Download JD-GUI to open JAR file and explore Java source code file (.class .java)
Click menu "File → Open File..." or just drag-and-drop the JAR file in the JD-GUI window scalavro_2.10-0.6.3-c3b519ae67902e6e94aab5b6635744250534e0d0.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.