How to compare two XML files in Java - XMLUnit Example

To compare two XML files in Java using XMLUnit, you can follow these steps:

Step 1: Set up your project

Ensure that you have XMLUnit added as a dependency in your project. You can download the XMLUnit JAR file from the XMLUnit website (https://www.xmlunit.org/) or include it as a Maven or Gradle dependency.

Step 2: Import the required classes

Import the necessary classes from XMLUnit and other Java libraries:

import org.custommonkey.xmlunit.Diff;
import org.custommonkey.xmlunit.XMLUnit;
import org.xml.sax.SAXException;

import java.io.File;
import java.io.IOException;

Step 3: Load the XML files Load the XML files that you want to compare. You can use the File class to represent the XML files:

File file1 = new File("path/to/file1.xml");
File file2 = new File("path/to/file2.xml");

Make sure to provide the correct paths to the XML files you want to compare. Step 4: Configure XMLUnit Configure XMLUnit to ignore whitespace differences, which are often irrelevant for XML comparison:

XMLUnit.setIgnoreWhitespace(true);

This step is optional, but it can make the comparison more flexible by ignoring differences in whitespace. Step 5: Compare the XML files Create a Diff object by comparing the XML files using the DiffBuilder class:

Diff xmlDiff;
try {
    xmlDiff = XMLUnit.compareXML(FileUtils.readFileToString(file1), FileUtils.readFileToString(file2));
} catch (IOException | SAXException e) {
    e.printStackTrace();
    return;
}

In this example, the FileUtils.readFileToString() method is used from the Apache Commons IO library to read the contents of the XML files as strings. 

You can use other methods to read the files as per your preference. Step 6: Check the comparison result Check the result of the comparison by calling the similar() method on the Diff object:

if (xmlDiff.similar()) {
    System.out.println("The XML files are similar.");
} else {
    System.out.println("The XML files are different.");
    System.out.println("Differences found: " + xmlDiff.toString());
}

If the XML files are similar, the similar() method will return true. Otherwise, it will return false, indicating differences between the files. 

That's it! You have successfully compared two XML files using XMLUnit in Java.