Java Web Services Interview Preparation Guide

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Java Architecture for XML Binding: The java classes are mapped to XML representations. The two main features of JAXB are the ability to marshal Java objects into XML and unmarshal XML back to Java objects.

The Java API for XML Messaging (JAXM) enables distributed software applications to communicate using XML (and SOAP). JAXM supports both asynchronous and synchronous messaging.

Java API for xml processing. It provides the validation capability and parsing XML documents. There are three basic parsing interfaces in JAXP are DOM, SAX and Straming API for XML STAX.

Java API for XML based RPC. Allows a java based web service that is to be invoked by a Java application provided the description, still being consistent with WSDL description. This can resemble as Java RMI over web services.

Allowing a web service to be implemented at server side as a servlet/jsp or EJB container is the advantage of JAX-RPC.

Included in the bundle are
Java API for XML Processing (JAXP)
JAXP enables applications to parse, transform, validate and query XML documents. It uses an API that is independent of a particular XML processor implementation.
JAXP enables vendors to provide their own implementations without introducing dependencies in application code.

XML is a standard for exchanging data across heterogeneous systems.
Java provides a platform for building portable applications.
A combination of these two enables users and application developers to program Web based functionality on an platform.

JAXM is a SOAP 1.1 based standard to send XML documents over the Internet from the Java platform.
JAXM can be extended to work with higher level messaging protocols by adding the protocol's functionality on top of SOAP.

JAX-RPC project provides the code base for the Reference Implementation of JAX-RPC, the Java APIs for XML based RPC. JAX-RPC RI is a production-quality implementation that is used directly in a number of products by Sun and other vendors.

JAXR gives you a uniform way to use business registries that are based on open standards (ebXML) or industry consortium-led specifications (UDDI).

The operations between different software applications, which are running on a variety of platforms and frameworks are supported by a standard called Web services. The web services architecture provides the concepts, model and understanding web services and relationships among the components.

The WSA specifies the minimal characteristics that are very common for all web services and a number of characteristics to the needed web services. WSA is called interoperability architecture that means the global elements of a global web service network are identified by this architecture in order to perform the interoperability between the web services.

JAX-RPC uses SOAP to call remote procedures. JAX-RPC enables JAX-RPC clients to invoke web services developed across heterogeneous platform.

A web service is a business function that is self-contained and operates over the internet. The W3C defined web service as “a software system designed to support interoperable machine-to-machine interaction over a network”. XML is the base for the web services. They communicate using open protocols.

Web services are more frequently like Web APIs. These services accessibility can be from internet. A remote system can host these services for different web services. A web service can convert a stand alone / desktop application into a web based / web application. A web services are published or found and utilized through the internet. The web services works on the XML + HTTP platform.

A smart web service understands the situational context and capable of sharing the context with other services. The result of this web service is based on the needs like who, what, when, where it was called.

The customer’s identity, role of a customer, security policies, physical location of a customer, type of client device are some of the number of the situational circumstances of that a smart web service is aware of.

SOAP is an XML-based protocol that enables 2 components to communicate each other. It has the rules to translate platform specific data into the XML format. Web services are based on SOAP protocol in order to expose their functionality to disparate application and platform.

Web Service Definition Language is used to describe a web service based on XML. WSDL is used for describing Web Services and to locate the services. WSDL consists of the information on what the service is all about, its residing location and the way of invocation the service.

To publish and discover the information about web services, UDDI is a specification. It is an XML based standard. This standard is used for describing, publishing, and finding services. These services are found in a distributed environment through the use of a server called registry server.

EBXML is one from XML family that is based on the standards of OASIS and UN/CEFACT. The mission of this standard is to provide an open xml-based infrastructure which could enable the global use of e-business in an interoperable, secure and consistent manner by all of the partners of trading. This is a unique architecture with unique concepts that are part theory and part implemented within the existing EBXML standards.

A java API for xml pack that integrates all of the programming interfaces by SUN for different web services development. All these interfaces are made as a single download. JAX PACK is a bundle of JAXB,JAXM,JAX-RPC,and JAXR. Jax pack includes the documentations for support for the SAX,DOM.SOAP,WSDL,XSLT,EBXML,UDDI standards.

A Simple Object Access Protocol (SOAP) enables the heterogeneous operating system to communicate with one another by using Hypertext Transfer Protocol (HTTP) and its Extensible Markup Language (XML) as the mechanisms for information exchange.

Web Services Description Language (WSDL) is an XML-based language used to describe the services business offers, which can be accessed electronically.

Universal Description Discovery and Integration (UDDI) is a specification for maintaining standardized directories of information about Web services in a universally recognized format. It records their capabilities, location and requirements.

The ebXML Messaging Service specification (ebMS) extends the SOAP specification. It provides the security and reliability features.
It is supported by a variety of commercial and open source software implementations.
Due to the interoperability of its implementations, ebMS is a strong complement or even alternative to other web service specifications.

The Java APIs for XML (JAX) Pack integrates all of Sun's programming interfaces for web services development and makes them available as a single download.

JARX is a standard API that are used to access XML registries (list of services available on the web) from the JAVA platform. Client application can use JARX API to query the registries. It acts as a pluggable layer that allows access to registries implemented on different standards such as UDDI.

UDDI, Universal description, discovery and integration
It is the directory that is used to publish and discover public web services.

DISCO, Discovery
Commonly known as Discovery. Discovery clubs together common services and exposes schema document of the web services.

WSDL, Web Service description language.
This is used to describe web services. The description includes
URL of web services
Method and properties supported by web services
Data type it supports.
Protocol detail it supports.

JAXM messaging models has two types of messaging model, synchronous and asynchronous.

Synchronous messaging model
In this type of model, client directly interacts with the source. The client sends a request and waits for the response.

Asynchronous messaging model
In this model, client sends message to the messaging provider and returns back. Messaging provider then performs the routing of message to the end source.