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In-Depth Information
Request/Response Aspects for Web Services
Ernst Juhnke
1
, Dominik Seiler
2
,RalphEwerth
1
,
Matthew Smith
3
, and Bernd Freisleben
1
1
Department of Mathematics & Computer Science, University of Marburg
Hans-Meerwein-Str. 3, D-35032 Marburg, Germany
{ejuhnke,ewerth,freisleb}@informatik.uni-marburg.de
2
Information Systems Institute, University of Siegen
Holderlinstr. 3, D-57068 Siegen, Germany
d.seiler@fb5.uni-siegen.de
3
RRZN, University of Hannover
Schloßwender Straße 5, D-30159 Hannover, Germany
smith@rvs.uni-hannover.de
Abstract.
Web services rely on standardized interface descriptions and
communication protocols to realize loosely-coupled distributed applica-
tions that are executed on several interconnected hosts. However, the
extension of a web service with non-functional requirements, such as e-
cient data transfer or security, is a tedious task that also requires access to
the web service implementations. In this paper, we present
request/re-
sponse aspects
for web services to allow software developers to easily
and transparently change the data exchange between web services
with-
out
modifying their implementations or their interfaces. A framework
supporting request/response aspects for web services is presented, and
implementation issues are discussed. The usefulness of request/response
aspects is illustrated by three use cases.
Keywords:
Aspect-oriented Programming, Web Service, Service-orien-
ted Architecture, SOAP.
1
Introduction
With the advent of service-oriented architectures (SOA) and web services as
their most widely used implementation technology, applications can be composed
of existing web services, promising higher reusability, faster development, and
consequently, reduced costs. Web services are identified by their interfaces that in
turn are defined using the Web Services Description Language (WSDL, [23]). A
WSDL document contains a set of operations and defines input/output messages,
faults and bindings for transport protocols. Typically, web services communicate
via SOAP [22], relying on a request/response message exchange pattern based
on XML documents. Given a set of web services, composition languages such
as the Business Process Execution Language for Web Services (BPEL, [2]) can
be used to compose them into a more complex service. The original services act
as the basic activities in the newly constructed service; hence, this paradigm is
