Class Context
- Direct Known Subclasses:
ContextImpl
Request
operations
to specify the context object in which context strings
must be resolved before being sent along with the request invocation.
A Context
object
contains a list of properties in the form of NamedValue
objects. These properties represent information
about the client, the environment, or the circumstances of a request
and generally are properties that might be inconvenient
to pass as parameters.
A Context
object is created by first calling the
ORB
method get_default_context
and then calling the method create_child
on the
default context.
Each property in a Context
object is represented by
a NamedValue
object. The property name is contained
in the NamedValue
object's name
field, and
the value associated with the name is contained in the Any
object that was assigned to the NamedValue
object's
value
field.
Context
properties can represent a portion of a client's
or application's environment that is meant to be propagated to
(and made implicitly part of) a server's environment.
(Examples might be a window identifier or user preference information).
Once a server has been invoked (that is, after the properties are
propagated), the server may query its Context
object
for these properties using the method get_values
.
When an operation declaration includes a context clause,
the stubs and skeletons will have an additional argument
added for the context. When an operation invocation occurs,
the ORB causes the properties that were named in the operation
definition in IDL and
that are present in the client's Context
object
to be provided in the Context
object parameter to
the invoked method.
Context
property names (which are strings)
typically have the form of an OMG IDL identifier or
a series of OMG IDL identifiers separated by periods.
A context property name pattern is either a property name
or a property name followed by a single "*". A property
name pattern without a trailing "*" is said to match only
itself. A property name pattern of the form "<name>*" matches any
property name that starts with <name> and continues with zero
or more additional characters.
Property name patterns are used in the context clause of
an operation definition and as a parameter for the
method Context.get_values
.
Context
objects may be "chained" together to achieve a
particular defaulting behavior. A Context
object created with the method create_child
will
be chained to its parent (the Context
object
that created it), and that means that the parent will be searched
after the child in a search for property names.
Properties defined in a particular Context
object
effectively override those properties in the next higher level.
The scope used in a search for properties may be restricted by specifying a
starting scope and by using the flag CTX_RESTRICT_SCOPE
when invoking the method get_values
.
A Context
object may be named for purposes of specifying
a starting search scope.
- Since:
- JDK1.2
- Version:
- 1.11, 09/09/97
-
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionabstract String
Retrieves the name of thisContext
object.abstract Context
create_child
(String child_ctx_name) Creates aContext
object with the given string as its name and with thisContext
object set as its parent.abstract void
delete_values
(String propname) Deletes from thisContext
object theNamedValue
object(s) whosename
field matches the given property name.abstract NVList
get_values
(String start_scope, int op_flags, String pattern) Retrieves theNamedValue
objects whosename
field matches the given name or name pattern.abstract Context
parent()
Retrieves the parent of thisContext
object.abstract void
set_one_value
(String propname, Any propvalue) Creates aNamedValue
object and adds it to thisContext
object.abstract void
set_values
(NVList values) I Sets one or more property values in thisContext
object.
-
Constructor Details
-
Context
public Context()
-
-
Method Details
-
context_name
Retrieves the name of thisContext
object.- Returns:
- the name of this
Context
object
-
parent
Retrieves the parent of thisContext
object.- Returns:
- the
Context
object that is the parent of thisContext
object
-
create_child
Creates aContext
object with the given string as its name and with thisContext
object set as its parent.The new
Context
object is chained into its parentContext
object. This means that in a search for matching property names, if a match is not found in this context, the search will continue in the parent. If that is not successful, the search will continue in the grandparent, if there is one, and so on.- Parameters:
child_ctx_name
- theString
object to be set as the name of the newContext
object- Returns:
- the newly-created child
Context
object initialized with the specified name
-
set_one_value
Creates aNamedValue
object and adds it to thisContext
object. Thename
field of the newNamedValue
object is set to the given string, thevalue
field is set to the givenAny
object, and theflags
field is set to zero.- Parameters:
propname
- the name of the property to be setpropvalue
- theAny
object to which the value of the property will be set. TheAny
object'svalue
field contains the value to be associated with the given propname; thekind
field must be set toTCKind.tk_string
.
-
set_values
I Sets one or more property values in thisContext
object. TheNVList
supplied to this method contains one or moreNamedValue
objects. In eachNamedValue
object, thename
field holds the name of the property, and theflags
field must be set to zero. TheNamedValue
object'svalue
field contains anAny
object, which, in turn, contains the value for the property. Since the value is always a string, theAny
object must have thekind
field of itsTypeCode
set toTCKind.tk_string
.- Parameters:
values
- an NVList containing the property names and associated values to be set- See Also:
-
delete_values
Deletes from thisContext
object theNamedValue
object(s) whosename
field matches the given property name. If theString
object supplied forpropname
has a trailing wildcard character ("*"), then allNamedValue
objects whosename
fields match will be deleted. The search scope is always limited to thisContext
object.If no matching property is found, an exception is returned.
- Parameters:
propname
- name of the property to be deleted
-
get_values
Retrieves theNamedValue
objects whosename
field matches the given name or name pattern. This method allows for wildcard searches, which means that there can be multiple matches and therefore multiple values returned. If the property is not found at the indicated level, the search continues up the context object tree until a match is found or allContext
objects in the chain have been exhausted.If no match is found, an error is returned and no property list is returned.
- Parameters:
start_scope
- aString
object indicating the context object level at which to initiate the search for the specified properties (for example, "_USER", "_GROUP", "_SYSTEM"). Valid scope names are implementation-specific. If a scope name is omitted, the search begins with the specified context object. If the specified scope name is not found, an exception is returned.op_flags
- an operation flag. The one flag that may be specified isCTX_RESTRICT_SCOPE
. If this flag is specified, searching is limited to the specifiedstart_scope
or thisContext
object.pattern
- the property name whose values are to be retrieved.pattern
may be a name or a name with a trailing wildcard character ("*").- Returns:
- an
NVList
containing all the property values (in the form ofNamedValue
objects) whose associated property name matches the given name or name pattern - See Also:
-