Web Services

Course IntroductionWeek1

Eva Rose, Ph.D.

Who am I?

● Became interested in programming in H.S. ● Masters thesis on Java and the Java Virtual

Machine.● Ph.D. thesis on the Java bytecode verifier.● Studied web services at IBM T.J.Watson

research center. ● Teach web services and advanced

programming language theory to graduate students and juniors.

● Attached to Center for Collaborative and On-Demand Computing (CCODC).

Syllabus

● also available from http://eva.rose.name● contact and course announcements ● course objective, approach, and assessment● class participation and attendance● course overview

Introduction to Web services.

● What is a web service?● SOA and distributed information systems● Web service architecture

Go and explore....

● go to the w3c.org website, or● go to the oasis.org website.

What does web services “solve”?

● Evolved around the problem of application integration in distributed systems.

● Removes the need for tightly coupled components,

● resulting in monolithic, inflexible applications.● Hides technical details about the service

behind the service Interface

When does SOA and web services apply?

● part of the solution exists in multiple networks.

● solution components are built and run by different organizations.

● the components which needs to be integrated have heterogenious platforms (OS, application server, programming language).

● the business process could be automated without human interaction.

● dynamic and flexible business environmet.

Example of an XML document

● Viewing Listing 2.1: purchase order iinformation in a browser.

The XML document prolog

● The processing instruction “?xml” identifies a document as an XML document.

● All XML documents begins with:

<?xml version=”1.0” encoding=”UTF-8” ?>

Comments in XML

● cannot be nested.

<--! this will not be processed as XML -->

XML syntax rules

● Elements● Attributes● Character data

● organized as a tree.● one root element● child, parent, sibling,

...

XML Element syntax

● Element start and end tags: <po> ... </po>● Empty element: <po />● Non-empty:

<po>...

</po>

Element content(ie, text, XML)

XML Attribute Syntax

● name-value pair● lives within an element (start) tag.

name = “ value”

Character data (reserved)

● encoding, whitespace, entities.

<>&'“

Character Escape sequences

&lt;&gt;

&amp;&apos;&quot;

Exercise: Escape characters

● Go to eclipse on your lab machine.● Use the text editor to enter the XML

document on p.43.● Open the XML document in your browser.

What do you see?

The CDATA construct

● Allows any sequence of characters.

<![ CDATA{ ...]]>

Exercise: CDATA

● Go to the previous file (corresponding to the XML document on p. 43). Use the CDATA construct instead of all the escape characters.

See you next week.

Lecture (please read in advance): p.44-91.