Refactor Instance Creation to Use Strategies

[Nylle]

This is related to #106.

Right now, we're handling different approaches to instantiating a class via exceptions - passing them down to each new attempt in order to better show what went wrong and what was attempted.

Although this is a good first approach (it works), I would like us to re-think this approach, potentially using strategies with results instead of exceptions.

[Nylle]

Analysis

There are three strategies of creating an object.

InstanceFactory.instantiate()

Is called by:

• GenericSpecimen.create()
• ObjectSpecimen.create()

InstanceFactory.construct()

Is called by:

• GenericSpecimen.create()
  • when customizationContext.useRandomConstructor()
  • when instantiate() failed
  • when populating failed
• ObjectSpecimen.create()
  • when customizationContext.useRandomConstructor()
  • when instantiate() failed
  • when populating failed

InstanceFactory.manufacture()

Is called by:

• AbstractSpecimen.create()
  • when proxy() failed
  • when populating failed
• InstanceFactory.construct()
  • when no public constructor was found
  • when constructor threw exception

[jk-idealo]

Use Cases

1) Cannot Create Instance Reflectively

The followng two "strategies" are attempted in order:

• Instance could not be created using Class.getDeclaredConstructor().newInstance()
• Instance could not be created using Objenesis.getInstantiatorOf(type.asClass())).newInstance()

2) Cannot Populate Fields Reflectively

If (1) was successful, each of the following errors might happen:

• Customization: Field not found in class
• Customization: Duplicate field names found
• Reflection: Unable to access field
• Reflection: Unable to set field

3) Cannot Create Instance via Constructor

If (1) or (2) failed, we try calling a random public constructor:

• No public constructor found
• All public constructors threw

4) Cannot Create Instance via Factory Method

If (3) failed, we try calling a random public factory method:

• No public static methods found
• All public static methods threw