I am converting the PHP plugin to ColdFusion. In PHP, there are used OO concepts so classes and objects are used.
How I can convert those classes to ColdFusion class and create objects for those classes.
Also I have created Java class and using <cfobject> tag, I have created object, but I need ColdFusion classes and created objects.
Please let me know if you have any ideas.
ColdFusion does have classes and objects and follows limited OOPS principles. You can do inheritance, interfaces. Polymorphic functions is still not allowed.
Classes in ColdFusion are called as Components. CFC -> ColdFusion component. Depending on the ColdFusion version, you can write them in script mode or in tag mode.
You can refer to the documentation for CF8 about creating component and their objects.
The createObject() method you have mentioned is one way of creating different type of objects. The other ways are to use <cfinvoke> or <cfobject>
Hope this helps. Just read the docs in detail and they will help you every time.
Realistically you should be able to solve this by reading the docs a bit more thoroughly than you already have. However this question is fairly easily answered. Firstly let me disabuse you of something though:
there is no option to create classes in coldfusion without using the
java,com and corba
This is just you not reading properly. Even on the page you link to (cfobject, which is pointing to an obsolete version of ColdFusion btw), the third link it provides "component object" discusses instantiating native CFML "classes" ("components" in CFML parlance, for some reason). It's perhaps not clear from top-level browsing that a "component" is a "class", but if you're learning something, you should be doing more than top-level browsing.
You are approaching your learning from a very odd angle: reading up on how to instantiate an object is not the direction you ought to be taking if you want to find out how to define the class the object will be an instance of. It kinda suggests a gap in your knowledge of OO (which could make this work a challenge for you).
Anyway, of course CFML allows for the definition of classes and the usage thereof, natively in the language. And has been able to do so since v6.0 (although this was not really production-ready until 6.1, due to some poor implementation decisions), over a decade ago.
The answer to your broader question, can be found by reading the docs starting with "Building and Using ColdFusion Components". But the basic form is:
// Foo.cfc
component {
public Foo function init(/* args here */){
// code here
}
// etc
}
And that sort of thing.
Related
In my search for this answer I have already read the following StackOverflow post.
Definition of a Java Container
My issue (lack of understanding ) at this point as a beginner is also learning the esoteric vocabulary. Therefore, even excellent examples often make little or no sense.
For this question please create an answer for the very, very, green beginner.
The actual question:
For the "Definition of a Java Container" give a tangible example, preferably using the NetBeans project tree, of what a Java Container is. A screen-shot would be very helpful for us extremely visual learners.
For example, if I were trying to answer the question "what is a container file" to a computer 101 student, I would probably not say something like this:"A container or wrapper format is a metafile format whose specification describes how different elements of data and metadata coexist in a computer file.
Rather, I would answer like this: "A container file is a ZIP file, MP3 or MP4 file. The reason it is called a container is that it actually contains many other files - much like a directory."
UPDATE
I found this Wikipedia article that I believe begins a decent explanation.
https://en.wikipedia.org/wiki/Container_%28abstract_data_type%29
For example, according to the above article, a simple example of a "container" in a programming language is an array. In object oriented programming languages fancier arrays such a Lists and Maps are also containers. However, for any beginning programmer reading this post, containers are also Classes that form a chain of inheritance (experts correct my terminology if I am wrong).
For beginners, if you do not know what inheritance is then go study that. There is another Wikipedia article to read.This whole article is describing "containers" in Java.
https://en.wikipedia.org/wiki/Java_collections_framework
To give the sort of example I was originally asking for, if you have NetBeans then go do this:
Create a new class, then inside of it create a new method, as shown below:
package InformationStorage;
public class MyClass {
public void MyMethod(){
}
}
Now, inside the method type the command "System", and then type a period. Like this:
["Screen shot from NetBeans"][3]
Notice the list of methods and other stuff included within "System". If you choose one (for example "out" as in System.out.), then when you type the period after "out" more sub-options appear, and so on.You will eventually end with something like "System.out.println();"
This is an example of Container Classes.
Frustrated-Me this question is posed just like your name haha. Anyway I will answer. There is allot of programming jargon that will not make sense to a beginner, I wouldn't worry about it at beginner stage. So yes there is a container which is the same as say a Collection (List,Map,Set...Array is maybe one too), which just contains other data members.
But then this term is used in another way in Java and other programming languages and frameworks.
What is a container in this sense? Well I guess I would say it's complicated thing that does allot of stuff for you in layman terms. You see, something like programming a website is very complex, and Java as a programming language can be considered verbose by some, this makes for a very difficult time for a developer. So there are all these fancy frameworks, for instance: Spring which may all share some similar concepts such as dependency injection, aspect orientated programming or whatever ever else. Even if you don't know what those things are they are just ways to help the programmer develop a complicated piece of software.
These concepts are often implemented in something that may be called a container. Basically you put your POJO (instances of a java class) in this container, and the container adds functionality to what you have done, via DI, or aspect orientated programing or something else. Usually these containers are built on design patterns such as the proxy or cake or MVC ect.
One might be able to say that a container in this sense does more than just storing your objects/data, but adds additional functionality to make your life easier.
When I first started using the Java Preferences API, the one glaring omission from the API was a putObject() method. I've always wondered why they did not include it.
So, I did some googling and I found this article from IBM which shows you how to do it: http://www.ibm.com/developerworks/library/j-prefapi/
The method they're using seems a bit hackish to me, because you have to break the Object up into byte matrices, store them, and reassemble them later.
My question is, has anyone tried this approach? Can you testify that it is a good way to store/retrieve objects?.
I'm also curious why the Java devs left putObject() out of the API. Does anyone have valuable insight?
I'm also curious why the Java devs left putObject() out of the API.
Does anyone have valuable insight?
From: http://docs.oracle.com/javase/7/docs/technotes/guides/preferences/designfaq.html
Why doesn't this API contain methods to read and write arbitrary
serializable objects?
Serialized objects are somewhat fragile: if the version of the program
that reads such a property differs from the version that wrote it, the
object may not deserialize properly (or at all). It is not impossible
to store serialized objects using this API, but we do not encourage
it, and have not provided a convenience method.
The article describes a reliable way to do it. I see there are a couple of things I may do differently (like I would store the count of the number of pieces as well as the pieces themselves so that I can figure things out easily when I retrieve them).
Your comment about Serialization is wrong though.... the object you want to store has to be Serializable.... that's how the ObjectOutputStream that the document uses does it's job.
So, Yes, it looks like a reliable mechanism, you need to have Serializable objects, and I imagine that the reason that putObject and getObject are not part of the API for two reasons:
it's not part of the way that is native to Windows registries
It risks people putting huge amounts of data in the registry.
Storing serialized objects in the registry strikes me as being somewhat concerning because they can be so big. I would only use it for occasions when there is no way to reconstruct the Object from constructors, and the serialized version is relatively small.
Is it possible to integrate the two worlds at least on the data transfer level?
Say i have Java objects which are provided through a Spring WebMVC REST endpoint and my Dart client access these resources with AJAX. It would be nice if the transfered type would be known by the Dart client aswell so i don't have to synchronize the Dart and Java version of the same type definition but the IDE could give me suggestion and errors if the data access on the client side is invalid.
EDIT
A little more explanation what i'm trying to do because it seems i was not clear enough:
On the Java side i define a bean which is converted to JSON by Spring WebMVC + Jackson. So the transfer unit IS already JSON. I can easily access data with Dart dynamically but that's not what i want to do.
I want to parse the retreived Data to a Dart class which as it turns out being a replicate of the original Java bean's class definition. Take a look at JsonObject's explanation on Dart's site, especially the Language abstract class. That's exactly what i'm doing right now. I'm defining an abstract class which defines the JSON data i'm retreiving from the server. This way Dart can give syntax errors if i'm accessing non existing fields or doing incompatible casts, etc. Of course this can still yield into a parse error but after that i can work with the data in a typed manner.
My problem is that to achieve this i have to manually synchronize the data bean's class definition on the Java side and the abstract class definition on the Dart side. I'm wondering if there's somebody working on creating something like a code generator which creates a Dart class definition from a Java class definition or so.
You are asking for Editor feature which would quitely lead to performance degradation of the editor. For any such feature the Editor might need to build/maintain Object Graph/Syntax Tree ( would this use AST in java world ) for java objects and then compare it with Dart's Syntax Tree.
Also different languages will put forward the same request example C#, Ruby, etc. There does not seem to be any sane way to validate the objects from different programming world within performance limits.
I can borrow some more points from below stackoverflow q/a on why its simpler to use JSON/XML rather than any other way to exchange data between java/c# world to dart world -\
How does Java's serialization work and when it should be used instead of some other persistence technique?
Read a BigInteger serialized from Java into C#
I'm just starting to learn and the books say that I can use "pre-coded" classes and objects. How do I call these classes/objects in the beginning of my program? I understand basically what they are, and the idea that I can use these classes/objects in place of writing fresh code every time, but I cannot seem to figure out where I find these things and how I implement them.
You certainly talk about the Java classes that come in JRE/JDK.
Those are used by including the jar in your classpath and provides the "default" java classes.
Like String in java.util package.
If you want to look at them, in the JDK you'll find the sources of these class.
"Pre-coded", or pre-written Java classes, are pretty much the same concept as the Java API - someone has written the code for you, was kind enough to document how you can use the code, and you may create instances (as necessary) through the prescribed way.
Say, for instance, I want an ArrayList holding Strings. I would then code ArrayList<String> words = new ArrayList<String>(). You wouldn't have to go through the process of writing a dynamic self-expanding vector.
I very much like the simplicity of calling remote methods via Java's RMI, but the verbosity of its serialization format is a major buzz kill (Yes, I have benchmarked, thanks). It seems that the architects at Sun did the obvious right thing when designing the RPC (speaking loosely) component, but pulled an epic fail when it came to implementing serialization.
Conversely, it seems the architects of Thrift, Avro, Kryo (especially), protocol buffers (not so much), etc. generally did the obvious right thing when designing their serialization formats, but either do not provide a RPC mechanism, provide one that is needlessly convoluted (or immature), or else one that is more geared toward data transfer than invoking remote methods (perfectly fine for many purposes, but not what I'm looking for).
So, the obvious question: How can I use RMI's method-invocation loveliness but employ one of the above libraries for the wire protocol? Is this possible without a lot of work? Am I evaluating one of the aforementioned libraries too harshly (N.B. I very much dislike code generation, in general; I dislike unnecessary annotations somewhat, and XML configuration quite a bit more; any sort of "beans" make me cringe--I don't need the weight; ideally, I'm looking to just implement an interface for my remote objects, as with RMI).
Once upon a time, I did have the same requirement. I had changed rmi methods arguments and return types to byte[].
I had serialized objects with my preferred serializer to byte array, then called my modified rmi methods.
Well, as you mentioned java serialization is too verbose, therefore 5 years ago I did implement a space efficient serialization algorithm. It saves too much space, if you are sending a very complex object graph.. Recently, I have to port this serialization implementation to GWT, because GWT serialization in Dev mode is incredibly slow.
As an example;
rmi method
public void saveEmployee(Employee emp){
//business code
}
you should change it like below ,
public void saveEmployee(byte[] empByte) {
YourPreferredSerializer serialier = YourPreferredSerializerFactory.creteSerializer();
Employee emp = (Employee) serializer.deSerialize(empByte);
//business code
}
EDIT :
You should check MessagePack . it looks promising.
I don't think there is a way to re-wire RMI, but it might be that specific replacement projects -- I am specifically thinking of DiRMI -- might? And/or project owners might be interest in helping with this (Brian, its author, is a very competent s/w engineer from Amazon.com).
Another interesting project is Protostuff -- its author is building a RPC framework too (I think); but even without it supports an impressive range of data formats; and does this very efficiently (as per https://github.com/eishay/jvm-serializers/wiki/).
Btw, I personally think biggest mistake most projects have made (like PB, Avro) is not keeping proper separation between RPC and serialization aspects nicely separate.
So ability to do RPC using a pluggable data format or serialization providers seems like a good idea to me.
writeReplace() and readResolve() is probably the best combo for doing so. Mighty powerful in the right hands.
Java serialization is only verbose where it describes the classes and fields it's serializing. Overall, the format is as "self describing" as XML. You can can actually override this and replace it with something else. This is what the writeClassDescriptor and readClassDescriptor methods are for. Dirmi overrides these methods, and so it is able to use standard object serialization with less wire overhead.
The way it works is related to how its sessions work. Both endpoints may have different versions of the object, and so simply throwing away the class descriptors won't work. Instead, additional data is exchanged (in the background) so that the serialized descriptor is replaced with a session-specific identifier. Upon seeing the identifier, a lookup table is examined to find the descriptor object. Because the data is exchanged in the background, there's a brief "warm up period" after a session is created and for every time an object type is written for the first time.
Dirmi has no way to replace the wire format at this time.