Please enable JavaScript.

Coggle requires JavaScript to display documents.

WebServices - Coggle Diagram

- - - - The client send the request and the server responds.
        
        a specific feature of REST is that communication is resource based. This means that messages are sent as representations of resources
        A resource can be any piece of information that is self-contained.
        
        Examples of resources are documents, images, object representations and so on.
  - - - This separation allows REST applications to be highly scalable. It allows the development of the client and the server to occur independently of each other.
    - - It can consist of multiple architectural layers of software or hardware called by the client and server. These layers can be used to improve performance, translate messages, manage traffic and more. This helps to improve reusability of REST web services because layers can be added and removed based on the needed services of the client
    - - This means that the server does not save information about the current client state or previous request made by the client. Other than when a request is made the server does not need to know that the client side exists
        
        Additionally, each request is independent of each other and must contain all necessary information for the server to understand and respond to the request. If there's any information needed by the server to complete a request, the client must send it every time because the server will not rely on information sent from previous request
        
        this constraint improves performance of web services because the server does not have to store any information about the current states of clients in the system. Without the overhead, the server can provide improved performance to the clients.
        
        However, this imposes significant restrictions on the way a client and a server communicate. Every time a client sends a request to a server, it must provide and store information about its current state in order to maintain this stateless constraint. For example, if authentication is needed by a server for a client to have access to data, the client side must send that authentication information in every request.
    - - This means that the clients can keep a local copy of a server response to use for later requests
        
        very time a server responds to a client request, the server adds information to the response to label it as cacheable or non-cacheable.
        
        It does this to improve performance so that it can reduce the number of requests for the same resources
        
        This can also relieve some of the negative impacts of applying the stateless constraint. The server decides for the client side what information should be temporarily saved and what can be deleted after use, so that the client does not keep any redundant or useless data.
    - - for communication between the client and server
        
        REST used the common HTTP methods. Get, put, post and delete to communicate the different actions the client want to perform on the resource.
        
        the resource must be identified in the request using a specific Uniform Resource Identifier, or URI
        
        the representations of the resources are uniform
        
        Responses have specific headers, like if the data should be cached and the resources written in three specific ways, XML, JSON or Simple Text.
  - - - This means that when a resource is related to another resource you can show the connection in the URI.
        
        GET /students/3/courses
        GET /students/3/courses/2
    - - content type and accept
    - - When there are large data sets to parse through, good APIs will often provide filters to help search through the data. This can often be done by allowing parameters to be passed in after the symbol question mark.
        
        GET courses?department=computer+science
        
        GET courses?offset=10&limit=5
    - - When your web services are being used by millions of users, changes to your API can break existing applications or services that call your APIs. To prevent future headaches for you and developers using your API, add version numbers
        
        http://api.yourservice.com/v2/students/34/courses
    - - First thing to think about is the services that I should provide.
        
        Because this is a web service about students and courses, there should be ways to retrieve information about the students, the courses and information about which courses students are taking.
        
        GET APIs
        
        Naturally, I will also need to provide services to create, update and delete these resources.
        
        POST, PUT and DELETE
      - Next, I create a resource representation class for a student
        
        This Java file will have constructors and accessor methods for the ID, full name, and department for a student object.
        
        After, I create the Java file that handles the HTTP request that we planned earlier. This can be done through many pre-built Java libraries that provide the client library to communicate with a RESTful service. Some Java examples include Restlet, Spring, Jersey and RESTEasy.
        
        Now, you can test your REST service by either creating your own client application that calls these URIs with a specific content for the API's you've created or by simply sending an HTTP request through the command line (CURL)
- - - - Web services start with TCP, the networking protocol responsible for reliable, ordered connection-oriented communication
      - On top of that it's HTTP, the Hypertext Transfer Protocol
    - - Invoke
        
        Invoking is like a method call in an object-oriented language
        
        it must be done through a request in XML. Invocation will include which operation is requested, since a service may offer several along with the parameters in Data.
        
        In web services invocation is done with SOAP, a protocol specification that is based on XML and allows services to send information to one another
        
        This request- response messaging pattern conform to SOAP, Simple Object Access Protocol.
        
        It defines how to organize requests and responses in XML, in a standard way that is understood by both parties. This standardize communication allows for inter-operability between platforms and languages
        
        SOAP also provides instructions for how the message is bound to the underlying transport protocol, which will be HTTP in this lesson
        
        3 more items...
        
        Because of a few disadvantages, SOAP has been superseded in many applications by lighter weight methods that use HTTP more directly such as RESTful Web services. XML encoding and decoding adds overhead and does not easily accommodate some data types.
      - Describe
        
        Web service description languages or WSDL is the standard protocol for describing the interface of a service. Like SOAP, WSDL descriptions are written in XML.
        
        A WSDL description will describe the interface of a service in a machine-readable fashion so that a service requester can bind itself to this interface. Binding is the act of generating the necessary code to interact with a service so that a service requester can begin invoking it. If a service interface is described unambiguously with WSDL, binding can be done by generating the necessary code automatically
        
        What if you are searching for a service to give you a currency exchange rate? Or you found a service provider but don't know how to interact with the service? How do you learn what the method name is or what parameters it needs? Compare a web service to a method in object oriented programming. How would you find out how to call a particular method?
        
        In web services, WSDL plays a similar role to a method signature.
        
        A service requestor can read a WSDL description to determine how to request the service, because the WSDL description is machine-readable. The service requestor can even generate the necessary code automatically. The process of generating the necessary code to interface with a service provider is called binding, whether it is done automatically or by the developer. Only after binding can the service requestor invoke the service using SOAP messages.
        
        interfaces to the services provided in terms of what operations can be performed and in what order. The order of operations can be described by one of the message exchange patterns covered in the SOAP lesson. Request response, solicit response, one way or notification.
      - Publish
        
        The internet is a big place, service requesters and service providers need ways to come into contact. Service providers can publish descriptions of their services using UDDI, universal description, discovery and integration
        
        Service requesters looking for a service can search by the WSDL descriptions or other aspects of the service. This is called Discovery,
      - Composition
        
        Composite services are services that are built with other services, which can either be composites themselves, or basic
        
        BPEL, which stands for Business Process Execution Language. BPEL allows developers to combine existing services into new composite services.
        
        This is similar to the composing objects principle in object oriented design
        
        web services are not usually compiled and run in the same physical location. Instead, composing services involves invoking services in a certain order and handling exceptions that may arise. The services that comprise a composite service still remain separate from that service. In a sense, a composite service could be like a script that uses the other services according to some pre-determined order as we can see in this UML sequence diagram.
        
        coordination This is when a process coordinates the activities of two or more services. The distinguishing feature of Composition as opposed to coordination is that it exposes the collection of actions as another service
- - - - Microservices can be thought of as a variation of SOA applied on an application scale rather than enterprise scale
        
        Additionally, some SOA principles have been refined to better support application scale systems.
        
        The microservice architectural style is the way of composing microservices to produce complex applications
        
        A microservice is the process that is responsible for performing a single independent task. A microservice typically is built to perform a specific business capability. For example in an application, one microservice can be responsible for implementing a search feature. Another microservice can implement a recommendation feature. And yet another microservice can be responsible for implementing a rating feature.
        
        Often each microservice does not obey a full layered architectural style because microservices are composed with other microservices and not always intended for end users
        
        Presentation and application layers may not always be present, that being said, usually each microservice controls and manages its own data. As a result, the overall application will not generally follow a layered architectural style
        see 'Microservices_OnlineLibrary'
        
        Most microservices communicate with each other over the web, using communication standards and protocols such as HTTP or XML. REST interfaces are use to keep communication between microservices stateless.
        
        A benefit of communication between microservices being independent of the implementation of each microservice is that microservices can use languages, frameworks and architectures that are best suited to the service. In other words, this means that different microservices can use different languages, frameworks and architectures, independent of what other microservices within the same application are using
        
        1 more item...