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Nov 10th, 2008

Re: Weird Question

Then I was correct in my last response.

Again, in Ruby, what you just described would look like this:

Ruby Syntax (Toggle Plain Text)
button_name = "button1"
eval(button_name).whatever # calls whatever() on the variable button1
button_name = "button1"
eval(button_name).whatever # calls whatever() on the variable button1

destin

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Nov 10th, 2008

Re: Weird Question

> It just lets me know about certain properties of an Object, such as its classname

It does much more than that.

> The concept of a Map is somewhat familiar, but it doesn't help avoid the work, does it?

It provides a solution to your problem. IMO, what you are looking for is not a solution but a syntactic sugary way of doing things. Like previously mentioned, either use an array, a map or a JVM targeted scripting language like maybe Groovy, Scala, Rhino etc.

> I guess this isn't possible in Java though.

Yes, in the same way it isn't possible to create classes in C.

~s.o.s~

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Failure as a human

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Nov 10th, 2008

Re: Weird Question

I don't know all that much on reflection, but I have used it before. I don't see how it is useful. I've seen plenty of examples of reflection, so I understand how it is used. Just not why. Can anyone provide a reasonable example of a situation that needs reflection and a short explanation of why? All the tutorials I see give examples of reflection, but they are never situations where reflection is necessary. For example, I saw reflection being used to print out hello world. Pointless.

BestJewSinceJC

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Posting Maven

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Nov 10th, 2008

Re: Weird Question

Think of all the frameworks which let you specify your custom class in their configuration file and load those classes at runtime. The servlet specification for instance has a deployment descriptor which allows the developer to configure servlets, filters for his application. All the developer has to do is to specify the class name and the required processing is done at runtime by the container.

Also look into Spring or Guice which are IOC/Dependency Injection frameworks.

That being said, there *are* a lot of uses of reflection; it's just that they aren't that obvious.

~s.o.s~

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Nov 10th, 2008

Re: Weird Question

If you make your object Serializable then you can store information about the object in String form. It won't be as readable as "germanShepard" but you could store objects serials somewhere to enter. Doesn't sound too practical.
Another thing you can do is make a factory class. The class would take certain strings and generate objects for you to use based on that string name. It's a common design pattern and I've seen it used while poking around with code at work.

bionicseraph

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Nov 10th, 2008

Re: Weird Question

Click to Expand / Collapse Quote originally posted by bionicseraph ...

If you make your object Serializable then you can store information about the object in String form. It won't be as readable as "germanShepard" but you could store objects serials somewhere to enter. Doesn't sound too practical.
Another thing you can do is make a factory class. The class would take certain strings and generate objects for you to use based on that string name. It's a common design pattern and I've seen it used while poking around with code at work.

s.o.s, no offense, but sifting through a ton of material to *maybe* answer my question doesn't sound too appealing. If reflection is indeed useful, there have to be some practical, simple explanations of why this is the case.

bionic: Making objects Serializable means you can write the objects to file in Binary form and read them back in this way, so that you can store and retrieve your Objects more easily than if you were to do text input and output. Maybe I misunderstood what you said, but it's actually much more practical than reading/writing Strings to a file.

Regarding your other point, you can also take Strings and make objects by using a simple if statement, so I don't see why that would be a good use of reflection.

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Nov 10th, 2008

Re: Weird Question

> Can anyone provide a reasonable example of a situation that needs reflection and a short explanation of why?

We use it on our current project for dynamic configuration of our UI. All panel components share an interface and with a simple XML file we can reconfigure the frames and panels with no change to the compiled jar file. We also use it for our reporting engine to load column classes that can be plugged in to our table-based reports. These are simple usages of loading classes that share a common interface by supplying their class name and other properties in simple xml files.

Ezzaral

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Posting Genius

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Nov 10th, 2008

Re: Weird Question

Reflection is a very specialized solution, much like the Java Native Interface, Remote-Method Invocation, Wildcards, Design Patterns, transient values, volatile values, concurrency, etc.

Don't expect simple solutions for something that is seemingly "simple."

Alex Edwards

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Nov 10th, 2008

Re: Weird Question

BestJew: Yeah, I meant an if statement. Reflection is probably overkill for your stated requirements.

bionicseraph

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Nov 10th, 2008

Re: Weird Question

Click to Expand / Collapse Quote originally posted by Ezzaral ...

> Can anyone provide a reasonable example of a situation that needs reflection and a short explanation of why?

We use it on our current project for dynamic configuration of our UI. All panel components share an interface and with a simple XML file we can reconfigure the frames and panels with no change to the compiled jar file. We also use it for our reporting engine to load column classes that can be plugged in to our table-based reports. These are simple usages of loading classes that share a common interface by supplying their class name and other properties in simple xml files.

I've reflection to make method calls on auto-generated DAO objects that were based on similar tables in my data base. There are good uses for reflection, but most of the time you can get by without using it.

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