This week's book giveaway is in the Testing forum.
We're giving away four copies of Data Structures the Fun Way: An Amusing Adventure with Coffee-Filled Examples and have Jeremy Kubica on-line!
See this thread for details.
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other Pie Elite all forums
this forum made possible by our volunteer staff, including ...
Marshals:
  • Campbell Ritchie
  • Liutauras Vilda
  • Tim Cooke
  • Jeanne Boyarsky
  • Paul Clapham
Sheriffs:
  • Devaka Cooray
  • Ron McLeod
  • paul wheaton
Saloon Keepers:
  • Tim Moores
  • Piet Souris
  • Tim Holloway
  • Stephan van Hulst
  • Carey Brown
Bartenders:
  • Al Hobbs
  • Frits Walraven
  • Scott Selikoff

access private variable and methods from other class using reflection.

 
Ranch Hand
Posts: 101
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
we can also access private variable or method from other class using reflection. then how java is highly secured language.
 
Marshal
Posts: 76845
366
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Because you can apply security managers to prevent people accessing private variables.

Access modifiers are not designed to assure security, but to impose encapsulation and data hiding, and to encourage good programming practice. You can of course apply bad programming practices if you wish.
Last year I showed our undergraduates my colour class, where you can increase the red component > 255, causing the colour to go green! I challenged them to work out how I created it, and nobody could. So I told them and was told, “but that’s cheating!”
“Of course it’s cheating. How do you think I could have done it without cheating?”
Using reflection out of its intended purpose is cheating.
 
Ritesh raushan
Ranch Hand
Posts: 101
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator

Campbell Ritchie wrote:
Using reflection out of its intended purpose is cheating.




ok but already api given by sun ms and method for access fields and method then how cheating.
 
Bartender
Posts: 10780
71
Hibernate Eclipse IDE Ubuntu
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator

Ritesh raushan wrote:ok but already api given by sun ms and method for access fields and method then how cheating.


Because it allows you to do things that the language didn't intend.

In my view, reflection in Java is an aberration. It operates totally outside the normal bounds of the language, so you need to understand that, quite apart from being complex, error-prone and SLOW, it is inherently unsafe.

There are a few (VERY few) things for which it is useful, but the chances of you running into them in your first couple of years of programming are almost nil. And if you ever find yourself wanting to use it, the first thing you should ask yourself is: Can I do this without reflection?

HIH

Winston
 
Campbell Ritchie
Marshal
Posts: 76845
366
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Isn’t reflection intended for IDE writing and similar?
 
Bartender
Posts: 6109
6
Android IntelliJ IDE Java
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator

Campbell Ritchie wrote:Isn’t reflection intended for IDE writing and similar?



It's very handy for plugins (into an IDE or whatever), for JavaBean manipulation, for hooking in with scripting languages...
 
Winston Gutkowski
Bartender
Posts: 10780
71
Hibernate Eclipse IDE Ubuntu
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator

Jeff Verdegan wrote:It's very handy for plugins (into an IDE or whatever), for JavaBean manipulation, for hooking in with scripting languages...


Hmmm. An IDE I could see, because it needs to be introspective - and maybe some sort of Bean manager too; but couldn't plugins (if properly designed) be handled by dependency injection? Or indeed a custom ClassLoader?

Also, what's the chance of a question in the Beginners forum having to do with these sorts of things, which are pretty advanced? Seems much more likely to me that reflection is being used to save typing.

Winston
 
Jeff Verdegan
Bartender
Posts: 6109
6
Android IntelliJ IDE Java
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator

Winston Gutkowski wrote:

Jeff Verdegan wrote:It's very handy for plugins (into an IDE or whatever), for JavaBean manipulation, for hooking in with scripting languages...


Hmmm. An IDE I could see, because it needs to be introspective - and maybe some sort of Bean manager too; but couldn't plugins (if properly designed) be handled by dependency injection?



DI definitely uses reflection.

Or indeed a custom ClassLoader?



For loading the classes, sure, but not for executing their methods.

Also, what's the chance of a question in the Beginners forum having to do with these sorts of things, which are pretty advanced? Seems much more likely to me that reflection is being used to save typing.



Fair point. I wasn't talking about the OP's use of it in this particular case, just addressing Campbell's comment, which I interpreted to be about its use in general.
 
Winston Gutkowski
Bartender
Posts: 10780
71
Hibernate Eclipse IDE Ubuntu
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator

Jeff Verdegan wrote:DI definitely uses reflection.


True, but from what I understand, frameworks like Guice use it only for instantiation, rather like the providers for things like JDBC. Everything else works through standard Java interfaces and classes.

However, it has to be said, I'm no expert; and I suspect there are lots of different "flavours" of DI.

Winston
 
Java Cowboy
Posts: 16084
88
Android Scala IntelliJ IDE Spring Java
  • Likes 1
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Reflection is a powerful thing, but it should really be used only for special cases, if there really is no other way to do things. Don't use reflection if you can solve your problem using normal language constructs.

Calling methods via reflection is relatively slow, it can prevent the JVM and JIT from performing certain optimizations, and it's not type-safe - type errors that you would normally catch at compile time won't be noticed until runtime.
 
Jeff Verdegan
Bartender
Posts: 6109
6
Android IntelliJ IDE Java
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator

Winston Gutkowski wrote:

Jeff Verdegan wrote:DI definitely uses reflection.


True, but from what I understand, frameworks like Guice use it only for instantiation, rather like the providers for things like JDBC. Everything else works through standard Java interfaces and classes.

However, it has to be said, I'm no expert; and I suspect there are lots of different "flavours" of DI.

Winston



I can see 3 ways in which that could be true:

1. The authors of the DI frameworks know ahead of time what your beans' properties will be.

2. They don't call any setters at all, and all the DI properties are passed to the constructor. This isn't really any safer or simpler than reflectively invoking setters, IMHO.

3. The DI framework generates Java source code to invoke the setters as needed. If it's doing this, it should be able to generate code to just use the new operator as well, rather than even constructing objects reflectively.
 
roses are red, violets are blue. Some poems rhyme and some are a tiny ad:
the value of filler advertising in 2021
https://coderanch.com/t/730886/filler-advertising
reply
    Bookmark Topic Watch Topic
  • New Topic