1. MC365 XML Parsers

2. Today We Will Cover: An overview of the Java API’s used for XML processing Creating an XML document in Java Parsing an XML document with SAX parsers Parsing an XML document with DOM

3. Overview of the Java API’s The main JAXP APIs are defined in the javax.xml.parsers package that comes with the sdk 1.4.1. –This package contains two vendor-neutral factory classes: SAXParserFactory and DocumentBuilderFactory that give you a SAXParser and a DocumentBuilder, respectively.SAXParserFactoryDocumentBuilderFactory The DocumentBuilder, in turn, creates DOM-compliant Document object.DocumentBuilderDocument These factory APIs give you the ability to plug in an XML implementation offered by another vendor without changing your source code.

4. Creating an XML Document As we have seen, XML is a standard way of communicating in the J2EE environment. To communicate a system needs to be able to both create an XML document and process an XML document. There are many ways to create this XML document –Two popular options are: Use a text editor Create it In Java –Here is an example of a Java application creating an XML document: http://www2.bc.edu/~bernier/MC365/Lecture Notes/XMLCreate.java http://www2.bc.edu/~bernier/MC365/Lecture Notes/XMLCreate.java

5. Parsing an XML Document in Java Once you have created an XML document, you need to be able to process/read it. –To do this in Java, you use the Java parsers. –You can use the parsers included in the sdk or you can use a vendor-developed parser. –There are two basic types of XML parser: SAX and DOM

6. Overview of the Parsers SAX stands for The "Simple API" for XML –This is an event-driven, serial-access mechanism that does element-by-element processing. –The API for this level reads and writes XML to a data repository or the Web. –Usually used for server-side and high-performance apps

7. Overview of the Parsers DOM stands for Document Object Model The DOM API is generally an easier API to use. –It provides a relatively familiar tree structure of objects. You can use the DOM API to manipulate the hierarchy of application objects it encapsulates. The DOM API is ideal for interactive applications because the entire object model is present in memory, where it can be accessed and manipulated by the user. –On the other hand, constructing the DOM requires reading the entire XML structure and holding the object tree in memory Makes it much more CPU and memory intensive. For that reason, the SAX API will tend to be preferred for server-side applications and data filters that do not require an in-memory representation of the data. Finally, the XSLT APIs defined in javax.xml.transform let you write XML data to a file or convert it into other forms.

8. Overview of the Parser Packages The SAX and DOM APIs are defined by XML-DEV group and by the W3C, respectively. The libraries that define those APIs are: W3C –javax.xml.parsers The JAXP APIs, which provide a common interface for different vendors' SAX and DOM parsers. –org.w3c.dom Defines the Document class (a DOM), as well as classes for all of the components of a DOM. –org.xml.sax Defines the basic SAX APIs. –javax.xml.transform Defines the XSLT APIs that let you transform XML into other forms.

9. Parsing an XML Document with SAX Parsers Serial Access with the Simple API for XML (SAX) –Use the SAX parser if the data structures have already been determined, and you are writing a server application or an XML filter that needs to do the fastest possible processing. –Here is an example of a Java application using a SAX parser to process an incoming XML document: http://www2.bc.edu/~bernier/MC365/Lecture Notes/SAXexample.java http://www2.bc.edu/~bernier/MC365/Lecture Notes/SAXexample.java

10. Parsing an XML Document with DOM If you need to build an object tree from XML data so you can manipulate it in an application, or convert an in-memory tree of objects to XML. Here is an example Java application using DOM: http://www2.bc.edu/~bernier/MC365/Lecture Notes/DomEcho02.java http://www2.bc.edu/~bernier/MC365/Lecture Notes/DomEcho02.java

11. Where to Get More Information There are many, many sites on XML, XML Parsers, XSLT and other related technology. Some good ones are: http://java.sun.com/xml/tutorial_intro.html http://java.sun.com/webservices/docs/1.1/tutorial/doc/inde x.html http://java.sun.com/xml/tutorial_intro.html http://java.sun.com/webservices/docs/1.1/tutorial/doc/inde x.html