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<TITLE>Using Attachments</TITLE>
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<H2 align="center">Using Attachments</H2>
<P>Even though SOAP is an XML-based protocol,
it's not always convenient to force all data
which is passed as part of a SOAP message
to be encoded in a way which can be embedded
inside of an XML document. Sometimes it would
be nicer just to allow data, such as JPEG
images, WAV files, etc., to be passed along
with the SOAP message, instead of inside
of it. To address this issue, the <A href="http://www.w3.org/TR/SOAP-attachments">SOAP Messages with Attachments</A> specification was created. The SOAP Messages
with Attachments specification allows for
the embedding of a SOAP message inside of
a MIME document, in a manner in which does
not alter the processing rules of the message.
The specification also describes how one
refers to the attachments from inside the
body of the SOAP message. Apache SOAP contains
an implementation of this specification.</P>
<H3>Using Attachments on the Client</H3>
<P>If you are interacting with an RPC-based
service, you may not need to do anything
special to transmit an attachment. Pre-defined
serializers/deserializers exist for interacting
with javax.activation.DataSource objects
and javax.activation.DataHandler objects.
If your objects can be passed through one
of these mechanisms, then the RPC-code will
handle creating and/or removing the attachment
for you.</P>
<P>If you are using a message-oriented service,
or need finer-grain control over the attachments,
then you can use methods in the org.apache.soap.messaging.Message,
org.apache.soap.rpc.Call, or org.apache.soap.rpc.Response
classes. The addBodyPart(...) methods will
allow you to add a javax.mail.internet.MimeBodyPart
object to your messages, while the findBodyPart(...)
and getBodyPart(...) methods will allow you
to retrieve them via the Content-URI and
location within the message, respectively.</P>
<H3>Using Attachments on the Server</H3>
<P>As in the client case, if you are implementing
an RPC-based service you may be able to take
advantage of the built-in serializers/deserializers
for the DataSource and DataHandler objects.</P>
<P>If you are implementing a message-oriented
service, or need finer-grain control over
the attachments, then you can use methods
on the org.apache.soap.rpc.SOAPContext class
to add or retrieve MimeBodyParts.</P>
<H3>Referencing Attachments from within a SOAP
Message</H3>
<P>To make attachments really useful, you need
to be able to refer to them from within the
contents of a SOAP message body. To refer
to an attachment from within a message, you
simply add an element like the following:</P>
<PRE><<B><I>elemName</I></B> href="cid:<B><I>cid-uri</I></B>"></PRE>
<P>where <B><I>elemName</I></B> is the name of some element within the message,
and <B><I>cid-uri</I></B> is the URL-encoded name of the Content-ID
for the attachment which you are referring
to, or alternatively, an absolute or relative
URI referring to the Content-Location of
the attachment. (The Content-ID is set as
part of the javax.mail.internet.MimeBodyPart.)</P>
<P>Last updated 5/23/2001 by Bill Nagy <<A href="mailto:nagy@watson.ibm.com">nagy@watson.ibm.com</A>>.</P>
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