public abstract class Context extends Object
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.
| Constructor and Description |
|---|
Context() |
| Modifier and Type | Method and Description |
|---|---|
abstract String |
context_name()
Retrieves the name of this
Context object. |
abstract Context |
create_child(String child_ctx_name)
Creates a
Context object with the given string as its
name and with this Context object set as its parent. |
abstract void |
delete_values(String propname)
Deletes from this
Context object the
NamedValue object(s) whose
name field matches the given property name. |
abstract NVList |
get_values(String start_scope,
int op_flags,
String pattern)
Retrieves the
NamedValue objects whose
name field matches the given name or name
pattern. |
abstract Context |
parent()
Retrieves the parent of this
Context object. |
abstract void |
set_one_value(String propname,
Any propvalue)
Creates a
NamedValue object and adds it to this
Context object. |
abstract void |
set_values(NVList values)
I Sets one or more property values in this
Context
object. |
public abstract String context_name()
Context object.Context objectpublic abstract Context parent()
Context object.Context object that is the
parent of this Context objectpublic abstract Context create_child(String child_ctx_name)
Context object with the given string as its
name and with this Context object set as its parent.
The new Context object is chained into its parent
Context 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.
child_ctx_name - the String object to be set as
the name of the new Context objectContext object
initialized with the specified namepublic abstract void set_one_value(String propname, Any propvalue)
NamedValue object and adds it to this
Context object. The name field of the
new NamedValue object is set to the given string,
the value field is set to the given Any
object, and the flags field is set to zero.propname - the name of the property to be setpropvalue - the Any object to which the
value of the property will be set. The
Any object's value
field contains the value to be associated
with the given propname; the
kind field must be set to
TCKind.tk_string.public abstract void set_values(NVList values)
Context
object. The NVList supplied to this method
contains one or more NamedValue objects.
In each NamedValue object,
the name field holds the name of the property, and
the flags field must be set to zero.
The NamedValue object's value field
contains an Any object, which, in turn, contains the value
for the property. Since the value is always a string,
the Any object must have the kind
field of its TypeCode set to TCKind.tk_string.values - an NVList containing the property
names and associated values to be setget_values(java.lang.String, int, java.lang.String),
NamedValue,
Anypublic abstract void delete_values(String propname)
Context object the
NamedValue object(s) whose
name field matches the given property name.
If the String object supplied for
propname has a
trailing wildcard character ("*"), then
all NamedValue objects whose name
fields match will be deleted. The search scope is always
limited to this Context object.
If no matching property is found, an exception is returned.
propname - name of the property to be deletedpublic abstract NVList get_values(String start_scope, int op_flags, String pattern)
NamedValue objects whose
name 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
all Context objects in the chain have been exhausted.
If no match is found, an error is returned and no property list is returned.
start_scope - a String 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 is CTX_RESTRICT_SCOPE.
If this flag is specified, searching is limited to the
specified start_scope or this
Context object.pattern - the property name whose values are to
be retrieved. pattern may be a
name or a name with a
trailing wildcard character ("*").NVList containing all the property values
(in the form of NamedValue objects)
whose associated property name matches the given name or
name patternset_values(org.omg.CORBA.NVList),
NamedValue Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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