A review of “SOA with Java” book from Packt.

Book Name: Service Oriented Architecture with Java

Authors      : Binildas A. Christudas,Malhar Barai,                      Vincenzo Caselli 

Publisher   : Packt

Language  : English

Why this book is Special?

• This book is special because of one reason. It collectively describes all the information and frameworks those a Java Web Service Programmer wants to know. If you are a Java developer and wants to implement SOA through Web Services then I am sure this book will give you a good idea about the frameworks those will help you for this.

To whom this book is helpful?

• If you are a Java Programmer who wants to learn more about SOA with web services..
• If you want to learn any of the Famous Java Web service Implementation frameworks like Axis2, Spring WS, CXF etc.. OR if you need to know more basic but mush needed information about SOA using Web services.
• If you want to get some idea about SCA and SDO.

Advantages:

• Even if you are new to the web service concepts also you can use this book. Its starts from the beginning.
• Start with explaining how SOA helps in the Software world and what all are its advantages.
• It explains about RPC and Document Based-WS and all its basics.
• If you are familiar with Ant then examples will be more easy because almost all examples are using Ant scripts.
• It also goes through JAXB binding and its examples.
• It will be very rare to get books related with Service Component Architecture this time. This book had a good explanation about this Architecture and it gives a good example with its description. Being a person who implemented SCA this section was very interesting to me.
• Gives a very good introduction about MOM and ESBs. If you are just starting to learn these then this book will be helpful to you.
• It gives web service implementation examples with multiple frameworks. CXF, Axis2 and Spring WS are the most famous two frameworks which we are using nowadays. And you can find examples for these three frameworks application examples.

Disadvantages:

• I think description is less for each topics. Book is covering a lot of topics and for each one we can write one entire book. But as a reader of this book I am expecting some more explanation for each topic. Sometimes I feel the author is just touching a topic and going to the next one.
• Some of the Described Versions became OLD. For example Axis2 is there now. Book is already mentioned Axis2 and CXF but taken Axis1.x and XFire for the further explanation.

Creating Web Services using CXF (Contract first Approach) Part 2 : WSDL Creation.

What is WSDL and what its Structure?

A WSDL document defines services as collections of network endpoints, or ports. In WSDL, the abstract definition of endpoints and messages is separated from their concrete network deployment or data format bindings. This allows the reuse of abstract definitions: messages, which are abstract descriptions of the data being exchanged, and port types which are abstract collections of operations.

The concrete protocol and data format specifications for a particular port type constitutes a reusable binding. A port is defined by associating a network address with a reusable binding, and a collection of ports define a service. Hence, a WSDL document uses the following elements in the definition of network services:

WSDL document describes a web service using these major elements:

Element	Defines
<types>	The data types used by the web service
<message>	The messages used by the web service
<portType>	The operations performed by the web service
<binding>	The communication protocols used by the web service
<port>	A single endpoint defined as a combination of a binding and a network address.
<service>	A collection of related endpoints.

The main structure of a WSDL document looks like this:

<definitions>              <types>                       definition of types……..              </types>              <message>                       definition of a message….              </message>              <portType>                       definition of a port…….              </portType>             <binding>                      definition of a binding….              </binding>               <service>                      definition of services….              </service> </definitions>

A WSDL document can also contain other elements, like extension elements and a service element that makes it possible to group together the definitions of several web services in one single WSDL document.

Creating WSDL for our Example

<types>:In the Types we are defining or configuring the Datatypes which we are using for the entire application. Here we are importing the XSD files here.

<message>:In our example we need to configure our input and our parameters/ the message which we are passing through Webservice. We are configuring request and response objects here.

<portType>: We have one operation which is called getProduct. So here we need to declare this getProduct operation.

<binding> : Here we will be providing our protocol types and we are using SOAP protocol.

<service> : Defining the Service End point. And for the ProductService we are defining it as “http://localhost:8080/ContractFirst/services/ProductService”

   1: <?xml version="1.0" encoding="UTF-8" standalone="no"?>

   2: <wsdl:definitions xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"

   3:     xmlns:tns="http://com/your/company/service/ProductService/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"

   4:     xmlns:xsd="http://www.w3.org/2001/XMLSchema" name="ProductService"

   5:     targetNamespace="http://com/your/company/service/ProductService/"

   6:     xmlns:prd="http://com/your/company/service/Product/">

   7:     <wsdl:types>

   8:         <xsd:schema targetNamespace="http://com/your/company/service/ProductService/"

   9:             xmlns:prd="http://com/your/company/service/Product/">

  10:             <xsd:import namespace="http://com/your/company/service/Product/"

  11:                 schemaLocation="../Product.xsd" />

  12:             <xsd:element name="getProductRequest">

  13:                 <xsd:complexType>

  14:                     <xsd:sequence>

  15:                         <xsd:element name="productRequest" type="prd:ProductRequest" />

  16:                     </xsd:sequence>

  17:                 </xsd:complexType>

  18:             </xsd:element>

  19:             <xsd:element name="getProductResponse">

  20:                 <xsd:complexType>

  21:                     <xsd:sequence>

  22:                         <xsd:element name="productResponse" type="prd:ProductResponse" />

  23:                     </xsd:sequence>

  24:                 </xsd:complexType>

  25:             </xsd:element>

  26:         </xsd:schema>

  27:     </wsdl:types>

  28:     <wsdl:message name="ProductRequest">

  29:         <wsdl:part element="tns:getProductRequest" name="parameters" />

  30:     </wsdl:message>

  31:     <wsdl:message name="ProductResponse">

  32:         <wsdl:part element="tns:getProductResponse" name="parameters" />

  33:     </wsdl:message>

  34:     <wsdl:portType name="ProductService">

  35:         <wsdl:operation name="getProduct">

  36:             <wsdl:input message="tns:ProductRequest" />

  37:             <wsdl:output message="tns:ProductResponse" />

  38:         </wsdl:operation>

  39:     </wsdl:portType>

  40:     <wsdl:binding name="ProductServiceSOAP" type="tns:ProductService">

  41:         <soap:binding style="document"

  42:             transport="http://schemas.xmlsoap.org/soap/http" />

  43:         <wsdl:operation name="getProduct">

  44:             <soap:operation

  45:                 soapAction="http://com/your/company/service/ProductService/getProduct" />

  46:             <wsdl:input>

  47:                 <soap:body use="literal" />

  48:             </wsdl:input>

  49:             <wsdl:output>

  50:                 <soap:body use="literal" />

  51:             </wsdl:output>

  52:         </wsdl:operation>

  53:     </wsdl:binding>

  54:     <wsdl:service name="ProductService">

  55:         <wsdl:port binding="tns:ProductServiceSOAP" name="ProductServiceSOAP">

  56:             <soap:address

  57:                 location="http://localhost:8080/ContractFirst/services/ProductService" />

  58:         </wsdl:port>

  59:     </wsdl:service>

  60: </wsdl:definitions>

In our next part we will go through Skelton creation using WSDL to Java tool which is giving by CXF. We will go through class path settings and wsdl2java commands.

Creating Web services using Apache CXF (Part 1) : The Basics.

As we discussed in the previous post, CXF is the combination of two projects: Celtix developed by IONA and XFire developed by Codehaus working together at the Apache Software Foundation.

If you want an Enterprise support  for CXF then please find the following links.

Click here to Read Full Article

Apache CXF- An ultimate web service open source framework : Lets start learning…

Apache CXF is an open source services framework which is a result of the merge between the XFire and Celtix projects. CXF helps us build and develop services using JAX-WS. These services can speak a variety of protocols such as SOAP, XML/HTTP, RESTful HTTP, or CORBA and work over a variety of transports such as HTTP, JMS or JBI.

Click here to Read Full Article

Spring Interview Questions Part: 1

• What is mean by Dependency Injection? Or What do you mean by Inversion of Control?

Dependency injection (DI) is a programming design pattern and architectural model, sometimes also referred to as inversion of control or IOC, although technically speaking, dependency injection specifically refers to an implementation of a particular form of IOC.

Dependancy Injection describes the situation where one object uses a second object to provide a particular capacity. For example, being passed a database connection as an argument to the constructor instead of creating one internally. The term "Dependency injection" is a misnomer, since it is not a dependency that is injected, rather it is a provider of some capability or resource that is injected. There are three common forms of dependency injection: setter-, constructor- and interface-based injection.

Dependency injection is a way to achieve loose coupling. Inversion of control (IOC) relates to the way in which an object obtains references to its dependencies. This is often done by a lookup method. The advantage of inversion of control is that it decouples objects from specific lookup mechanisms and implementations of the objects it depends on. As a result, more flexibility is obtained for production applications as well as for testing.

• What are the modules in Spring?

1. The core container:

   The core container provides the fundamental functionality of the Spring framework. In this module primary component is the BeanFactory, an implementation of the Factory pattern. The BeanFactoryapplies the Inversion of Control (IOC) pattern to separate an application’s configuration and dependency specification from the actual application code.

2. Spring context module :

   TThe Spring context is a configuration file that provides context information to the Spring framework. The Spring context includes enterprise services such as e-mail, JNDI, EJB, internalization, validation, scheduling and applications lifecycle events. Also included is support for the integration with templating frameworks such as velocity.

3. Spring AOP module:

   The Spring AOP module allows a software component to be decorated with additional behavior, through its configuration management feature. As a result you can easily AOP-enable any object managed by the Spring framework. The Spring AOP module provides transaction management services for objects in any Spring-based application. With Spring AOP you can incorporate declarative transaction management into your applications without relying on EJB components.

4. Spring DAO module:

   The Spring DAO module provides a JDBC-abstraction layer that reduces the need to do tedious JDBC coding and parsing of database-vendor specific error codes. Also, the JDBC package provides a way to do programmatic as well as declarative transaction management, not only for classes implementing special interfaces, but for all your POJOs (plain old Java objects).

5. Spring ORM module:

   : Spring provides integration with OR mapping tools like Hibernate, JDO and iBATIS. Spring transaction management supports each of these ORM frameworks as well as JDBC.

6. Spring Web module:

   The Web context module provides basic web-oriented integration features builds on top of the application context module, providing contexts for Web-based applications. As a result, the Spring framework supports integration with Jakarta Struts. The Web module also eases the tasks of handling multi-part requests and binding request parameters to domain objects.

7. Spring MVC framework module:

   Spring provides a pluggable MVC architecture. The users have a choice to use the web framework or continue to use their existing web framework. Spring separates the roles of the controller; the model object, the dispatcher and the handler object which makes it easier to customize them. Spring web framework is view agnostic and does not push the user to use only JSPs for the view. The user has the flexibility to use JSPs, XSLT, velocity templates etc to provide the view.

• What is a BeanFactory and XMLBeanFactory?

Bean factory is a container. It configures, instantiates and manages a set of beans. These beans are collaborated with one another and have dependencies among themselves. The reflection of these dependencies are used in configuring data that is used by BeanFactory.

XMLBeanFactory is a bean factory that is loaded its beans from an XML file.

• What are Inner Beans?

A bean inside another bean is known as Inner Bean. They are created and used on the fly, and can not be used outside the enclosing beans. The Id and scope attributes for inner beans are of no use.

• What is DataAccessException?

DataAccessException is an unchecked RuntimeException. These type of exceptions are unforced by users to handle. This exception is used to handle the errors occurring when the details of the database access API in use, such as JDBC.

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