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Archive for the ‘JSON’ Category

XML/JSON symmetric REST web services providers for Jersey

Posted by Igor Moochnick on 07/27/2009

Many times I’ve been asked to provide a set of Web Services interfaces where both JSON and XML clients can communicate with the server. Primarily it’s done for a set of reasons:

  1. XML is very convenient to use for inter-service communication.
  2. JSON is great for AJAX (web) clients. It’s perfect for GWT too.

In the recent project we’ve been using XStream for all serialization aspects and, since it can serialize both to XML and JSON, it was plugged into Jersey as a provider too. Following you can see XML and JSON providers implemented using XStream library.

XML Provider (annotated to be a default provider, it’ll be used if no Content-Type or Accept headers provided):

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Posted in GWT, Java, Jersey, JSON, REST, Tutorials, XML, XStream | 2 Comments »

Building GWT web clients [Part 4.1] – How to create an Azure RESTful web service?

Posted by Igor Moochnick on 06/08/2009

Prerequisites: make sure that you have all the Azure SDK tools installed for your VS2008.

 

(1) Start by creating a new “Web Cloud Service” project in the Visual Studio. Give it a nice name.

(2) Add a new “WCF Service” to the WebRole project.

(3) Define a required contract:

The most important part here is to put attributes that will tell the WCF in what format to send/receive the message body (XML or JSON) …

[ServiceContract(Name = "service", Namespace = "http://www.igorshare.com")]
public interface IContactManagerService
{
    [OperationContract]
    [WebGet(UriTemplate = "/contacts", BodyStyle = WebMessageBodyStyle.Bare,
       ResponseFormat = WebMessageFormat.Json)]
    List GetAllContacts();

    [OperationContract]
    [WebGet(UriTemplate = "/contacts/{filter}", BodyStyle = WebMessageBodyStyle.Bare,
       ResponseFormat = WebMessageFormat.Json)]
    List GetContacts(string filter);
}

[DataContract]
public class Contact
{
    [DataMember]
    public string FirstName { get; set; }

    [DataMember]
    public string LastName { get; set; }

    [DataMember]
    public string Company { get; set; }
}

(4) Implement the service logic:

public class ContactManagerService : IContactManagerService
{
    private static readonly List Contacts = new List() { ... };

    public List GetAllContacts()
    {
        return Contacts;
    }

    public List GetContacts(string filter)
    {
        string f = filter.ToLower();

        var contacts = from contact in Contacts
                       where contact.FirstName.ToLower().Contains(f) 
                            || contact.LastName.ToLower().Contains(f)
                            || contact.Company.ToLower().Contains(f)
                       select contact;

        return contacts.ToList();
    }
}

(5) Configure it to be exposed as a RESTful service:

To make it REALLY, REALLY simple for you, do this trick:

a) Comment out the system.serviceModel section in the Web.config file

b) Add the Factory attribute to the .svc file


(6) Build the service

 

You’re interested in 2 artifacts of the build:

  1. .cscfg file – configuration for the Cloud Service deployment
  2. .cspkg file – all the bits packaged (zipped)

 

At this moment you have 2 choices:

  1. Run your project in the local Development Fabric (for testing and debugging), or …
  2. Deploy it to the Azure Cloud (for staging or production)

 

To deploy your application to the cloud, do right-click on the CloudService project and select “Publish”.

Visual Studio will launch the Azure Service Developer Portal page. Log-in to your account, create a project and deploy your bits to the staging environment:

clip_image001

 

This is it!  You’re good to go.

BTW: make sure that your application works in the staging environment and then you can push it to Production by just switching it with the Staging.

 

 

Note: Check out a great explanation about the difference between the WCF REST Configuration for ASP.NET AJAX and plain REST Services by Rick Strahl.

Posted in .NET, Azure, C#, Cloud, JSON, REST, Tutorials, WCF | 2 Comments »

Building GWT web clients [Part 4] – How to connect GWT client to Azure web service?

Posted by Igor Moochnick on 06/08/2009

Stay tuned …

Posted in Azure, Cloud, GWT, Java, JSON, REST, Tutorials | Leave a Comment »

Building GWT web clients [Part 3] – How to connect GWT client to JAX-RS Jersey server?

Posted by Igor Moochnick on 06/08/2009

Stay tuned …

Posted in Cloud, GWT, Java, JAX-RS, Jersey, JSON, REST, Tutorials | 7 Comments »

Building GWT web clients [Part 2.1] – How to control JSON output format from Jersey?

Posted by Igor Moochnick on 05/21/2009

As you know that in XML you can represent the same data in variety of ways by using fields, names, attributes, etc..

The same is true to JSON. In many cases different serializers produce different JSON representation of the same objects.

JAX-RS (as well as Jersey) provide you control over what and how you want to serialize. This is accomplished via providers.

Here is an example of such provider (Note that the class should be marked with @Provider annotation):

@Provider
public class JAXBContextResolver implements ContextResolver<JAXBContext> { 
    private JAXBContext context;
    private Class<?>[] types = { ListDescription.class }; 

    public JAXBContextResolver() throws Exception {
        JSONConfiguration config = JSONConfiguration.natural().build();
        context = new JSONJAXBContext(config, types);
    } 

    public JAXBContext getContext(Class<?> objectType) {
        for (Class<?> type : types) {
            if (type == objectType) {
                return context;
            }
        }
        return null;
    }
}

Note that by creating an appropriate JSONConfiguration (JSONConfiguration.natural().build()) you, in fact, control the output JSON format. The JSONConfiguration class provide 4 different JSON formatters:

  1. natural (Jackson)
  2. mapped
  3. mappedJettison
  4. Badgerfish

Here is how the output will vary, depending on the choice of the configuration. Don’t forget that the class should be annotated with A simple class (with fields (int)ID and (String)Name) added to an ArrayList and then returned back as a @GET return value:

@XmlRootElement
public class ListDescription
{
	public int ID;
	public String Name;
}

@GET
@Produces({MediaType.APPLICATION_JSON })
public List<DataListInfo> getAllLists()
{
	List<ListDescription> lists = new ArrayList<ListDescription>();
	ListDescription ls = new ListDescription();
	ls.ID = 1;
	ls.Name = "Test";
	lists.add(ls);
	return lists;
}

This is what you’ll get from each configuration (respectively):

mappedJettison:

{"listDescriptions":{"listDescription":{"ID":1,"Name":"Test"}}}

mapped:

{"listDescription":{"ID":"1","Name":"Test"}}

natural (jackson):

[{"ID":1,"Name":"Test"}]

Badgerfish:

{"listDescriptions":{"listDescription":{"ID":{"$":"1"},"Name":{"$":"Test"}}}}

Posted in Java, JAX-RS, JAXB, Jersey, JSON, REST | 1 Comment »

Building GWT web clients [Part 2] – How to expose REST-full JAX-RS service with Jersey on Tomcat server?

Posted by Igor Moochnick on 05/20/2009

In the previous article (Part 1) we’ve seen how to create a web-based REST-full client (and an appropriate server) by using GWT. GWT is not providing any “standard” REST (if you can use this word in REST context at all) interface, but, merely, exposes the server-side logic via a proprietary GWT RPC interface.

Today, the most common REST standard is the JAX-RS specification. By implementing your code along the JAX-RS guidelines you can be rest assured that you can easily switch one REST-RX library with another.

As of today there are a couple of JAX-RS libraries used by the Java community:

  1. Jersey
  2. Restlet
  3. Portlet
  4. etc…

On the other hand, being a big fan of Spring, I was hoping that Spring will provide the JAX-RS support in it’s Spring v3 release, but, looking at the M3 drop, I have realized that it’s nowhere near that promise (check my discussion on the StackOverflow).

For this post I’m going to use Jersey JAX-RS implementation. Let’s start with creating

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Posted in Java, JAX-RS, JAXB, Jersey, JSON, REST, Tomcat, XML | 6 Comments »

 
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