| Sun ONE Application Server 7 Administrator's Configuration File Reference |
Chapter 4
MIME TypesThis appendix discusses the MIME types file. The sections are:
The mime.types file interacts with the obj.conf file. For more information about obj.conf, see the Sun ONE Application Server Developer’s Guide to NSAPI.
IntroductionThe MIME types file in the instance_dir/config directory contains mappings between MIME (Multipurpose Internet Mail Extensions) types and file extensions. For example, the MIME types file maps the extensions .html and .htm to the type text/html:
type=text/html exts=htm,html
When the Sun ONE Application Server receives a web request for a resource from a client, it uses the MIME type mappings to determine what kind of resource is being requested.
MIME types are defined by three attributes: language (lang), encoding (enc), and content-type (type). At least one of these attributes must be present for each type. The most commonly used attribute is type. The server frequently considers the type when deciding how to generate the response to the client. (The enc and lang attributes are rarely used.)
The default MIME types file is called mime.types.
Determining the MIME TypeDuring the ObjectType step in the request handling process, the server determines the MIME type attributes of the resource requested by the client. Several different functions can be used to determine the MIME type, but the most commonly used one is type-by-extension. This function tells the server to look up the MIME type according to the requested resource’s file extension in the MIME types table.
The directive in obj.conf that tells the server to look up the MIME type according to the extension is:
ObjectType fn=type-by-extension
If the server uses a different function, such as force-type, to determine the type, then the MIME types table is not used for that particular request.
How the Type Affects the ResponseThe server considers the value of the type attribute when deciding which Service directive in obj.conf to use to generate the response to the client.
By default, if the type does not start with magnus-internal/, the server just sends the requested file to the client. The directive in obj.conf that contains this instruction is:
Service method=(GET|HEAD|POST) type=*~magnus-internal/* fn=send-file
By convention, all values of type that require the server to do something other than just send the requested resource to the client start with magnus-internal/.
For example, if the requested resource’s file extension is .map, the type is mapped to magnus-internal/imagemap. If the extension is .cgi, .exe, or .bat, the type is set to magnus-internal/cgi:
type=magnus-internal/imagemap exts=map
type=magnus-internal/cgi exts=cgi,exe,batIf the type starts with magnus-internal/, the server executes whichever Service directive in obj.conf matches the specified type. For example, if the type is magnus-internal/imagemap, the server uses the imagemap function to generate the response to the client, as indicated by the following directive:
Service method=(GET|HEAD) type=magnus-internal/imagemap fn=imagemap
What Does the Client Do with the MIME Type?The Service function generates the data and sends it to the client that made the request. When the server sends the data to the client, it also sends headers. These headers include whichever MIME type attributes are known (which is usually type).
When the client receives the data, it uses the MIME type to decide what to do with the data. For browser clients, the usual thing is to display the data in the browser window.
If the requested resource cannot be displayed in a browser but needs to be handled by another application, its type starts with application/, for example application/octet-stream (for .bin file extensions) or application/x-maker (for .fm file extensions). The client has its own set of user-editable mappings that tells it which application to use to handle which types of data.
For example, if the type is application/x-maker, the client usually handles it by opening Adobe FrameMaker to display the file.
Syntax of the MIME Types FileThe first line in the MIME types file identifies the file format and must read:
#--Sun Microsystems MIME Information
Other non-comment lines have the following format:
type=type/subtype exts=[file extensions]
Sample MIME Types FileHere is an example of a MIME types file:
