KB-1826 Documents cannot be downloaded from Appian Designer

Symptoms

The document was uploaded using the file upload field and after clicking on the document in Appian Designer (/design):

Clicking on the 'Download file' link does not initiate a download of the file.
The parent folder is set to [Not Visible].
The file preview has no thumbnail.

The application server log prints the following error:

WARNING [com.sun.jersey.spi.container.servlet.WebComponent] (ajp-/0.0.0.0:8009-66) A servlet POST request, to the URI https://<SITE_URL>/suite/rest/a/content/latest/document/download, contains form parameters in the request body but the request body has been consumed by the servlet or a servlet filter accessing the request parameters. Only resource methods using @FormParam will work as expected. Resource methods consuming the request body by other means will not work as expected.

Cause

This is a design issue caused by uploading a file to the file upload field when it has the target, value and saveInto fields set to the same value.

Example of sail code:

a!fileUploadField(
 label: "File upload field example",
 labelPosition: "ABOVE",
 target: ri!file,
 value: ri!file,
 saveInto: ri!file,
 maxSelections: 1,
 validations: {}
)

Action

Search for the affected document(s) in Appian Designer.
Select the document by checking the checkbox on the left hand side of the document.

3. Click More and then click Download.

4. A zip file will be generated and downloaded. The zip file contains all the documents selected.

Affected Versions

This article applies to Appian 17.1 and later.