Modern Internet applications use various software platforms for developing web applications. Some applications can be developed in Java, others in .Net, Angular JS, Node.js. Based on this, the question may arise, what are web services and how they are used. Basically, the work environment is not visible to ordinary users.
Most often, these unique applications require some kind of communication between them. Because they are built using different development languages, it becomes really difficult to provide accurate communication between applications.
Relevance of development
Considering the question of what are web services, it is worth determining how relevant such a development is and whether it has analogues. The technology presented summarizes services and applications and enables them to communicate with each other.
Web services provide a common platform that allows many applications built in different programming languages to be able to communicate with each other.
The article will talk in more detail about what web services are, about the various elements that make them up, and a little about the principles of SOA (service-oriented architecture). Although technologies have complex definitions, they are an accessible environment for development and programming.
Technology definition
Answering the question of what are web services, we can say that this is a standardized environment for the distribution of communication between client and server applications on the World Wide Web. It can be edited and have improvement packs.
In addition, a web service can be designated as a software module designed to perform a specific set of tasks. Structural elements of applications can be found on the Web, and can also be called accordingly. When called, the web service will be able to provide functionality to the client who requests this portal. This happens within a couple of seconds.
Operating principle
Speaking of what web services are, it is necessary to consider their working conditions. This will help to understand how the system functions.
The client will make a series of calls to the web service by querying the server on which the real web service will be hosted.
These requests are made through so-called remote procedure calls. Remote procedure calls (RPCs) are method calls that are placed in the corresponding request.
An example of a web service is Amazon. The organization has a network of online stores and delivery systems. It provides a web service that requests prices for products sold online through amazon.com. The external or presentation layer can be in .Net or Java, but any programming language interacts with the web service in its own way. This happens on a common platform.
Component parts
The main component of web services on the Internet is the data that is transferred between the client and server, and this is XML (Extensible Markup Language). It is an analogue of HTML and is easy to understand for an intermediate language that many programming languages understand. Therefore, when applications communicate with each other, they actually communicate in XML. This provides a common platform for applications developed in different programming languages to communicate with each other.
Portals use what is called SOAP (Simple Object Access Protocol) to send XML data between applications. Data is sent using regular HTTP. The information that is sent from the web service to the application is called SOAP messages.
A SOAP message is nothing more than an XML document. Because the document is written in XML, the client application that invokes the web service can be written in any programming language.
What are the types of applications
There are basically two types of web services:
- SOAP
- RESTful.
In order for the developed environment to be fully functional, the presence of certain components is necessary. These components must be present no matter what development language is used to program a particular request. You can create a web service yourself. To do this, create a portal to host it and establish a working programming environment.
SOAP (Simple Object Access Protocol)
The use of web services depends on the technology used. With their help, the necessary conversion and adjustment of outgoing and streaming data transmitted by the system occurs. SOAP is known as a version and system independent messaging protocol. It is based on the transmission of XML data in the form of encoded messages. Each message contains an XML document. Only the structure of the XML document follows a specific template, but not the content. The best part of web services and SOAP is that they are all sent over HTTP, which is the standard web protocol.
This is what a SOAP message consists of:
- Each SOAP document must have a root element known as an <Envelope> element. The root element is the first element in the XML document.
- "Envelope", in turn, is divided into 2 parts. The first is the headline, and the next is the body.
- The header contains routing data, which is mainly information to which client the XML document should be sent.
- The body will contain the actual message.
WSDL (application description language)
A web service cannot be used if it cannot be found. The client calling the service must know where its protocol is actually located.
In addition, the client application must know what a particular service is actually doing so that it can invoke the correct web service. This is done using WSDL, known as the Web Services Description Language. The WSDL file is again an XML-based file that basically tells the client application what the web service does. Using a WSDL document, the client application can understand where the web service is located and how it can be used.
Development benefits
Web services arose primarily to provide a platform that would allow different applications to communicate with each other.
Now you need to look at some other advantages of why it is important to use web services:
- Representation of business functions on the Web. A web service is a unit of managed code that provides some functionality to client applications or end users. This function can be called over HTTP, which means that it can also be called over the Internet. Currently, all applications are located on the Internet, which makes the appointment of web services more useful. This means that the web service can be anywhere on the Internet and provide the necessary functionality as needed.
- Interaction between applications - web services allow different applications to communicate with each other and exchange data and services among themselves. All types of applications can communicate with each other. Thus, instead of writing specific code that can be understood only for certain applications, you can now write general code that is understandable for all applications.
- A standardized protocol that everyone understands - Web services use a standardized industry protocol for communication. All four layers (transmission levels of services, XML messages, service descriptions, and service discovery) use well-defined protocols in the system.
- Reducing the cost of communication - web services use the SOAP protocol over HTTP, so you can use the existing low-cost Internet to implement web services.
These are one of the main advantages that portal owners and developers give out. It is worth noting that if an error occurred while calling the web service, you need to check the outgoing data. Perhaps the server or the application itself is disconnected from the common database, which prevents the transfer of data and sending requests via the specified protocols.
Application architecture
The development of web services is a simple task, but quite voluminous. It is necessary to develop your own environment, where all working protocols will be uploaded in the future, as well as connect databases.
Each framework needs some kind of architecture to make sure that the entire portal works as it should. Similarly, web services has an architecture that consists of three separate roles, as follows:
- The provider creates a web service and makes it available for the client application that wants to use it.
- The requester is a client application that needs to contact the web service. The client application can be .Net, Java, or any other language application that is looking for some kind of functionality through a web service.
- A broker is an application that provides access to UDDI. UDDI allows a client application to find a web service.
Interaction with other systems
Without local and virtual databases, applications cannot function. Web services allow you to use protocols and requests to process and receive information from all media. Administrators can independently connect directories and create new directions.
There are 3 main types of request for work and interaction between systems and applications:
- Publishing is the action when the provider informs the broker (service registry) about the existence of a web service using the broker publishing interface to make the service available to customers.
- Find - A requestor who consults with a broker to find a published web service.
- Snapping. Having received information from a web service received from a broker (service registry), the requesting party can bind or call the web service.
Development Characteristics
All incoming information in the system is redirected to the root directories. Each operation on the Web during the operation of the protocol is recorded. Description of web services on each specific portal makes it possible to quickly integrate and connect the necessary source of information.
They have the following special behavioral characteristics:
- They are XML-based - Web services use XML to represent data at the presentation and transport levels. Using XML eliminates any dependencies on networks, operating systems, or platforms, because XML is a common language that everyone understands.
- A loosely coupled system means that the client and the web service are not connected to each other. Even if the application changes over time, it should not change the way the client calls the web service. Using loosely coupled architecture makes software systems more manageable and simplifies integration between different systems.
- Synchronous or asynchronous functionality - synchronization refers to the binding of the client to the execution of the service. In synchronous operations, the client will actually wait for the operation to complete the operation by the web service. An example of this is probably a scenario in which read and write operations to the database are performed. If data is read from one database and subsequently written to another, then operations must be performed sequentially. Asynchronous operations allow the client to call the service and then perform other functions in parallel. This is one of the most common and probably most preferred methods for ensuring that other services do not stop when performing a specific operation.
- Remote Procedure Call (RPC) Support — Web services enable clients to call procedures, functions, and methods for remote objects using an XML-based protocol. Remote procedures provide the input and output parameters that the web service must support.
- Support document sharing. One of the key benefits of XML is its general way of representing not only data, but also complex documents. These documents may be as simple as representing the current address, or as complex as representing the entire book.
The listed parameters describe in detail the structure and properties of services on the Internet. With their help, application developers and portal owners can integrate various operation scenarios, while using different programming languages.