What is 'Push Approach' and 'Pull Approach' to parsing?

java xml saxparser stax
An SO User picture An SO User · Apr 9, 2013 · Viewed 12.5k times · Source

Under the push parsing approach, a push parser generates synchronous events as a document is parsed, and these events can be processed by an application using a callback handler model

This is the text given in the book Pro XML Development with Java about SAX 2.0.

As for StAX, the book says:

Under the pull approach, events are pulled from an XML document under the control of the application using the parser.

I want to ask, what is the meaning of the highlighted text ? An answer befitting a beginner is appreciated :)

Answer

yshavit picture yshavit · Apr 9, 2013

Basically, a push is when the parser says to some handler, "I have a foo, do something with it." A pull is when the handler says to the parser, "give me the next foo."

Push:

if (myChar == '(')
    handler.handleOpenParen(); // push the open paren to the handler

Pull:

Token token = parser.next(); // pull the next token from the parser

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