Programming Web Services with Perl

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

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Chapter 12: Advanced Web Services Topics

The SOAP::Lite module provides transparent access to data packaged this way (there

is nothing to do on the client or server side to accept MIME-encoded messages; the

value of the image element in this example will be the picture itself when accessed

using

SOAP::Lite), however, the current version (0.55) doesn’t help to create mes-

sages with attachments. The

SOAP::MIME package (created by Byrne Reese and avail-

able from CPAN) extends support for parsing MIME messages providing direct

access to the attachments and also allows composing messages with attachments. Its

interface is simple:

use SOAP::Lite;

use SOAP::MIME;

use MIME::Entity;

my $cid = "bar";

my $ent = build MIME::Entity

Type => "image/gif",

Encoding => "base64",

Path => "image.gif",

'Content-Id' => "<$cid>",

Disposition => "attachment";

my $som = SOAP::Lite

->uri("...")

->proxy("...")

->parts($ent)

->send_image(SOAP::Data->name("foo")->attr({href => "cid:$cid"}));

It’s quite possible that this functionality will be included in a future version of the

SOAP::Lite module.

DIME and WS-Attachments

The structure of DIME message is somewhat similar to the structure of MIME mes-

sages (yet it uses a different terminology). Parts are called records and they consist of

a header and a payload, which can be either a complete object or a chunk of an

object. Similar to the MIME format, DIME uses headers to carry metadata about an

object encoded in a payload.

There are several important differences between the DIME and MIME formats. First,

MIME identifies the structure of content stored in the body by a type specified in a

Content-Type header, whereas DIME indicates the type of the payload in two ways.

The first way is identical to the usage of MIME media type as type identifier; the sec-

ond (optional) method defines the type through the use of the URI. The second dif-

ference between the formats is that even though DIME records are 32-bit word

aligned variable length records, each record includes a fixed length binary array with

flags and lengths of four elements that follow:

OPTIONS, TYPE, ID, and DATA.Asa

result, the length of the record is always known, and it’s easy to implement random

access.