The Tools library is an important part of gvSIG. It provides a number of utilities and services which support the other modules in gvSIG. The main functionality provided by this library relates to:

• Registration of extension points
• Initialisation of libraries
• Utilities for the separation of the API and implementation (Registration of APIs, registration of implementations for the APIs, registration of SPI service providers or localisation of an API implementation)
• Monitoring of Tasks

Although these are the most important services the library provides, it also provides other tools that can be considered structural to the application. These include:

• Disposables
• Interfaces for managing Observers-observables
• Interfaces for managing visitors
• Definition of data types
• Base interfaces for evaluators
• Object Persistence

We will focus now on three basic concepts that are repeated throughout the code that we see, and that are linked to utilities that enable a strict separation of the API from the implementation:

• Libraries. These are pieces of code normally associated with a jar that provides a functionality. Each of these libraries must be a class that implements the Library interface, usually extending the AbstractLibrary class. They have methods for initialising the library that are invoked when it is loaded.
• Managers. These components provide functionality to the application, acting as an agent for the various services offered by the library and for their configuration. Acts as a singleton, since in the application there is usually only one instance of each of these components. Libraries will have one or more of these according to their logic.
• Locators. This is a utility that allows you to register implementations of managers for a given library, and to retrieve the manager implementation of a specific API.

These three components play a major role whenever we want to use or create new components, as they are the devices that allow us to access different parts of gvSIG