Class Command
- java.lang.Object
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- org.eclipse.core.commands.common.EventManager
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- org.eclipse.core.commands.common.HandleObject
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- org.eclipse.core.commands.common.NamedHandleObject
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- org.eclipse.core.commands.Command
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- All Implemented Interfaces:
Comparable
,IIdentifiable
,IObjectWithState
public final class Command extends NamedHandleObject implements Comparable
A command is an abstract representation for some semantic behaviour. It is not the actual implementation of this behaviour, nor is it the visual appearance of this behaviour in the user interface. Instead, it is a bridge between the two.
The concept of a command is based on the command design pattern. The notable difference is how the command delegates responsibility for execution. Rather than allowing concrete subclasses, it uses a handler mechanism (see the
handlers
extension point). This provides another level of indirection.A command will exist in two states: defined and undefined. A command is defined if it is declared in the XML of a resolved plug-in. If the plug-in is unloaded or the command is simply not declared, then it is undefined. Trying to reference an undefined command will succeed, but trying to access any of its functionality will fail with a
NotDefinedException
. If you need to know when a command changes from defined to undefined (or vice versa), then attach a command listener.Commands are mutable and will change as their definition changes.
- Since:
- 3.1
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Field Summary
Fields Modifier and Type Field Description static boolean
DEBUG_COMMAND_EXECUTION
This flag can be set totrue
if commands should print information toSystem.out
when executing.static boolean
DEBUG_HANDLERS
This flag can be set totrue
if commands should print information toSystem.out
when changing handlers.static String
DEBUG_HANDLERS_COMMAND_ID
This flag can be set to a particular command identifier if only that command should print information toSystem.out
when changing handlers.-
Fields inherited from class org.eclipse.core.commands.common.NamedHandleObject
description, name
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Fields inherited from class org.eclipse.core.commands.common.HandleObject
defined, id, string
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Method Summary
All Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description void
addCommandListener(ICommandListener commandListener)
Adds a listener to this command that will be notified when this command's state changes.void
addExecutionListener(IExecutionListener executionListener)
Adds a listener to this command that will be notified when this command is about to execute.void
addState(String id, State state)
Adds a state to this command.int
compareTo(Object object)
Compares this command with another command by comparing each of its non-transient attributes.void
define(String name, String description, Category category)
Defines this command by giving it a name, and possibly a description as well.void
define(String name, String description, Category category, IParameter[] parameters)
Defines this command by giving it a name, and possibly a description as well.void
define(String name, String description, Category category, IParameter[] parameters, ParameterType returnType)
Defines this command by giving it a name, and possibly a description as well.void
define(String name, String description, Category category, IParameter[] parameters, ParameterType returnType, String helpContextId)
Defines this command by giving it a name, and possibly a description as well.Object
execute(ExecutionEvent event)
Deprecated.Please useexecuteWithChecks(ExecutionEvent)
instead.Object
executeWithChecks(ExecutionEvent event)
Executes this command by delegating to the current handler, if any.Category
getCategory()
Returns the category for this command.String
getDescription()
Returns the description for this handle.IHandler
getHandler()
Returns the current handler for this command.String
getName()
Returns the name for this handle.IParameter
getParameter(String parameterId)
Returns the parameter with the provided id ornull
if this command does not have a parameter with the id.IParameter[]
getParameters()
Returns the parameters for this command.ParameterType
getParameterType(String parameterId)
Returns theParameterType
for the parameter with the provided id ornull
if this command does not have a parameter type with the id.ParameterType
getReturnType()
Returns theParameterType
for the return value of this command ornull
if this command does not declare a return value parameter type.State
getState(String stateId)
Gets the state with the given id.String[]
getStateIds()
Gets the identifiers for all of the state associated with this object.boolean
isEnabled()
Returns whether this command has a handler, and whether this handler is also handled and enabled.boolean
isHandled()
Returns whether this command has a handler, and whether this handler is also handled.void
removeCommandListener(ICommandListener commandListener)
Removes a listener from this command.void
removeExecutionListener(IExecutionListener executionListener)
Removes a listener from this command.void
removeState(String stateId)
Removes a state from this command.void
setEnabled(Object evaluationContext)
Called be the framework to allow the handler to update its enabled state.boolean
setHandler(IHandler handler)
Changes the handler for this command.String
toString()
The string representation of this command -- for debugging purposes only.void
undefine()
Makes this command become undefined.-
Methods inherited from class org.eclipse.core.commands.common.HandleObject
equals, getId, hashCode, isDefined
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Methods inherited from class org.eclipse.core.commands.common.EventManager
addListenerObject, clearListeners, getListeners, isListenerAttached, removeListenerObject
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Field Detail
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DEBUG_COMMAND_EXECUTION
public static boolean DEBUG_COMMAND_EXECUTION
This flag can be set totrue
if commands should print information toSystem.out
when executing.
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DEBUG_HANDLERS
public static boolean DEBUG_HANDLERS
This flag can be set totrue
if commands should print information toSystem.out
when changing handlers.
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DEBUG_HANDLERS_COMMAND_ID
public static String DEBUG_HANDLERS_COMMAND_ID
This flag can be set to a particular command identifier if only that command should print information toSystem.out
when changing handlers.
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Method Detail
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addCommandListener
public void addCommandListener(ICommandListener commandListener)
Adds a listener to this command that will be notified when this command's state changes.- Parameters:
commandListener
- The listener to be added; must not benull
.
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addExecutionListener
public void addExecutionListener(IExecutionListener executionListener)
Adds a listener to this command that will be notified when this command is about to execute.- Parameters:
executionListener
- The listener to be added; must not benull
.
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addState
public void addState(String id, State state)
Adds a state to this command. This will add this state to the active handler, if the active handler is an instance of
IObjectWithState
.A single instance of
State
cannot be registered with multiple commands. Each command requires its own unique instance.- Specified by:
addState
in interfaceIObjectWithState
- Parameters:
id
- The identifier of the state to add; must not benull
.state
- The state to add; must not benull
.- Since:
- 3.2
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compareTo
public int compareTo(Object object)
Compares this command with another command by comparing each of its non-transient attributes.- Specified by:
compareTo
in interfaceComparable
- Parameters:
object
- The object with which to compare; must be an instance ofCommand
.- Returns:
- A negative integer, zero or a postivie integer, if the object is greater than, equal to or less than this command.
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define
public void define(String name, String description, Category category)
Defines this command by giving it a name, and possibly a description as well. The defined property automatically becomes
true
.Notification is sent to all listeners that something has changed.
- Parameters:
name
- The name of this command; must not benull
.description
- The description for this command; may benull
.category
- The category for this command; must not benull
.- Since:
- 3.2
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define
public void define(String name, String description, Category category, IParameter[] parameters)
Defines this command by giving it a name, and possibly a description as well. The defined property automatically becomes
true
.Notification is sent to all listeners that something has changed.
- Parameters:
name
- The name of this command; must not benull
.description
- The description for this command; may benull
.category
- The category for this command; must not benull
.parameters
- The parameters understood by this command. This value may be eithernull
or empty if the command does not accept parameters.
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define
public void define(String name, String description, Category category, IParameter[] parameters, ParameterType returnType)
Defines this command by giving it a name, and possibly a description as well. The defined property automatically becomes
true
.Notification is sent to all listeners that something has changed.
- Parameters:
name
- The name of this command; must not benull
.description
- The description for this command; may benull
.category
- The category for this command; must not benull
.parameters
- The parameters understood by this command. This value may be eithernull
or empty if the command does not accept parameters.returnType
- The type of value returned by this command. This value may benull
if the command does not declare a return type.- Since:
- 3.2
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define
public void define(String name, String description, Category category, IParameter[] parameters, ParameterType returnType, String helpContextId)
Defines this command by giving it a name, and possibly a description as well. The defined property automatically becomes
true
.Notification is sent to all listeners that something has changed.
- Parameters:
name
- The name of this command; must not benull
.description
- The description for this command; may benull
.category
- The category for this command; must not benull
.parameters
- The parameters understood by this command. This value may be eithernull
or empty if the command does not accept parameters.returnType
- The type of value returned by this command. This value may benull
if the command does not declare a return type.helpContextId
- The identifier of the help context to associate with this command; may benull
if this command does not have any help associated with it.- Since:
- 3.2
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execute
@Deprecated public Object execute(ExecutionEvent event) throws ExecutionException, NotHandledException
Deprecated.Please useexecuteWithChecks(ExecutionEvent)
instead.Executes this command by delegating to the current handler, if any. If the debugging flag is set, then this method prints information about which handler is selected for performing this command. This method will succeed regardless of whether the command is enabled or defined. It is generally preferred to callexecuteWithChecks(ExecutionEvent)
.- Parameters:
event
- An event containing all the information about the current state of the application; must not benull
.- Returns:
- The result of the execution; may be
null
. This result will be available to the client executing the command, and execution listeners. - Throws:
ExecutionException
- If the handler has problems executing this command.NotHandledException
- If there is no handler.
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executeWithChecks
public Object executeWithChecks(ExecutionEvent event) throws ExecutionException, NotDefinedException, NotEnabledException, NotHandledException
Executes this command by delegating to the current handler, if any. If the debugging flag is set, then this method prints information about which handler is selected for performing this command. This does checks to see if the command is enabled and defined. If it is not both enabled and defined, then the execution listeners will be notified and an exception thrown.- Parameters:
event
- An event containing all the information about the current state of the application; must not benull
.- Returns:
- The result of the execution; may be
null
. This result will be available to the client executing the command, and execution listeners. - Throws:
ExecutionException
- If the handler has problems executing this command.NotDefinedException
- If the command you are trying to execute is not defined.NotEnabledException
- If the command you are trying to execute is not enabled.NotHandledException
- If there is no handler.- Since:
- 3.2
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getCategory
public Category getCategory() throws NotDefinedException
Returns the category for this command.- Returns:
- The category for this command; never
null
. - Throws:
NotDefinedException
- If the handle is not currently defined.
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getHandler
public IHandler getHandler()
Returns the current handler for this command. This is used by the command manager for determining the appropriate help context identifiers and by the command service to allow handlers to update elements.This value can change at any time and should never be cached.
- Returns:
- The current handler for this command; may be
null
. - Since:
- 3.3
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getParameter
public IParameter getParameter(String parameterId) throws NotDefinedException
Returns the parameter with the provided id ornull
if this command does not have a parameter with the id.- Parameters:
parameterId
- The id of the parameter to retrieve.- Returns:
- The parameter with the provided id or
null
if this command does not have a parameter with the id. - Throws:
NotDefinedException
- If the handle is not currently defined.- Since:
- 3.2
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getParameters
public IParameter[] getParameters() throws NotDefinedException
Returns the parameters for this command. This call triggers provides a copy of the array, so excessive calls to this method should be avoided.- Returns:
- The parameters for this command. This value might be
null
, if the command has no parameters. - Throws:
NotDefinedException
- If the handle is not currently defined.
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getParameterType
public ParameterType getParameterType(String parameterId) throws NotDefinedException
Returns theParameterType
for the parameter with the provided id ornull
if this command does not have a parameter type with the id.- Parameters:
parameterId
- The id of the parameter to retrieve theParameterType
of.- Returns:
- The
ParameterType
for the parameter with the provided id ornull
if this command does not have a parameter type with the provided id. - Throws:
NotDefinedException
- If the handle is not currently defined.- Since:
- 3.2
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getReturnType
public ParameterType getReturnType() throws NotDefinedException
Returns theParameterType
for the return value of this command ornull
if this command does not declare a return value parameter type.- Returns:
- The
ParameterType
for the return value of this command ornull
if this command does not declare a return value parameter type. - Throws:
NotDefinedException
- If the handle is not currently defined.- Since:
- 3.2
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isEnabled
public boolean isEnabled()
Returns whether this command has a handler, and whether this handler is also handled and enabled.- Returns:
true
if the command is handled;false
otherwise.
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setEnabled
public void setEnabled(Object evaluationContext)
Called be the framework to allow the handler to update its enabled state.- Parameters:
evaluationContext
- the state to evaluate against. May benull
which indicates that the handler can query whatever model that is necessary. This context must not be cached.- Since:
- 3.4
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isHandled
public boolean isHandled()
Returns whether this command has a handler, and whether this handler is also handled.- Returns:
true
if the command is handled;false
otherwise.
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removeCommandListener
public void removeCommandListener(ICommandListener commandListener)
Removes a listener from this command.- Parameters:
commandListener
- The listener to be removed; must not benull
.
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removeExecutionListener
public void removeExecutionListener(IExecutionListener executionListener)
Removes a listener from this command.- Parameters:
executionListener
- The listener to be removed; must not benull
.
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removeState
public void removeState(String stateId)
Removes a state from this command. This will remove the state from the active handler, if the active handler is an instance of
IObjectWithState
.- Specified by:
removeState
in interfaceIObjectWithState
- Parameters:
stateId
- The identifier of the state to remove; must not benull
.- Since:
- 3.2
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setHandler
public boolean setHandler(IHandler handler)
Changes the handler for this command. This will remove all the state from the currently active handler (if any), and add it tohandler
. If debugging is turned on, then this will also print information about the change toSystem.out
.- Parameters:
handler
- The new handler; may benull
if none.- Returns:
true
if the handler changed;false
otherwise.
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toString
public String toString()
The string representation of this command -- for debugging purposes only. This string should not be shown to an end user.- Specified by:
toString
in classHandleObject
- Returns:
- The string representation; never
null
.
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undefine
public void undefine()
Makes this command become undefined. This has the side effect of changing the name and description tonull
. This also removes all state and disposes of it. Notification is sent to all listeners.- Specified by:
undefine
in classHandleObject
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getDescription
public final String getDescription() throws NotDefinedException
Description copied from class:NamedHandleObject
Returns the description for this handle.- Overrides:
getDescription
in classNamedHandleObject
- Returns:
- The description; may be
null
if there is no description. - Throws:
NotDefinedException
- If the handle is not currently defined.
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getName
public final String getName() throws NotDefinedException
Description copied from class:NamedHandleObject
Returns the name for this handle.- Overrides:
getName
in classNamedHandleObject
- Returns:
- The name for this handle; never
null
. - Throws:
NotDefinedException
- If the handle is not currently defined.
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getState
public final State getState(String stateId)
Description copied from interface:IObjectWithState
Gets the state with the given id.- Specified by:
getState
in interfaceIObjectWithState
- Parameters:
stateId
- The identifier of the state to retrieve; must not benull
.- Returns:
- The state; may be
null
if there is no state with the given id.
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getStateIds
public final String[] getStateIds()
Description copied from interface:IObjectWithState
Gets the identifiers for all of the state associated with this object.- Specified by:
getStateIds
in interfaceIObjectWithState
- Returns:
- All of the state identifiers; may be empty, but never
null
.
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