MailcapCommandMap extends the CommandMap
abstract class. It implements a CommandMap whose configuration
is based on mailcap files
(
RFC 1524).
The MailcapCommandMap can be configured both programmatically
and via configuration files.
Mailcap file search order:
The MailcapCommandMap looks in various places in the user's
system for mailcap file entries. When requests are made
to search for commands in the MailcapCommandMap, it searches
mailcap files in the following order:
- Programatically added entries to the MailcapCommandMap instance.
- The file
.mailcap
in the user's home directory.
- The file <java.home>
/lib/mailcap
.
- The file or resources named
META-INF/mailcap
.
- The file or resource named
META-INF/mailcap.default
(usually found only in the activation.jar
file).
Mailcap file format:
Mailcap files must conform to the mailcap
file specification (RFC 1524, A User Agent Configuration Mechanism
For Multimedia Mail Format Information).
The file format consists of entries corresponding to
particular MIME types. In general, the specification
specifies applications for clients to use when they
themselves cannot operate on the specified MIME type. The
MailcapCommandMap extends this specification by using a parameter mechanism
in mailcap files that allows JavaBeans(tm) components to be specified as
corresponding to particular commands for a MIME type.
When a mailcap file is
parsed, the MailcapCommandMap recognizes certain parameter signatures,
specifically those parameter names that begin with x-java-
.
The MailcapCommandMap uses this signature to find
command entries for inclusion into its registries.
Parameter names with the form x-java-<name>
are read by the MailcapCommandMap as identifying a command
with the name name. When the name is
content-handler
the MailcapCommandMap recognizes the class
signified by this parameter as a DataContentHandler.
All other commands are handled generically regardless of command
name. The command implementation is specified by a fully qualified
class name of a JavaBean(tm) component. For example; a command for viewing
some data can be specified as: x-java-view=com.foo.ViewBean
.
When the command name is fallback-entry
, the value of
the command may be true
or false
. An
entry for a MIME type that includes a parameter of
x-java-fallback-entry=true
defines fallback commands
for that MIME type that will only be used if no non-fallback entry
can be found. For example, an entry of the form text/*; ;
x-java-fallback-entry=true; x-java-view=com.sun.TextViewer
specifies a view command to be used for any text MIME type. This
view command would only be used if a non-fallback view command for
the MIME type could not be found.
MailcapCommandMap aware mailcap files have the
following general form:
# Comments begin with a '#' and continue to the end of the line.
<mime type>; ; <parameter list>
# Where a parameter list consists of one or more parameters,
# where parameters look like: x-java-view=com.sun.TextViewer
# and a parameter list looks like:
text/plain; ; x-java-view=com.sun.TextViewer; x-java-edit=com.sun.TextEdit
# Note that mailcap entries that do not contain 'x-java' parameters
# and comply to RFC 1524 are simply ignored:
image/gif; /usr/dt/bin/sdtimage %s