sequenceName )};
	}

	/**
	 * A query used to find all sequences
	 *
	 * @see org.hibernate.tool.hbm2ddl.SchemaUpdate
	 */
	public String getQuerySequencesString() {
		return null;
	}

	/**
	 * Get the <tt>Dialect</tt> specified by the current <tt>System</tt> properties.
	 *
	 * @return Dialect
	 * @throws HibernateException
	 */
	public static Dialect getDialect() throws HibernateException {
		String dialectName = Environment.getProperties().getProperty( Environment.DIALECT );
		if ( dialectName == null ) throw new HibernateException( "The dialect was not set. Set the property hibernate.dialect." );
		try {
			return ( Dialect ) ReflectHelper.classForName( dialectName ).newInstance();
		}
		catch ( ClassNotFoundException cnfe ) {
			throw new HibernateException( "Dialect class not found: " + dialectName );
		}
		catch ( Exception e ) {
			throw new HibernateException( "Could not instantiate dialect class", e );
		}
	}


	/**
	 * Get the <tt>Dialect</tt> specified by the given properties or system properties.
	 *
	 * @param props
	 * @return Dialect
	 * @throws HibernateException
	 */
	public static Dialect getDialect(Properties props) throws HibernateException {
		String dialectName = props.getProperty( Environment.DIALECT );
		if ( dialectName == null ) return getDialect();
		try {
			return ( Dialect ) ReflectHelper.classForName( dialectName ).newInstance();
		}
		catch ( ClassNotFoundException cnfe ) {
			throw new HibernateException( "Dialect class not found: " + dialectName );
		}
		catch ( Exception e ) {
			throw new HibernateException( "Could not instantiate dialect class", e );
		}
	}

	/**
	 * Retrieve a set of default Hibernate properties for this database.
	 *
	 * @return a set of Hibernate properties
	 */
	public final Properties getDefaultProperties() {
		return properties;
	}

	/**
	 * Completely optional cascading drop clause
	 *
	 * @return String
	 */
	public String getCascadeConstraintsString() {
		return "";
	}

	/**
	 * Create an <tt>OuterJoinGenerator</tt> for this dialect.
	 *
	 * @return OuterJoinGenerator
	 */
	public JoinFragment createOuterJoinFragment() {
		return new ANSIJoinFragment();
	}

	/**
	 * Create a <tt>CaseFragment</tt> for this dialect.
	 *
	 * @return OuterJoinGenerator
	 */
	public CaseFragment createCaseFragment() {
		return new ANSICaseFragment();
	}

	/**
	 * The name of the SQL function that transforms a string to
	 * lowercase
	 *
	 * @return String
	 */
	public String getLowercaseFunction() {
		return "lower";
	}

	/**
	 * Does this <tt>Dialect</tt> have some kind of <tt>LIMIT</tt> syntax?
	 */
	public boolean supportsLimit() {
		return false;
	}

	/**
	 * Does this dialect support an offset?
	 */
	public boolean supportsLimitOffset() {
		return supportsLimit();
	}

	/**
	 * Add a <tt>LIMIT</tt> clause to the given SQL <tt>SELECT</tt>
	 *
	 * @return the modified SQL
	 */
	public String getLimitString(String querySelect, boolean hasOffset) {
		throw new UnsupportedOperationException( "paged queries not supported" );
	}

	public String getLimitString(String querySelect, int offset, int limit) {
		return getLimitString( querySelect, offset>0 );
	}

	public boolean supportsVariableLimit() {
		return supportsLimit();
	}

	/**
	 * Does the <tt>LIMIT</tt> clause specify arguments in the "reverse" order
	 * limit, offset instead of offset, limit?
	 *
	 * @return true if the correct order is limit, offset
	 */
	public boolean bindLimitParametersInReverseOrder() {
		return false;
	}

	/**
	 * Does the <tt>LIMIT</tt> clause come at the start of the
	 * <tt>SELECT</tt> statement, rather than at the end?
	 *
	 * @return true if limit parameters should come before other parameters
	 */
	public boolean bindLimitParametersFirst() {
		return false;
	}

	/**
	 * Does the <tt>LIMIT</tt> clause take a "maximum" row number instead
	 * of a total number of returned rows?
	 */
	public boolean useMaxForLimit() {
		return false;
	}

	/**
	 * The opening quote for a quoted identifier
	 */
	public char openQuote() {
		return '"';
	}

	/**
	 * The closing quote for a quoted identifier
	 */
	public char closeQuote() {
		return '"';
	}

	/**
	 * SQL functions as defined in general. The results of this
	 * method should be integrated with the specialisation's data.
	 */
	public final Map getFunctions() {
		return sqlFunctions;
	}

	public boolean supportsIfExistsBeforeTableName() {
		return false;
	}

	public boolean supportsIfExistsAfterTableName() {
		return false;
	}
	
	/**
	 * Does this dialect support column-level check constraints?
	 */
	public boolean supportsColumnCheck() {
		return true;
	}
	
	/**
	 * Does this dialect support table-level check constraints?
	 */
	public boolean supportsTableCheck() {
		return true;
	}

	/**
	 * Whether this dialect have an Identity clause added to the data type or a
	 * completely seperate identity data type
	 *
	 * @return boolean
	 */
	public boolean hasDataTypeInIdentityColumn() {
		return true;
	}

	public boolean supportsCascadeDelete() {
		return true;
	}

	/**
	 * Method <code>appendLockHint</code> appends according to the given
	 * lock mode a lock hint behind the given table name, if this dialect
	 * needs this. MS SQL Server for example doesn't support the
	 * standard "<code>select ... for update</code>" syntax and use a
	 * special "<code>select ... from TABLE as ALIAS with (updlock, rowlock)
	 * where ...</code>" syntax instead.
	 *
	 * @param tableName name of table to append lock hint
	 * @return String
	 *         <p/>
	 *         author <a href="http://sourceforge.net/users/heschulz">Helge Schulz</a>
	 */
	public String appendLockHint(LockMode mode, String tableName) {
		return tableName;
	}

	public Class getNativeIdentifierGeneratorClass() {
		if ( supportsIdentityColumns() ) {
			return IdentityGenerator.class;
		}
		else if ( supportsSequences() ) {
			return SequenceGenerator.class;
		}
		else {
			return TableHiLoGenerator.class;
		}
	}

	public String getSelectGUIDString() {
		throw new UnsupportedOperationException( "dialect does not support GUIDs" );
	}

	public boolean supportsOuterJoinForUpdate() {
		return true;
	}

	public String getSelectClauseNullString(int sqlType) {
		return "null";
	}
	
	public boolean supportsNotNullUnique() {
		return true;
	}

	/**
	 * Build an instance of the SQLExceptionConverter preferred by this dialect for
	 * converting SQLExceptions into Hibernate's JDBCException hierarchy.  The default
	 * Dialect implementation simply returns a converter based on X/Open SQLState codes.
	 * <p/>
	 * It is strongly recommended that specific Dialect implementations override this
	 * method, since interpretation of a SQL error is much more accurate when based on
	 * the ErrorCode rather than the SQLState.  Unfortunately, the ErrorCode is a vendor-
	 * specific approach.
	 *
	 * @return The Dialect's preferred SQLExceptionConverter.
	 */
	public SQLExceptionConverter buildSQLExceptionConverter() {
		// The default SQLExceptionConverter for all dialects is based on SQLState
		// since SQLErrorCode is extremely vendor-specific.  Specific Dialects
		// may override to return whatever is most appropriate for that vendor.
		return new SQLStateConverter( getViolatedConstraintNameExtracter() );
	}

	private static final ViolatedConstraintNameExtracter EXTRACTER = new ViolatedConstraintNameExtracter() {
		public String extractConstraintName(SQLException sqle) {
			return null;
		}
	};

	public ViolatedConstraintNameExtracter getViolatedConstraintNameExtracter() {
		return EXTRACTER;
	}

	public final String quote(String column) {
		if ( column.charAt( 0 ) == '`' ) {
			return openQuote() + column.substring( 1, column.length() - 1 ) + closeQuote();
		}
		else {
			return column;
		}
	}

	public boolean hasSelfReferentialForeignKeyBug() {
		return false;
	}
	

	public boolean useInputStreamToInsertBlob() {
		return true;
	}

	public int registerResultSetOutParameter(CallableStatement statement, int col) throws SQLException {
		throw new UnsupportedOperationException(
				getClass().getName() + 
				" does not support resultsets via stored procedures"
			);
	}

	public ResultSet getResultSet(CallableStatement ps) throws SQLException {
		throw new UnsupportedOperationException(
				getClass().getName() + 
				" does not support resultsets via stored procedures"
			);
	}
	
	public boolean supportsUnionAll() {
		return false;
	}
	
	public boolean supportsCommentOn() {
		return false;
	}
	
	public String getTableComment(String comment) {
		return "";
	}

	public String getColumnComment(String comment) {
		return "";
	}
	
	public String transformSelectString(String select) {
		return select;
	}

	public boolean supportsTemporaryTables() {
		return false;
	}

	public String generateTemporaryTableName(String baseTableName) {
		return "HT_" + baseTableName;
	}

	public String getCreateTemporaryTableString() {
		return "create table";
	}

	public boolean performTemporaryTableDDLInIsolation() {
		return false;
	}

	public String getCreateTemporaryTablePostfix() {
		return "";
	}

	public boolean dropTemporaryTableAfterUse() {
		return true;
	}

	public String getForUpdateString(LockMode lockMode) {
		if ( lockMode==LockMode.UPGRADE ) {
			return getForUpdateString();
		}
		else if ( lockMode==LockMode.UPGRADE_NOWAIT ) {
			return getForUpdateNowaitString();
		}
		else {
			return "";
		}
	}
	
	public int getMaxAliasLength() {
		return 10;
	}

	public boolean supportsCurrentTimestampSelection() {
		return false;
	}

	public String getCurrentTimestampSelectString() {
		throw new UnsupportedOperationException( "Database not known to define a current timestamp function" );
	}

	public boolean isCurrentTimestampSelectStringCallable() {
		throw new UnsupportedOperationException( "Database not known to define a current timestamp function" );
	}
	
	/**
	 * The SQL value that the JDBC driver maps boolean values to
	 */
	public String toBooleanValueString(boolean bool) {
		return bool ? "1" : "0";
	}

	/**
	 * Does this dialect support parameters within the select clause of
	 * INSERT ... SELECT ... statements?
	 *
	 * @return True if this is supported; false otherwise.
	 */
	public boolean supportsParametersInInsertSelect() {
		return true;
	}

	/**
	 * The name of the database-specific SQL function for retrieving the
	 * current timestamp.
	 *
	 * @return The function name.
	 */
	public String getCurrentTimestampSQLFunctionName() {
		// the standard SQL function name is current_timestamp...
		return "current_timestamp";
	}

	
}