Handles is a module for creating and managing dynamic identifier handles. It consists of four main classes, as well as four handle-related collections, one configuration class and one extra interface from the API module.

Handle is the main part of the Handles module. It is identified with a String id, and belongs in a Space that acts as a namespace for handles. It may have any number of tags, which are handles stored in a special tag space. It may also have any number of subhandles, which are handles that use a normal handle as an extra namespace. A handle may also belong in any number of Groups, which are also space-specific. It contains two methods for creating subhandles, createSubHandle(String) and getOrCreateSubHandle(String). Their difference is that createSubHandle throws an exception if a subhandle with that id is already present in the handle, while getOrCreateSubHandle returns the existing handle if it is present. Handles extend Comparable<Handle> where the comparison of handles within the same space are done by their index within that space, and handles in different spaces are ordered by the index of their respective space’s identifying handle in the “space space”.

Space is a namespace for Handles. It may contain any number of Handles, as well as any number of Groups. A space is identified by a handle that is stored in a special “space space”. A space has two methods for creating handles, createHandle(String) and getOrCreateHandle(String), which work in the same way as the methods for creating subhandles, as explained above in the section for handles. Two similar methods exist for creating groups, createGroup(String) and getOrCreateGroup(String).

HandleManager is a singleton class that manages all Spaces and Handles. It has two main methods, createSpace(String) and getOrCreateSpace(String) which work in the same way as the methods for creating subhandles, handles and groups, as explained above in the section for handles. It also contains references to the two special spaces, accessible with getSpaceSpace() and getTagSpace(). The implementation, HandleManagerImpl, is annotated as a @Component for the Injector module and will be automatically instantiated by it.

Groups are extra containers of Handles that are managed by Spaces. Like spaces, groups are identified by a handle, but these handles are always subhandles of the handle that identifies the space containing the group in question. Handles can be added to a group with getHandles().add(Object), the details of which are explained below in the section for HandleSets.

HandleSet is an extension of Set<Handle> that may only contain Handles from one Space. In addition to normal set behavior, it also allows for strings to be given to all methods that take in arbitrary objects for elements (remove(Object), contains(Object), removeAll(Collection<?>), containsAll(Collection<?>) and so on), where the string is automatically resolved to a handle in the space. It also has an extra add(String) method, which automatically creates a handle in the space if it does not already exist. Keep in mind that handle sets for the special “space space” are not able to create handles automatically, since handles in that space are created exclusively when creating spaces or Groups.

Two implementations for HandleSet exist, HashHandleSet and TreeHandleSet, which are backed by a HashSet and a TreeSet respectively.

HandleMap<T> is an extension of Map<Handle,T> that may only contain Handle keys from one Space. Much like HandleSet, all of its methods that take in arbitrary objects for keys also take in strings, where the string is automatically resolved to a handle in the space.

Two implementations for HandleMap<T> exist, HashHandleMap<T> and TreeHandleMap<T>, which are backed by a HashMap and a TreeMap respectively.

HandleManagerConfiguration is used to configure the HandleManager and by extension all other classes in the module. Specifically, it determines whether sorted or unsorted collections should be used in various places of the module. The options are:

• orderedSpaces determines if Spaces within the handle manager should be ordered. Default is true
• orderedHandlesInSpaces determines if Handles within spaces should be ordered. Default is true
• orderedHandlesInGroups determines if handles within Groups should be ordered. Default is false
• orderedGroups determines if groups within spaces should be ordered. Default is true
• orderedSubHandles determines if subhandles within handles should be ordered. Default is true
• orderedTags determines if tag handles within handles should be ordered. Default is false

The default configuration is registered as a @Component for the Injector module and can be overridden with a method annotated with @Component that returns the desired configuration.

Handled is an interface in the Handles API that indicates that its implementing class is identified by a Handle. Spaces and Groups implement handled by default. HandleMap has a method putHandled(T) which puts an object into the map based on its identifying handle. Handled also implements Comparable<Handled> that where the comparison is based on Handle.compareTo(Handle) using identifying handles.