Designing Interopable Web Services

Designing Interoperable Web Services Lawrence Chan Jeff Pennal OpenRoad Communications Ltd. Vancouver Java Users group http:// www.openroad.ca/vanjug /

Overview
The promise and reality of Web Services
Designing flexible web services
Debugging web services
Designing for performance
Recommendations
Fabulous prizes!
http://www.flickr.com/photos/josefstuefer/9500503/

The Promise It’s just XML! Cross Platform! A standard! Network Transparent! http://www.flickr.com/photos/tookie/183503927/

The Reality Hard to debug Poor Performance Poor compatibility http://www.flickr.com/photos/tom_vac/373021521/

So why bother? It works.

Real World Examples : Performance

Court Services Online
Java e-commerce for searching and filing court records
https:// webapps.ag.gov.bc.ca/cso
Multiple backend content providers in different locations with different technologies
Technical solution: Use Web Services!

Challenges
Dealing with large databases
Performance, performance, performance
Security

Solutions
Benchmarked different Java SOAP providers
Systinet vs. Axis vs. Oracle
Optimized web service API calls to match screens
Used Layer 7 XML Firewall to inspect and secure network traffic

Real World Examples : Debugging

Supreme Court Scheduling System
.NET web application for Supreme Court, hosted in Vancouver
New project goal: Integrate with Java based Ministry of AG case tracking application in Victoria
Technical solution: Use Web Services!

Challenges
Client was .Net 1.1 talking to Systinet Server for Java
Interoperability ended up being a huge problem!
Kept seeing NoSuchMethodError
How to debug?

Debugging SOAP
Recommendation: use proxy-based SOAP debugger
Microsoft Soap Toolkit 3.0
Proxy debuggers sit between SOAP client and server, and display traffic

How .NET encoded the method parameters
<soap:Body>
<p1 xmlns="http://systinet.com/xsd/SchemaTypes/">772</p1>
<p0_10 xmlns="http://systinet.com/xsd/SchemaTypes/">16882</p0_10>
</soap:Body>
versus
How Systinet encoded the method parameters
<e:Body>
<n0:p0_10 xmlns:n0= http://systinet.com/xsd/SchemaTypes/ i:type="d:decimal" >772</n0:p0_10>
<n1:p1 xmlns:n1= http://systinet.com/xsd/SchemaTypes/
i:type="d:decimal" >16882</n1:p1>
</e:Body>
.NET vs Systinet

Real World Examples: Flexibility

Hip Digital
B2B provider specializing in digital music downloads of over 1 million tracks from the 4 majors
Clients include Pepsi, Nissan and Country Music Television
Needed both a web front end and an API
Technical Solution: Use Web Services!

Hip Digital Challenges
API must integrate seamlessly into any platform
Must keep track downloads secure
Need to keep Hip Digital hidden from end users
Need to integrate with varied payment models

Hip Digital Solutions
Kept API to simple data types - strings and ints
Used one-time passwords that could be revoked at any time to authorize every download
Authorization, redemption and error handling handled via web services
Only direct connection to HD for actual track download and DRM authorization

Summary
Not all implementations are equal
Network trace tools are useful for debug
Minimize the data being sent
Design your Web Services with reuse in mind
Keep your interfaces simple
http://www.flickr.com/photos/jerryjohn/63351338

Interop Gotchas: Arrays
Problem: Arrays can be bad
Solution: Keep them simple

Interop Gotchas: Naming
Problem: Code compiles but there are runtime errors
Solution: Make class names unique, don’t rely on the namespace

Interop Gotchas: Datatypes
Problem: Datatype conversion
Solution: Keep it simple

Java vs .NET type comparison System.DateTime DateTime DateTime Calendar System.Double Double double double System.Single Single float float System.Int64 Long long long System.Int32 Integer int int System.Int16 Decimal short short System.SByte -N/A- sbyte byte System.Boolean Boolean bool boolean System.String String string String .NET Framework Type VB.NET C#.NET Java

Interop Gotchas: OO
Problem: Object Oriented features do not translate well across platforms.
Solution: Denormalize your objects, stick to simple types

Pop Quiz! This technology originally developed by Dave Winer, is considered to be the precursor to SOAP. What is XML-RPC?

Pop Quiz! This technology provides a platform-independent , XML-based registry for businesses worldwide to list themselves on the Internet. What is Universal Description, Discovery, and Integration (UDDI)?

Pop Quiz! These are the two encoding mechanisms for SOAP attachments. What are MIME and DIME?

Any Questions?
Jeff Pennal
[email_address]
Lawrence Chan
[email_address]
VanJug www.openroad.ca/vanjug
http://www.flickr.com/photos/feaverish/19544565

Designing Interopable Web Services

by dgibbons on Feb 27, 2007

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