About BLOB Support in Reports

Oracle Application Express includes BLOB support for both classic and interactive reports. If you use a wizard to create a report and include a column of type BLOB, basic support will be included. Additional information should be added after generation to make the download capability more user friendly.

Providing a Download Link

To facilitate the inclusion of a download link in a report, the report includes the selection of the length of the BLOB (for example, dbms_lob.getlength(RESUME)). If the length is 0, the BLOB is NULL and no download link is displayed. In the same way you specify a format mask for a date or number you can format a download link. The DOWNLOAD format is more complex however then other format masks in that you are required to specify at least three parameters, for example:

DOWNLOAD:EMP:RESUME:EMPNO

The parameters of the DOWNLOAD format are described in the following table:

Position	Attribute	Required	Description
1	DOWNLOAD	Yes	Identifies the DOWNLOAD report format mask.
2	Table Name	Yes	Case sensitive name of table containing target column of type `BLOB`.
3	Column containing BLOB	Yes	Case sensitive name of column of type `BLOB`.
4	Primary Key Column 1	Yes	Case sensitive name of primary key column 1.
5	Primary Key Column 2	No	Case sensitive name of primary key column 2.
6	MIME type Column	No	Case sensitive column name used to store the `MIME` type.
7	Filename Column	No	Case sensitive column name used to store the filename of the `BLOB`. If `NULL`, the column name is used as the default when a user downloads the file.
8	Last Update Column	No	Case sensitive column name used to store the last update date of the `BLOB`. If used, the HTTP header of the file download indicates the date of last modification and Web browsers will be able to cache the `BLOB`. If not specified, the browser may not be able to cache files.
9	Character Set Column	No	Case sensitive column name used to store the character set of the `BLOB`. Most relevant for Asian languages which may need to maintain the character set encoding.
10	Content Disposition	No	Specify `inline` or `attachment`. All other values ignored. If a `MIME` type is provided and the file is a type that can be displayed, the file will be displayed. If `MIME` type is not provided, or the file cannot be displayed inline, the user will be prompted to download.
11	Download Text	No	String used for the download link. If nothing provided, `Download` is used. Note that this will support substitutions (useful for translated applications).

Consider the following example:

DOWNLOAD:EMP:RESUME:EMPNO::RESUME_MIMETYPE:RESUME_FILENAME:RESUME_LAST_UPDATE::attachment:Resume

If you have a report column with a format mask that begins with DOWNLOAD:, you will see a link below the format 'BLOB Download Format Mask'. This popup assists in entering all the parameters necessary for the DOWNLOAD format.

Tip:

To see a real example, go to Sample Application, page 29 (Master Detail), Items for Order #&P29_ORDER_ID. region, Product Image column. See "Running a Demonstration Application".

Displaying the BLOB

If the BLOB you are working with is an image, you can display it in the report as well. To do this, you use the new report format mask of 'IMAGE'. Regardless of the MIME type, the report will always attempt to display the BLOB. If the BLOB cannot be rendered, a broken image will be displayed.

The parameters of the IMAGE format mask are described in the following table:

Position	Attribute	Required	Description
1	IMAGE	Yes	Identifies the IMAGE report format mask.
2	Table Name	Yes	Case sensitive name of table containing target column of type `BLOB`.
3	Column containing BLOB	Yes	Case sensitive name of column of type `BLOB`.
4	Primary Key Column 1	Yes	Case sensitive name of primary key column 1.
5	Primary Key Column 2	No	Case sensitive name of primary key column 2.
6	MIME type Column	No	Case sensitive column name used to store the `MIME` type.
7	Filename Column	No	Not used for IMAGE format but left in so that the format can easily be changed between IMAGE and DOWNLOAD.
8	Last Update Column	No	Case sensitive column name used to store the last update date of the `BLOB`. If used, the HTTP header of the file download indicates the date of last modification and Web browsers will be able to cache the `BLOB`. If not specified, the browser may not be able to cache files.
9	Character Set Column	No	Not used for IMAGE format but left in so that the format can easily be changed between IMAGE and DOWNLOAD.
10	Content Disposition	No	Not used for IMAGE format but left in so that the format can easily be changed between IMAGE and DOWNLOAD.
11	Alt Text	No	String used for the alt tag associated with the image.

Consider the following example:

IMAGE:EMP:RESUME:EMPNO::RESUME_MIMETYPE:RESUME_FILENAME:RESUME_LAST_UPDATE::attachment:Resume

If you have a report column with a format mask that begins with 'IMAGE:', you will see a link below the format 'BLOB Download Format Mask'. This popup assists in entering all the parameters necessary for the IMAGE format.