Eclipse Plug-in Developer Guide (Galileo) - Location (Eclipse Platform API Specification)

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Eclipse Platform
Release 3.5

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org.eclipse.osgi.service.datalocation
Interface Location

public interface Location

A Location represents a URL which may have a default value, may be read only, may or may not have a current value and may be cascaded on to a parent location.

This interface is not intended to be implemented by clients.

Since:: 3.0
Restriction:: This interface is not intended to be implemented by clients.

Field Summary

static String CONFIGURATION_FILTER
          Constant which defines the filter string for acquiring the service which specifies the configuration location.

static String ECLIPSE_HOME_FILTER
          Constant which defines the filter string for acquiring the service which specifies the eclipse home location.

static String INSTALL_FILTER
          Constant which defines the filter string for acquiring the service which specifies the install location.

static String INSTANCE_FILTER
          Constant which defines the filter string for acquiring the service which specifies the instance location.

static String USER_FILTER
          Constant which defines the filter string for acquiring the service which specifies the user location.

Method Summary

boolean allowsDefault ()
          Returns true if this location allows a default value to be assigned and false otherwise.

Location createLocation ( Location parent, URL defaultValue, boolean readonly)
          Constructs a new location.

URL getDefault ()
          Returns the default value of this location if any.

Location getParentLocation ()
          Returns the parent of this location or null if none is available.

URL getURL ()
          Returns the actual URL of this location.

boolean isLocked ()
          Returns true if this location is locked and false otherwise.

boolean isReadOnly ()
          Returns true if this location represents a read only location and false otherwise.

boolean isSet ()
          Returns true if this location has a value and false otherwise.

boolean lock ()
          Attempts to lock this location with a canonical locking mechanism and return true if the lock could be acquired.

void release ()
          Releases the lock on this location.

boolean set ( URL value, boolean lock)
          Sets and optionally locks the location's value to the given URL .

boolean set ( URL value, boolean lock, String lockFilePath)
          Sets and optionally locks the location's value to the given URL using the given lock file.

boolean setURL ( URL value, boolean lock)
          Deprecated. use set(URL, boolean) instead.

Field Detail

INSTANCE_FILTER

static final 
String INSTANCE_FILTER

Constant which defines the filter string for acquiring the service which specifies the instance location.

Since:: 3.2

INSTALL_FILTER

static final 
String INSTALL_FILTER

Constant which defines the filter string for acquiring the service which specifies the install location.

Since:: 3.2

CONFIGURATION_FILTER

static final 
String CONFIGURATION_FILTER

Constant which defines the filter string for acquiring the service which specifies the configuration location.

Since:: 3.2

USER_FILTER

static final 
String USER_FILTER

Constant which defines the filter string for acquiring the service which specifies the user location.

Since:: 3.2

ECLIPSE_HOME_FILTER

static final 
String ECLIPSE_HOME_FILTER

Constant which defines the filter string for acquiring the service which specifies the eclipse home location.

Since:: 3.4

Method Detail

allowsDefault

boolean allowsDefault()

Returns true if this location allows a default value to be assigned and false otherwise.

Returns:: whether or not this location can have a default value assigned

getDefault


URL getDefault()

Returns the default value of this location if any. If no default is available then null is returned. Note that even locations which allow defaults may still return null.

Returns:: the default value for this location or null

getParentLocation


Location getParentLocation()

Returns the parent of this location or null if none is available.

Returns:: the parent of this location or null

getURL


URL getURL()

Returns the actual URL of this location. If the location's value has been set, that value is returned. If the value is not set and the location allows defaults, the value is set to the default and returned. In all other cases null is returned.

Returns:: the URL for this location or null if none

isSet

boolean isSet()

Returns true if this location has a value and false otherwise.

Returns:: boolean value indicating whether or not the value is set

isReadOnly

boolean isReadOnly()

Returns true if this location represents a read only location and false otherwise. The read only character of a location is not in enforced in any way but rather expresses the intention of the location's creator.

Returns:: boolean value indicating whether the location is read only

setURL

boolean setURL(
URL value,
               boolean lock)
               throws 
IllegalStateException

Deprecated. use set(URL, boolean) instead.

Sets and optionally locks the location's value to the given URL . If the location already has a value an exception is thrown. If locking is requested and fails, false is returned and the URL of this location is not set.

Parameters:: value - the value of this location; lock - whether or not to lock this location
Returns:: whether or not the location was successfully set and, if requested, locked.
Throws:: IllegalStateException - if the location's value is already set

set

boolean set(
URL value,
            boolean lock)
            throws 
IllegalStateException,
                   
IOException

Parameters:: value - the value of this location; lock - whether or not to lock this location
Returns:: whether or not the location was successfully set and, if requested, locked.
Throws:: IllegalStateException - if the location's value is already set; IOException - if there was an unexpected problem while acquiring the lock
Since:: 3.4

set

boolean set(
URL value,
            boolean lock,
            
String lockFilePath)
            throws 
IllegalStateException,
                   
IOException

Sets and optionally locks the location's value to the given URL using the given lock file. If the location already has a value an exception is thrown. If locking is requested and fails, false is returned and the URL of this location is not set.

Parameters:: value - the value of this location; lock - whether or not to lock this location; lockFilePath - the path to the lock file. This path will be used to establish locks on this location. The path may be an absolute path or it may be relative to the given URL. If a null value is used then a default lock path will be used for this location.
Returns:: whether or not the location was successfully set and, if requested, locked.
Throws:: IllegalStateException - if the location's value is already set; IOException - if there was an unexpected problem while acquiring the lock
Since:: 3.5

lock

boolean lock()
             throws 
IOException

Attempts to lock this location with a canonical locking mechanism and return true if the lock could be acquired. Not all locations can be locked.

Locking a location is advisory only. That is, it does not prevent other applications from modifying the same location

Returns:: true if the lock could be acquired; otherwise false is returned
Throws:: IOException - if there was an unexpected problem while acquiring the lock

release

void release()

Releases the lock on this location. If the location is not already locked, no action is taken.

isLocked

boolean isLocked()
                 throws 
IOException

Returns true if this location is locked and false otherwise.

Returns:: boolean value indicating whether or not this location is locked
Throws:: IOException - if there was an unexpected problem reading the lock
Since:: 3.4

createLocation


Location createLocation(
Location parent,
                        
URL defaultValue,
                        boolean readonly)

Constructs a new location.

Parameters:: parent - the parent location. A null value is allowed.; defaultValue - the default value of the location. A null value is allowed.; readonly - true if the location is read-only.
Returns:: a new location.
Since:: 3.4