If your method takes multiple parameters, they must be put in an Object[] array. To do this, you need a copy of your service interface and all your data objects locally to use. This can simplify consuming web services if you already have access to the code used to build the service. This allows you to talk to web services outside of mule configurations.
There are two ways to use CXF clients. The following is an example of how to construct a client using the service that was developed in Building Web Services with CXF :. XML is a markup language that specifies or describes the format of the data to be exchanged between two parties.
The data is significantly structured as tags or elements in a hierarchical order. XML has become the de facto standard for representing structured information. Some of the important standard technologies associated with an XML document are listed below:.
The XML namespace concept is similar to package definitions in Java, which provide conflict resolution of class names based on package declarations. The XML Schema data model includes the vocabulary element and attribute names , the content model relationships and structure , and data types. An example of XML Schema describing address information is provided below:. In the above example, xs represents the namespace of the XML Schema. The address represents an element whose type is Address.
The Address type in turn is represented as complexType similar to a Java bean Address class which stores address information , which is comprised of elements " addressLine1 ", " addressLine2 ", " city ", " state ", and " country " with data type as string. The headers optionally contain context related information, such as security or transaction, while the body contains actual payload or application data. Under WSDL, a web service is described as a set of communication endpoints that are capable of exchanging messages.
These communication endpoints are called ports. The first part is the abstract definitions of operations similar to methods in Java provided by the services and messages input and output parameter types for methods which are needed to invoke the service.
The set of abstract operation definitions is referred to as port type. The second part is the concrete binding of those abstract definitions of operations to concrete network protocol, where the service is located, and message format for the service. Typically, the WSDL files would be created using the tool provided by the web service framework.
Please refer to the inline comments for an explanation of the elements in the below WSDL file:. REST Representational State Transfer is neither a technology nor a standard; it's an architectural style—a set of guidelines for exposing resources over the Web. The resource can be any piece of information such as a book, order, customer, employee, and so on. The client queries or updates the resource through the URI and, therefore, influences a state change in its representation.
All resources share a uniform interface for the transfer of state between client and resource. HTTP provides a uniform interface and set of methods to manipulate the resource. Service Registry provides a mechanism to look up web services. Traditionally, there was UDDI specification that defined the standards on registering and discovering a web service, but it lacked enterprise-wide adoption.
Enterprises started shipping their own version of Service Registry, providing enterprise capabilities like service versioning, service classifications, and life cycle management. There are many different definitions available for a web service. Its definition can be discovered by other software systems. These systems may then interact with the web service in a manner prescribed by its definition, using XML-based messages conveyed by Internet protocols.
Simply, put web service is a software component that provides a business function as a service over the web that can be accessed through a URL.
Web services are next generation web applications, modules, or components that can be thought of as a service provided over the web. Traditionally, we had static HTML pages as web content, which evolved into more dynamic full featured web applications providing business functionality and rich GUI features to the end user. A web service component is one step ahead of this web paradigm and provides only business service, usually in the form of raw XML data that can be digested by virtually all client systems.
The GUI and business functionality are well separated. A web service can be thought of as a self contained, self describing, modular application that can be published, located, and invoked across the web.
The greatest benefit that web services provide is interoperability. Web services can be ported on any platform and can be written in different programming languages.
Similarly, the client accessing the web service can be an application written in a different language and running on a different platform than that of a service itself. A web service involves three types of roles—a service consumer , a service provider, and an optional service registry. The following diagram shows the interaction between the service provider, the service consumer, and the service registry:. The service providers furnish the services over the web and respond to web service requests.
The service consumer consumes the services offered by the service provider. In SOAP-based web services, the service provider publishes the contract WSDL file of the service over the web where a consumer can access it directly or by looking up a service registry. The service consumer usually generates a web service client code from a WSDL file using the tools offered by the web service framework to interact with the web service.
In the next chapter you will look at how to create web service clients from a WSDL file. However, if your requirement consists of various contracts to be defined and negotiated between the provider and consumer such as using a WSDL Web Service Description Language file and adhering to various web services specifications WS Specifications such as web service security for enterprise adoption, then SOAP-based web services is the right option.
A SOAP binding can have either an encoded use or a literal use. Encoding as the term implies, the message would be encoded using some format, while literal specifies plain text messages without any encoding logic.
Document style, as the name suggests, deals with XML documents as payloads which adhere to well defined contracts, typically created using XML schema definitions. The XML schema format specifies the contract for business messages being exchanged between web service provider and consumer, which the consumers can call and adhere to. The XML schema defines the request and response message format between the service provider and the service consumer. Document literal style is the preferred way of web service communication for achieving interoperability.
In order to serialize method parameters into the SOAP message so it can be deserialized back by any web service implementation, the SOAP specification defines a standard set of encoding rules. You should probably avoid developing RPC style web services as it has a lot of interoperability issues. There are lot of specifications designed for SOAP-based web services.
These web service specifications are designed for interoperable protocols for Security, Reliable Messaging, Management, and Transactions in loosely coupled systems. Apache CXF is an open source web service framework that provides an easy to use, standard-based programming model for developing web services. Exactly what does CXF stand for? The project was sponsored by IONA. Both Celtix and XFire, while in their initial versions, had many things in common and therefore the developers of both projects decided to bring out the best of both worlds and planned a better 2.
The communities of both these projects entered incubation at the Apache Software foundation to develop version 2. It took about 20 months at the Apache incubator before CXF finally rolled out. To deploy our server, you will need to make few more modifications to your project as listed below. Finally, to deploy the server application, you will need to make one more modification in pom.
The code that you need to add into your pom. Before you deploy the application, you need to add two more files to your project. The code within the web. In the cxf-servlet. Here we define the id for our service endpoint, the address on which the service will be available, the service name and the endpoint name.
Now, you learnt how your service gets routed and processed by a CXF servlet. The pom. Rather than describing all the dependencies, we have included the final version of pom. Note that it also includes a profile for building client that we will be learning in the later sections of this tutorial.
Now, you are ready to run the web app. In the command window, run the build script using the following command. As we did not specify any operation, only a fault message is returned to the browser by our application. So our server application is running as expected. Writing the client in a CXF application is as trivial as writing a server. Here, we use the CXF supplied Service class to bind to the known service. We call the create method on the Service class to get an instance of the service.
We set the known port by calling the addPort method on the service instance. Now, we are ready to consume the service, which we do by first obtaining the service interface by calling the getPort method on the service instance. Finally, we call our greetings method to print the greetings message on the console.
Giving a direct access to the service interface can also pose severe security threats. For providing decoupling, starting with a WSDL is a preferred way. For this, you need to first learn a new language - WSDL. Writing WSDL needs a careful approach and it would be better if you can gain some understanding on this before you start working on it. In this lesson, we will start by defining a web service interface in a WSDL document.
We will keep the application simple to maintain focus on the use of CXF. The webservice that we are going to implement will have one single webmethod called greetings that accepts a string parameter holding the user name and returns a string message to the caller after appending a greetings message to the user name.
Note that writing a syntactically correct wsdl has always been a challenge to the developers; there are many tools and online editors are available for creating a wsdl. These editors ask for the names of messages that you want to implement along with the parameters that you wish to pass in a message and the type of return message that you want your client application to receive. If you know wsdl syntax, you may hand code the entire document or use one of the editors to create your own.
In the above wsdl, we have defined a single message called greetings. With this, we will now proceed to server development. Before developing the server, we need to generate Apache CXF interface to our web service. This is to be done from the given wsdl. To do this, you use a tool called wsdl2java. As we will be using maven to build the project, you will need to add the following plugin to the pom.
You will have to make sure that you create an appropriate directory structure for your project and add the earlier shown hello.
The wsdl2java plugin will compile this wsdl and create Apache CXF classes in a pre-defined folder. The full project structure is shown here for your ready reference. Now, you are ready to create a server using the wsdl2java generated classes.
Examine this file in your code editor. Note that the interface contains a method called greetings. This was a message type in our wsdl. The wsdl2java tool has added this method to the generated interface. Now, you can understand that whatever messages you write in your wsdl, a corresponding method would be generated in the interface.
Now, your task would be to implement all these methods corresponding to the various messages that you have defined in your wsdl. In this case, the Apache CXF interface is created from wsdl. The implementation of service interface is trivial. The code implements the sole interface method called greetings. The method takes one parameter of string type, prepends a "hi" message to it and returns the resultant string to the caller. Developing server application is once again trivial.
Here, we will use the CXF supplied Endpoint class to publish our service. First, we create an object of our service implementor class - HelloWorldImpl. Then, we pass this reference as a second parameter to the publish method. The first parameter is the address to which the service is published - the clients would use this URL to access the service. To build this server class you will need to add a build profile in your pom.
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