1. CIS*6650.01 Service-Oriented Computing
Qusay H. Mahmoud, Ph.D.
Qusay H. Mahmoud
CIS*

2. Web Services… RPC the XML way (two ways) JAX-RPC, JAX-WS, …
1) XML-RPC (xml-rpc.com)
2) SOAP
JAX-RPC, JAX-WS, …
Document vs. RPC Style
REST
Web Services Architecture
Qusay H. Mahmoud
CIS*

3. XML-RPC
A specification and implementation that enable applications running in a heterogeneous environment to make procedure calls over the Internet
Defined at UserLand Software in 1998
Uses HTTP as the transport protocol and XML for encoding
Designed to be as simple as possible, allowing complex data structures to be transmitted, processed, and returned
Qusay H. Mahmoud
CIS*

4. XML-RPC Not a solution to every problem.
Simple and effective mean for exchanging information (spec is less than 10 pages with examples and FAQ)
"We wanted a clean, extensible format that's very simple. It should be possible for an HTML coder to be able to look at a file containing an XML-RPC procedure call, understand what it's doing, and be able to modify it and have it work on the first or second try... We also wanted it to be an easy to implement protocol that could quickly be adapted to run in other environments or on other operating systems." - xmlrpc.com
Simplicity makes it limited
Qusay H. Mahmoud
CIS*

5. Sample XML-RPC request testcase.getMonthName(3) CIS*6650.01
Qusay H. Mahmoud
CIS*

6. Sample
XML-RCP Response
Qusay H. Mahmoud
CIS*

7. XML-RPC to Java Mapping
Explore mapping to other languages
Qusay H. Mahmoud
CIS*

8. SOAP
A Lightweight XML-based protocol for exchanging information in a distributed environment
More complex than XML-RPC (over 40 pages)
Makes extensive use of XML namespaces and attribute specification tags in every element of a message
Adds features that don’t exist in XML-RPC: user-defined data types, specify recipient, message specific processing control, and others
Qusay H. Mahmoud
CIS*

9. Sample
See Week2 slides
Qusay H. Mahmoud
CIS*

10. Comparison
XML-RPC vs. SOAP
Qusay H. Mahmoud
CIS*

11. XML-RPC vs. SOAP
SOAP supports request routing and pre-processing of requests via SOAP headers
XML-RPC is lighter, taking up less bandwidth, and requiring less processing power
SOAP is namespace-aware (in fact every element must be namespace-qualified)
SOAP has a heavy-weight, robust data typing mechanism based on XML Schemas
XML-RPC is easily sent and consumed, and is easily readable by humans
SOAP messages have a considerable amount of packaging contained in the envelope, but this allows for flexibility in the messaging paradigm used (publish-subscribe, point-to-point, etc.)
Qusay H. Mahmoud
CIS*

12. JAX-RPC The push for Java API started in 2001 as JSR-101 (jcp.org)
V1.0 released in 2003
Java primitives are tied to XML schema types
Supports more Java standard library objects (e.g. BigInteger)
Architects of JAX-RPC has XML-RPC and SOAP in mind
Qusay H. Mahmoud
CIS*

13. JAX-WS
Next version of the spec is known as JAX-WS (JSR-224) Java API for XML-based Web Services
Aims to reduce the complexity of web service development
Java WSDP 1.6 (use GlassFish)
Use JAX-RPC if:
Using simple requests
You control both the client/server
You don’t need to publish WSDL
Want to keep client-side parsing simple
But remember…using standards is a good thing for interoperability (your apps need to interact with other third party apps)
Qusay H. Mahmoud
CIS*

14. Resources XML-RPC spec: xml-rpc.com/spec SOAP: w3.org/TR/soap
JAX-WS (JAX-RPC 2.0): (JSR 224:
Apache XML-RPC:
UserLand Frontier (frontier.userland.com)
Many others…explore on your own
Qusay H. Mahmoud
CIS*

15. Document vs. RPC Style
SOAP was originally designed to support RPC style
Later (starting with SOAP 1.0), the spec expanded to support RPC and unstructured messages (document)
RPC style: SOAP Body must conform to a structure that indicates the method name and a set of parameters
Document style: SOAP Body can be structured in any way you like
Qusay H. Mahmoud
CIS*

16. Source: Anne Thomas Manes Blog, atmanes.blogsport.com
RPC vs. Document Style
Source: Anne Thomas Manes Blog, atmanes.blogsport.com
Message encoding: literal means Body contents conform to a specific XML Schema, SOAP encoding uses a set of rules based on XML Schema data types to encode the data
RPC: includes an operation name or place holder and document style doesn’t (significant architectural style)
This document style example uses a state transfer style
See more examples:
Qusay H. Mahmoud
CIS*

17. State Transfer Style
Such as MOM (Message-Oriented Middleware), pipe-and-filter
Architectural constraint: all components expose the same application interface
Through a single operation such as “process Data”
If a server exposes this operation, any client can submit data to it for processing
Since there is one operation, its use is implicit and doesn’t need to be included in the message
Qusay H. Mahmoud
CIS*

18. REST REpresentational State Transfer An architectural style
Think of it as a design pattern
Underlying concept for today’s Web architecture
Every distinguishable entity is a resource
URLs identify resources
An approach for creating Web services
Qusay H. Mahmoud
CIS*

19. REST See the slides from http://www.xfront.com/REST.ppt CIS*6650.01
Qusay H. Mahmoud
CIS*

20. When to use REST or SOAP REST SOA
The web services are stateless
A caching infrastructure can be leveraged
Service’ producer and consumer have mutual understanding of the context and content being passed along
Bandwidth is limited
Web service delivery into exiting web sites can be enabled easily with a RESTful style
SOA
A formal contract must be established to describe the interface that the Web service offers
The architecture must address complex non-functional requirements
The architecture needs to handle asynchronous processing and invocation
See details at: (read the section When to use REST)
Qusay H. Mahmoud
CIS*

21. Web Services Architecture
Provides a common definition of a Web service, and defines its place within a larger Web services framework to guide the community
Provides a conceptual model and a context for understanding Web services and the relationships between the components of this model
Defines minimal characteristics common to all Web services, and characteristics that are needed by some but not all Web services
Doesn’t specify how Web services are implemented
Qusay H. Mahmoud
CIS*

22. Web Services Architecture
Four models: Message-Oriented, Service-Oriented, Resource-Oriented, Policy)
Core concepts and relationships of WS
Source:
Qusay H. Mahmoud
CIS*