Converting Legacy Data to XML using a Lexer and Parser Generator

10/6/2002

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Table of Contents

Converting Legacy Data to XML using a Lexer and Parser Generator

The Lexer and Parser Generator we will use: JFlex and CUP

Regular Expressions

Regular Expression Syntax*

Regular Expression Syntax

Building a JFlex Lexical Analyzer

3 Parts of a JFlex Specification

Running the examples

Inserting our own code into the lexer

line count and column count

Distinguishing the Title token

Total number of chars

Using a Macro Definition within another Macro

Start to generate XML

Add a root element

Add xml declaration

Customizing the tags

Legend for Showing State Transitions

States and the transitions

yypushback(int)

Outputting the xml declaration and <BookCatalogue> in YYINITIAL

Declaring states, transitioning states

How much knowledge of the semantics of the data do we put in the scanner?

Handling Errors

Golden Rule of Regex Matching

Golden Rule of Regex Matching

Common Tactic - a catch-all regex

Syntax of Regex with Lookahead

Distinguish these two

Cannot use lookahead in a macro

Convert Books and Magazines

How will we recognize a Title as a Book Title or a Magazine Title?

Adding a Parser on top of the lexer

First parser example

Parser defines a "grammar"

Steps to Build a Parser

Debugging a Parser

Debugging Example15

Add xml declaration and root element

More descriptive tokens

Parser uses descriptive tokens

More semantics in lexer enabled more descriptive parser

Allow for empty elements

Adding Methods that may be Invoked

Validate Input as the XML is Generated

Author: Roger L. Costello