How do I generate Javadocs from Java in a cross-platform way?

Question

I'm working on improving the lein-javadoc plugin to the Leiningen build tool. It runs in a JVM process and has the project's classpath at its disposal. What is the most cross-platform way of generating javadocs?

1. Find $JAVA_HOME/../lib/tools.jar and include it on the plugin's classpath, then call com.sun.tools.javadoc.Main. (Old approach.)
2. Find $JAVA_HOME/../lib/tools.jar and construct a call to java -cp path/to/tools.jar:rest:of:project:classpath com.sun.tools.javadoc.Main -javadoc -options -here. (New approach.)
3. Call javadoc and pass it the options.

Choice 3 sounds right in retrospect and I only discovered it after realizing that OpenJDK doesn't have tools.jar. [Actually, it does! I only had the JRE packages installed for that version -- the JDK package does have tools.jar.]

However, before I rework the code to use that, are there any tradeoffs I should know about? Examples:

• Does calling javadoc make things harder on Windows? (Do I have to sniff out that it's Windows and call javadoc.exe instead?)
• Am I likely to encounter problems shelling out to one version of java (whatever's on the shell PATH) and using a different version's tools.jar (the version of the current JVM)?