GroupDocs.Viewer for Java API depends on Bouncy Castle for encryption and decryption features, that is; if the program is required to load or save encrypted spreadsheets, it is required to add reference of bcprov-jdk16-1.46.jar in the project’s class path.
Symptoms
You may get exception like java.lang.ClassNotFoundException: org.bouncycastle.jce.provider.BouncyCastleProvider.
Solution
The solution is actually very simple as detailed below.
Download bcprov-jdk16-1.46.jar library as JAR file from Maven repository.
Put the file into your project directory.
Reference the bcprov-jdk16-1.46.jar in the class path of the project.
Alternatively, you can add the dependency in the pom.xml and let the project resolve the dependency via maven.