Binary Columns

Owned by Shaun Forbes
Last updated: 27 Jul, 2022
3 min read

As of Weave version 2.6.8, if a database data definition contains a Blob (or another binary type) column you can create a “blob” configuration for that column, this will expose that columns values via a URL, which can then be referenced in a data definition (or elsewhere) to allow the display of the content.

The table that the blob configuration references must have at least two columns, one containing a unique key value, used to reference the row to display the content from, and another containing the content to display. Additionally, if the content type is not the same for every row then you can also include a content type column that contains the mime type that will be used when sending the content to the user.

blob

Properties

Name

Type

Required

Description

Name

Type

Required

Description

id

string

yes

The id to reference this configuration

datasource

ref urn:com.cohga.server.datasource.jdbc#1.0:datasource

yes

A reference to the data source that contains the content

table

string

yes

The name of the table that provides the content

key

string

yes

The name of the column in the table that contains the unique key value

column

string

yes

The name of the column in the table that contains the content

contenttype

string

no

The mime type of the content that the column contains

contenttypecolumn

string

no

The name of the column in the table that contains the mime type

fallbackurl

string

no

A URL that the response will redirect to if there is no matching record

acl

ref urn:com.cohga.server.acl#1.0:acl

no

An ACL to apply to the content

Content

None

Notes

  • If neither contenttype or contenttypecolumn is provided then “application/octet-stream” will be used.

  • The content is then exposed at /data/blob/<id>/<key>

  • If fallbackurl is not set and there is no row with a matching key then a 404 response will be sent

clob

Properties

Name

Type

Required

Description

Name

Type

Required

Description

id

string

yes

The id to reference this configuration

datasource

ref urn:com.cohga.server.datasource.jdbc#1.0:datasource

yes

reference to the data source that contains the content

table

string

yes

The name of the table that provides the content

key

string

yes

The name of the column in the table that contains the unique key value

column

string

yes

The name of the column in the table that contains the content

contenttype

string

no

The mime type of the content that the column contains

contenttypecolumn

string

no

The name of the column in the table that contains the mime type

fallbackurl

string

no

A URL that the response will redirect to if there is no matching record

acl

ref urn:com.cohga.server.acl#1.0:acl

no

An ACL to apply to the content

Content

None

Notes

  • If neither contenttype or contenttypecolumn is provided then “text/plain” will be used.

  • The content is then exposed at /data/clob/<id>/<key>

  • If fallbackurl is not set and there is no row with a matching key then a 404 response will be sent

Examples

Assuming a postgres table that contains JPEG images in the content column:

create table blob_test ( pid integer not null, content bytea not null ); create index blob_test_idx on blob_test(prupi);
<data:blob id="example" acl="private"> <datasource>postgres</datasource> <table>blob_test</table> <key>pid</key> <column>content</column> <contenttype>image/jpg</contenttype> <fallbackurl>/resources/images/missing.jpg<fallbackurl> </data:blob>

The images can then be references using the URL http://weave.hostname/weave/data/blob/example/1234 (assuming there is a row that has the value 1234 in the pid column)

For a data definition you could then reference the column in a parameter with something like:

<parameter type="url" name="image" label="Image" text="Show" column="{fn concat('data/blob/example/', pid)}"/>