Validating java xml parser
building the full AST of an XML document for convenience of the user, SAX parsers operate on each piece of the XML document sequentially, issuing parsing events while making single pass A SAX parser only needs to report each parsing event as it happens, and normally discards almost all of that information once reported (it does, however, keep some things, for example a list of all elements that have not been closed yet, in order to catch later errors such as end-tags in the wrong order).Thus, the minimum memory required for a SAX parser is proportional to the maximum depth of the XML file (i.e., of the XML tree) and the maximum data involved in a single XML event (such as the name and attributes of a single start-tag, or the content of a processing instruction, etc.). A DOM parser, in contrast, has to build a tree representation of the entire document in memory to begin with, thus using memory that increases with the entire document length.Processing XML documents larger than main memory is sometimes thought impossible because some DOM parsers do not allow it.
These examples simply print a message to standard output, but your application can contain any arbitrary code in these handlers: most commonly, the code will build some kind of an in-memory tree, produce output, populate a database, or extract information from the XML stream. If the input document did not include the Start document Start element: poem Characters: "\n" Start element: title Characters: "Roses are Red" End element: title Characters: "\n" Start element: l Characters: "Roses are red," End element: l Characters: "\n" Start element: l Characters: "Violets are blue;" End element: l Characters: "\n" Start element: l Characters: "Sugar is sweet," End element: l Characters: "\n" Start element: l Characters: "And I love you." End element: l Characters: "\n" End element: poem End document You will most likely work with both types of documents: ones using XML namespaces, and ones not using them.
This takes considerable time and space for large documents (memory allocation and data-structure construction take time).
The compensating advantage, of course, is that once loaded any part of the document can be accessed in any order.
In particular, environments with JAXP 1.1 support include SAX2.
Start by creating a class that extends Default Handler: method that uses the the create XMLReader method from the XMLReader Factory class to choose a SAX driver dynamically. Default Handler; public class My SAXApp extends Default Handler You can compile this code and run it (make sure you specify the SAX driver class in the sax.driver property), but nothing much will happen unless the document contains malformed XML, because you have not yet set up your application to handle SAX events.