ODS – Introduction to Web Services and BPEL Vakgroep Informatietechnologie Web Services & BPEL...

ODS – Introduction to Web Services and BPEL Vakgroep Informatietechnologie

Web Services & BPEL

Design of Distributed Software

Objectives

After this lab session you should be able to Create a Web Service Create composite applications using BPEL Use the following technologies: WSDL, BPEL, SOAP, Web

Service annotations, Jax-WS

Web Service A service is a self-contained software module that performs a

predetermined task Web Services are services accessible on the web

BPEL (Business Process Execution Language) provides a relatively easy way to compose several Web

Services into new composite services called business processes

ODS – Introduction to Web Services and BPEL Vakgroep Informatietechnologie p. 2

What you should know for Exercise1


Jax-WS: @WebService()@WebService(

name="CatalogService",

targetNamespace=”http://ods.intec.ugent.be/catalog”

)

This annotation makes clear that this class is a Web Service

Default behavior The targetNamespace for the generated WSDL definition is generated

from the package name The name of the PortType corresponds to the name of your class-file The operation name in the portType has the same name as the method

in your class. All public methods in your class are now available in the web service

The @WebService() annotation can also be customized Name: Change the name of the PortType targetNamespace: Change the targetNamespace


Jax-WS: @WebMethod()@WebMethod(operationName=”searchMyCatalogForSong”)

Public CDLookupOperation(String track){

return null;

}

Will declare a method in your class as being a web method

Default behavior No @WebMethod() annotations: all public methods exposed as web

service operations One or more @WebMethod() annotations: only those methods exposed as

web service operations Relates to an operation in a portType in the WSDL Gives the WSDL operation the same name as the java method

This annotation can off course also be customized operationName: Change the name of the operation in the portType.


Jax-WS: @WebParam()CDLookupOperation(

@WebParam(name="song",targetNamespace=“http://ods.intec.ugent.be/operation”,header=true) String track){

return null;

}

Gives control over how the arguments of the methods are mapped onto the Web Service operation

Default behavior Names for the parameters is the WSDL file are arg0, arg1,… The namespace where these parameters are defined is also derived from the

package name of the class file

This annotation can off course also be customized Name: the name of the parameter targetNamespace: the namespace the parameter will be defined in Header: declares that the xml of this parameter should be transmitted in the

SOAPHeader instead of the SOAPBody. This is recommended for transmitting metadata.


Invoking a Web Service

Code generated by Netbeans When creating the Web Service client: fill in the URL of the WSDL of the Web

Service In the methods of your client

Right-click and select Web Service Client Resource call Web Service operation The operations of the Web Service will be shown choose one Netbeans generates the skeleton code!

The method on the port object executes the web service operation for you and hides all its complexity

Prepare the input for the operation Write some code to process and display the result (output)


public static void main(String[] args) {

try {

// Call Web Service Operation

be.ugent.intec.ods.catalog.MyCDCatalogServiceService service = new be.ugent.intec.ods.catalog.MyCDCatalogServiceService();

be.ugent.intec.ods.catalog.CatalogService port = service.getCatalogServicePort();

// initialize WS operation arguments

be.ugent.intec.ods.catalog.SearchMyCatalogForSong parameters = new be.ugent.intec.ods.catalog.SearchMyCatalogForSong();

java.lang.String song = "Believe";

// process result be.ugent.intec.ods.catalog.SearchMyCatalogForSongResponse result = port.searchMyCatalogForSong(parameters, song);

System.out.println("Result = "+result);

}

catch (Exception ex) {

ex.getStackTrace();

}

}


What you should know for Exercise 2


BPEL

BPEL stands for Business Process Execution Language for Web Services

It provides a relatively easy way to compose several Web Services into new composite services called business processes

The NetBeans BPEL designer allows you to graphically construct BPEL processes

On the right you will a palette with all the BPEL Activities you can use to construct the process

A BPEL file is an XML file and you can take a look at the XML source by clicking on the Source button in the BPEL Designer


Structure of a BPEL Process Generally it looks something like this:

<process name="QuotationProcess"

targetNamespace=http://enterprise.netbeans.org/bpel/

QuotationProcess/QuotationProcess

xmlns=http://docs.oasis-open.org/wsbpel/2.0/process/executable

xmlns:xsd=http://www.w3.org/2001/XMLSchema

xmlns:tns=http://enterprise.netbeans.org/bpel/QuotationProcess/QuotationProcess>

<partnerLinks> 

</partnerLinks>

<variables> 

</variables>

<sequence> 

</sequence>

</process>

The Process element is the root of the process. Here you can name the process and declare prefixes for namespaces used in the process definition.

Partner Links A BPEL-file consists of a series of activities describing the

execution flow of the process

Some of these activities handle the communication between the process and external services called the external services Partners

includes the Web services the BPEL process invokes Includes the client that invokes the BPEL process

The Partner links define the parties that interact with the BPEL Process

is linked to a PartnerLinkType which is defined in the WSDL of the partner service

Partner link types represent the interaction between a BPEL Process and the involved parties (input/output)


Invoke

The invoke activity can be used to invoke one of the partner links involved in the process

How to? Drag an invoke activity on the BPEL designer Connect this activity to the operation of the partner link you want to invoke Create input and output variables for this invoke operation


Assign

An activity that can be used to assign data to a variable

This data can be copied from another variable or be the result of a series of XPath expressions

How to? Drag an assign activity on the BPEL designer The BPEL Mapper is used to copy data from one variable to another

You copy data from left to right In the center column you can place operations that perform

transformations on the data


Reply

Used to return the result to the client partner link

How to? Drag a reply activity on the BPEL designer Connect this activity to the operation of the client partner link Create an output variable for this reply activity Use an assign activity to assign data to this output variable


Predicates and Xpath

The mapper tool can easily be used to provide mappings between source and target variables

When you look at the source view you’ll see that this mapping is done using an Xpath expression

Predicates are used when the selection is not as trivial as the previous examples


Predicates and Xpath: Example

A variable named “parameters” This variable is defined in XMLSchema to represent a table It exists of a collection of rows (maxOccurs=”unbounded”)

with each row an unbounded number of cells



We are interested in the value of the cell where the name attribute equals the string ‘unit’

To get this you must add a predicate Editing the predicate is similar to defining for example an IF condition

using the mappertool You can see in the screenshot below that the focus is set to a cell, and a

filter on those cells is defined using a predicate



You want to select the first row in an array of rows Assign in the predicate editor a number literal to the predicate The resulting code is an Xpath expression According to the Xpath specification the first element in an array of

elements has index 1!


ODS – Introduction to Web Services and BPEL Vakgroep Informatietechnologie Web Services & BPEL...

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