jsoup extract CSS class name of HTML element in Java

Introduction

In this post, we are going to explore how to use jsoup library in a Java application to extract css class names of an element in the HTML document.

Add jsoup library to your Java project

To use jsoup Java library in the Gradle build project, add the following dependency into the build.gradle file.

compile 'org.jsoup:jsoup:1.13.1'

To use jsoup Java library in the Maven build project, add the following dependency into the pom.xml file.

<dependency>
    <groupId>org.jsoup</groupId>
    <artifactId>jsoup</artifactId>
    <version>1.13.1</version>
</dependency>

To download the jsoup-1.13.1.jar file you can visit jsoup download page at jsoup.org/download

Sample HTML File

For example, we have a sample.html file as below.

<!DOCTYPE html>
<html>
<body>
    <div id="container" class="class1 class2 class3">
        <p>Simple Solution</p>
    </div>
</body>
</html>

Extract CSS class names as a String

Following Java code example using Element.className() method to get CSS all class names from class attribute as a Java String.

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;

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

public class ExtractCssClassExample1 {
    public static void main(String... args) {
        try {
            String fileName = "sample.html";
            File file = new File(fileName);
            Document document = Jsoup.parse(file, "UTF-8");
            Element element = document.getElementById("container");

            String cssClassName = element.className();

            System.out.println(cssClassName);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Output:

class1 class2 class3

We also can use the Element.attr() method to get the class attribute which returns the same result as Element.className() method.

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;

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

public class ExtractCssClassExample2 {
    public static void main(String... args) {
        try {
            String fileName = "sample.html";
            File file = new File(fileName);
            Document document = Jsoup.parse(file, "UTF-8");
            Element element = document.getElementById("container");

            String cssClass = element.attr("class");

            System.out.println(cssClass);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Output:

class1 class2 class3

Extract CSS class names as a Set of String

The jsoup library also provides Element.classNames() method to return all of element’s class names as a Java Set of String.

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;

import java.io.File;
import java.io.IOException;
import java.util.Set;

public class ExtractCssClassExample3 {
    public static void main(String... args) {
        try {
            String fileName = "sample.html";
            File file = new File(fileName);
            Document document = Jsoup.parse(file, "UTF-8");
            Element element = document.getElementById("container");

            Set<String> cssClassNames = element.classNames();

            for(String name : cssClassNames) {
                System.out.println(name);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}