XML and Java Technologies

XML and Java Technologies

* Extensible Markup Language(XML)

XML stands for EXtensible Markup Language. Its a markup language much like HTML. XML was designed to carry data, not to display data. XML tags are not predefined. You must define your own tags. XML is designed to be self-descriptive. XML is a W3C Recommendation

* Java API for XML Processing (JAXP), v 1.3

The Java API for XML Processing, or JAXP for short, enables applications to parse and transform XML documents using an API that is independent of a particular XML processor implementation. JAXP also provides a pluggability feature which enables applications to easily switch between particular XML processor implementations.
To achieve the goal of XML processor independence, an application should limit itself to the JAXP API and avoid implementation-dependent APIs and behavior. This may or may not be easy depending on the application. See this question for more information. JAXP includes industry standard APIs such as DOM and SAX. See these slides (PDF) for more information.
The reason for the existance of JAXP is to facilitate the use of XML on the Java platform. For example, current APIs such as DOM Level 2 do not provide a method to bootstrap a DOM Document object from an XML input document, JAXP does. (When DOM Level 3 provides this functionality, a new version of the JAXP specification will probably support the new Level 3 scheme also.) Other parts of JAXP such as the javax.xml.transform portion do not have any other equivalent XSLT processor-independent APIs.

* Java Architecture for XML Binding (JAXB), v 1.0 and 2.0

Java Architecture for XML Binding (JAXB) provides an API and tool that allow automatic two-way mapping between XML documents and Java objects. With a given Document Type Definition (DTD) and a schema definition, the JAXB compiler can generate a set of Java classes that allow developers to build applications that can read, manipulate and recreate XML documents without writing any logic to process XML elements. The generated codes provide an abstraction layer by exposing a public interface that allows access to the XML data without any specific knowledge about the underlying data structure. In addition to DTD support, future versions of JAXB will add support for other schema languages, such as the W3C XML Schema. These features enable the JAXB to provide many benefits for the developers, which are further explained in the next section.

* JAX-RPC v 1.1

To aid developers in building XML-based requests such as SOAP requests, The JCP is developing the Java APIs for XML based RPC (JAX/RPC). JAX/RPC is used for sending and receiving (including marshalling and unmarshalling) method calls using XML-based protocols such as SOAP, or others such as XMLP (XML Protocol. For more information, see http://www.w3.org/2000/xp/). JAX/RPC isolates you from the specifics of these protocols, enabling rapid application development. There is no longer any need for developers to interact directly with the XML representation of the call.

* JAX-WS v 2.0

JAX-WS (Java API for XML Web Services) is a technology designed to simplify the construction of web services and web service clients in Java. The latest version, JAX-WS 2.0, which is part of the new Java EE 5 platform, provides powerful new tools and techniques to facilitate web service development.

* SAAJ (SOAP with Attachments API for Java)

SOAP with Attachments API for Java (SAAJ) is used mainly for the SOAP messaging that goes on behind the scenes in JAX-RPC and JAXR implementations. Secondarily, it is an API that developers can use when they choose to write SOAP messaging applications directly rather than use JAX-RPC. The SAAJ API allows you to do XML messaging from the Java platform: By simply making method calls using the SAAJ API, you can read and write SOAP-based XML messages, and you can optionally send and receive such messages over the Internet (some implementations may not support sending and receiving). This chapter will help you learn how to use the SAAJ API.
The SAAJ API conforms to the Simple Object Access Protocol (SOAP) 1.1 specification and the SOAP with Attachments specification. The SAAJ 1.2 specification defines the javax.xml.soap package, which contains the API for creating and populating a SOAP message.

* Java API for XML Registries (JAXR)

The Java API for XML Registries (JAXR) API provides a uniform and standard Java API for accessing different kinds of XML Registries. XML registries are an enabling infrastructure for building, deployment, and discovery of Web services.
An abstraction-based JAXR API gives developers the ability to write registry client programs that are portable across different target registries. This is consistent with the Java philosophy of Write Once, Run Anywhere. It also enables value-added capabilities beyond what the underlying registries are capable of. For example, a non-JAXR UDDI client does not have the ability to do taxonomy browsing and taxonomy-aware smart queries, which are available to a JAXR client for UDDI.

* Java API for XML Messaging (JAXM) - Optional

When receiving a web service request from say a business partner, we need a Java API to process XML messages, in a similar way to how we processed SOAP requests using JAX/RPC. The Java API for XML Messaging (JAXM) is a forthcoming specification for interacting with XML messaging standards such as ebXML messaging and SOAP messaging. This API is designed to facilitate the processing of XML message protocols, particularly those where a predetermined “contract” exists (ebXML in particular) to determine the format and constraints of the message. This API will handle all the “envelope” information, such as routing information and the “cargo” manifest, in an intuitive way separate from the actual payload of the message. This allows developers to focus on interacting with the payload and not worry about the other message administrivia.