Given Perl's natural fit for web applications development, it's no surprise that Perl is also a natural choice for web services development. It's the most popular. Download Read Programming Web Services with Perl | eBooks Textbooks Ebook Free Download Here. Programming Web Services with Perl is written for Perl programmers who have no prior knowledge of web services. No understanding of XML-RPC or SOAP is.
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Arthur Brisbane was a run-of-the-mill newspaperman, no better and no worse than a he receives free publicity in newspa. Programming Web Services with Perl. Randy J. Ray and Pavel Kulchenko. O' REILLY®. Beijing " Cambridge - Farnham " On " Paris " Sebastopol " Taipei " Tokyo. Programming Web Services with SOAP introduces you to building distributed Wb -based applications using the SOAP, WSDL, and UDI protocols. You'll learn the.
Every programming language can understand the XML markup language.
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Hence, XML was used as the underlying medium for data exchange. But there are no standard specifications on use of XML across all programming languages for data exchange. That is where SOAP comes in. We will look into further details on the SOAP protocol in the subsequent chapters.
Below are some of the reasons as to why SOAP is used. When developing Web services, you need to have some of language which can be used for web services to talk with client applications.
SOAP is the perfect medium which was developed in order to achieve this purpose. This protocol is also recommended by the W3C consortium which is the governing body for all web standards.
SOAP is a light-weight protocol that is used for data interchange between applications. Note the keyword 'light. SOAP is designed to be platform independent and is also designed to be operating system independent. Hence, there is no sort of customization which is required to run the web services built on the SOAP protocol to work on the World Wide Web.
Programming Web Services with Perl
This is the root element in the SOAP message. A Header element that contains header information — The header element can contain information such as authentication credentials which can be used by the calling application.
It can also contain the definition of complex types which could be used in the SOAP message. By default, the SOAP message can contain parameters which could be of simple types such as strings and numbers, but can also be a complex object type.
A simple example of a complex type is shown below. Suppose we wanted to send a structured data type which had a combination of a "Tutorial Name" and a "Tutorial Description," then we would define the complex type as shown below.
All of the required elements of the structure along with their respective data types are then defined in the complex type collection.
Below is an example of the SOAP body which actually works on the complex type defined in the header section. Here is the response of the Tutorial Name and Tutorial Description that is sent to the calling application which calls this web service.
Whenever a client application calls a method in the web service, the web service will automatically generate a SOAP message which will have the necessary details of the data which will be sent from the web service to the client application. The next element is the SOAP body which contains the details of the actual message. Our message contains a web service which has the name of "Guru99WebService".
Now, the above SOAP message will be passed between the web service and the client application. You can see how useful the above information is to the client application.
The SOAP message tells the client application what is the name of the Web service, and also what parameters it expects and also what is the type of each parameter which is taken by the web service.
This enables the client application which calls the web service to know when the SOAP message ends. The following points can be noted on the SOAP envelope element.
It is absolutely mandatory for SOAP message to have an envelope element. Every Envelope element needs to have at least one soap body element. If an Envelope element contains a header element, it must contain no more than one, and it must appear as the first child of the Envelope, before the body element. The envelope changes when SOAP versions change.
Below is an example of version 1.
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When a success is generated, the response from the server will always be a SOAP message. So the application could have a specific error message for different business logic scenarios. Example for Fault Message An example of a fault message is given below. The error is generated if the scenario wherein the client tries to use a method called TutorialID in the class GetTutorial.
The below fault message gets generated in the event that the method does not exist in the defined class. This was the simplest type of communication, but it had a lot of limitations. Let's consider the below diagram to see how this communication works. In this example, let's assume the server hosts a web service which provided 2 methods as GetEmployee - This would get all Employee details SetEmployee — This would set the value of the details like employees dept, salary, etc.
In the normal RPC style communication, the client would just call the methods in its request and send the required parameters to the server, and the server would then send the desired response. The above communication model has the below serious limitations Not Language Independent — The server hosting the methods would be in a particular programming language and normally the calls to the server would be in that programming language only.
Not the standard protocol — When a call is made to the remote procedure, the call is not carried out via the standard protocol. This was an issue since mostly all communication over the web had to be done via the HTTP protocol. Firewalls — Since RPC calls do not go via the normal protocol, separate ports need to be open on the server to allow the client to communicate with the server.
Normally all firewalls would block this sort of traffic, and a lot of configuration was generally required to ensure that this sort of communication between the client and the server would work.
To overcome all of the limitations cited above, SOAP would then use the below communication model The client would format the information regarding the procedure call and any arguments into a SOAP message and sends it to the server as part of an HTTP request. The server would then unwrap the message sent by the client, see what the client requested for and then send the appropriate response back to the client as a SOAP message.
The practice of unwrapping a request sent by the client is known as Demarshalling. This topic will look at using the Microsoft.
Programming Web Services with Perl
Net framework to build an ASMX web service. The prefix SOAP::Transport is also prepended to the name, so the module will be loaded and an object also with an appended "::Client" will be created. For example, we can specify an HTTP timeout or any required cookie-specific parameters. That's because all the methods with parameters will return the current object. After the call is processed by the web service, it returns the current temperature in degrees Fahrenheit in a float data type.
Because Perl does not have strong typing, the temperature is returned as a scalar. Note that the result is returned in a result object instead of just a value. This object can then be used to retrieve the returned value or print out an error message if an error was returned by the web service. The result is retrieved from the object by using an access method named result.
Before we move on to the next example, take a look at Listing After the server receives this call, it is responsible for parsing the request and providing the information requested as a SOAP response. The simple return message for this RPC is shown in Listing WSDL describes all functions available for the web service, all the data types for response and request messages, web service location information, and the transport protocol binding information. WSDL facilitates web service invocation by providing both descriptive and connectivity information about a web service in a single XML document.
The Perl application to do this is shown in Listing As you can see, this is a very short example, but I believe it is an important example. So far, the examples have only been SOAP clients. In the next example, I'll show you what is required to build your own web service provider application.
So, if you wanted to register this application as a web service with a web services directory, it would be accessible through the Internet. As long as a web service conforms to the SOAP standards, we know our client will be able to communicate with the web service.
NOTE To run this example, you'll need a web server for example, Apache installed, running, and configured to accept incoming connections on port Web Service Description Let's pretend that you work for an online reseller, and you've been asked to develop a web service application that provides real-time access to the current book inventory.
Currently, the book inventory is stored in an XML document that contains the following information for each book: name, publisher, author, pages, and price. Our SOAP-based application is a web services client that retrieves information about any published book. Keep this in mind in case you ever need to build a real-life application to track books; the ISBN number provides a perfect unique key.
As you can see, this is a fairly simple XML document that contains the important information for several books. It will then parse the XML document shown in Listing The source code for the Perl module is shown in Listing Filename: Books. This is the method that will be available as a Web service. Instantiate a new handler object. Handler package definition As you can see, Books.Code is presented to the reader filtered down to highlight each particular issue as it is discussed.
It s the most withpopular the web programming language. Currently, the book inventory is stored in an XML document that contains the following information for each book: name, publisher, author, pages, and price. Addison Wesley in my opinion is the only serious quality technical publisher left.
We will then invoke the web service and see the result that is returned by the web service. NET to communicate across the network and pass data around. English ISBN More Login. Now, the above SOAP message will be passed between the web service and the client application.
So rather than everyone knowing all the best tools, what we tend to s.