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https://issues.apache.org/jira/browse/LANG-307?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12967257#action_12967257
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Griffin DeJohn edited comment on LANG-307 at 12/8/10 6:10 PM:
--------------------------------------------------------------
Initial version of AutoClone source code attached. Please let me know if you
have any comments or questions, and if anybody can contribute good test cases,
I'd appreciate it.
The way it works is this. Given a target object that is a reference type, the
first step is to reflectively create a new instance of the dynamic type of that
object. This is accomplished by trying to invoke each declared constructor in
that object's class until a working one is found (starting with the fewest
parameters and working up from there). For each constructor, an argument to
match each parameter is recursively instantiated (with primitives as one base
case, for which the respective default value is passed, and arrays as the other
base case, for which an empty array of the same component type is passed). Once
an instance of the target object's class has been successfully instantiated,
all non-static fields in the target object from its class and superclasses are
recursively cloned (with primitives as a base case once again, as well as
Strings and enum types, for which the value is simply assigned to the
corresponding field in the clone), ensuring a deep copy.
It works with the null type, primitive types, reference types, and arbitrarily
nested arrays of any type. Classes that maintain their state partly or wholly
in instance variables declared in a superclass (e.g. StringBuilder) are
handled, as are instances of static nested classes, inner classes (nested in a
concrete class or an interface), local classes, and anonymous classes.
It doesn't work yet with an array that contains itself, and it fails with
instances of inner classes (i.e. non-static nested classes) that are dependent
on enclosing abstract classes (haven't figured out a way to dynamically
instantiate such a class; any ideas?). It also fails if necessary fields or
constructors are private and can't be made accessible due to a restrictive
security manager, or if a necessary constructor is picky and throws an
exception when passed arguments that don't meet certain requirements, or if a
necessary constructor has parameters that can't be instantiated (e.g. abstract
classes, enum types, or interfaces). I'm looking into using
java.lang.reflect.Proxy for that last bit.
The attached version is written to be generic through the use of unchecked
casts (the generated compiler warnings are suppressed). It seems to work well
enough, since e.g. "int foo = AutoClone.toClone(0.0d)" won't compile, but I'd
still like to hear what other people think about it.
was (Author: gdejohn):
Initial version of AutoClone source code attached. Please let me know if
you have any comments or questions, and if anybody can contribute good test
cases, I'd appreciate it.
The way it works is this. Given a target object that is a reference type, the
first step is to reflectively create a new instance of the dynamic type of that
object. This is accomplished by trying to invoke each declared constructor in
that object's class until a working one is found (starting with the fewest
parameters and working up from there). For each constructor, an argument to
match each parameter is recursively instantiated (with primitives being the
base case, at which point the respective default value is passed). Once an
instance of the target object's class has been successfully instantiated, all
non-static fields in the target object from its class and superclasses are
recursively cloned (again, with primitives being the base case, at which point
the value is simply assigned to the corresponding field in the clone), ensuring
a deep copy.
It works with the null type, primitive types, reference types, and arbitrarily
nested arrays of any type. Classes that maintain their state partly or wholly
in instance variables declared in a superclass (e.g. StringBuilder) are
handled, as are instances of static nested classes, inner classes (nested in a
concrete class or an interface), local classes, and anonymous classes.
It doesn't work yet with an array that contains itself, and it fails with
instances of non-static nested classes that are dependent on enclosing abstract
classes (haven't figured out a way to dynamically instantiate such a class; any
ideas?). It also fails if necessary fields or constructors are private and
can't be made accessible due to a restrictive security manager, or if a
necessary constructor is picky and throws an exception when passed arguments
that don't meet certain requirements.
The attached version is not generic. It returns the clone as an Object, which
must be cast to the appropriate type. I have already rewritten it to be generic
by using unchecked casts and suppressing the generated compiler warnings, but
while it seems to work well enough, since e.g. "int foo =
AutoClone.toClone(0.0d)" won't compile, I'd still like to hear what other
people think about it.
> CloneUtils - utility class to enable cloning via various different mechanisms
> -----------------------------------------------------------------------------
>
> Key: LANG-307
> URL: https://issues.apache.org/jira/browse/LANG-307
> Project: Commons Lang
> Issue Type: New Feature
> Components: lang.*
> Reporter: Henri Yandell
> Fix For: 3.1
>
> Attachments: AutoClone.java, lang-307.patch
>
>
> Taken from the tasks.html. No idea if we want to do it or not.
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