5. The Plain Java Object Model Extended

This chapter marks yet another fresh start, although we are far from abandoning what was gained last chapter. The Plain Object model is considered established, we retain much of the apparatus of method exposure and calling, and the Python byte code interpreter frame is little changed.

In the fourth model run-time system rt4, we aim initially for these new things:

1. Properly address Java classes as Python types.

2. Handle special methods as methods first: type slots are just optimisation.

3. Control visibility of the Jython API using Java modules.

We elaborate on these aims in the Introduction.

• 5.1. Introduction
  • 5.1.1. Java Classes as Python Types
  • 5.1.2. Special Methods
  • 5.1.3. A Jython API using Java modules
• 5.2. Object and PyType Basic Patterns
  • 5.2.1. Concepts
    • From Java Class to Python Type
    • Classes of Type
    • Primary Representation
    • Canonical Base Class
    • Accepted Class
    • Defining Class
    • How this has Evolved
  • 5.2.2. Class Models for the Concepts
    • Simple (One Type to One) Representation
    • Shared Representation (Replaceable Types)
    • Adoptive Types
• 5.3. Instance Models of object and type
  • 5.3.1. Representing list
    • Simple Sub-classes of list
    • Sub-classes of list using __slots__
  • 5.3.2. Object, object and Python class
  • 5.3.3. Type Objects for type
  • 5.3.4. Representing float
    • A Unary Operation float.__neg__
    • A Subclass of float
  • 5.3.5. Possibility of Caching on the Representation
    • Model
    • Motivation for Caching
    • Is Caching Beneficial for Jython?
  • 5.3.6. Representing int and bool
    • The Unary Operation __neg__
  • 5.3.7. Summary Examples
• 5.4. Subclasses in Python
  • 5.4.1. Implementation to Pull from VSJ3
    • Use of Special Methods
    • Descriptors for Special Methods
    • Type Exposer
    • Abstract API
    • Exceptions
  • 5.4.2. Exceptions
    • A Serendipitous Detour
    • The Bad News and the Good
    • Exceptions and their Representations
    • Coding __new__
    • Creating a NameError Exception
      • Sequence Diagram for Constructor Call
      • Narrative for Constructor Call
    • The __init__ of Exceptions
    • Type Objects for Exceptions
  • 5.4.3. Subclasses Defined as in Python
    • Specifying the Representation of a Subclass
    • The __new__ of built-in types
    • Generating Java Bytecode for a Subclass
    • Some examples reworked
• 5.5. Instance Models for Java Objects
  • 5.5.1. The Challenge of Subclasses
    • Need for a Synthetic Class
    • Overriding Methods
    • Creating a Representation
• 5.6. Type System Initialisation
  • 5.6.1. A Thread-Safe Type System
    • Type Registry and Factory
    • Strategy
  • 5.6.2. Specifying a Python Type
    • Common Idiom
    • General Thread-Safety Issue
    • Special Idiom for Bootstrap Types
    • Bootstrap Types