The Competing Architectures. Technologies on the Programmable Web. Leftover Terminology. 2. Writing Web Service Clients. What's a Web Service? ○ Web Services require an architectural style to make sense of them, because there's no smart human being on the client end to keep. quick tips, which can be used for REST web services design. DELETE http:// wm-greece.info HTTP/ Verbs. (GET . Parts specification in PDF format.
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It is used to define how we can call this method via a URL. This section of code is used to go through our list of strings in the 'lst' variable and return all of them to the calling program. The web service would then need to return the Tutorial name which had the Tutorial id 1. This section of code is used to return the "Tutorial name" which has the Tutorial id passed to the web method. By default, what needs to be remembered is that whatever is passed to the URL in the browser is a string.
But you have to remember that the Index to our list has to be an integer, so we are adding the necessary code to first convert the Tutorialid to an Integer and then use it to access the index position in our list and Then return the value to the calling program accordingly.
This method will be invoked whenever we want to add a string value to our list of Tutorials via the POST method. Code Explanation:- The first line is the 'WebInvoke' attribute which has been attached to our method. This allows the method to be invoked via the POST call.
The second line of code is used to add the string value passed via the POST call to our existing list of Tutorial strings.
TryParse Tutorialid, out pid ; 1st. The Int32 function in code is used to convert the Tutorial ID from a string variable to an integer. Running your first Restful web service Now that we have created our entire web service in the above section.
Let's see how we can run the Tutorial service so that it can be invoked from any client. To run the web service, please follow the below steps Step 1 Right click on the Project file — Webservice. This will ensure that this project is run when Visual Studio runs the entire solution Step 3 The next step is to run the project itself. Now depending on the default browser installed on the system, the appropriate browser name will come next to the run button in Visual Studio.
In our case, we have Google Chrome showing up. Just click on this button. Output:- When the project is run, you can browse to your TutorialService. In the above output, You can see that the browser is invoking the 'GET' verb and executing the 'GetAllTutorial' method in the web service.
This module is used to display all the Tutorials exposed by our web service. Testing your first Restful web service In the above section, we have already seen how to use the browser to execute the 'GET' verb and invoke the 'GetAllTutorial.
If you hit the enter button, you will get the below output Now you will see the output of Queues which actually corresponds to the number 1 in our list of Tutorial Strings. It also shows that the value of 1 is being passed successfully via the browser to our web service and to our method and that is why we are getting the correct corresponding value of "Queues" in the browser.
Next let's consume our web service by executing the below scenario. For this, you need to install the tool called "Fiddler" which is a free downloadable tool from the site. Run the Filddler tool and perform the below steps; Go to the composer section. This is used to create requests which can be submitted to any web application. Remember that our POST request method in our Web service only accepts json style data so we need to ensure this is specified when we are sending a request to our application.
Finally, we need to enter our data. Remember that our method for POST accepts a parameter called 'str. Finally, just click the Execute button in fiddler.
Now, when we browse to the Tutorial URL to show all the strings in our Tutorial list, you will now see the value of "Trees" is also present. This shows that the POST request to the web service was successfully executed and that it was successfully added to our Tutorial List.
Run the Filddler tool and perform the below steps Go to the composer section. Response Body — This is the main body of the response. So in our example, if we were to query the web server via the request http: Response Status codes — These codes are the general codes which are returned along with the response from the web server.
An example is the code which is normally returned if there is no error when returning a response to the client.
Let's assume that we have a RESTful web service is defined at the location. Below is what would happen If the respective verbs were sent by the client. Let's say there was an employee record with the employee number of 1.
The following actions would have their respective meanings. POST — This would not be applicable since we are fetching data of employee 1 which is already created. Heterogeneous languages and environments — This is one of the fundamental reasons which is the same as we have seen for SOAP as well. It enables web applications that are built on various programming languages to communicate with each other With the help of Restful services, these web applications can reside on different environments, some could be on Windows, and others could be on Linux.
But in the end, no matter what the environment is, the end result should always be the same that they should be able to talk to each other. Restful web services offer this flexibility to applications built on various programming languages and platforms to talk to each other. The below picture gives an example of a web application which has a requirement to talk to other applications such Facebook, Twitter, and Google.
Now if a client application had to work with sites such as Facebook, Twitter, etc. Based on this, we can write the interfacing code for our web application, but this could prove to be a nightmare. Facebook, Twitter, and Google expose their functionality in the form of Restful web services. This allows any client application to call these web services via REST.
The event of Devices — Nowadays, everything needs to work on Mobile devices, whether it be the mobile device, the notebooks, or even car systems.
Can you imagine the amount of effort to try and code applications on these devices to talk with normal web applications? Again Restful API's can make this job simpler because as mentioned in point no 1, you really don't need to know what is the underlying layer for the device. Finally is the event of the Cloud — Everything is moving to the cloud.
Applications are slowly moving to cloud-based systems such as in Azure or site.
Hence, applications now need to be developed in such a way that they are made compatible with the Cloud. So since all Cloud-based architectures work on the REST principle, it makes more sense for web services to be programmed on the REST based architecture to make the best use of Cloud-based services.
So if someone wanted to get a file from a server, they should be able to issue the GET request and get the file. Stateless means that the state of the application is not maintained in REST. For example, if you delete a resource from a server using the DELETE command, you cannot expect that delete information to be passed to the next request.
In order to ensure that the resource is deleted, you would need to issue the GET request. The GET request would be used to first get all the resources on the server. After which one would need to see if the resource was actually deleted. These characteristics are also known as design principles which need to be followed when working with RESTful based services.
It means that the server will have a RESTful web service which would provide the required functionality to the client. The client send's a request to the web service on the server. The server would either reject the request or comply and provide an adequate response to the client. Stateless The concept of stateless means that it's up to the client to ensure that all the required information is provided to the server. This is required so that server can process the response appropriately. The server should not maintain any sort of information between requests from the client.
It's a very simple independent question-answer sequence. The client asks a question, the server answers it appropriately. The client will ask another question. The server will not remember the previous question-answer scenario and will need to answer the new question independently.
Cache The Cache concept is to help with the problem of stateless which was described in the last point. Since each server client request is independent in nature, sometimes the client might ask the server for the same request again. This is even though it had already asked for it in the past.
This request will go to the server, and the server will give a response. This increases the traffic across the network. The cache is a concept implemented on the client to store requests which have already been sent to the server. So if the same request is given by the client, instead of going to the server, it would go to the cache and get the required information. This saves the amount of to and fro network traffic from the client to the server. Layered System The concept of a layered system is that any additional layer such as a middleware layer can be inserted between the client and the actual server hosting the RESTFul web service The middleware layer is where all the business logic is created.
This can be an extra service created with which the client could interact with before it makes a call to the web service.
But the introduction of this layer needs to be transparent so that it does not disturb the interaction between the client and the server. NET Web services can be created in a variety of languages. Many integrated development environments can be used to create REST-based services. In this example, we are going to create our REST application in.
Net using Visual Studio. In our example, for Restful web services we are going to emulate the following example. We are going to have a Restful web service which will work on the below set of data. The below set of data represents an example of having a company which exposes the Tutorial's they have based on the Tutorialid.
The web service will then add the submitted Tutorial name to the collection. The web service will then delete the submitted Tutorial name from the collection. Let's follow the below steps in creating our first RESTful web services, which carries out the above implementation.
Step 1 The first step is to create an empty Asp. Net Web application. Once you click on the New Project option, Visual Studio will then give you another dialog box for choosing the type of project and to give the necessary details of the project.
NET Web application. The project has to be of this type in order to create web services project. By choosing this options, Visual Studio will then carry out the necessary steps to add required files which are required by any web-based application. Give a name for your project which in our case has been given as "Webservice.
Then ensure to give a location, where the project files will be stored. Once done you will see the project file created in your solution explorer in Visual Studio AJAX allows web pages to be updated asynchronously by exchanging small amounts of data with the server behind the scenes. Next give a name for the service which is TutorialService in our case. Finally, click the Add button to add the service to the solution. Step 4 The next step is to actually make a configuration change to enable this project to complete work with RESTful web services.
This requires to make a change to the file called Web. This file appears in the same window as the Webservice project file. The file Web. The change being made actually allows the application to send and receive data as a pure RESTful web service.
Click on the Web. All of the below-mentioned code has to be written in the TutorialService. So we are going to have a list of string variables with values of "Arrays", "Queues" and "Stacks". This will represent the tutorials name available through our hosting web service.
This code will also reside in the same TutorialService. This code will run whenever we call the service from our browser.