In this Java and XML tutorial, you will learn how to compare two XML documents in Java by following a simple example using XMLUnit.Overall it's a nice, handy utility library for testing and comparing XML files in Java applications. It at least needs JAXP 1.2 which is included in Java 1.5 but if you want to use a more advanced XPath engine based upon JAXP 1.3 then you need to include Java 1.5 or higher version in the classpath.

It internally uses JAXP for XSLT transformation and XPath evaluation. Java program to compare two XML documents in Java. The default validation is using DTD but if you want to confirm against XSD schema, you can do that by using option eXMLSChema flag. So, if you want to check if an XML file confirms to DTD or not, you can do that using XMLUnit's Validator class. The XMLUnit library can also provide validation support. It can even check if XPath contains the expected value or not. it can check if an XPATH exists or not exists. The XMLUnit library not only compares complete XML documents but also can perform a lot of useful activities related to XPath e.g. They provide a comparison engine for comparing XML.

Instead, you will use Diff and DetailedDiff the two important classes for XML comparison. The heart and soul of XMLUnit are the DifferenceEngine class but we won't use it directly. Also while comparing XML files, it's very important to know exactly which content or part is different and XMLUnit not only shows the content which is different but also the XPath of elements which is getting compared.

Btw, comparing XML is completely different than comparing String in Java or comparing objects using equals(), as two XML which contains different comments and whitespace can be equals, which is not true for String or character comparison. It is a rich library and provides a detailed comparison of XML files. Similar to JUnit, XMLUnit can also be used to test XML files for comparison by extending the XMLTestcase class. The XMLUnit library can be used to compare two XML files in Java.

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