[cfaussie] Re: Call Java Class (Java Code Attached)

Mon, 20 Mar 2006 20:04:30 -0800

In Java it is possible to create custom constructors for a class. Often these constructors don't take any arguments, but occassionally you come up against a class that needs parameters to initialize properly. In those cases the class's constructors will require arguments: ie using init() will be invalid.

In your case this code is valid:
<cfscript>
myObj = createObject("java", "IceKey").init(3 );
</cfscript>

but this isn't:
<cfscript>
myObj = createObject("java", "IceKey").init();
</cfscript>

For future reference, a Java class's constructor method has the same name as the class. If you think the constructor (init) might require arguments, you can look through the source code for that method.

BTW I have no idea what the argument is for, or whether "3" is a good value.

Cheers
Blair

On 3/21/06, Dale Fraser < [EMAIL PROTECTED]> wrote:

What does that mean in english.

Regards
Dale Fraser


> -----Original Message-----
> From: [email protected] [mailto:[email protected] ] On
> Behalf Of Shib71
> Sent: Tuesday, 21 March 2006 14:07 PM
> To: [email protected]
> Subject: [cfaussie] Re: Call Java Class (Java Code Attached)
>
> That's because the class doesn't have a no-arguments constructor. You need
> to provide an int argument "level".
>
> Blair
>
>
> On 3/21/06, Dale Fraser < [EMAIL PROTECTED]> wrote:
>
>
>       This
>
>       <cfobject action="" type="java" class="IceKey" name="myObj" />
>       <cfset ret= myObj.init() />
>       <cfdump var="#myObj#" />
>
>       Gives this
>
>       Error Occurred While Processing Request
>       Unable to find a constructor for class IceKey that accepts
> parameters of
>       type ( ).
>
>
>       The error occurred in D:\Tools\Web\test.cfm: line 2
>
>       1 : <cfobject action="" type="java" class="IceKey"
> name="myObj" />
>       2 : <cfset ret=myObj.init() />
>       3 : <cfdump var="#me#" />
>
>
>
>
>       Regards
>       Dale Fraser
>
>
>       > -----Original Message-----
>       > From: [email protected] <mailto:[email protected] >
> [mailto:[email protected]] On
>       > Behalf Of Mark Mandel
>       > Sent: Tuesday, 21 March 2006 13:42 PM
>       > To: [email protected] <mailto:[email protected]>
>       > Subject: [cfaussie] Re: Call Java Class (Java Code Attached)
>       >
>       > To copy paste out of the coldfusion documentation:
>       >
>       >
> http://livedocs.macromedia.com/coldfusion/7/htmldocs/wwhelp/wwhimpl/common
> <http://livedocs.macromedia.com/coldfusion/7/htmldocs/wwhelp/wwhimpl/commo
> n>
>       >
> /html/wwhelp.htm?context=ColdFusion_Documentation&file=part_dev.htm
>       >
>       >
>       >
>       >       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
>       >
> <http://livedocs.macromedia.com/coldfusion/7/htmldocs/00000302.htm#2820239
>       > >  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.
>       >
>       >
>       > Btw - you may want to brush up on your OO vocabulary.  I think you
> meant
>       > to say you could 'not find a init method in this class' or
> something to
>       > that effect.
>       >
>       > Mark
>       >
>       >
>       >
>       > On 3/21/06, Dale Fraser <[EMAIL PROTECTED]> wrote:
>       >
>       >
>       >       Hey,
>       >
>       >       I'm no Java guru, but I don't see a constructor class or
> init method
>       > in this
>       >       function.
>       >
>       >       Regards
>       >       Dale Fraser
>       >
>       >
>       >       > -----Original Message-----
>       >       > From: [email protected]
> <mailto: [email protected]>  <mailto:[email protected]>
>       > [mailto: [email protected]] On
>       >       > Behalf Of Mark Mandel
>       >       > Sent: Tuesday, 21 March 2006 13:02 PM
>       >       > To: [email protected]
> <mailto:[email protected] >
>       >       > Subject: [cfaussie] Re: Call Java Class (Java Code
> Attached)
>       >       >
>       >       > Actually - what just popped into my head -
>       >       >
>       >       > Try this -
>       >       >
>       >       > <cfscript>
>       >       >   myObj = createObject("java", "IceKey").init();
>       >       > </cfscript>
>       >       >
>       >       > I have found on occasion you actually need to explicitly
> call the
>       > default
>       >       > constructor on the Java object, otherwise you get
> weirdness.
>       >       >
>       >       > I'm not really sure why it is, I have a feeling it may
> have
>       > something to
>       >       > do with static attributes - therefore I tend to call
> init() on all
>       >       > constructors by default.
>       >       >
>       >       > Try that, and see if that works.
>       >       >
>       >       > Mark
>       >       >
>       >       >
>       >
>       >
>       >
>       >
>       >
>       > --
>       > E: [EMAIL PROTECTED]
>       > W:

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