I would like to override the Implementation of FXMLLoader and recompile the JDK 8.
Where can I find the source code of the JDK8 / JavaFX 8 ?
The source for JavaFX 8 is available at:
http://hg.openjdk.java.net/openjfx/8/master/rt
JavaFX 8 is almost completely open source today.
Instructions for building JavaFX 8 with OpenJDK 8
Quoting from this answer: For Java 8, the source of the public parts of JavaFX are actually laying right along in the JDK installation as a sibling of src.zip: javafx-src.zip - on the root of your normal JDK Java 8 installation.
Eclipse doesn't by default link them up when you add the JRE (or it finds it itself) - obviously a bug - so you'll have to do that yourself, by hitting Preferences -> Installed JREs. Find your JDK 8, hit Edit button. On the list JRE system libraries, expand the jfxrt.jar node, and link in the javafx-src.zip file.
The OpenJFX wiki has a page on how to build JavaFX 8 from the source.
These answers may also be useful if you're trying to get the JavaFX source code to appear in your IDE:
来源：https://stackoverflow.com/questions/19045831/where-can-i-find-the-jdk-8-javafx-8-source-code