Spring MVC uses HttpMessageConverter to convert the Http request to an object representation and back.Spring Framework then uses one of the Jackson message converters to marshall and unmarshall Java Objects to and from JSON over HTTP.Spring will use the “Accept” header to determine the media type that it needs to respond with and uses the “Content-Type” header to determine the media type of the request body.

Default Message Converters in Spring MVC
StringHttpMessageConverter: it converts Strings from the HTTP request and response.
FormHttpMessageConverter: it converts form data to/from a MultiValueMap.
ByteArrayHttpMessageConverter: it converts byte arrays from the HTTP request and response.
MappingJackson2HttpMessageConverter: it converts JSON from the HTTP request and response.
Jaxb2RootElementHttpMessageConverter: it converts Java objects to/from XML.
SourceHttpMessageConverter: it converts javax.xml.transform.Source from the HTTP request and response.
AtomFeedHttpMessageConverter: it converts Atom feeds.
RssChannelHttpMessageConverter: it converts RSS feeds.

Customizing HttpMessageConverters with Spring MVC

Annotation Usage
@RequestMapping
@RequestMapping(value = "/{name}", 
                method = RequestMethod.GET, 
                consumes="application/json"
                produces ="application/json",
                headers={"name=pankaj", "id=1"})
path (or) (or) name (or) and value: which URL the method is mapped to
method: compatible HTTP methods
params: filters requests based on presence, absence, or value of HTTP parameters
headers: filters requests based on presence, absence, or value of HTTP headers
consumes: which media types the method can consume in the HTTP request body
produces: which media types the method can produce in the HTTP response body
@RequestBody
@RequestMapping(method = RequestMethod.POST)
@ResponseBody
public HttpStatus something(@RequestBody MyModel myModel) 
{
    return HttpStatus.OK;
}
with @RequestBody, Spring will bind the incoming HTTP request body(for the URL mentioned in @RequestMapping for that method) to that parameter. While doing that, Spring will [behind the scenes] use HTTP Message converters to convert the HTTP request body into domain object [deserialize request body to domain object], based on Accept header present in request.
@ResponseBody
@RequestMapping(value = "/user/all", method = RequestMethod.GET)
public @ResponseBody List<User> listAllUsers() {
    return userService.findAllUsers();
}
with @ResponseBody, Spring will bind the return value to outgoing HTTP response body. While doing that, Spring will [behind the scenes] use HTTP Message converters to convert the return value to HTTP response body [serialize the object to response body], based on Content-Type present in request HTTP header
@RequestParam
http://localhost:8080/springmvc/hello/101?param1=10¶m2=20

public String getDetails(
    @RequestParam(value="param1", required=true) String param1,
        @RequestParam(value="param2", required=false) String param2){
...
}
@RequestParam is to obtain an parameter from the URI as well.@RequestParam annotation used for accessing the query parameter values from the request
defaultValue – This is the default value as a fallback mechanism if request is not having the value or it is empty.
name – Name of the parameter to bind
required – Whether the parameter is mandatory or not. If it is true, failing to send that parameter will fail.
value – This is an alias for the name attribute
@PathVariable
'http://localhost:8080/springmvc/hello/101?param1=10&param2=20

@RequestMapping("/hello/{id}")    public String getDetails(@PathVariable(value="id") String id,
    @RequestParam(value="param1", required=true) String param1,
    @RequestParam(value="param2", required=false) String param2){
.......
}

@GetMapping("/user/{firstName}/{lastName}")
   @ResponseBody
   public String handler(@MatrixVariable("firstName") String firstName,
         @MatrixVariable("lastName") String lastName
         ) {

      return "<br>Matxrix variable <br> "
            + "firstName =" + firstName +"<br>"
            + "lastName =" + lastName;
   }
@PathVariable is to obtain some placeholder from the URI
@MatrixVariable – a name-value pair within a path segment is referred as matrix variable. Matrix variables can appear in any path segment, each variable separated with a semicolon (;) and multiple values are separated by comma (,)
i.e.
http://www.example.com/employee/Mike;salary=45000;dept=HR
http://www.example.com/car/Audi;color=RED,BLACK,WHITE

@RequestHeader
@Controller
public class HelloController {
 @RequestMapping(value = "/hello.htm")
 public String hello(
   @RequestHeader(value="Accept") String accept,
   @RequestHeader(value="Accept-Language") String acceptLanguage,
   @RequestHeader(value="User-Agent", defaultValue="foo") String userAgent,
   HttpServletResponse response) {

  System.out.println("accept: " + accept);
  System.out.println("acceptLanguage: " + acceptLanguage);
  System.out.println("userAgent: " + userAgent);
  
  return null;
 }
}
Reading http requestheader is written in HelloController
The advantage of using Spring @RequestHeader is that it will automatically throw an exception like HTTP Status 400 – Missing request header ‘X’ for method parameter of type, if the header is NOT sent in the input request (by setting required=true)

@RequestHeader for facilitating use to get the header details easily in our controller class

GET

  1. GET is idempotent and can be requested any number of times
  2. GET requests can be cached, can be distributed & shared
  3. GET request is less secured compared to POST.

POST

  1. Used to Create a resource
  2. Post is not idempotent.x++ is not idempotent
  3. POST is NOT idempotent. So if you retry the request N times, you will end up having N resources with N different URIs created on server.

PUT

  1. Used to Create or Modify a resource
  2. PUT is idempotent, so if you PUT an object twice, it has no effect.
  3. x=5 is idempotent.You can PUT a resource whether it previously exists, or not (eg, to Create, or to Update)!

When to use Put and Post
You can use both PUT or POST for creating the resource until the client decides the resource location in the Server.But if the server decides the resource location using

POST /questions/ HTTP/1.1
Host: www.example.com/

Note that the following is an error:

POST /questions/ HTTP/1.1
Host: www.example.com/

If the URL is not yet created, you should not be using POST to create it while specifying the name. This should result in a ‘resource not found’ error because does not exist yet. You should PUT the resource on the server first.

You could though do something like this to create a resources using POST:

POST /questions HTTP/1.1
Host: www.example.com/

Note that in this case the resource name is not specified, the new objects URL path would be returned to you.

PUT is Used to create a resource, or overwrite it. While you specify the resources new URL.

PUT /questions/ HTTP/1.1
Host: www.example.com/

To overwrite an existing resource:

PUT /questions/ HTTP/1.1
Host: www.example.com/

PATCH
Patch request says that we would only send the data that we need to modify without modifying or effecting other parts of the data. Ex: if we need to update only the first name, we pass only the first name.PATCH – HTTP.PATCH can be used when the client is sending one or more changes to be applied by the server. The PATCH method requests that a set of changes described in the request entity be applied to the resource identified by the Request-URI. The set of changes is represented in a format called a patch document.

In PUT request, the enclosed entity would be considered as the modified version of a resource which residing on server and it would be replaced by this modified entity.

In PATCH request, enclosed entity contains the set of instructions that how the entity which residing on server, would be modified to produce a newer version.

DELETE

DELETE is pretty easy to understand. It is used to delete a resource identified by a URI.On successful deletion, return HTTP status 200 (OK) along with a response body, perhaps the representation of the deleted item (often demands too much bandwidth), or a wrapped response (see Return Values below). Either that or return HTTP status 204 (NO CONTENT) with no response body. In other words, a 204 status with no body, or the JSEND-style response and HTTP status 200 are the recommended responses.

  1. Caching is the ability to store copies of frequently accessed data in several places along the request-response path. When a consumer requests a resource representation, the request goes through a cache or a series of caches (local cache, proxy cache or reverse proxy) toward the service hosting the resource.
  2. If any of the caches along the request path has a fresh copy of the requested representation, it uses that copy to satisfy the request. If none of the caches can satisfy the request, the request travels all the way to the service (or origin server as it is formally known).
  3. Using HTTP headers, an origin server indicates whether a response can be cached and if so, by whom, and for how long. Caches along the response path can take a copy of a response, but only if the caching metadata allows them to do so.
  4. Few are the advantages of Caching
    • Reduce bandwidth
    • Reduce latency
    • Reduce load on servers
    • Hide network failures
  5. GET requests are cachable by default – until special condition arises. Usually, browsers treat all GET requests cacheable.
  6. POST requests are not cacheable by default but can be made cacheable if either an Expires header or a Cache-Control header with a directive, to explicitly allows caching, is added to the response. Responses to PUT and DELETE requests are not cacheable at all.

There are two main HTTP response headers that we can use to control caching behavior:
Expires : The Expires HTTP header specifies an absolute expiry time for a cached representation. Beyond that time, a cached representation is considered stale and must be re-validated with the origin server. To indicate that a representation never expires, a service can include a time up to one year in the future.

Expires: Wed, 6 March 2019 15:09:49 IST

Cache-Control:
The header value comprises one or more comma-separated directives. These directives determine whether a response is cacheable, and if so, by whom, and for how long e.g. max-age or s-maxage directives.

Cache-Control: max-age=3600
ETag: "abcd1234567n34jv"
(or)
Last-Modified: Fri, 10 May 2016 09:17:49 IST

Cacheable responses (whether to a GET or to a POST request) should also include a validator — either an ETag or a Last-Modified header.

ETag
An ETag value is an opaque string token that a server associates with a resource to uniquely identify the state of the resource over its lifetime. When the resource changes, the ETag changes accordingly.

Last-Modified
Whereas a response’s Date header indicates when the response was generated, the Last-Modified header indicates when the associated resource last changed. The Last-Modified value cannot be later than the Date value.

@RequestBody, spring will try to convert the content of the incoming request body to your parameter object on the fly.@ResponseBody, spring will try to convert its return value and write it to the http response automatically

@Controller
@RequestMapping(value = "/bookcase")
public class BookCaseController 
{ 
    private BookCase bookCase;
 
    @RequestMapping(method = RequestMethod.GET)
    @ResponseBody
    public BookCase getBookCase() {
        return this.bookCase;
    }
 
    @RequestMapping(method = RequestMethod.PUT)
    @ResponseStatus(HttpStatus.NO_CONTENT)
    public void setBookCase(@RequestBody BookCase bookCase) {
        this.bookCase = bookCase;
    } 
}

Depending on your configuration, spring has a list of HttpMessageConverters registered in the background. A HttpMessageConverters responsibility is to convert the request body to a specific class and back to the response body again, depending on a predefined mime type. Every time an issued request is hitting a @RequestBody or @ResponseBody annotation spring loops through all registered HttpMessageConverters seeking for the first that fits the given mime type and class and then uses it for the actual conversion.

Refer here

Q1:Difference between concrete wsdl and abstract wsdl
Typically a wsdl contains – types, Messages, porttype, Binding and service
Using Types ,messages and porttype we can’t do anything with that.. which is abstract part. Binding and service has more info about the webservices. So it’s concrete.abstract wsdl is enough to consume a soap service … If we use a abstract wsdl and if we try to generate classes we will not be able to see the java files and only class files can be obtained …
Concrete wsdl can provide complete details about the service…

It is not safe to provide the concrete wsdl to the consumer if he is not to be trusted ..
Please Refer Here

Q2:What is the Difference between SOAP and REST
Refer Here

Q3:What do you mean by Stateless in terms of RESTAPI?
The state of the client application is never stored on the server and is passed on. In this process, the client send all the information that is required for the server to fulfill the HTTP request and the server responds make with HTTP Response.The following are the advantages of Statelessness
HTTP protocol and REST web service, both shares the feature of statelessness. Every method required for communication is identified as an independent method i.e. there are no dependencies to other methods.Any previous communication with the client and server is not maintained and thus the whole process is very much simplified.If any information or metadata used earlier in required in another method, then the client sends again that information with HTTP request.

Q4:What is Resource in RESTApi? What is Resource Representation? Why its important?
‘Resource’ is defined as an object of a type which can be an image, HTML file, text data, and any type of dynamic data.JSON
YAML,XML,HTML are some of the Resource Types.Representation of Resource is important because it determines the easy identification of resources. With proper representations of resource in the proper format, allows the client to easily understand the format.

Q5:What is Caching?Use of Cache Control Header?
Caching is the process in which server response is stored so that a cached copy can be used when required and there is no need of generating the same response again. This process not only reduces the server load but in turn increase the scalability and performance of the server. Only the client is able to cache the response and that too for a limited period of time.

Cache control header can help in attaining cache ability.
Public: Resources that are marked as the public can be cached by any intermediate components(gateways) between the client and server.
Private: Resources that are marked as private can only be cached by the client.
No cache means that particular resource cannot be cached and thus the whole process is stopped.

Q6:What is Payload?
Request data which is present in the body part of every HTTP message is referred as ‘Payload’. In Restful web service, the payload can only be passed to the recipient through POST method.

Q7:Different HTTP methods
GET: This is a read only operation which fetches the list of users on the server.
PUT: This operation is used for the creation of any new resource on the server.
POST: This operation is used for updating an old resource or for creating a new resource.
DELETE: As the name suggests, this operation is used for deleting any resource on the server.
OPTIONS: This operation fetches the list of any supported options of resources that are available on the server.

Q8:What is the difference between PUT method and POST method?
PUT is idempotent, so if you PUT an object twice, it has no effect. You can update or create a resource with PUT with the same object URL.POST is to create new resource.If you are depending on server to create new resource using POST will result in multiple resource creation since server is the one which decides where to place the object. refer here

Q9:What is JAX-RS and what are its implementations?
JAX-RS is defined as the Java API for RESTful web service. Few of its implementations include Jersey,RESTEasy,Apache CFXPlay

Q10:What is use of OPTIONS and HEAD?
OPTIONS tells you things such as “What methods are allowed for this resource”.OPTIONS Identifying which HTTP methods a resource supports, e.g. can we DELETE it or update it via a PUT?OPTIONS method returns info about API (methods/content type)

HTTP/1.1 200 OK
Allow: GET,HEAD,POST,OPTIONS,TRACE
Content-Type: text/html; charset=UTF-8
Date: Wed, 08 May 2013 10:24:43 GMT
Content-Length: 0

HEAD Checking whether a resource has changed. This is useful when maintaining a cached version of a resource.Retrieving metadata about the resource, e.g. its media type or its size, before making a possibly costly retrieval.HEAD gets the HTTP header you would get if you made a GET request, but without the body. This lets the client determine caching information, what content-type would be returned, what status code would be returned.

HTTP/1.1 200 OK
Accept-Ranges: bytes
Content-Type: text/html; charset=UTF-8
Date: Wed, 08 May 2013 10:12:29 GMT
ETag: "780602-4f6-4db31b2978ec0"
Last-Modified: Thu, 25 Apr 2013 16:13:23 GMT
Content-Length: 1270

Q11.Maximum length of HTTP GET request?
The limit is dependent on both the server and the client.As already mentioned, HTTP itself doesn’t impose any hard-coded limit on request length; but browsers have limits ranging on the 2kb – 8kb .If the limit is exceeded in either the browser or the server, most will just truncate the characters outside the limit without any warning

HTTP 1.1 defines Status Code 414 Request-URI Too Long for the cases where a server-defined limit is reached which is usually configureable somewhere in the server configuration.For the case of client-defined limits, there is no sense on the server returning something, because the server won’t receive the request at all.

Q12.What is need for HttpMessageConverter?
Spring MVC uses HttpMessageConverter to convert the Http request to an object representation and back.Spring Framework then uses one of the Jackson message converters to marshall and unmarshall Java Objects to and from JSON over HTTP.Spring will use the “Accept” header to determine the media type that it needs to respond with and uses the “Content-Type” header to determine the media type of the request body.

Default Message Converters in Spring MVC
StringHttpMessageConverter: it converts Strings from the HTTP request and response.
FormHttpMessageConverter: it converts form data to/from a MultiValueMap.
ByteArrayHttpMessageConverter: it converts byte arrays from the HTTP request and response.
MappingJackson2HttpMessageConverter: it converts JSON from the HTTP request and response.
Jaxb2RootElementHttpMessageConverter: it converts Java objects to/from XML.
SourceHttpMessageConverter: it converts javax.xml.transform.Source from the HTTP request and response.
AtomFeedHttpMessageConverter: it converts Atom feeds.
RssChannelHttpMessageConverter: it converts RSS feeds.

@EnableWebMvc annotation, it automatically registered default Http message converters with application as listed above according to available library in the class path.

WSDL(Web Services Definition Language) – A WSDL is an XML document that describes a web service.WSDL tells about the functions that you can implement or exposed to the client. For example: add, delete, subtract and so on.

UDDI(Universal Description, Discovery and Integration)- It is directly that is used to publish and discover public web services. UDDI is an obsolete failure that is almost never used in practice.UDDI works just like a telephone directory where a business can be registered as per its name, geography and the web services it publishes.UDDI registers the WSDL address URL of a web service. A client of the web service searches and finds the WSDL in the UDDI registry. Once received the WSDL can be invoked by using the URL.

SOAP(Simple Object Access Protocol) – SOAP is an XML-based protocol that lets you exchange info over a particular protocol (can be HTTP or SMTP, for example) between applications. It stands for Simple Object Access Protocol and uses XML for its messaging format to relay the information.

WSDL: When we go to a restaurant we see the Menu Items, those are the WSDL’s.

Proxy Classes: Now after seeing the Menu Items we make up our Mind (Process our mind on what to order): So, basically we make Proxy classes based on WSDL Document.

SOAP: Then when we actually order the food based on the Menu’s: Meaning we use proxy classes to call upon the service methods which is done using SOAP

SEI(service endpoint interface):The endpoint is a connection point where HTML files or active server pages are exposed. .A web service endpoint is the URL that another program would use to communicate with your program. To see the WSDL you add ?wsdl to the web service endpoint URL.

Parts of WSDL
Definitions – variables – ex: myVar, x, y, etc.

Types – data types – ex: int, double, String, myObjectType

Operations – methods/functions – ex: myMethod(), myFunction(), etc.

Messages – method/function input parameters & return types

ex: public myObjectType myMethod(String myVar)
Porttypes – classes (i.e. they are a container for operations) – ex: MyClass{}, etc.

Example of a Endpoint URL

protocol://host:port/partOfThePath

where

host=someIp
port=8080
partOfThePath=/some/service/path

serviceAEndpoint=http://host:port/some/service/path?dynamicParam=

Simple SOAP Request and Response

 package com.mugil.org;

import java.util.ArrayList;
import java.util.List;

import javax.jws.WebService;

@WebService
public class Products 
{
  List<String> arrProducts = new ArrayList<String>();
	
  public Products()
  {
	arrProducts.add("Books");
	arrProducts.add("EReader");
	arrProducts.add("PDF");	
  }
  
  public String getProduct(int index)
  {
	return arrProducts.get(index);  
  }
}

SOAP Request

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:org="http://org.mugil.com/">
   <soapenv:Header/>
   <soapenv:Body>
 
      <org:getProduct>
         <arg0>0</arg0>
      </org:getProduct>
   </soapenv:Body>
</soapenv:Envelope>

SOAP Request

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
   <soap:Body>
      <ns2:getProductResponse xmlns:ns2="http://org.mugil.com/">
         <return>Books</return>
      </ns2:getProductResponse>
   </soap:Body>
</soap:Envelope>

Di-section of WSDL

  1. service – Contains the port which defines the Endpoint URL, port number
  2. portType – Contains input and output for an operation.Though there are multiple input and output arguments they would be bundled together as one message
  3. binding – Defines how the SOAP service could be accessed like over http,https
  4. types – Type defined as complex type defines the Input and output
  5. message – Kind of input and output taken as argument, mostly represented as Message

Service

 <wsdl:service name="ProductsService">
  <wsdl:port binding="tns:ProductsServiceSoapBinding" name="ProductsPort">
   <soap:address location="http://localhost:8096/WebService1/Products"/>
  </wsdl:port>
  </wsdl:service>

Porttype

 <wsdl:portType name="Products">
   <wsdl:operation name="getProduct">
    <wsdl:input message="tns:getProduct" name="getProduct"></wsdl:input>
    <wsdl:output message="tns:getProductResponse" name="getProductResponse"></wsdl:output>
   </wsdl:operation>
  </wsdl:portType>

Binding

<wsdl:binding name="ProductsServiceSoapBinding" type="tns:Products">
      <soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http" />
      <wsdl:operation name="getProduct">
         <soap:operation soapAction="" style="document" />
         <wsdl:input name="getProduct">
            <soap:body use="literal" />
         </wsdl:input>
         <wsdl:output name="getProductResponse">
            <soap:body use="literal" />
         </wsdl:output>
      </wsdl:operation>
   </wsdl:binding>

Types

 <wsdl:types>
      <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="unqualified" targetNamespace="http://org.mugil.com/" version="1.0">
         <xs:element name="getProduct" type="tns:getProduct" />
         <xs:element name="getProductResponse" type="tns:getProductResponse" />
         <xs:complexType name="getProduct">
            <xs:sequence>
               <xs:element name="arg0" type="xs:int" />
            </xs:sequence>
         </xs:complexType>
         <xs:complexType name="getProductResponse">
            <xs:sequence>
               <xs:element minOccurs="0" name="return" type="xs:string" />
            </xs:sequence>
         </xs:complexType>
      </xs:schema>

Message

 <wsdl:message name="getProduct">
      <wsdl:part element="tns:getProduct" name="parameters" />
   </wsdl:message>
   <wsdl:message name="getProductResponse">
      <wsdl:part element="tns:getProductResponse" name="parameters" />
   </wsdl:message>

Service(Class name with @WebService Annotation) 
                | 
Port(has Binding which defines portType)
                | 
    PortType(defines Operations)
                | 
Operations(defines input and output Type)

Annotations for WebService

@Webservice(name="MartCatalogue", portName="MartCataloguePort", serviceName="ProductsService", targetNamespace="MartProducts.com")
.
.
@WebMethod(action="fetch_products", operationName="fetchProducts")
.

name

<wsdl:portType name="MartCatalogue">
.
.

portName and serviceName

wsdl:port binding="tns:productServiceSoapBinding" name="productPort">
  <soap:address location="http://localhost:8096/WebService1/productService"/>
</wsdl:port>
.
.

targetNamespace
Defines unique set of operations under namespace.Defaults to package name in java in reverse order
targetNamespace=”MartProducts.com”

targetNamespace

<wsdl:operation name="fetchProducts">
.
.
 <wsdl:operation name="fetchProducts">
      <soap:operation soapAction="fetch_products" style="document" />
  .
  .

WS-Addressing is useful in situations where the SOAP response can’t be served immediately. Either the resources to form the response are not available right away or the result itself takes a long time to be generated. There are times where your business takes time.something which needs manually intervention, something to be approved, whatever, but it takes days to do it. keeping the connection opened all that time and waiting for the response would be inefficient.notification process comes to rescue in these kind of scenarios.The client makes a requests but does not wait for the response. It instead instructs the server where to send the response by use of a “reply to” address. Once the response is available, the server connects to that address and sends the response.Instead of relying on network-level transport to convey routing information, a message utilizing WS-Addressing may contain its own dispatch metadata in a standardized SOAP header.WS-Addressing you are not tied to that. You can demand the response on another type of channel. Request comes on HTTP for example, but you can instruct the server to send the response back over SMTP, for example.

Scenario – Asynchronous Web Services

Implement a web service to make two systems communicate. The “client” system is interested in events that are generated on the “server” system. But the “client system” is itself a server for a different app. The server is Java (WAR in tomcat). The client is .Net.

  1. Server is running.Client initiates conversation, “registers” to the server, and requests some initial data.
  2. Server keeps a list of registered clients’ endpoints
  3. In the server there is a listener that is notified when certain events happen. It will then go through the list of registered clients and forwards the event to each of them
  4. At some point, the client can “unregister” no notify the server that it doesn’t want to receive events any more.

 

Challenges

  1. SOAP/HTTP communication path for requests from server-to-client – not guaranteed when firewalls exist
  2. The client needs to be aware of your notification schema – in fact the client needs to act as a Service endpoint to recieve the SOAP notification request.
  3. Many clients are “just clients” – they might not have a HTTP server to accept SOAP requests.So both sides need to servers and both need to publish their SOA interfaces. Alternatively, you can pull the notification to the client. The client can use a notification request to the server that is either blocking or polling. The server can respond with the notification or nothing or error.

Solution

An async callback mechanism is defined in JAX-WS 2.0, where the service obtains the endpoint reference of the client. SOAP payload schemas and message exchange pattern should
be custom developed as per requirement.

Incase of Arbitrary anonymous client SOAP would not be a appropriate solution. But with few changes and challenges it could be customized as below

Challenges

  1. HTTP servers (i.e. the SOAP server) do not support blocking requests, as a rule, meaning you must poll
  2. the client needs to be aware of your notification schema – in fact the client needs to act as a Service endpoint to recieve the SOAP notification request. That’s two very big assumptions for an arbitrary anonymous client – that’s not something SOAP “just supports” both ends need to design all this in detail. In fact to do this in a service typesafe manner, the client should actually declare it’s own service WSDL interface so that you can invoke it.

Solution

Other options for above scenario

WS-addressing data in SOAP headers to inform either side of the other’s endpoint address.WS-addressing addresses will help you intelligently route SOAP messages to the right URL address, but no more.

WS-notification WS-BaseNotification sub-standard would meet your needs. It provides WSDL port definitions for notification producers and consumers. It provides a WS- standards compliant solution for subscription from a consumer to a producer, and a notification from producers to consumers.

Challenges

  1. It does NOT define the format of notification payloads. The Notification payload is application-domain specific (proprietary design). The standard does not define any “standard” or “built-in” notification situations or messages.
  2.  It has the same problems with HTTP notifications passing through firewalls as mentioned above.
  3. WS-Notification is not a supported standard of Java EE/JAX-WS

Use a Message queuing solution (e.g. JMS) with traffic encapsulated in HTTP This requires proprietary design of payloads passing between client and server and back – forming contracts between the two sides. An advantage is that the client can be a pure client, with a message listener invoked in a thread when a message is recieved.It has the same problems with HTTP notifications passing through firewalls as mentioned above and do-it-yourself implementation.

 

 

JAX-WS – is Java API for the XML-Based Web Services – a standard way to develop a Web- Services in SOAP notation (Simple Object Access Protocol).

Calling of the Web Services is performed via remote procedure calls. For the exchange of information between the client and the Web Service is used SOAP protocol. Message exchange between the client and the server performed through XML- based SOAP messages.

Clients of the JAX-WS Web- Service need a WSDL file to generate executable code that the clients can use to call Web- Service.

JAX-RS – Java API for RESTful Web Services. RESTful Web Services are represented as resources and can be identified by Uniform Resource Identifiers (URI). Remote procedure call in this case is represented a HTTP- request and the necessary data is passed as parameters of the query. Web Services RESTful – more flexible, can use several different MIME- types. Typically used for XML data exchange or JSON (JavaScript Object Notation) data exchange