Chapter 1 defines a software module as a deployable, manageable, natively reusable, composable, and stateless unit with a concise interface. It discusses the characteristics of modules, including their independent testability and the ability to improve development efficiency. The chapter concludes by identifying the jar file as the best candidate for modularity on the Java platform.

1. Chapter 1: The Case for
Modularity
By Syed Ali Raza

2. Define a Module
 “chunk of software”
 A software module is a deployable,
manageable, natively reusable,
composable, stateless unit of software
that provides a concise interface to
consumers.

3. Elements of a module
 DEPLOYABLE
 MANAGEABLE
 TESTABLE
 NATIVELY
REUSABLE
 COMPOSABLE
 STATELESS

4. Deployable
 a unit of deployment
 a module is a discrete unit of
deployment that can alongside other
software modules.
 modules represent something more
physical and coarse-grained than
classes or packages, which are
intangible software entities.
 Examples of deployable units of
software include EAR, WAR, and JAR
files.

5. MANAGEABLE
 They can be installed, uninstalled, and
refreshed.
 This includes improving build
efficiency, allowing developers to
independently develop autono-mous
modules, and planning the
development effort along module
boundaries.
 It include EAR, WAR, and JAR files.

6. TESTABLE
 A module is a unit of testability.
 A module can also be independently
tested.
 It include classes, packages, and
JAR files

7. NATIVELY REUSABLE
 Modules are a unit of intraprocess reuse.
 modularity is a way to organize units of
deployment in a way that they can be
reused across applications, but a module
is always invoked natively (the
operations exposed by a module are
invoked by calling the method directly.)
 a module is deployed with each process
that intends to reuse its functionality.
 It include classes, packages, and JAR
files.

8. COMPOSABLE
 Modules can be composed of other
modules
 this involves coarse-grained modules
being a composition of finer-grained
modules.

9. STATELESS
 Modules are stateless.
 There exists only a single instance of
a specific version of a module.
 We don’t instantiate software
modules, although we do instantiate
instances of the classes within
software modules,
 WAR, EAR, and JAR files

10. SUCCINCT DEFINITION OFA
SOFTWARE MODULE
 After applying each segment of the
definition
◦ The best candidate as the unit of
modularity on the Java platform is the
JAR file!

11. Reference
 Java Application Architecture by Kirk
Knoernschild.