The Context.java Java example source code
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package org.omg.CORBA;
/**
* An object used in <code>Request operations
* to specify the context object in which context strings
* must be resolved before being sent along with the request invocation.
* A <code>Context object
* contains a list of properties in the form of <code>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.
* <P>
* A <code>Context object is created by first calling the
* <code>ORB method get_default_context
* and then calling the method <code>create_child on the
* default context.
* <P>
* Each property in a <code>Context object is represented by
* a <code>NamedValue object. The property name is contained
* in the <code>NamedValue object's name field, and
* the value associated with the name is contained in the <code>Any
* object that was assigned to the <code>NamedValue object's
* <code>value field.
* <P>
* <code>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 <code>Context object
* for these properties using the method <code>get_values.
*
*<P>
* 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 <code>Context object
* to be provided in the <code>Context object parameter to
* the invoked method.
* <P>
* <code>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.
* <P>
* Property name patterns are used in the context clause of
* an operation definition and as a parameter for the
* method <code>Context.get_values.
* <P>
* <code>Context objects may be "chained" together to achieve a
* particular defaulting behavior. A <code>Context
* object created with the method <code>create_child will
* be chained to its parent (the <code>Context object
* that created it), and that means that the parent will be searched
* after the child in a search for property names.
*<P>
* Properties defined in a particular <code>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 <code>CTX_RESTRICT_SCOPE
* when invoking the method <code>get_values.
* <P>
* A <code>Context object may be named for purposes of specifying
* a starting search scope.
*
* @since JDK1.2
*/
public abstract class Context {
/**
* Retrieves the name of this <code>Context object.
*
* @return the name of this <code>Context object
*/
public abstract String context_name();
/**
* Retrieves the parent of this <code>Context object.
*
* @return the <code>Context object that is the
* parent of this <code>Context object
*/
public abstract Context parent();
/**
* Creates a <code>Context object with the given string as its
* name and with this <code>Context object set as its parent.
* <P>
* The new <code>Context object is chained into its parent
* <code>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.
*
*
* @param child_ctx_name the <code>String object to be set as
* the name of the new <code>Context object
* @return the newly-created child <code>Context object
* initialized with the specified name
*/
public abstract Context create_child(String child_ctx_name);
/**
* Creates a <code>NamedValue object and adds it to this
* <code>Context object. The name field of the
* new <code>NamedValue object is set to the given string,
* the <code>value field is set to the given Any
* object, and the <code>flags field is set to zero.
*
* @param propname the name of the property to be set
* @param propvalue the <code>Any object to which the
* value of the property will be set. The
* <code>Any object's value
* field contains the value to be associated
* with the given propname; the
* <code>kind field must be set to
* <code>TCKind.tk_string.
*/
public abstract void set_one_value(String propname, Any propvalue);
/**
I Sets one or more property values in this <code>Context
* object. The <code>NVList supplied to this method
* contains one or more <code>NamedValue objects.
* In each <code>NamedValue object,
* the <code>name field holds the name of the property, and
* the <code>flags field must be set to zero.
* The <code>NamedValue object's value field
* contains an <code>Any object, which, in turn, contains the value
* for the property. Since the value is always a string,
* the <code>Any object must have the kind
* field of its <code>TypeCode set to TCKind.tk_string.
*
* @param values an NVList containing the property
* names and associated values to be set
*
* @see #get_values
* @see org.omg.CORBA.NamedValue
* @see org.omg.CORBA.Any
*/
public abstract void set_values(NVList values);
/**
* Deletes from this <code>Context object the
* <code>NamedValue object(s) whose
* <code>name field matches the given property name.
* If the <code>String object supplied for
* <code>propname has a
* trailing wildcard character ("*"), then
* all <code>NamedValue objects whose name
* fields match will be deleted. The search scope is always
* limited to this <code>Context object.
* <P>
* If no matching property is found, an exception is returned.
*
* @param propname name of the property to be deleted
*/
public abstract void delete_values(String propname);
/**
* Retrieves the <code>NamedValue objects whose
* <code>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 <code>Context objects in the chain have been exhausted.
* <P>
* If no match is found, an error is returned and no property list
* is returned.
*
* @param start_scope a <code>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.
* @param op_flags an operation flag. The one flag
* that may be specified is <code>CTX_RESTRICT_SCOPE.
* If this flag is specified, searching is limited to the
* specified <code>start_scope or this
* <code>Context object.
* @param pattern the property name whose values are to
* be retrieved. <code>pattern may be a
* name or a name with a
* trailing wildcard character ("*").
*
* @return an <code>NVList containing all the property values
* (in the form of <code>NamedValue objects)
* whose associated property name matches the given name or
* name pattern
* @see #set_values
* @see org.omg.CORBA.NamedValue
*/
abstract public NVList get_values(String start_scope, int op_flags,
String pattern);
};
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