Web Services versus Distributed Objects

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1 Web Services versus Distributed Objects A Case Study of Performance and Interface Design Norddin HABTI [4/12/2006]

2 AUTHORS William R. Cook, Janel Barfield Department of Computer Sciences University of Texas at Austin Austin, Texas

programming languages and databases, distributed computing and web

3 William R. Cook Assistant Professor Research Programming languages, interfacing programming languages and databases, distributed computing and web services, software engineering, type theory, mixins, object-oriented oriented programming, web-based based information systems.

4 Janel Barfield She is a Technical Consultant for Solutions Enablement Deep Computing supporting a number of ISVs including Dassault Systèmes. She has been a pseries software developer in Server and Technology Group for five years and led development of products such as InstallShield Multi- Platform for AIX and pseries server provisioning support in the IBM Virtualization Engine. She is a primary coordinator for IBM's EXITE Camp in Austin, a summer engineering program for middle school girls, and she currently attends the University of Texas.

5 Fri 22 Sep 2006 Paper Awards for IEEE ICWS 2006 Best Paper Award: William R. Cook & Janel Barfield Web Services versus Distributed Objects: A Case Study of Performance and Interface Design

6 DEFINITIONS RPC RMI Web Services XML XML-RPC SOAP WSDL

7 RPC In order to make an RPC, you need to know the following things: Where does the code you want to call reside? Does the code need any parameters? If so, what type of parameters? Will the procedure return any data? If so, in what format?

8 RMI Java provides the Remote Method Invocation system for distributed computing. Since Java objects can be run from any platform, the idea behind RMI is to just write everything in Java and then have those objects communicate with each other.

9 Web Services Web services are a means for requesting information over the Internet all right, but they typically involve the encoding of both the request and the response in XML.

10 XML-RPC One of the easiest ways to see Web services in action is to look at the XML-RPC protocol. Designed to be simple, it provides a means for calling a remote procedure by specifying the procedure to call and the parameters to pass. The client sends a command, encoded as XML, to the server, which performs the Remote Procedure Call and returns a response, also encoded as XML.

11 The New RPC Protocol: SOAP Simple Object Access Protocol According to the current SOAP specification, SOAP is "a lightweight protocol for exchange of information in a decentralized, distributed environment.'' Advantages of SOAP over other protocols such as DCOM or Java RMI: It's platform-,, language-,, and vendor-neutral. neutral. It's easy to implement. It's firewall-safe.

12 WSDL Web Services Definition Language WSDL provides a standardized way to describe a Web service. How to call the service What to expect as a response from the service

13 The Article Web Services versus Distributed Objects: A Case Study of Performance and Interface Design

14 ABSTRACT Previous comparisons are based on an RPC communication style Web services support a documentoriented style of communication that performs well even in the face of the high latency found in internet or business transactions.

15 I. INTRODUCTION Examining the performance and design of an example application using distributed objects and web services.

16 II. FILE SERVER INTERFACES AND IMPLEMENTATIONS

17 A. Object-Oriented Interface for File Server

18 public interface Container { Container sub(string name) throws FileNotFound; File get(); File invoke(hashmap params); } public interface File { String getrequest(); long getmodified(); int getlength(); String gettext(); String gettype(); String getencoding(); } Fig. 1. Object-oriented file-server interface.

19 Container file; file = root.sub("base").sub("index.htm"); String s = file.get().gettext(); Fig. 2. Example client using the objectoriented interface

20 B. Distributed Object Implementation: an RMI File Server

21 C. Document-Oriented Interface for File Server

22 // server processes requests and returns files public interface ResourceServer { public FileResult[] perform(request doc); } // hierarchical requests can specify multiple // files in different directories public interface Request { String getname(); void setname(string name); Request[] getitemlist(); void setitemlist(request[] items); boolean getresultid(); void setresultid(int ID); Param[] getparams(); void setparams(param[] params); } // the result ID matches results to requests public interface FileResult extends File { int getstatuscode(); int getresultid(); } Fig. 3. Request interface for web services.

23 // create a request for base/index.htm Request base = new Request("base"); Request index = new Request("index.htm"); base.setitemlist(new Request[] { base }); index.setresultid(0); // perform the request File[] docs = server.perform(base); // access the text of the result String s = docs[0].gettext(); Fig. 6. Example client using the document-oriented interface.

24 D. Web Service Implementation of the File Server

25 III. PERFORMANCE

29 IV. IMPROVING USABILITY AND PERFORMANCE

30 A. An Object-Oriented Wrapper for the Web Service Client

31 B. Document-Oriented RMI Implementation

33 Conclusion

INTRODUCTION TO XML-RPC, A SIMPLE XML-BASED RPC MECHANISM

INTRODUCTION TO XML-RPC, A SIMPLE XML-BASED RPC MECHANISM INTRODUCTION TO, A SIMPLE XML-BASED RPC MECHANISM Peter R. Egli INDIGOO.COM 1/11 Contents 1. What is? 2. architecture 3. protocol 4. server implementation in Java 5. Where to use 2/11 1. What is? is a