Repository Roadmap for Logical Model Integration
To provide full support for logical models, a repository provider
can perform the following steps:
- Contribute the appropriate repository operations to elements
that adapt to
- Ensure that operations performed on resource mappings include
all the appropriate model elements and resources by using an
- Allow model providers to participate in headless merging
interface and supporting API.
- Allow model providers to participate in merge previews by
for the models involved in the merge. A
class is provided to help manage the relationship between the model
content, a merge context and the Compare framework.
- Provide access to the history of workspace files through the
- Provide access to remote configurations using the Eclipse File
System API in the org.eclipse.core.filesystem plug-in and link
this to workspace projects through the
- Support logical model element decoration by providing a
Subscriber for use with the
- Allow models to group related changes by implementing the
The following sections describe each of these points in more
detail. The org.eclipse.team.examples.filesystem
plug-in contain an example that illustrate several of these points.
You can check the project out from the CVS repository and use it as
a reference while you are reading this tutorial. Disclaimer: The source
code in the example plug-ins may change over time. To get a copy that matches
what is used in this example, you can check out the project using the 3.3 version
tag (most likely R3_3) or a date tag of June 30, 2007.
Contributing Actions to Resource
The Basic Resource Mapping API
The resource mapping API consists of the following classes:
The class to which logical model elements adapt to indicate that the
model corresponds to a set of resources in the workspace. The methods
of interest are:
Object getModelObject(): The model object from
which the mapping was derived (or adapted).
getTraversals(ResourceMappingContext, IProgressMonitor): The resource
traversal that cover the resources that constitute the model object.
ResourceTraversal contains a set of resources and a
depth flag that indicates the depth to which the resources in the
traversal are associated with the originating model object. Resource
traversals are provided to a client by a resource mapping in order to
describe the contents of a model in such a way that the client (e.g. a
repository provider) can perform its operations in as efficient a means
as possible. Methods of interest are:
a context that is provided to the resource mapping by the client when
obtaining traversals. This context allows the logical model to
determine what the remote state of the model is so that the proper
resources can be covered by the resource traversals returned by the
resource mapping. The use of the
is a bit more complicated and is described later.
There are two types of plugins that should be interested in
resource mappings. Those who provide a model that consists of, or is
persisted in, resources in the workspace and those that want to perform
operations on resources. The former case will be covered in the model roadmap and the later case is
covered in the next section.
Resource Mappings and Object Contributions
Plug-ins that contribute extensions to adaptable extension points
will have to make two changes to support the new
- Update any objectContributions of the popupMenus
extension point in their plugin.xml file to target
IResource (for those for which this is
- Update their actions to work on
IResource and respect the depth constraints
provided in the traversals.
Plug-ins that add object contributions to
can now add them to
ResourceMapping instead, if the action
can apply to multiple resources. Here is an XML snippet that contributes
a menu action to objects that adapt to resource mappings:
ResourceMapping will automatically
apply to objects that adapt to
IResource. This transitive
association is handled by the Workbench. Filtering of the contributions
to resource mappings can be done using enablement expressions. An
expression for filtering by project persistent property has been added
to allow repository providers to have their menus appear on projects
that are mapped to their repositories.
Actions that have been contributed to the
class will be given a selection that contains one or more
It is the actions responsibility to translate the resource mapping into
a set of resources to be operated on. This can be done by calling
to get the traversals of the mapping. Traversals are used to allow the
clients of the traversal to optimize their operations based on the depth
of the resources being traversed. A client may traverse the resource
manually or may use the resource and the depth as input into an
operation that the action delegates to do the work. As an example, if
the user performs a CVS update on a java package and the java package
resource mapping maps to a folder of depth one, CVS would issue an
appropriate command ("cvs update -l" for those who are curious) which
would perform a shallow update on the folder the package represents.
Although it is possible to obtain a set of traversals directly
from the selected resource mappings, there are model relationships (or
repository relationships) that may require the inclusion of additional
resources or model elements in an operation. The next section describes
how to ensure that all required resources are included in an operation
For team operations, the selected mappings need to be translated
into the set of mappings to be operated on. This process involves
consulting all model providers to ensure that they get included in
operations on resources that match their enablement rules. The term we
use to describe the complete set of resource mappings to be operated on
is the operation scope. The following API has been provided for
Interface that defines the API for accessing the scope of the
operation. It provides access to all the resource mappings being
operated on and the traversals for those mappings as they were
calculated during the scope building process.
Interface that defines the API for creating and managing a scope.
Extendable class that provides a default implementation of the
Extendable operation class that generates a scope using a provided
scope manager and prompts if additional resources or mappings have been
included in the operation due to model provider relationships.
The initialize(IProgressMonitor) method of the
class handles the entire process of converting an input set of resource
mappings into the complete set of mappings that need to be operated on
as well as the complete set of traversals that cover these mappings. A
repository provider can tailor the process by:
- Providing a
RemoteResourceMappingContext for use
when obtaining resource traversals from resource mappings.
SynchronizationScopeManager to tailor
the scope management process as required.
The next two sections describe these points in more detail.
Remote Resource Mapping
In order to guarantee that all necessary resources get included
in a team operation, the model provider may need the ability to glimpse
at the state of one or more resources in the repository. For some
models, this may not be required. For instance, a java package is a
container visited to a depth of one, regardless of the remote state of
the model. Given this, a repository provider can easily determine that
outgoing deletions should be included when committing or that incoming
additions should be included when updating. However, the resources that
constitute some logical models may change over time. For instance, the
resources that constitute a model element may depend of the contents of
a manifest file (or some other similar mechanism). In order for the
resource mapping to return the proper traversal, it must access the
remote contents of the manifest file (if it differs from the local
contents) in order to see if there are additional resources that need to
be included. These additional resources may not exist in the workspace
but the repository provider would know how to make sure they did when
the selected action was performed.
In order to support these more complex models, a
can be passed to the
When a context is provided, the mapping can use it to ensure that all
the necessary resources are included in the traversal. If a context is
not provided, the mapping can assume that only the local state is of
The remote resource mapping context provides three basic queries:
- What type of comparison is being performed: two-way or
- For two-way, does the local contents differ from the remote
- For three-way, are there local changes and are there remote
- What are the contents of the remote (and base for three-way)
counterparts of the file?
- What are the remote members of a folder?
The answer to the first question above depends on the type of
operation that is being performed. Typically, updates and merges are
three-way while comparisons and replace operations (at least for CVS)
The Eclipse Team API includes a
that defines an API for providing the synchronization state between the
local workspace and a remote server. A
is provided that uses a
to access the necessary remote state. Clients that have a
do not need to do any additional work to get a resource mapping context.
SynchronizationScopeManager class can be
subclassed to tailor the scope generation and management process. The
two main reasons for subclassing the scope manager are:
- The repository provider needs to include additional resources
due to some repository level relationship (e.g. change set). This can
be accomplished by overriding the adjustInputTraversals(ResourceTraversal)
- The synchronization has a longer lifecycle (e.g. Synchronize
view vs. dialog) and needs the potential to react to scope changes. The
interface defines the API that model providers can use to participate
in the scope management process. The
class is a
Subscriber based subclass of
that involves participants in the scope management process. An example
of why this type of process is needed is working sets. If a working set
is one of the resource mappings in a scope, the set of traversals
covered by the scope would increase if resources were added to the
The main repository operation type that requires model
participation is merging. In many cases, models only need to participate
at the file level. For this, the
IStorageMerger API was
introduced to allow model providers to contribute mergers that should be
used to merge files of a particular extension or content type. However,
in some cases, models may need additional context to participate
properly in a merge. For this purpose, we introduced the
Merge operations are still triggered by actions associated with a
repository provider. However, once a merge type operation is requested
by the user, the repository provider needs to involve the model
providers in the merge process to ensure that the merge does not corrupt
the model in some way.
There are two main pieces of repository provider API related to
the model-based merging support.
- API to describe the synchronization state of the resources
involved in the merge.
- API to allow model providers to merge model elements.
The following sections describe these two pieces.
API for Synchronization State Description
An important aspect of model-based merging is the API used to
communicate the synchronization state of the resources involved to the
model provider. The following interfaces are used to describe the
provides access to the synchronization state of all resources within
the scope of the operation. The following API pieces are used to
describe the synchronization state of resources.
A generic path-based diff that consist of a diff kind (NO_CHANGE, ADD,
A diff that provides more details about a change between two states of
an element (CONTENT, MOVE_TO, MOVE_FROM, COPY_FROM, REPLACE).
A diff that consists of either a local or remote two-way diff or both
and provides a direction description for the change (INCOMING,
OUTGOING, CONFLICTING) based on the presence of either or both the
local and remote change.
A two-way diff that applies to resources and provides access to the
before state and after state of files through the IFileRevision
A generic path-based data structure for accessing a tree of diffs.
A resource-based data structure that contains the synchronization
state for all resources in the operation scope that are out-of-sync.
Abstract classes are provided for all these interfaces with the
convention that the class names match the interface names with the "I"
prefix removed. The only class that repository providers must override
ResourceDiff class so that appropriate before and
after file revisions can be provided.
API for Model Merging
interface extends synchronization context with additional methods that
support merging. Callback methods exist for:
- Merging one or more diffs.
- Rejecting the remote changes in one or more diffs
- Indicating that one or more conflicts have been merged by the
- Performing a group of operations while holding an appropriate
An abstract MergeContext
class is provided that contains default implementations for much of the
merging behavior and also uses the IStorageMerger
to perform three-way merges. A SubscriberMergeContext
class is also provided which handles the population and maintenance of
the synchronization state description associated with the merge context.
An operation class, ModelMergeOperation
is provided which uses the
IResourceMappingMerger API to
perform a model-based merge operation. Subclasses need to override the
method to return a merge context. The operation uses this context to
attempt a headless model-based merge. If conflicts exist, the preview of
the merge is left to the subclass. As we'll see in the next section,
there is a ModelParticipantMergeOperation
that provides preview capabilities using a ModelSynchronizeParticipant.
Model Content in Team Viewers
Support for the display of logical models in a team operation is
provided using the Common Navigator framework which was introduced in
Eclipse 3.2. Logical models can associate a content extension with a
model provider using the
extension point. Team providers access these content providers through
There are several places where a team provider may wish to
display logical models:
- When the scope of an operation has been expanded due to model
provider relationships. The
ModelOperation class provides
a prompt that uses the registered team content providers to inform the
user of a scope expansion.
- When a merge preview is required. The ModelSynchronizeParticipant
class makes use of the team content providers and a merge context to
display a merge preview. Team providers can extend this class in
several ways to tailor the preview.
ModelSynchronizeParticipant provides integration
into the Synchronize view or any container that can display
The participant makes use of both the pre-existing synchronization
participant capabilities and the Common Navigator capabilities to allow
for team providers and models to tailor the toolbar, context menu and
other aspects of the merge preview. The
provides the following:
- A synchronize page that defines the link between a scope
manager, merge context and team content providers.
- Toolbar actions for displaying direction modes (Incoming,
Outgoing, Both and Conflicting modes).
- Toolbar action for cycling through models involves (i.e. Show
All, Show Resources, Show Java, etc).
- Refresh and scheduled refresh actions.
- Action to open elements in a compare editor.
- Change Navigation actions.
- Standard Merge actions (Merge, Overwrite and MarkasMerged) for
which models can register handlers and team providers can provide
appropriate labels (e.g. Update for CVS).
Here's a checklist of steps for tailoring a model synchronize
participant for a particular Team provider:
- Define the participant using the
extension point. This will require team providers to create a subclass
- Define a viewer for the participant using the
extension point. The viewer definition is used to specify what menu
groups appear in the context menu.
- Override the initializeConfiguration method of the
participant in order to set the
to the id of the viewer specified in the previous step.
- Override the createMergeActionGroup to provide a
custom subclass of
MergeActionGroup in order to tailor the
appearance of the merge related actions.
- If the participant is persistable, override the createScopeManager
and restoreContext methods to recreate the scope manager and
merge context for the participant when it is restored on startup.
- Implement a subclass of
for handling the transition from a model-based merge to a preview in a
dialog or Synchronize view.
The following XML snipets illustrate how the CVS participant class
is registered and how it's viewer is defined.
<insertionPoint name="edit" separator="true"/>
<insertionPoint name="navigate" separator="true"/>
<insertionPoint name="update" separator="true"/>
<insertionPoint name="commit" separator="false"/>
<insertionPoint name="overrideActions" separator="true"/>
<insertionPoint name="otherActions1" separator="true"/>
<insertionPoint name="otherActions2" separator="true"/>
<insertionPoint name="sort" separator="true"/>
<insertionPoint name="additions" separator="true"/>
<insertionPoint name="properties" separator="true"/>
A file history API has been added to allow models to access the
history of files. The file history API consists of the following
Obtained from a RepositoryProvider, the file history provider allows
clients to obtain the file history of a particular file.
A data structure that allows access to the history of a file
The description of a single revision or state of a file at a particular
point in time in its history.
Along with this API, a generic file History view has been added.
This will allow Team providers to display their file/resource history in
a shared view and also allows models to display model element history
for elements that do not map directly to files. The History view is a
page-based view which obtains a page for the selected element in the
- A history page for workspace resources is obtained by adapting
RepositoryProvider associated with the project that
contains the resource to an IHistoryPageSource.
- A history page for other objects is obtained by adapting the
object itself to an
Project Set Capability
Methods have been added to
support the translation between a reference string used to identify a
mapping between a project and remote content and URIs that identify a
file-system scheme registered with the
extension point. Team providers can optionally provide support for this
in order to allow logical models to performing remote browsing and
Decorating Model Elements
Team providers can decorate model elements by converting their
lightweight decorators to work for resource mappings in the same way
object contributions are converted to work for resource mappings.
However, there is one aspect of logical model element decoration that is
problematic. If a model element does not have a one-to-one mapping to a
resource, the model element may not receive a label update when the
underlying resources change.
To address this issue, the
was introduced in order to give model
providers access to state changes that may affect team decorations. In addition,
model views can use a
to determine when the
labels of logical model elements need to be updated. This API relies on
ITeamStateProvider interface to determine when the team state
of resource has changed and can be passed to a team decorator as part of an
Grouping Related Changes
Some logical models need to ensure that a set of changed files get committed or checked-in to the repository at the same time.
To facilitate this, repository providers can adapt their
to an instance of
This API allows models to request that a set of files get committed or checked-in as a single unit.