23 November, 2010

How to expose a JSON endpoint from a WCF-service

Having seen the small footprint set by JSON – I’ve begun using it extensively for mobile device (WP7) communication. In particular the phone scenario makes it desirable to have an as small as possible data load to transfer between server and device. When using the JSON formatting, you can really minimize the load as documented here. Below is what is returned in JSON-format (compare that to the verbose OData or SOAP formatting!):

[{"BirthYear":1900,"FirstName":"Anders","LastName":"And"},{"BirthYear":1900,"FirstName":"Anders","LastName":"And"},{"BirthYear":1900,"FirstName":"Anders","LastName":"And"},{"BirthYear":1900,"FirstName":"Anders","LastName":"And"},{"BirthYear":1900,"FirstName":"Anders","LastName":"And"}]

How to do ?
To expose a WCF-implemented service with JSON support, you need to setup these artifacts:

Service Contract:
First define the contract for the service to expose.

namespace WebService1
{
[ServiceContract(Namespace="http://someethingelse.com")]
public interface IEmployeeService
{
[OperationContract]
[WebInvoke(BodyStyle=WebMessageBodyStyle.Bare, ResponseFormat=WebMessageFormat.Json)]
Employee[] GetAll_POST();

[OperationContract]
[WebGet(BodyStyle = WebMessageBodyStyle.Bare, ResponseFormat = WebMessageFormat.Json)]
Employee[] GetAll_GET();
}

[DataContract(Namespace="http://somethingunique.com")]
public class Employee
{
[DataMember]
public int BirthYear { get; set; }
[DataMember]
public string FirstName { get; set; }
[DataMember]
public string LastName { get; set; }
}
}

Note the WebInvoke and WebGet attributes on the service definition. The WebInvoke attribute specifies that the method will obey POST-requests, where as the WebGet attribute will make the method obey GET-requests.

The two attributes takes parameters that allows for specifying in which format the data should be formatted. When the ResponseFormat=WebMessageFormat.Json is set, the data returned by the method is formatted as a clean and simple JSON notation.


Web.config
Of-course you also need to setup configuration in the web.config. Here you should pay special attention to the binding and the behaviorConfiguration attributes.
Important: In particular the endpointBehavior should have <webHttp> set as content to gain the clean JSON formatting (see below).

  <system.serviceModel>
<
services>
<
service name="WebService1.EmployeeService">
<
endpoint name="jsonEP"
address=""
binding="webHttpBinding"
behaviorConfiguration="json"
contract="WebService1.IEmployeeService"/>
</
service>
</
services>
<
behaviors>
<
endpointBehaviors>
<
behavior name="json">
<
webHttp/>
</
behavior>
</
endpointBehaviors>
</
behaviors>
</
system.serviceModel>

Client:
When calling the above service, you will receive a nicely formatted JSON string like this:


[{"BirthYear":1900,"FirstName":"Anders","LastName":"And"},{"BirthYear":1900,"FirstName":"Anders","LastName":"And"},{"BirthYear":1900,"FirstName":"Anders","LastName":"And"},{"BirthYear":1900,"FirstName":"Anders","LastName":"And"},{"BirthYear":1900,"FirstName":"Anders","LastName":"And"}]


That’s how easy it is setting up when using WCF.


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12 comments:

Promothash said...

great work man :-).

Anonymous said...

is there a sample code?????
i have a little problem,

Claus Konrad said...

If it is problematic, attempt with a very simple class (DataContract). Problems often arise in serialization areas, hence to try with a simple class (like the Person class above).

I do not have a sample for this simple construction.

Scott Duncan said...

So does the service need to be exposed as a web application then?

Adi said...

How do you test it?

Claus Konrad said...

Quite easy from a browser (IE will do). Just type the proper address in the browser and you will see the result in the browser rendered as text.

Steven Lundahl said...

Can we still take advantage of security features in WCF? We have a partner that would like to pull data from a JSON-based endpoint but as it is customer data, we need it to be secure.

Thanks!

Claus Konrad said...

Sure - WCF is made in a pretty clever and "combination-wise" manner. Please, see here:
http://msdn.microsoft.com/en-us/library/bb924478.aspx

Ken said...

I have a WCF service that is sending and receiving encrypted information and the service injects characters into the stream. It escapes forward slashes, replaces plus signs with spaces and place \" in the strings.

Up until now I have been writing parsing code to overcome these issues but now IIS running on Windows 7 is having different issues than IIS running on Server 2008 R2.

Is there any way to stop this behavior?

Claus Konrad said...

Instead of doing manual processing of the received stream; I would first see it not the encryption algorithms/classes are able to decrypt the data into plain data? Usually, that is possible.
What type of encryption are you using for creating the data to be sent to the client?

Unknown said...

How would one call this method using jQuery AJAX?

Unknown said...
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