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https://issues.apache.org/jira/browse/FELIX-4455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13933101#comment-13933101
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Guillaume Sauthier commented on FELIX-4455:
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Ok understood
>From the iPOJO point of view, your component is invalid because it miss a
>"manageable constructor". I think that iPOJO should complain with an
>understandable error message :)
I'm not sure it's a good practice to generate a default constructor for the
user if he (maybe intentionally) omit it. It make things harder to debug
because, you'll assume that what is executed is your code where in fact, iPOJO
is doing its own stuff.
What you see is a side effect of the ipojo manipulation: because it does not
stop if no "manageable constructor" is found, it process the class as usual:
build a new default constructor from scratch, and doing this, it miss the
assignment. This is because, in bytecode, the assignment is done in the
constructor, so if you generate one (instead of modifying one that contains the
instruction), you won't have the assignment for free...
> Missing default constructor creates invalid class instances
> -----------------------------------------------------------
>
> Key: FELIX-4455
> URL: https://issues.apache.org/jira/browse/FELIX-4455
> Project: Felix
> Issue Type: Bug
> Components: iPOJO
> Affects Versions: ipojo-manipulator-1.10.1, ipojo-manipulator-1.11.1
> Reporter: Benjamin Debeerst
>
> Consider the following component definition:
> @Component
> @Instantiate
> public class ComponentWithoutDefaultConstructor
> {
> private Object internal = new Object();
> @Property
> private String property;
> /* Constructor for unit tests */
> public ComponentWithoutDefaultConstructor(String property)
> {
> System.out.println("Non-default constructor call!");
> this.property = property;
> }
> @Validate
> public void activate()
> {
> System.out.println("ComponentWithoutDefaultConstructor: activating!");
> System.out.println(this.internal);
> }
> }
> As per definition, I would expect every instance of this class to have a
> non-null member {{internal}} at class creation. This is all fine for my unit
> tests in a non-OSGi environment.
> However, having this processes by iPOJO and putting this in an OSGi
> container, the component outputs
> ComponentWithoutDefaultConstructor: activating!
> null
> The existing non-default constructor is not called, while it seems that a
> separate constructor has been created that does non instantiate the member
> variable.
> If I extend the code by an empty default constructor, that one is called and
> all works perfectly fine.
> I have no idea how iPOJO creates the object instance anyways, as it should
> not be possible to create such an invalid object instance. I don't know much
> about the reflection APIs or byte code manipulation though.
> I have put a sample maven project on GitHub[1], which can be built and
> droppped into a fresh Karaf container + iPOJO, which shows the problem.
> If there is no constructor iPOJO can use, I would expect iPOJO to either A)
> throw a warning/error (and build or runtime) and fail to instantiate the
> component or B) synthesize the default constructor properly, including the
> implicit instantiation of member variables.
> I encountered this problem both with iPOJO 1.10.1 and 1.11.1.
> [1] https://github.com/BenjaminDebeerst/ipojo-component-constructor-sample
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