1 Lecture 22 George Koutsogiannakis Summer 2011 CS441 CURRENT TOPICS IN PROGRAMMING LANGUAGES

Topics Web Services- APIs used in EE5 – JAX-RPC (before EE5) – JAX-WS – JAXB 2

Web Services-JAX-RPC JAX-RPC enables a Web Service endpoint to be developed using either a Java Servlet or Enterprise JavaBeans (EJB) component model. A Web service endpoint is deployed on either the Web container or EJB container based on the corresponding component model. These endpoints are described using a WSDL document. This WSDL document can be published in public or private registry, though this is not required. A client uses this WSDL document and invokes the Web service endpoint. A JAX-RPC client can use stubs-based, dynamic proxy or dynamic invocation interface (DII) programming models to invoke a heterogeneous Web service endpoint. 3

Web Services-JAX-RPC RPC stands for Remote Procedure Call. – A protocol used by Microsoft in their systems. – RMI (and its offsprings) is similar to RPC. JAX-RPC allows the communication of a web service client with a web component/ejb session bean so that the web service can be invoked via the business rules model. 4

Web Services-JAX-RPC 5

It is assumed that the client is aware of the Web service and the remote procedure that it can execute on the Web service. This is what happens: – The client calls the method on the stub that represents the remote procedure. – The stub executes the necessary routines on the JAX-RPC runtime system. – The runtime system converts this method call into a SOAP message and transmits the message to the server as an HTTP request. – The server, upon receipt of the SOAP message, invokes the methods on the JAX-RPC runtime. The JAX-RPC runtime converts the SOAP request into a method call. – The JAX-RPC runtime then calls the method on the tie object. – Finally, the tie object calls the method on the implementation of the Web service. – The response to the RPC call is sent in a SOAP response message as an HTTP response. 6

Web Services-JAX-RPC The Web service is represented by two files: the service definition interface, and the corresponding implementation class. The service definition interface and the implementation class are collectively known as the service endpoint. 7

EE5 and Web Services-JAX-WS Java EE5 provides annotations for Web Services. JAX-WS 2.0 is the new API for web services in the Java EE 5 platform and it is a successor to JAX-RPC. 8

EE5 and Web Services-JAX-WS Example comparing the approach between JAX-RPC and JAX-WS 2.0 JAX-RPC Web Service: public interface HelloService extends Remote { public String sayHello(String name) throws RemoteException; } public class HelloServiceBean implements SessionBean { public String sayHello(String name) { return "Hello "+ name + " from HelloServiceBean"; } 9

EE5 and Web Services-JAX-WS Example using JAX-WS public class HelloServiceBean { public String sayHello(String name) { return "Hello "+ name + " from HelloServiceBean"; } Notice that: – No need for an interface! – annotation defines the class as a web service end point. 10

EE5 and Web Services-JAX-WS Here is another example with more targetNamespace=” public class CreditRating public Score Customer c { //... implementation code... } 11

EE5 and Web Services-JAX-WS 12 Our diagram is now revised to show that the JAX-WS runtime environment is used instead of JAX-RPC. Notice that the service can also be an ejb.

EE5 and Web Services-JAX-WS You may specify an explicit interface by adding the endpointInterface element to annotation in the implementation class. You must then provide an interface that defines the public methods made available in the endpoint implementation class. 13

EE5 and Web Services-JAX-WS The wsgen tool and the Application Server provide the Application Server’s implementation of JAX-WS. – wsgen generates all articrafts (files) needed for the implementation of the web service. 14

EE5 and Web Services-JAX-WS Building a Web Service With Java WSDP 2.0 – Write an endpoint implementation class. – Compile the endpoint implementation class. – Generate portable artifacts required for web service by using wsgen tool. – Package the web service as a WAR file and deploy it. – Code the client class. – Use wsimport tool to generate and compile the web service artifacts needed to connect to the service. – Compile the client class. – Run the client. 15

EE5 and Web Services-JAX-WS Suppose our end point service class is: package helloservice.endpoint; import public class Hello { private String message = new String("Hello, "); public void Hello() {} public String sayHello(String name) { return message + name + "."; } 16

EE5 and Web Services-JAX-WS You can build, package, and deploy the helloservice application using either NetBeans IDE or ant. Notice that the WSDL file is generated automaticaly (as well as the descriptor files needed). Also, notice that XML is totally hidden from the developer. Keep in mind that annotations come with attributes: i.e. annotation has attributes: 17

EE5 and Web Services-JAX-WS – endpointInterface – name – portName – serviceName – targetNamespace – wsdlLocation 18

EE5 and Web Services-JAX-WS Coding the Client When invoking the remote methods on the port, the client performs these steps: – Uses the javax.xml.ws.WebServiceRef annotation to declare a reference to a web service. uses the wsdlLocation element to specify the URI of the deployed service’s WSDL file. ello?wsdl") static HelloService service; – Retrieves a proxy to the service, also known as a port, by invoking getHelloPort on the service. – Hello port = service.getHelloPort();The port implements the SEI defined by the service. – Invokes the port’s sayHello method, passing to the service a name. – String response = port.sayHello(name); 19

EE5 and Web Services-JAX-WS public class HelloClient helloservice/hello?wsdl") static HelloService service; ……………………………………………………… Hello port = service.getHelloPort(); String response = port.sayHello(name); System.out.println(response); ……………………………………………………………. 20

EE5 and Web Services-JAXB JAX-WS delegates the mapping of the Java language data types to JAXB API. – JAXB stands for Java Architecture for XML Binding. – JAXB converts XML schemas to Java Content trees (see example in previous lecture of a content tree) and vice versa. 21

EE5 and Web Services-JAXB Architecture. 22

EE5 and Web Services-JAXB Architecture. Basically JAXB is the translator of XML schemas (and data types) to Java and vice versa. – Since the WSDL describes the XML schema there is a need to translate that schema to Java. – It is the job of JAXB to do just that. 23

EE5 and Web Services-JAXB Architecture. XML Schema Type Java Data Type xsd:stringjava.lang.String xsd:integerjava.math.BigInteger xsd:intint xsd.longlong xsd:shortshort xsd:decimaljava.math.BigDecimal xsd:floatfloat 24

EE5 and Web Services-JAXB Architecture 25

EE5 and Web Services-JAXB Architecture Generate classes: An XML schema is used as input to the JAXB binding compiler to generate JAXB classes based on that schema. Compile classes: All of the generated classes, source files, and application code must be compiled. Unmarshal: XML documents written according to the constraints in the source schema are unmarshalled by the JAXB binding framework. Note that JAXB also supports unmarshalling XML data from sources other than files/documents, such as DOM nodes, string buffers, SAX Sources, and so forth. Generate content tree: The unmarshalling process generates a content tree of data objects instantiated from the generated JAXB classes; this content tree represents the structure and content of the source XML documents. 26

EE5 and Web Services-JAXB Architecture Validate (optional): The unmarshalling process optionally involves validation of the source XML documents before generating the content tree. Note that if you modify the content tree in step below, you can also use the JAXB Validate operation to validate the changes before marshalling the content back to an XML document. Process content: The client application can modify the XML data represented by the Java content tree by means of interfaces generated by the binding compiler. Marshal: The processed content tree is marshalled out to one or more XML output documents. The content may be validated before marshalling. 27

EE5 and Web Services-NetBeans support. NetBeans 6.5 provides support for web services using JAX-WS and JAXB. For more information on how to use NetBeans to develop a web service by utilizing JAX-WS and JAXB see the NetBeans tutorial at: ws.html 28

Study Guide EE5 Tutorial text chapter 15. EE5 Tutorial text chapter 16 NetBeans tutorial online. EE5 Tutorial chapters 11,12 29