Exception in thread “main” java.lang.reflect.InvocationTargetException

When you use Maven for your Java project, then all you need to do, is add a dependency to iText. Maven will then take care of all transitive dependencies like BouncyCastle. Maven takes away all the heavy lifting. The same principle applies for other build systems like Gradle etc.

Now, if you want to do it all manually and put the correct jars on your classpath, then you need to do some homework. This means looking at the pom.xml of each and every of your dependencies, see which transitive dependencies they have, which dependencies those dependencies have, and so on ad nauseam.

In case of iText, you take a look at the pom.xml that you can find on Maven Central: https://search.maven.org/#artifactdetails%7Ccom.itextpdf%7Citextpdf%7C5.5.11%7Cjar

In particular this part:

  <dependencies>
    <dependency>
      <groupId>org.bouncycastle</groupId>
      <artifactId>bcprov-jdk15on</artifactId>
      <version>1.49</version>
      <optional>true</optional>
    </dependency>
    <dependency>
      <groupId>org.bouncycastle</groupId>
      <artifactId>bcpkix-jdk15on</artifactId>
      <version>1.49</version>
      <optional>true</optional>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.8.2</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.apache.santuario</groupId>
      <artifactId>xmlsec</artifactId>
      <version>1.5.1</version>
      <optional>true</optional>
    </dependency>
  </dependencies>

This tells you that iText 5.5.11 has an optional dependency on BouncyCastle 1.49.

BouncyCastle has a bad reputation of randomly changing and breaking their API even with minor updates, that is why you need to be very precise with your BouncyCastle version.