MACROMEDIA COLDFUSION MX 61-DEVELOPING COLDFUSION MX, Develop Manual, Page: 746 / 860

746 Chapter 33: Integrating J2EE and Java Elements in CFML Applications
Using Java objects
You use the
cfobject
tag to create an instance of a Java object. You use other ColdFusion tags,
such as
cfset
and
cfoutput
, or CFScript to invoke properties (attributes), and methods
(operations) on the object.
Method arguments and return values can be any valid Java type; for example, simple arrays and
objects. ColdFusion does the appropriate conversions when strings are passed as arguments, but
not when they are received as return values. For more information on type conversion issues, see
“Java and ColdFusion data type conversions” on page 751 .
The examples in the following sections assume that the
name
attribute in the
cfobject
tag
specified the value obj, and that the object has a property called Property, and methods called
Method1, Method2, and Method3.
Note: The cfdump tag displays an object’s public methods and data.
Using basic object techniques
The following sections describe how to invoke Java objects.
Invoking objects
The
cfobject
tag makes Java objects available in ColdFusion MX. It can access any Java class
that is available on the JVM classpath or in either of the following locations:
•
In a Java archive (.jar) file in web_root /WEB-INF/lib
•
In a class (.class) file in web_root /WEB-INF/classes
For example:
<cfobject type="Java" class="MyClass" name="myObj">
Although the
cfobject
tag loads the class, it does not create an instance object. Only static
methods and fields are accessible immediately after the call to
cfobject
.
If you call a public non-static method on the object without first calling the
init
method, there
ColdFusion makes an implicit call to the default constructor.
To call an object constructor explicitly, use the special ColdFusion
init
method with the
appropriate arguments after you use the
cfobject tag
; for example:
<cfobject type="Java" class="MyClass" name="myObj">
<cfset ret=myObj.init(arg1, arg2)>
Note: The
init
method is not a method of the object, but a ColdFusion identifier that calls the
new
function on the class constructor. So, if a Java object has an init method, a name conflict exists and
you cannot call the object’s init method.
To have persistent access to an object, you must use the
init
function, because it returns a
reference to an instance of the object, and
cfobject
does not.
An object created using
cfobject
or returned by other objects is implicitly released at the end of
the ColdFusion page execution.