Introduction to Open Source Java Libraries

Why Open Source Libraries?

Open source libraries save thousands of hours. Instead of reinventing the wheel, you add a JAR (or a Maven/Gradle dependency) and get production-tested functionality. Almost every Java project today starts from Maven Central, the largest repository of Java artefacts.

Adding a Library with Maven

<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>itext7-core</artifactId>
    <version>7.2.5</version>
    <type>pom</type>
</dependency>

Adding the Same Library with Gradle

implementation group: 'com.itextpdf', name: 'itext7-core', version: '7.2.5', ext: 'pom'

What This Tutorial Covers

• iText - create PDF documents programmatically.
• Apache POI - read and write Microsoft Excel (and Word).
• Log4j, SLF4J, Logback - structured logging you can control.
• Quartz - run jobs on a schedule.
• JavaMail - send and receive email.
• JMF - capture and play media in desktop apps.
• AspectJ - aspect oriented programming.
• JFreeChart - draw charts from data.

Key Points

• Prefer a library over hand-written code whenever it is stable and well maintained.
• Always depend on a real version; never on the range or SNAPSHOT builds in production.
• Check the license of a library before shipping it in a commercial product.