An introduction into the use of Java inside ColdFusion. With CF being a J2EE application, we always have the ability to use Java if it's necessary. We look at how to get hold of Java objects, the difference between a class and an instance and how CF differentiates between them. Then we look at some examples...

4. Server compiles them to {_filename_}.class Java Virtual Machine JVM

5. Instance (object) Classes and Instances .class is like a blueprint. It gives the builder the instructions HOW to build something..all the implementation details.. BUT ..you wouldn’t want to live in a blueprint. For a real house, we have to ‘construct’ the house. Class C:ocuments and Settingsick.harveyocal Settingsemporary Internet Filesontent.IE50BPZ5RVPj03995150000[1].jpg

7. Square footage and size information

9. In Java, these are referred to in the docs as 'static'

11. The location of the house

14. <cfset javaMath = createObject(“java”, “java.lang.Math”)>

15. We can now call class methods on this

16. Q. How do you know what are class methods? A. Check out the Java API docs.

17. Example of Java Doc http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Math.html

20. To create an instance from a class we call the constructor method. In CF, we call the constructor by using init()

21. HOWEVER...

22. In CF, if we don’t call it ourselves, CF will do it for us.

23. BEWARE, sometimes, WE must pass data in via the constructor, in which case, WE have to call it ourselves.

25. To create an instance of java.lang.StringBuffer, we don’t pass anything in the constructor, so we can leave it to CF.

26. <cfset javaSB = createObject(“java”, “java.lang.StringBuffer”)>

27. <cfset javaSB.init()>

28. <cfset javaSB.append(“some text for my buffer”)>

29. append() is an instance method, CF automatically calls the constructor. (demo)

31. To create an instance of java.io.File, we need to pass in the path/URI of the file.

32. <cfset javaFile = createObject(“java”, “java.io.File”)>

33. <cfset javaFile.init()>

34. <cfset ok2read = javaFile.exists()>

37. Some objects are immutable, which means their value can't change. Assigning them new values, causes Java to destroy the old one and create a new one.

38. The CF String (==Java String) is a good example

40. The example shows how to use Java's networking API to do (reverse) DNS lookups directly from within CF

43. Compile the .java to a .class and copy to {server_root}/WEB-INF/classes/

44. Restart CF