TL:DR; Java Mail library.
Java Mail library. This is a small java package that can send and receive emails. Including MIME and attachements.
Aspose.Pdf for JasperReports is a Java component to export reports from JasperReports and JasperServer to PDF format. It allows you to convert .jrxml reports to PDF; supports all reporting features and many chart layouts as well.
The Java Excel Connector (JEC) allows Java developers to access the Excel application, read, create or modify Excel workbooks and charts.
Software development kit for working with native code from any Java application without using Java Native Interface (JNI) technology. You can call functions from any dynamic library or use system API without necessity to waste time on studying JNI.