XML Application Architecture

Every program starts with a set of specifications a customer or user declares that he or she wants a piece of software that does something in particular. In the event that a user wants to see some sort of results that are based upon information extracted from an XML file that's accessed across a network, we can divide the functionality of your application into the following steps:

1 . Retrieving the data.
2. Parsing the data.
3. Processing the data.
4. Presenting the data.

To retrieve the data users request the XML files must be accessed and read wherever they are located on the network.

After the data is drawn from the XML file it must be examined and then assigned relevant variables for next step. This is called parsing.

The parsed data must then be processed to supply the user with the information he or she needs. To do this the data is run through appropriate computational processes. The result of computation process extracts the numerical values and gives the required answers to the user.

After the data has been retrieved, parsed and processed the result must be formatted attractively and presented to the user in such a way that she or he can manipulate them as needed. This format will vary from Concern to concern.

Role of Java in XML Application Architecture

With the assumption that we all know the java features, it is the competent tool for all the tasks you need to perform in building an XML application. That is, it is good at parsing, processing and displaying data and also is simply excellent at accessing files across a network.

Java Parsers

Java, as a full fledged programming language, has considerable capacity to muck around with strings of text. You can use methods of the string objects to do dozens of things with strings, including:
Extracting a substring from a larger string.
Converting a string to a series of pieces and dividing the string at a particular delimiter.
Chopping the end off a string.
Attaching two or more strings together.
Replacing substrings with other strings.

After the raw XML data is parsed, additional formatting may be needed in order to bring the data into suitable format as required by the program being used.

Java being a full fledged programming language, it has the power to do any calculation or processing operation. If particular situation is not possible by Java then a reference from a Java program to a non Java resource can handle this work.

Java also has the capacity to create full featured user interfaces far more elaborate than one can create using HTML. In addition, Java supports a complete suite of textformatting and graphics tools. If one wants the extracted data from an XMI fileto be attractive, then we can use Java. Likewise, if we want to insert data to be displayed into some other documents then Java makes it easy to do well.

Examining XML Parsers for Java

In this section we examine some of the XML parsers written in Java and consider its features.

XJParser

XJParsers from DataChannel Inc. is designed with server side processing in mind, the XJParser provides a complete suite of XML validation and parsing utilities. It is a reliable, high speed tool kit for handling many complex XML transactions. XJParser includes capacity to handle XSL documents, making it possible for one to take XML text, get the information bit needed, apply the required formatting information to the resulting text and put out something which is ready for rendering in a web browser.

P3P parser is a P3P protocol parser and constructor written in 100% pure Java. The package contains classes and methods for parsing, generating, manipulating and evaluating P3P proposals and responses. It also contains a parser and evaluator for "A P3P Preference Exchange Language" (APPEL).

Platform for Privacy Preferences TV) is a protocol that enables the private exchange of personal information on the web. "The goal of P3P is to enable Web sites to express their privacy practices and enable users to exercise preferences over those practices. P3P products will allow users to be informed of site practices (in both machine and human readable formats), to delegate decisions to their computer when appropriate, and allow users to tailor their relationship to specific sites" (W3C).

AElfred (Microstar)

AElf red from Microstar Software Ltd. is a complete package of Java Classes that provides some excellent tools for parsing and processing XML data.

According to Microstar, AElfred is "a small, fast, DTD aware Java based XML parser, especially suitable for use in Java applets. It is designed for Java programmers who want to add XML support to their applets and applications without doubling their size: AElfred consists of only two core class files, with a total size of about 26K, and requires very little memory to run. There is also a complete SAX driver available in this distribution for interoperability. "

IBM's XML Parser for Java

IBM's XML Parser for Java runs on any platform for, which there is a JVM that complies with the Java 1. 1 //Java1.2 standard.

XML Parser for Java also called as XML4J has an interface that follows you to take a string of XML formatted text, pick the tags out of it and use those tags as your keys for extracting the tagged information.

XML Parser for Java supports the XML Namespaces standard.

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