Tài liệu Java Testing and Design- P7 pdf

This section shows how an intelligent test agent that wasbuilt in TestMaker interacts with relational database systems.. # DB_meister.a # Created on: July 3, 2002 # Author: fcohen@pushto

Preparation and Setup Agents 279

The agent begins the main body of the commands by opening the

The agent then creates variables used during command processing,including a counter for the number of commands processed, an identifier forthe next new message, and an integer value to track the indentation of thenext reply message in the tree of reply messages

Setup_agent processes each command in the commands file The for

command loops through every line in the commands file.

for line in dbfile.readlines():

The agent creates a list variable called commands by reading a line from

the commands file and splitting it into a list of individual values by delimiting

each value by a comma character using the split function

commands = line.split(",")The commands variable is a list so commands[0] refers to the first value

found in the current line of the commands file In the discussion system

example, the first time through this loop commands[0] contains anew_thread command

The agent handles commands and takes action accordingly When dling a new_thread command, the agent indicates the command has beenhandled, bumps up the number of handled commands, posts the messageusing the post_message() function, pushes the indentation value onto thestack using the push() function, then bumps up the number of messages andthe indentation value

if int( command ) == new_thread:

handled=1 tick += 1 node=post_message(next_message,indent, \

280 Chapter 8 State, Design, and Testing

"top-message",commands[1],commands[2]) push( indent )

next_message += 1 indent += 1

The handled variable is a simple flag that the agent uses to make sureevery command is recognized and executed If handled is still 0 at the end ofthe next block of code, then an error is thrown

if handled==0:

print "Unknown command!"

print line Prepare_Setup_Agent automatically runs Setup_agent using the exec- file command When execfile is used, Setup_agent exits back to Prepare _Setup_Agent then execution continues after the execfile command

Using Databases to Configure Tests

Earlier in this chapter we learned how the preparation stage of a test formatsconfiguration instructions into a command file The configuration instruc-tions may be manually coded into a preparation test agent retrieved from afile or database This section shows how an intelligent test agent that wasbuilt in TestMaker interacts with relational database systems

TestMaker provides a rich environment for building intelligent test agents,but at its heart TestMaker is just another application written in Java The Javalanguage provides database connectivity through the JDBC API JDBC driv-ers are available for most commercial and open source databases, includingOracle, Microsoft SQL Server, and PostgreSQL

Following is a test agent that demonstrates how to use JDBC functionsfrom within a test agent environment

# DB_meister.a

# Created on: July 3, 2002

# Author: fcohen@pushtotest.com print "Agent running: DB_meister.a"

print "Description:"

print " Shows how an agent may use a relational "

print " database to receive or record data."

print

Using Databases to Configure Tests 281

print " NOTE: THIS AGENT DOES NOT ACTUALLY RUN since "

print " there is no relational database source"

print " available and this agent print depends on "

print " a JDBC driver that you must supply."

print

# Please configure this agent and then remove the

# sys.exit command

print print "Stopping agent: Please configure this agent to your"

print "own JDBC driver and relational database source."

print sys.exit

# Import tells TestMaker where to find TOOL, JDBC objects import sys

from java.sql import DriverManager

# JDBC Driver information

# Note: You must provide these parameters to

# use your provided JDBC driver You must also add the JDBC

# driver code to the TestMaker classpath Set the classpath

# by changing the testmaker/testmaker/bin/ide.cfg file.

except:

print print "Could not load JDBC driver: ", \ JDBCDriverClassName

sys.exit

282 Chapter 8 State, Design, and Testing

# Show example of reading from a relational database

print print "===================================================" print "Information from the Customers table:"

# Customer count

query1 = "select count(*) from Customers"

try:

statement = myConn.createStatement() results = statement.executeQuery( query1 ) results.next()

except Exception, ex:

print "Exception while counting customers: ",ex sys.exit

print print " Customer count: ", results.int

# Customer list

query2 = "select customer_number, last_name, "

query2 += "salutation, city, year"

query2 += " from table"

query2 += " order by last_name"

try:

statement2 = myConn.createStatement() r2 = statement.executeQuery( query2 ) except Exception, ex:

print "Exception while getting customer list: ",ex sys.exit

print print " Complete customer list (sorted by last name):"

while results2.next():

print " ",r2.getString,r2.getString,r2.getString, \ r2.getString(4),r2.getString(5)

# -Using Databases to Configure Tests 283

# Inserting data into a table

insert1 = "insert into customers files (id, name,"

insert1 += "manager, phone) "

insert1 += "VALUES (1001, 'Simpson', 'Mr.', "

insert1 += "'Springfield', 2001)"

try:

i1 = myConn.createStatement();

ir1 = s2.executeQuery( insert1 );

except Exception, ex:

print "Exception while inserting a record: ",ex

print print "Agent ended."

Let us look at the agent script’s individual sections to learn what the scriptdoes to communicate with a relational database Unlike most of the other testagents presented in this book, the DB_meister agent does not actually runsince at the time of writing this book there was no publicly available relationaldatabase source for the agent to connect to Check the http://examples.push-totest.com Web site to see if an example database source is now available

sys.exit

By default this agent starts and then exits To run this agent, please ure the agent to connect to an available database and then remove thesys.exit command

config-The Import command tells TestMaker where to find the standard Javalibraries that implement an interface to the JDBC driver

from java.sql import DriverManager

A JDBC driver implements all the code needed to communicate with aspecific type of database and an interface that conforms to the JDBC specifi-cation published by Sun for the Java platform Database providers and third-party driver manufacturers provide JDBC drivers A driver is packaged as aJAR file Adding the driver JAR file to the TestMaker classpath is required togive test agents access to the driver’s functions For instructions on addingresources to the classpath, see the TestMaker documentation

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The test agent sets four basic parameters to tell the JDBC driver whereand how to connect to the database JDBCDriverClassName points to thedriver object in a Java namespace defined by the driver manufacturer ThejdbcURL parameter describes which JDBC driver to use (JTurbo), the URL

to the database, and the database name (ORCL.)JDBCDriverClassName = "com.ashna.jturbo.driver.Driver"

jdbcURL = "jdbc:JTurbo://myrelationaldatabase:1527:ORCL"Driver and database manufacturers define the format to the JDBCDriver- ClassName and jdbcURL parameters Here is a short list of common JDBCdrivers and their parameters:

For IBM DB2 (http://www.ibm.com), the agents use:

"jdbc:oracle:thin:@myrelationaldata-JTurbo is a JDBC driver for MS SQL server (http://www.newatlanta.com/index.jsp):

JDBCDriverClassName = "com.ashna.jturbo.driver.Driver"

jdbcURL = "jdbc:JTurbo://myrelationaldatabase.com:1433/ \ dbhost/sql70=true"

JDBC drivers use Java’s class loader functions to find and access a driver’sfunctions Note that the agent code uses the try/except format so as to trap

an error that may happen when the driver loads Possible errors include Javanot finding the driver, the driver not being able to connect to the database, orthe wrong configuration information

try:

java.lang.Class.forName( JDBCDriverClassName ) myConn = DriverManager.getConnection( jdbcURL, \ jdbcUserID, jdbcPassword )

except:

print print "Could not load driver: ", JDBCDriverClassName sys.exit

Using Databases to Configure Tests 285

Now that the driver is loaded, the agent shows a few SQL functions toretrieve data from the Customers table in the database The Customers tablehas these fields and descriptions:

query1 = "select count(*) from Customers"

Executing the query requires a connection object and statement object

The agent uses the try/except format to catch errors that happen whileprocessing the database function

try:

statement = myConn.createStatement() results = statement.executeQuery( query1 ) results.next()

except Exception, ex:

print "Exception while counting customers: ",ex sys.exit

The query result is returned in the results object Using the next() methodretrieves the first row of the database results In this case there is only a singlerow, which is formatted and printed to the TestMaker output window

print " Customer count: ", results.intThe second query demonstrates a more complex database command thatreturns more than one row of results The query2 += "" format builds thequery statement from multiple parts

query2 = "select customer_number, last_name, "

query2 += "salutation, city, year"

query2 += " from table"

query2 += " order by last_name"

286 Chapter 8 State, Design, and Testing

The agent makes a connection to the database and returns the results2object that holds the response from the database The while command loopsthrough all the rows in the response

while results2.next():

print " ",r2.getString,r2.getString,r2.getString, \ r2.getString(4),r2.getString(5)

The third example shows how the agent inserts new rows into the ers table The setup for the database command is the same as the previoustwo queries

Custom-insert1 = "insert into customers files (id, name, "

insert1 += "manager, phone) "

insert1 += "VALUES (1001, 'Simpson', 'Mr.', "

ir1 = s2.executeQuery( insert1 );

except Exception, ex:

print "Exception while inserting a record: ",exThe TestMaker script language provides access to all of JDBC’s manymethods Consult your driver documentation for examples of additionalJDBC functions

Using Lingo to Make Test Content Close to Real

In the discussion system example presented earlier in this chapter, theSetup_agent creates a new discussion group by posting messages and replymessages Experience shows us that when the message content is uniform, theunderlying systems (Web-enabled application servers, database servers, net-work routers, and load balancers) try to use optimization technology toenhance the performance of the system Rarely, if ever, in the real world would

we find a discussion where every message contained the same content

There-Using Lingo to Make Test Content Close to Real 287

fore, TestMaker includes a handy Lingo utility to automatically generatepseudo-English-like content for message subject lines and message bodies

For example, suppose the test agent needed to create a new message TheLingo utility object creates this paragraph:

Lipsem it quantos surbatton ditchek surbatton deplorem ventes so surbatton quantos infreteres ipsem aqua sit ventes Campus ad surbatton ad infreteres ad novus surbatton deplorem it delorum novus Campus quantos ditchek quantos

Via surbatton novus surbatton Novato quantos ditchek rem novus ditchek ventes.

deplo-The important thing is that Lingo creates a different paragraph each time

it is called, which defeats the system’s attempt to optimize performance whilerunning tests where the message content is always the same

Following is a test agent in its entirety that demonstrates Lingo’s manyuses An explanation of the Lingo functions follows the agent

print "Technique 1: A simple message example"

myLingo = Lingo()

print "Subject:",myLingo.getSubject( 4 ) print "Message:"

print myLingo.getMessage() print "-end of message-"

print print "==================================================="

print "Technique 2: URL encoded message example"

print print "If we needed to include a message in an HTTP POST"

print "command the message would need to be URL encoded."

print "Here is a Lingo message that is URL encoded:"

print

288 Chapter 8 State, Design, and Testing

print myLingo.getMessageEncoded( 100 )

print print "===================================================" print "Technique 3: A complete Lingo letter"

print print "Here is an example business memo using several" print "Lingo methods."

print

print "Dear Mr.",myLingo.getSingleCap(),":"

print print "We have found the manuscript you were searching" print "for and it includes the following excerpt:"

print

# Next we use a special version of getMessage

# to include a starting capital letter, ending period

# and encoding The format is:

# getMessage(int size, boolean startCap,

# boolean endPeriod, boolean encoded)

print myLingo.getMessage(15, 1, 1, 0)

print print "As you can see we are not certain what dialect the" print "text is written in Please do your best to let us" print "know what it means."

print print "Sincerely,"

print print myLingo.getSingleCap()

print print "===================================================" print "Technique 4: Making your own Lingo language"

print print "Here is the same example business memo from"

print "technique 3 but using French words to form the" print "Lingo gibberish."

print

caps = [ "Francois", "Sanjournais", "Berjerack", "Mon", \

"La", "Le", "Incroyable! " ] tokens = [ "devrait","ouvrir","le","cortËge,","entourÈ", \

Using Lingo to Make Test Content Close to Real 289

print print "We have found the manuscript you were searching"

print "for and it includes the following excerpt:"

print

# Next we use a special version of getMessage which

# has options to include a starting capital letter,

# ending period and encoding The format is:

# getMessage(int size, boolean startCap,

# boolean endPeriod, boolean encoded) print frenchLingo.getMessage(15, 1, 1, 0) print

print "As you can see we are not certain what dialect the"

print "text is written in Please do your best to let us"

print "know what it means."

print print "Sincerely,"

print print frenchLingo.getSingleCap() print

print "Agent done."

Lingo_meister is a simple agent to show the capabilities of the Lingoobject provided in TestMaker’s TOOL Lingo provides English-like gibberishthat is well suited to be the content of a posted test message Lingo objectsare created by using an Import command to identify the Lingo object to theJython script language

from com.pushtotest.tool.util import LingoThe Lingo object is instantiated and then used by accessing its manymethods

myLingo = Lingo()

290 Chapter 8 State, Design, and Testing

The getSubject() function returns a string of gibberish words with a riage return character terminating the string The optional value in getSub- ject() identifies how many gibberish words to include in the result

car-print "Subject:",myLingo.getSubject( 4 )The getMessage() function returns a random amount of paragraphs of gib-berish words Each paragraph is terminated with two carriage return characters.print myLingo.getMessage()

When working in HTTP/HTML environments, a request to a host mustoften be URL encoded In URL encoding, characters such as < and > wouldinvalidate the HTML code so they are encoded into &lt; and &gt; codesthat the host will decode The getMessageEncoded() function returns aURL-encoded group of paragraphs of gibberish

print myLingo.getMessageEncoded( 100 )The third example in Lingo_meister shows how a Lingo object may beused within print commands to generate a sample memorandum letter.print "Dear Mr.",myLingo.getSingleCap(),":"

The getSingleCap() method returns a single gibberish word that is talized The body of the memo uses a special version of the getMessage()function that features options to include a starting capital letter, endingperiod, and encoding The format for the special method is:

capi-getMessage(int size, boolean startCap, boolean endPeriod,\ boolean encoded)

The last technique in Lingo_meister shows how an agent can define itsown dictionary of gibberish words Lingo requires a list of capitalized wordsand lowercase words These are passed to Lingo when the agent instantiates

a new Lingo object

frenchLingo = Lingo( caps, tokens )Now, Lingo chooses gibberish words from the new list of capital and low-ercase words

Summary 291

Summary

This chapter discussed system state, including the repeatable lifecycle thatdefines the preparation, setup, execution, and analysis stages of a test Thischapter showed TestMaker test agent script examples that use the resources

of a database system to initialize the state of a system prior to testing

The next chapter shows how to use intelligent test agents in Microsoft.NET environments and in secure environments

.NET is a product strategy that overhauls and elevates the Microsoftdevelopment environment and tools to a new level of sophistication, ease-of-use, and interoperability over previous Microsoft development tools .NET isMicrosoft’s way to add a new Common Language Runtime (CLR) to itsobject-oriented development tools and to add XML technology to everythingMicrosoft does.

Microsoft is working with the European Computer Manufacturers ation to put forward open standards for CLR (TG3) and the C# language(TG2) The ECMA Web site hosts working documents on these efforts: http://www.ecma-international.org/ Additional information is at http://www.dotne-texperts.com/ecma/index.html and at http://msdn.microsoft.com/net/ecma/ NET defines the Microsoft Intermediate Language (IL) code and CLR isthe IL runtime virtual machine environment that provides memory manage-ment, automatic garbage collection, security, and threading CLR enables

Associ-M

294 Chapter 9 Integrating with NET Web Services

Microsoft development tools to support a variety of object-oriented guages, including C, C++, VB.NET, C#, and J# The single CLR run-timecan run components built in any of these languages that can output IL Sothe Microsoft development tools work with all those languages Following is

lan-an example C# lan-and C++ program written in Microsoft Visual Studio NETthat features a mixture of programming languages Visual Studio NET com-piles this program into a single unit that CLR runs.1

# We begin with a method defined using C# class Vector

{ /// <summary>

/// Compute the length of the vector /// </summary>

public double Length {

get { return(Math.Sqrt(x * x + y * y));

} } }

# then add some C++ code to the mix unsafe static int AddArrayUnsafe(int[] numbers) {

int* pCurrent = pNumber;

int* pLimit = pNumber + numbers.Length;

while (pCurrent < pLimit) {

result += *pCurrent;

pCurrent++;

} } } return result;

}

1 A pretty good introduction to NET is on the Microsoft Web site at http://www.microsoft.com/net/basics/whatis.asp

Interoperability and Integration 295

The example code shows NET’s mechanism to manage C++ pointers inthe otherwise memory-managed safe environment of C# The same mecha-nism works in other CLR compatible languages

In many ways NET is Microsoft’s best effort yet to use XML XMLenables Microsoft development tools to offer standardized configuration,description, and deployment definitions For example, while Microsoft Biz-Talk Server, SQL Server, and Exchange Server still use the Windows Regis-try, they also now use XML for configuration and management features

Microsoft product strategies build XML into all its technology by codingconfiguration information in XML formats stored in files and databases

XML also becomes the Microsoft common language for all its APIs Ineffect, it is not unreasonable for software developers to expect any MicrosoftAPI to be available as a SOAP-based XML interface that adheres to aWSDL description

.NET benefits IT managers, software developers, and QA analysts:

• With the emphasis on XML, configuration and management files become more open and more standardized Third-party system management solutions such as HP’s OpenView and IBM Tivoli should more easily and rapidly support Microsoft servers

• QA analysts will find testing NET applications easier than prior Microsoft-built applications since the APIs to these applications self-describe valid data

Microsoft’s adoption of XML and delivery of a single run-time engineenables increased productivity and efficiency as developers, IT managers,and QA analysts deliver products built with Microsoft development tools Ofcourse, like all new technologies, the NET products come with problemsand issues that need to be understood and tested

Interoperability and Integration

The good news for Java developers working with systems built with NET isthat there have been no major train wrecks For the most part, systems builtwith NET offer good interoperability with Java-based systems The biggerproblem for Java developers is usually integration

Consider an example where a product supply company offers a Web vice to take purchase orders The service receives SOAP encoded orders

ser-296 Chapter 9 Integrating with NET Web Services

pop-1 The Java client function uses a floating-point double variable to

hold the price while the NET function uses a string

2 Neither the Java client nor the NET service explicitly know the

currency expressed in the price element For example, the Java client may send a price expressed in U.S dollars while the NET Web service expects Euros

3 Java uses a naming convention where method names that begin

with a capital letter are usually reserved for operating system calls On the other hand, NET’s convention is to use capital let-ters to define all method names This isn’t a show stopper like the other two problems, but it may raise some eyebrows between Java and NET developers

These are not really interoperability issues as much as they are the systemsintegration issues that we typically have to deal with everyday

Figure 9–1 The Java placeOrder function makes a SOAP request to the TakeOrder method of the published Web service

How Is NET Different? 297

.NET’s support of XML and SOAP offers a solution to problems 1 and 2

By using XML Schemas, the NET Web service provides data typing for therequest method The XML Schema below defines the price element to be aString type

<xs:element name="name" type="xs:string"/>

<xs:element name="product" type="xs:int"/>

<xs:element name="price" type="xs:string"/>

This likely means modifying the client-side code to express prices as strings in therequest and to decode the response back into a floating-point double value

See Chapter 7 for additional SOAP-related problems you will likelyencounter, including data type interoperability, adherence to standards, andunderlying platform differences More discussion of NET’s use of WSDLcomes later in this chapter

How Is NET Different?

By their nature, the development tools we use enforce a certain thinking thatwinds up in the software applications For example, Visual Studio NET auto-matically generates C# code to access a given Web service using document-style SOAP requests by default Developers that rely solely on automateddevelopment tools risk building interoperability problems into their systemswithout knowing where to look when problems happen

Document-style SOAP turns out to be a shrewd architectural decision, as

we will see later However, from a testing perspective, if your NET Web vice uses document-style SOAP encoding (the default in ASP.NET), there

ser-298 Chapter 9 Integrating with NET Web Services

may be interoperability problems with other SOAP clients who only speakRPC-encoded SOAP

Chapter 7 shows the various styles of SOAP requests and responses Thetwo most popular styles are RPC and Document Most development environ-ments include utilities that examine method declarations in source code filesthat define an object Then they automatically build the needed code to offerthe object’s methods as Web services The local object makes a call to a spe-cific method and object running on a remote server and passes parametersdefined in the method declaration For example, the following C# code isautomatically deployed as a SOAP-based Web service:

public class myService: System.Web.Services.WebService {

public HelloService() {

//CODEGEN: This call is required by //the ASP.NET Web Services Designer InitializeComponent();

} [WebMethod]

public string greetingService (String strMyName)

{ return "Hello, " + name +", \ and welcome to my service.";

} [WebMethod]

public string SayGoodBye() {

return "Goodbye!";

} }

}

How Is NET Different? 299

This code is exposed as a Web service that has a greetingServicerequest interface The SOAP call receives a string as a parameter andresponds with a string in its return value

RPC-style SOAP requests are very attractive to developers because theWeb service tools that generate SOAP interfaces and WSDL descriptions do

a lot of heavy lifting for the developer For example, the following methodreturns a complex data type:

public class myComplexService{

public Hashmap greetingService( firstname name ) { Hashmap ht = new Hashmap();

ht.put( "Event", name );

ht.put( "Keycode", keycode );

ht.put( "PcAssemblyNumber", pcassembly );

ht.put( "SoftwareDottedString", dottedsw );

ht.put( "CurrentTime", new Date() );

ht.put( "CommandKey", "7" );

return ht;

In an RPC-style SOAP request, the developer may depend on a ment tool to build the SOAP request code to handle marshaling a Hashmapobject into XML that is sent in a SOAP request to the server This codewould also make use of custom serializers that would convert objects like theHashmap into XML

develop-Document-style SOAP requests begin with the XML document alreadydefined Instead of depending on the development tool, document-style SOAPrequests are built by populating an XML tree in the application code itself

public class myComplexService{

public void callGreetingService( firstname name ) { body = new SOAPBody();

body.addElement ( "Event", name );

body.addElement ( "Keycode", keycode );

body.addElement ( "PcAssemblyNumber", pcassembly );

body.addElement ( "SoftwareDottedString",dottedsw);

body.addElement ( "CurrentTime", new Date() );

body.addElement ( "CommandKey", "" );

SOAPRequest.send( body );

.NET is a document-style environment By default NET developmenttools create document-style SOAP requests While NET tools provide a

300 Chapter 9 Integrating with NET Web Services

switch to use SOAP RPC calls, there is very little support in NET for RPC

If an application makes a SOAP RPC call to a NET Web service that expects

a document-style request, then NET returns a fault—the Web serviceequivalent of throwing an exception

Microsoft’s choice for document-style SOAP puts a bend in the directionmost developers were headed Many Web services developers come from thecomponent software worlds that are dominated by CORBA, RMI, and COM.SOAP RPC is a natural bridge from component software architectures toWeb services On the other hand, business-to-business (B2B) exchange infra-structure has been XML based from the start so document-style SOAP is anatural there

To see a vivid example of the divergence between Web service developers

in the J2EE and NET camps, take a look at the list of publicly available Webservices published on XMethods.net This list cleaves in two: SOAP RPCWeb services are written in Java and document-style Web services are writ-ten in NET

One last thing to consider in both RPC and document-style SOAP calls isthat the SOAP standard does not cover more complicated data elements thanarrays and structures In the previous example we would find that Microsofthas its own encoding for Hashmaps that do not interoperate with the otherWeb service platforms The developer is left to encode arrays of arrays as well

We have seen the stylistic differences between SOAP RPC and style SOAP Under the covers and in the implementations of SOAP lie scal-ability and performance issues that come with decisions to use RPC and doc-ument-style SOAP

document-Document-Style Scalability

Regardless of the SOAP call style, each SOAP message goes through thesame stages of creation The creation process begins with a value stored in anobject When the value is passed to a Web service, the object is translatedinto a Document Object Model element and stored in memory When therequest is marshaled to be sent to the Web service host, the Elements arerounded up and serialized into strings in XML format The final step thengathers the XML formatted strings and sends the combined group over atransport to the Web service host Figure 9–2 illustrates this process

The steps depicted in Figure 9–2 show four possible places where ity and performance problems can be introduced The Object to Elementtransformation might run into problems inherent in the way that CLR repre-

scalabil-How Is NET Different? 301

sents data The Object to Element transition could introduce problems sincethe performance of many XML parsers is not sufficient The serializers forthe XML-to-UTF-8 transition can be susceptible to bugs and performanceissues Many other problems lower system scalability and performance

In tests of Web service application servers, the early systems turned out tohave significant scalability and performance problems, especially when com-paring SOAP RPC to document-style SOAP The results of these tests con-clude the following:

• Document-style SOAP operations outperform SOAP RPC

• SOAP RPC displays significant scalability problems as the payload size of a request and response increases

Compare the TPS results from one popular application server:

Figure 9–2 SOAP requests start with data in an object, converts the object into a DOM Element, and serializes the Element into an XML string Then, they combine the strings and send them across a transport to the Web service host

302 Chapter 9 Integrating with NET Web Services

The test measured the round-trip time it took to make a request andreceive a response as measured at the client side To run this test in yourenvironment, this test code and many others are available for free download

at http://www.pushtotest.com/ptt/kits/index.html

Note that in every case the TPS values for SOAP RPC transactions wereslower than document-style calls Additionally, while the document-style TPSvalues remained steady even under the weight of increasing payload sizes,the SOAP RPC TPS values declined significantly

These tests do not conclude that architecturally document-style SOAP isany better than SOAP RPC, or vice versa However, they do show that theSOAP implementations tested have serious limitations and flaws As new andbetter implementations become available, a scalability and performance test

of the new SOAP stacks is needed to understand how the performance acteristics change

char-SOAP Headers in NET

In the formative time of Web services, Microsoft was the first to strongly port XML Schema, WSDL, and SOAP headers Other Web service platformswere less convinced So to a developer on WebSphere, Apache SOAP, andBEA WebLogic, the XML Schema in WSDL documents and the contents ofSOAP headers in Microsoft-built Web services may appear odd SOAP wasoriginally introduced in Chapter 4 with an explanation of common SOAP val-ues and formats This section shows how Microsoft puts its own touch onSOAP headers

sup-Before we explore how NET uses the SOAP header, you may want toreview the specifics of the SOAP header element The SOAP 1.1 Specifica-tion (found at http://www.w3.org/2000/xp/Group/) and the SOAP 1.2 Work-ing Draft indicate that a SOAP message has three possible elements: the top-level Envelope element and two child elements (Header and Body) Follow-ing is an example of a SOAP message with all three elements:

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xmlns:xsd="http://www.w3.org/2001/XMLSchema">

<soap:Header>

<PriorityHeader xmlns="http://msdn.microsoft.com/AYS/6/2002/">

<Priority>HighPriority</Priority>

How Is NET Different? 303

</PriorityHeader>

</soap:Header>

<soap:Body>

<PlaceOrder xmlns="http://msdn.microsoft.com/AYS/6/2002/">

be a little ahead of the Header usage curve

The SOAP specification defines three optional attributes that can apply toheader blocks: the encodingStyle attribute, the actor attribute, and themustUnderstand attribute While encodingStyle is meant to be optional,.NET servers and the SunONE Application Server expect the encoding- Style attribute to be present

SOAP is going through the same evolutionary transformation as servletsand other middleware have While a single standalone object would respond

to Web service requests, the new architecture implements several smallerobjects that each handle a single facet of a Web service request, and arestrung together in a string of handlers The SOAP header elements are pro-cessed by individual NET programs as the SOAP message moves through achain of handlers

The SOAP message is already defined to be in well-formed XML format,

so unlike the headers in an HTTP request, the SOAP headers do not need todescribe the data in the SOAP message SOAP headers, especially in NET,help process the data in the body For example, in a banking environment, aSOAP header transmits authentication and transaction information that iden-tifies the person who sent the SOAP message and the context in which it will

be processed Another example is an airline reservation service where theSOAP header defines a time limit on the validity of airfares sent in the SOAPmessage

While the SOAP specification provides for any valid XML data to beincluded as a SOAP header, Microsoft really levers SOAP header values So it