DAM core module

The DAM core module is a Magnolia Maven module.

• It has a module class - DamCoreConfiguration - which implements ModuleLifecycle.
• It contains (and registers) the DamDownloadServlet.
• Provides an implementation of AssetProviderRegistry.
• The module is configured in /modules/dam/config. 

Installing

Asset providers and renderers

In order to have a working DAM you must have configured at least: 

• an AssetProvider
• an AssetRenderer

Configuring AssetProvider

To enable DAM at least one AssetProvider must be configured as subnode of /modules/dam/config/providers/.

Configuring an AssetRenderer

AssetRenderer objects can be configured:

• globally 
• or per AssetProvider. 

When an asset rendition is requested, AssetProviderRegistry#getRendererFor(Asset asset, MediaType to)  first is looking for a provider specific renderer but will fallback to the globally defined renderer if no specific can be found.

The example configuration above has 2 renderers defined: 

• /modules/dam/config/providers/example-provider/ renderers/imaging configures a renderer for images specifically for the asset provider example-provider.
• /modules/dam/config/ renderers/noOp is a global fallback if a provider lacks a renderer for the requested media type.

NoOpAssetRenderer

The module magnolia-dam-core provides NoOpAssetRenderer which can be used to define global AssetRenderer. Per default, NoOpAssetRenderer does only wrap the original Asset.

NoOpAssetRenderer is registered by 

Implementation specific configuration

Please read Magnolia dam JCR implementation configuration to get a complete example of a specific configuration.

Download servlet

DamDownloadServlet handles asset downloads. The main task is to retrieve an Asset Object based on the current URI:

• If no Asset is found, an error is sent to the response.
• If an Asset is found, the response header is set and the asset binary is put in the response.

The servlet is backwards compatible and maps static UUIDs to the new DAM format.

DamDownloadServlet is registered in the filter chain at /server/filters/servlets/DamDownloadServlet.

Content disposition

Content-disposition is a HTTP header. If the Content-disposition field is set in a HTTP response header, the browser opens the "save file as" dialog instead of rendering the requested resource.

Per default, DamDownloadServlet serves assets with set Content-Disposition header. However, it is possible to define exceptions to omit the content disposition header.

Disabling content disposition headers per mime type

DAM standard configuration already defines 2 exceptions based on mime type:

• application/x-shockwave-flash
• video/mp4

To disable the Content-Disposition header for other content types, add their MIME types to /dam/config/contentDisposition/contentType/rejected.

Nodes and properties:

• contentDisposition: Defines content disposition header exceptions.
  • contentType: Arbitrary node name
    
    • rejected: Content map of MIME types for which content disposition headers are not served.
    • class: ResponseContentTypeVoter is a voter that checks the content type set on the response object against a list of allowed and/or rejected content types. It is typed to Object, as it can vote on both a passed HttpServletRequest, or the current MgnlContext.webContext, if any.
  • class: VoterSet supports a set of voters. The voting can be set, as well the returned level. If the level is not set (0) the votings result is returned.

Disabling content disposition headers based on path

To disable serving Content-Disposition headers based on path:

1. Create a new node inline under contentDisposition.
2. Under the new content node, create three property nodes:
   
   • class and set the value to info.magnolia.voting.voters.URIStartsWithVoter.
   • not and set the value to true.
   • pattern and set the value to /dam/inline.
3. Under the contentDisposition node add an op property and set the value to and. This acts as an operator between voters and is only necessary if there you have more than one voter in the set.

This will configure all files in folder inline to be sent without content disposition headers. The new content node should look like this: