How to open Javadoc JAR file in web browser
- Rename the file poi-spring-boot-start-2.2.7-RELEASE-javadoc.jar to poi-spring-boot-start-2.2.7-RELEASE-javadoc.zip
- Use your favourite unzip tool (WinRAR / WinZIP) to extract it, now you have a folder poi-spring-boot-start-2.2.7-RELEASE-javadoc
- Double click index.html will open the index page on your default web browser.
How to generate Javadoc from a source JAR?
Running the command javadoc:
javadoc --ignore-source-errors -encoding UTF-8 -sourcepath "poi-spring-boot-start-2.2.7-RELEASE-sources.jar" -d "poi-spring-boot-start-2.2.7-RELEASE-javadoc" -subpackages 
