Monday, October 22, 2018

Difference between DOM and SAX parsers in Java

A difference between the SAX and the DOM Parser is a very popular Java interview and frequently asked when interviewing with Java and XML. The DOM and SAX analyzers are used extensively to read and analyze the XML file in java and have their own set of advantages and disadvantages that we will address in this article. Although there is another way to read the XML file using XPath in Java, which is the more selective approach, such as SQL statements, people tend to stick with XML parsers. The Parser vs SAX analyzers are also often seen in terms of speed, memory consumption and their ability to process large XML files.

Difference between the DOM XML parser and SAX in Java

DOM XML parser in Java

DOM Stands for Document Object Model and represents an XML document in tree format, each element representing tree branches. The DOM parser creates an in-memory tree representation of the XML file and then parses it, so it requires more memory and it is advisable to increase the heap size for the DOM parser to avoid Java.lang.OutOfMemoryError: java heap space.

Analyzing the XML file using the DOM parser is quite fast if the XML file is small, but if you try to read a large XML file using the DOM parser, there is a greater chance that it will be delayed a lot or until you cannot fully load it because it requires a lot of memory to create XML Dom Tree. Java provides support for DOM analysis and can analyze XML files in Java using the DOM analyzer. The DOM classes are in the w3c.dom package, while the DOM Parser for Java is in the JAXP package (Java API for XML Parsing).



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SAX XML parser in Java

SAX Stands for simple API for XML analysis. It is an XML analysis based on events and analyzes the XML file step by step, very suitable for large XML files. The SAX XML Parser triggers an event when the tag, element or opening attribute was found and the analysis works accordingly. It is recommended to use the SAX XML parser to analyze large XML files in Java, since it is not necessary to load the entire XML file into Java and can read a large XML file in small parts. Java provides support for SAX Parser and you can analyze any XML file in Java using SAX Parser, I have covered an example of reading XML file using SAX Parser here. One disadvantage of using the SAX Parser in java is that reading the XML file in Java using the SAX Parser requires more code in the comparison of the DOM analyzer.

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Difference between the XML DOM and SAX parser

Here are some high-level differences between the DOM analyzer and the SAX Parser in Java:

1) The DOM analyzer loads the entire XML document into memory while the SAX only loads a small part of the XML file into memory.

2) The DOM analyzer is faster than the SAX because it accesses the entire XML document in memory.

3) The SAX analyzer in Java is more suitable for a large XML file than the DOM analyzer because it does not require much memory.

4) The DOM analyzer works in Document Object Model, while the SAX is an XML analyzer based on events.


This is all about the difference between SAX and DOM analyzers in Java, now it's up to you to choose in which XML analyzer you will choose. I recommend using the DOM parser on the SAX parser if the XML file is small enough and using the SAX parser if you do not know the size of the XML files that are processed or if they are large.




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