Difference between DOM vs SAX Parser in Java - XML Parsing in Java

DOM vs SAX parser in Java
DOM and SAX parser are the two most popular parsers used in the Java programming language to parse XML documents. DOM and SAX concept is originally XML concept and Java programming language just provide an API to implement these parsers. Despite both DOM and SAX are used in XML parsing, they are completely different from each other. In fact difference between DOM and SAX parser is a popular Java interview question asked during Java and XML interviews. DOM and SAX parser has a different way of working, which makes Java programmer understand the difference between DOM and SAX parser even more important.

Careless use of DOM parser may result in java.lang.OutOfMemoryError if you try to parse a huge XML file and with a small heap size while careless use of SAX parser may result in poor performance while parsing small and medium-sized XML files with good enough heap space in Java. In this Java article, we will compare DOM and SAX parser and learn the difference between them.

8 Difference between SAX vs DOM parser in Java

In this section, we will see some behavioral differences between DOM and SAX parser.  These differences will help you to choose DOM over SAX or vice-versa based upon the size of XML files and the availability of heap memory in JVM.

1. Working
The first and major difference between DOM vs SAX parsers is how they work. DOM parser loads a full XML file in memory and creates a tree representation of XML document, while SAX is an event-based XML parser and doesn't load the whole XML document into memory.

2. XML Size
For small and medium-sized XML documents DOM is much faster than SAX because of in memory operation.

3. Full form
DOM stands for Document Object Model while SAX stands for Simple API for XML parsing.

4. API Type
The DOM parser creates an in-memory tree and allows you to access elements while the API type of SAX is push and streaming-based. 

5. Ease of Use
DOM is relatively easier to use than SAX parser. 

6. XPath Capability
DOM allows you to use Xpath to access elements this is not available with the SAX parser. This is also a powerful feature and most of the time people use DOM to leverage XPath. 

7. Direction
SAX is a forward-only parser which means you cannot go backward but DOM allows you to go on any direction. 

8. When to use DOM and SAX parsers
Another difference between DOM vs SAX is that, learning where to use DOM parser and where to use SAX parser. DOM parser is better suited for small XML files with sufficient memory, while SAX parser is better suited for large XML files. You can also see these free Java courses to learn more about XML  parsing in Java.

Difference between DOM vs SAX Parser in Java

That's all about the difference between DOM vs SAX parser in XML and Java. These are the best option for XML parsing in Java but requires careful decision making while choosing DOM or SAX. The above chart gives you a nice overview of SAX, DOM, and StAX XML parsers in terms of API Type, Ease of Use, XPath Capability, CPU and Memory Efficiency, Parsing Direction, and ability to create, read, update and delete XML. 

Further Learning
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HashMap vs ConcurrentHashMap in Java
Top 10 tough Java Interview questions and answers
Spring MVC FAQ

P. S. - At the bare minimum just remember to use DOM parser for parsing small files and SAX parser for parsing the large XML files. DOM is also faster than SAX. 

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