When using SOAP, users often see the firewall security mechanism as the biggest obstacle. This block all the ports leaving few like HTTP port 80 and the HTTP port used by SOAP that bypasses the firewall. The technical complaint against SOAP is that it mixes the specification for message transport with the specification for message structure.
The Service Discovery layer is used for centralizing services into a universal registry and providing easy publish/find functionality.
Currently, service discovery is handled via Universal Description, Discovery, and Integration (UDDI).
The Service Description layer is used to describe the public interface to a specific web service. Currently, service description is handled via the Web Service Description Language (WSDL).
The Service Transport Layer is used to transport messages between applications.
This layer includes Hypertext Transport Protocol (HTTP), Simple Mail Transfer Protocol (SMTP), File Transfer Protocol (FTP), and newer protocols like Blocks Extensible Exchange Protocol (BEEP).
Synchronicity is used to bind the client to the execution of the service. In synchronous invocations, the client blocks and waits for the service to complete its operation before continuing. On the other hand, synchronous operations facilitate a client to invoke a service and then execute different functions.
Service Oriented Architecture (SOA) is an architectural pattern where applications are designed in terms of services that can be accessed through communication protocol over network. SOA is a design pattern and doesn’t go into implementation.
Web Services can be thought of as Services in SOAP architecture and providing means to implement SOA pattern.
The implementations I know are Apache SOAP, JAX-WS Reference Implementation, JAX-RS Reference Implementation, Metro, Apache CXF, MS.NET and Java 6.
No, you don’t need to install any special application to access web service. You can access web service from any application that supports XML based object request and response.
wsimport is utility which generates java classes from WSDL. It is part of JDK 6.
The only requirement for accessing web services from any application is that it must support the XML-based request and response. There is no need or the requirement of installing any application for accessing web services.
End point is nothing but URL which other application can use to access it.
for example:
end point:http://localhost:8080/WS/HelloWorld
In my point of view, the first approach that is the contract-first approach is more feasible as compared to the second one but still it depends on other factors too.
We can develop SOAP based web service with two different types of approaches such as contract-first and contract-last. In the first approach, the contract is defined first and then the classes are derived from the contract while in the later one, the classes are defined first and then the contract is derived from these classes.
It means Public-Key Infrastructure.
There is no need to explicitly making the resources thread-safe because, upon every request, new resource instances are created which makes them thread-safe by default.
Yes, we can. TLS does the task of encrypting the communication between the REST client and the server and provides the means to authenticate the server to the client. It is used for secure communication as it is the successor of the Secure Socket Layer (SSL). HTTPS works well with both TLS and SSL thereby making it effective while implementing RESTful web services. One point to mention here is, the REST inherits the property of the protocol it implements. So security measures are dependent on the protocol REST implements.
UDDI is an XML-based standard in the service discovery layer of web service protocol stack. It is used for publishing and finding web services over the web as it acts like a directory. Some of the features of UDDI are explained below:
It is an open framework and is platform-independent.
SOAP, COBRA, and Java RMI protocols are used for communication.
It helps businesses to discover each other and enable interaction between them over the Internet.
It acts as a database containing all WSDL files.
The Web services facilitate various applications to communicate with each other and share data and services among themselves. Other applications can also use the web services. For example, a VB or .NET application can communicate with a Java web services and vice versa. Web services are used to make the application platform and technology independent.
These are some of the important disadvantages of SOAP web services:
* Slow - It uses XML format that must be parsed to be read and defines many standards that must be followed while developing the SOAP applications. So it is slow and consumes more bandwidth and resource.
* WSDL Dependent - It uses WSDL and doesn't have any other mechanism to discover the service.
In Top Down approach first WSDL document is created to establish the contract between web service and client and then code is written, it’s also termed as contract first approach. This is hard to implement because classes need to be written to confirm the contract established in WSDL. Benefit of this approach is that both client and server code can be written in parallel.
In Bottom Up approach, first web service code is written and then WSDL is generated. It’s also termed as contract last approach. This approach is easy to implement because WSDL is generated based on code. In this approach client code have to wait for WSDL from server side to start their work.
We have already discussed web services, its architecture, components. Now, let us see some of its advantages:
* Every application is now on the internet and it the web service which provides some sort of required functionality to the client applications.
* Web services help in exposing the existing functionalities over the network to help other applications to use in their programs.
* It has features like ‘Interoperability’ which determines the communication between various applications, sharing of data as well as services among themselves.
* Web services use the standardized web service protocol stack for communication which consists of 4 layers namely, Service Transport, XML messaging, Service description and Service discovery.
* It has the feature of the low cost of communication because of the usage of SOAP (Simple Object Access Protocol) over HTTP protocol.
* Easy to deploy, integrate and is reusable.
* Allows simple integration between different feature as a part of the loose coupling feature.
As its name implies, it deals with security and confidentiality. This service encrypts data to ensure that only concerned parties can access the data.
This service verifies entities that attempt to access a web service. For Example, the authentication service, the Entitlements Service ensures security in business operations.
UDDI stands for Universal, Description, Discovery, and Integration. It is the discovery layer in the web services protocol stack.
Entrust Identification Service comes from the Entrust Security Transaction Platform. This platform allows companies to control the identities that are trusted to perform transactions for Web services transactions.
As implies from its name, these services are the foundation or basics of integration, authentication, authorization, digital signatures and encryption processes.
The security level for web services should be more than that of what we say Secure Socket Layer (SSL). This level of security can be only achieved from Entrust Secure Transaction Platform. Web services need this level of security to ensure reliable transactions and secure confidential information .
It is a protocol that makes use of XML messages to do Remote Procedure Calls.
The Service Transport layer transfer messages between different applications, such as HTTP, SMTP, FTP, and Blocks Extensible Exchange Protocol (BEEP). The XML Messaging layer encodes messages in XML format so that messages can be understood at each end, such as XML-RPC and SOAP. The Service Description layer describes the user interface to a web service, such as WSDL. The Service Discovery layer centralizes services to a common registry and offer simple publish functionality, such as UDDI.
It is basically set of various protocols that can be used to explore and execute web services. The entire stack has four layers i.e. Service Transport, XML Messaging, Service Description and Service Discovery.
One example of web services is IBM Web Services browser. You can get it from IBM Alphaworks site. This browser shows various demos related to web services. Basically web services can be used with the help of SOAP, WSDL, and UDDI . All these, provide a plug-and-play interface for using web services such as stock-quote service, a traffic-report service, weather service etc.
Testing tools for web services for REST APIs includes
* Spring REST web service using MVC
* Jersey API
* CXF
* Axis
* Restlet,
In document style web services, we can transport an XML message as part of SOAP request which is not possible in RPC style web service. Document style web service is most appropriate in some application where XML message behaves as document and content of that document can alter and intention of web service does not rely on the content of XML message.
JSON and XML are the two markup language that can be used in restful web api.
The initiation of XML in this field is the advancement that provides web service a single language to communicate in between the RPCs, web services and their directories.
“PUT†puts a file or resource at a particular URI and exactly at that URI. If there is already a file or resource at that URI, PUT changes that file or resource. If there is no resource or file there, PUT makes one
POST sends data to a particular URI and expects the resource at that URI to deal with the request. The web server at this point can decide what to do with the data in the context of specified resource
PUT is idempotent meaning, invoking it any number of times will not have an impact on resources.
However, POST is not idempotent, meaning if you invoke POST multiple times it keeps creating more resources.
JAXB stands for java arch for XML binding.
The different integration styles include
* Shared database
* Batch file transfer
* Invoking remote procedure (RPC)
* Swapping asynchronous messages over a message oriented middle-ware (MOM)
No, you are not supposed to use PUT for GET. GET operations should only have view rights, while PUT resource is used for updating a data.
RPC is Remote Procedure Call and as the name suggests, it is the method of calling a procedure or function available on any remote computer.
XML stands for Extensible Markup Language. Thus XML-RPC represents a simple protocol that performs RPCs by using XML messaging. This has been considered an excellent tool for connecting different environments and also establishing connections between wide variety of computers.
HTTP methods supported by REST are:
GET: It requests a resource at the request URL. It should not contain a request body as it will be discarded. Maybe it can be cached locally or on the server.
POST: It submits information to the service for processing; it should typically return the modified or new resource
PUT: At the request URL it update the resource
DELETE: At the request URL it removes the resource
OPTIONS: It indicates which techniques are supported
HEAD: About the request URL it returns meta information
Web service framework architecture consists of three different layers. The roles of these layers are defined as below:
Service Provider: As the name denotes, the service provider role is to create the web service and makes it accessible to the client applications over the internet for their usage.
Service Requestor: Service Requestor is basically any consumer of web service like any client application. Client applications are written in any language. They contact web service for any type of functionality by sending XML requests over the available network connection.
Service Registry: Service Registry is the centralized directory that helps locate web services for client applications. Here we can find the existing web services, as well as developers, can also create the new one.
Some of the different tags in WSDL xml are:
* xsd:import namespace and schemaLocation: provides WSDL URL and unique * namespace for web service.
* message: for method arguments
* part: for method argument name and type
* portType: service name, there can be multiple services in a wsdl document.
* operation: contains method name
* soap:address for endpoint URL.
WSDL stands for Web Service Description Language. WSDL is an XML based document that provides technical details about the web service. Some of the useful information in WSDL document are: method name, port types, service end point, binding, method parameters etc.
SOAP stands for Simple Object Access Protocol. SOAP is an XML based industry standard protocol for designing and developing web services. Since it’s XML based, it’s platform and language independent. So our server can be based on JAVA and client can be on .NET, PHP etc. and vice versa.
There are two types of web services:
SOAP Web Services: Runs on SOAP protocol and uses XML technology for sending data.
Restful Web Services: It’s an architectural style and runs on HTTP/HTTPS protocol almost all the time. REST is a stateless client-server architecture where web services are resources and can be identified by their URIs. Client applications can use HTTP GET/POST methods to invoke Restful web services.
<> PutAddress(): It is used to enter an address in the webpage and has an address instance on the SOAP call.
<> PutListing(): It is used to allow the insertion of a complete XML document into the web page. It receives the XML file as an argument and transports the XML file to XML parser liaison, which reads it and inserts it into the SOAP call as a parameter.
<> GetAddress(): It is used to get a query name and gets the result that best matches a query. The name is sent to the SOAP call in the form of text character string.
<>GetAllListing(): It is used to return the full list in an XML format.
Use the SOAP API to create, retrieve, update, or delete records, like accounts, leads, and use-defined objects. With more than 20 different calls, you can also use the SOAP API to manage passwords, perform searches, etc. by using the SOAP API in any language that supports web services.
SOAP is used to provide a user interface that can be accessed by the client object, and the request that it sends goes to the server, which can be accessed using the server object. The user interface creates some files or methods consisting of server object and the name of the interface to the server object. It also contains other information such as the name of the interface and methods. It uses HTTP to send the XML to the server using the POST method, which analyzes the method and sends the result to the client. The server creates more XML consisting of responses to the request of user interface using HTTP. The client can use any approach to send the XML, like the SMTP server or POP3 protocol to pass the messages or reply to queries.
SOAP is defined as an XML-based protocol. It is known for designing and developing web services as well as enabling communication between applications developed on different platforms using various programming languages over the Internet. It is both platform and language independent.