xml-parser

Simple XML parser written in Java

Requirements

• Java 11 or higher

Build

# unix
./mvn clean package

# windows
./mvnw clean package

Usage

java -jar .\target\xml-parser-1.0-SNAPSHOT-jar-with-dependencies.jar <xml string>

Assumptions

Since the XML parser is a simple one, these are not supported:

• XML attributes
• XML comments
• XML CDATA
• XML entity references (<, & etc. are treated as normal text)
• XML namespaces

This also means that angle brackets (<, >) are not allowed as text, as they are treated as special characters in our syntax.

Implementation

I perform a basic lexical analysis on a string and breaks them down into meaningful tokens. With the tokens, I feed it through a syntax analyser to check if the tokens are in the correct order. If the syntax is correct, I will then build a tree structure to represent the XML document.

Tokens

The tokens are defined as follows:

• L_START_TAG: <
• R_TAG: >
• L_END_TAG: </
• TAG_NAME: anything between < and > or </ and >
• CONTENT: anything between > and </

Syntax

The syntax is defined as follows:

• A single root tag
• Start with start tag, end with end tag
• TAG_NAME is case and whitespace sensitive
• TAG_NAME must be the same for both start and end tags
• CONTENT can be empty
• A valid start tag is defined as [L_START_TAG] [TAG_NAME] [R_TAG]
• A valid end tag is defined as [L_END_TAG] [TAG_NAME] [R_TAG]
• A valid tag is defined as [START_TAG] [CONTENT] [END_TAG] and [L_END_TAG] [TAG_NAME] [R_TAG] where [TAG_NAME] is the same for both
• A valid content is defined as [CONTENT] between a valid start tag and valid end tag