jdbcresultsetmetadata.java

hsql是很有名的嵌入式数据库

     *
     * </div>
     * <!-- end release-specific documentation -->
     *
     * @param column the first column is 1, the second is 2, ...
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    public boolean isAutoIncrement(int column) throws SQLException {

        checkColumn(column);

        return columnMetaData[--column].isAutoIncrement;
    }

    /**
     * <!-- start generic documentation -->
     * Indicates whether a column's case matters. <p>
     * <!-- end generic documentation -->
     *
     * <!-- start Release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB 1.7.1 did not report this value accurately.  <p>
     *
     * Starting with 1.7.2, this feature is better supported.  <p>
     *
     * This method returns true for any column whose data type is a character
     * type, with the exception of VARCHAR_IGNORECASE for which it returns
     * false. It also returns false for any column whose data type is a
     * not a character data type. <p>
     *
     * </div>
     * <!-- end release-specific documentation -->
     *
     * @param column the first column is 1, the second is 2, ...
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    public boolean isCaseSensitive(int column) throws SQLException {

        checkColumn(column);

        return columnMetaData[--column].isCaseSensitive;
    }

    /**
     * <!-- start generic documentation -->
     * Indicates whether the designated column can be used in a where
     * clause. <p>
     * <!-- end generic documentation -->
     *
     * <!-- start Release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB 1.7.1 did not report this value accurately.  <p>
     *
     * Starting with 1.7.2, this feature is better supported.  <p>
     *
     * If the data type of the column is definitely known to be searchable
     * in any way under HSQLDB, then true is returned, else false.  That is,
     * if the type is reported in DatabaseMetaData.getTypeInfo() as having
     * DatabaseMetaData.typePredNone or is not reported, then false is
     * returned, else true.
     *
     * </div>
     * <!-- end release-specific documentation -->
     *
     * @param column the first column is 1, the second is 2, ...
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    public boolean isSearchable(int column) throws SQLException {

        checkColumn(column);

        return columnMetaData[--column].isSearchable;
    }

    /**
     * <!-- start generic documentation -->
     * Indicates whether the designated column is a cash value. <p>
     * <!-- end generic documentation -->
     *
     * <!-- start Release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * Up to and including HSQLDB 1.7.2, this method always returns
     * false. <p>
     *
     * This is because true fixed (precision,scale) data types are not yet
     * supported.  That is, DECIMAL and NUMERIC types are implemented
     * as a thin wrap of java.math.BigDecimal, which cannot, without
     * additional, as yet unimplemented constraint enforcement code, be
     * said to be a fixed (precision,scale) types. <p>
     *
     * </div>
     * <!-- end release-specific documentation -->
     *
     * @param column the first column is 1, the second is 2, ...
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    public boolean isCurrency(int column) throws SQLException {

        checkColumn(column);

        return columnMetaData[--column].isCurrency;
    }

    /**
     * <!-- start generic documentation -->
     * Indicates the nullability of values in the designated column. <p>
     * <!-- end generic documentation -->
     *
     * <!-- start Release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * Up to 1.7.1, HSQLDB did not report this value accurately. <p>
     *
     * Starting with 1.7.2, this feature is better supported.  <p>
     *
     * columnNullableUnknown is always returned for result set columns that
     * do not directly represent table column values (i.e. are calculated),
     * while the corresponding value in SYSTEM_COLUMNS.NULLABLE is returned
     * for result set columns that do directly represent table column values. <p>
     *
     * Those wishing to determine the nullable status of a table column in
     * isolation from ResultSetMetaData and in a DBMS-independent fashion
     * can do so by calling DatabaseMetaData.getColumns() with the appropriate
     * filter values and inspecting the result at the position described in
     * the API documentation. <p>
     *
     * </div>
     * <!-- end release-specific documentation -->
     *
     * @param column the first column is 1, the second is 2, ...
     * @return the nullability status of the given column; one of
     *      <code>columnNoNulls</code>,
     *      <code>columnNullable</code> or <code>columnNullableUnknown</code>
     * @exception SQLException if a database access error occurs
     */
    public int isNullable(int column) throws SQLException {

        checkColumn(column);

        return columnMetaData[--column].isNullable;
    }

    /**
     * <!-- start generic documentation -->
     * Indicates whether values in the designated column are signed
     * numbers. <p>
     * <!-- end generic documentation -->
     *
     * <!-- start Release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB 1.7.1 introduced support for this feature and 1.7.2
     * reports identical values (although using a slightly different
     * implementation).<p>
     *
     * </div>
     * <!-- end release-specific documentation -->
     *
     * @param column the first column is 1, the second is 2, ...
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    public boolean isSigned(int column) throws SQLException {

        checkColumn(column);

        return columnMetaData[--column].isSigned;
    }

    /**
     * <!-- start generic documentation -->
     * Indicates the designated column's normal maximum width in
     * characters. <p>
     * <!-- end generic documentation -->
     *
     * <!-- start Release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * Up to and including HSQLDB 1.7.1, this method always returned
     * 0, which was intended to convey unknown display size.
     * Unfortunately, this value is not universally handled by all
     * clients and in the worst case can cause some applications to
     * crash. <p>
     *
     * Starting with 1.7.2, this feature is better supported.  <p>
     *
     * The current calculation follows these rules: <p>
     *
     * <ol>
     * <li>Long character types and datetime types:<p>
     *
     *     The maximum length/precision, repectively.<p>
     *
     * <li>CHAR and VARCHAR types: <p>
     *
     *      <ul>
     *      <li> If the result set column is a direct pass through of a table
     *           column value, column size was declared and the connection is
     *           to an embedded database instance, then the declared value is
     *           returned.<p>
     *
     *      <li> Otherwise, the value of the system property
     *           hsqldb.max_xxxchar_display_size or the magic value
     *           32766 (0x7FFE) (tested usable/accepted by most tools and
     *           compatible with assumptions made by java.io read/write
     *           UTF) when the system property is not defined or is not
     *           accessible, due to security constraints. <p>
     *
     *      </ul>
     *
     *      It must be noted that the latter value in no way affects the
     *      ability of the HSQLDB JDBC driver to retrieve longer values
     *      and serves only as the current best effort at providing a
     *      value that maximizes usability across a wide range of tools,
     *      given that the HSQLDB database engine does not require the
     *      length to be declared and does not necessarily enforce it,
     *      even if declared. <p>
     *
     * <li>Number types: <p>
     *
     *     The max precision, plus the length of the negation character (1),
     *     plus (if applicable) the maximum number of characters that may
     *     occupy the exponent character sequence.  Note that some legacy tools
     *     do not correctly handle BIGINT values of greater than 18 digits. <p>
     *
     * <li>BOOLEAN (BIT) type: <p>
     *
     *     The length of the character sequence "false" (5), the longer of the
     *     two boolean value String representations. <p>
     *
     * <li>Remaining types: <p>
     *
     *     The maximum length/precision, respectively, as reported by
     *     DatabaseMetaData.getTypeInfo(), when applicable.  If the maximum
     *     display size is unknown, unknowable or inapplicable, then zero is
     *     returned. <p>
     *
     * </ol>
     *
     * </div>
     * <!-- end release-specific documentation -->
     *
     * @param column the first column is 1, the second is 2, ...
     * @return the normal maximum number of characters allowed as the width
     *      of the designated column
     * @exception SQLException if a database access error occurs
     */
    public int getColumnDisplaySize(int column) throws SQLException {

        checkColumn(column);

        return columnMetaData[--column].columnDisplaySize;
    }

    /**
     * <!-- start generic documentation -->
     * Gets the designated column's suggested title for use in printouts and
     * displays. <p>
     * <!-- end generic documentation -->
     *
     * <!-- start Release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * In HSQLDB a <code>ResultSet</code> column label is determined in the
     * following order of precedence:<p>
     *
     * <OL>
     * <LI>The label (alias) specified in the generating query.</LI>
     * <LI>The name of the underlying column, if no label is specified.<br>
     *    This also applies to aggregate functions.</LI>
     * <LI>An empty <code>String</code>.</LI>
     * </OL> <p>
     *
     * </div>
     * <!-- end release-specific documentation -->
     *
     * @param column the first column is 1, the second is 2, ...
     * @return the suggested column title
     * @exception SQLException if a database access error occurs
     */
    public String getColumnLabel(int column) throws SQLException {

        checkColumn(column);

        return columnMetaData[--column].columnLabel;
    }

    /**
     * <!-- start generic documentation -->
     * Get the designated column's name. <p>
     * <!-- end generic documentation -->
     *
     * <!-- start Release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * In HSQLDB a ResultSet column name is determined in the following
     * order of prcedence:<p>
     *
     * <OL>
     * <LI>The name of the underlying columnm, if the ResultSet column
     *   represents a column in a table.</LI>
     * <LI>The label or alias specified in the generating query.</LI>
     * <LI>An empty <code>String</code>.</LI>
     * </OL> <p>
     *
     * If the <code>jdbc.get_column_name</code> property of the database
     * has been set to false, this method returns the same value as
     * {@link #getColumnLabel(int)}.<p>
     *
     * </div>
     * <!-- end release-specific documentation -->
     *
     * @param column the first column is 1, the second is 2, ...
     * @return column name
     * @exception SQLException if a database access error occurs
     */
    public String getColumnName(int column) throws SQLException {

        checkColumn(column);

        column--;

        return useColumnName ? columnMetaData[column].columnName
                             : columnMetaData[column].columnLabel;
    }

    /**
     * <!-- start generic documentation -->
     * Get the designated column's table's schema. <p>
     * <!-- end generic documentation -->
     *
     * <!-- start Release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * Up to 1.7.1, HSQLDB did not support the notion of schemas at all,
     * including schema names in result set metadata; this method always
     * returned "". <p>
     *
     * Staring with 1.7.2, schema name reporting is supported only as an
     * optional, experimental feature that is disabled by default.
     * Enabling this feature requires setting the database property
     * "hsqldb.schemas=true". <p>
     *
     * Specifically, when this feature is enabled under 1.7.2, only very
     * limited support is provided by the engine for executing SQL containing
     * schema-qualified database object identifiers.  That is, when this
     * feature is enabled under 1.7.2, it is not yet possible in most cases
     * to use what would otherwise be the correct, canonical SQL calculated
     * from ResultSetMetaData. <p>
     *
     * Regardless, reporting is done only in system table content and is
     * not yet carried over to ResultSetMetaData. <p>
     *
     * For greater detail, see discussion at:
     * {@link jdbcDatabaseMetaData}. <p>
     *
     * </div>
     * <!-- end release-specific documentation -->
     *
     * @param column the first column is 1, the second is 2, ...
     * @return schema name or "" if not applicable
     * @exception SQLException if a database access error occurs
     */
    public String getSchemaName(int column) throws SQLException {

        checkColumn(column);