omg/DynamicAny/package.html

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<P>Provides classes and interfaces that enable traversal of the data value
 associated with an <code>any</code> at
runtime, and extraction of the primitive constituents of the data value.


<P>An <code>any</code> can be passed to a program that doesn't have any static information
for the type of the <code>any</code> (code generated for the type by an IDL compiler has not
been compiled with the object implementation). As a result, the object receiving the
<code>any</code> does not have a portable method of using it.

<P><code>DynAny</code>s enable traversal of the data value associated with an
<code>any</code> at runtime, and extraction of the primitive constituents of the data value.
This is especially helpful for writing powerful generic servers (bridges, event channels
supporting filtering).  Similarly, this facility enables the construction of an
<code>any</code> at runtime, without having static knowledge of its type. This is especially
helpful for writing generic clients (bridges, browsers, debuggers, user interface tools).

<P><code>Any</code> values can be dynamically interpreted (traversed) and constructed through
<tt>DynAny</tt> objects.  A <tt>DynAny</tt> object is associated with a data
value which corresponds to a copy of the value inserted into an <tt>Any</tt>.  A
<tt>DynAny</tt> object may be viewed as an ordered collection of component
<tt>DynAny</tt>s. For <tt>DynAny</tt>s representing a basic type, such as <code>long</code>,
or a type without components, such as an empty exception, the ordered collection of
components is empty.

<P>Each <tt>DynAny</tt> object maintains the notion of a current position into its collection
of component <tt>DynAny</tt>s. The current position is identified by an index value that runs
from 0 to n-1, where <em>n</em> is the number of components.  The special index value -1
indicates a current position that points nowhere.
 For values that cannot have a current position (such as an empty exception),
 the index value is fixed at -1.
 If a <code>DynAny</code> is initialized with a value that has components, the index is
initialized to 0.
 After creation of an uninitialized <code>DynAny</code> (that is, a <code>DynAny</code> that
has no value but a <code>TypeCode</code>
 that permits components), the current position depends on the type of value represented by
 the <code>DynAny</code>. (The current position is set to 0 or -1, depending on whether the
new <code>DynAny</code>
 gets default values for its components.)


<P>The iteration operations <code>rewind</code>, <code>seek</code>, and <code>next</code>
can be used to change the current position
 and the <code>current_component</code> operation returns the component at the current
position.
 The <code>component_count</code> operation returns the number of components of a
<code>DynAny</code>.
 Collectively, these operations enable iteration over the components of a
<code>DynAny</code>, for example,
 to (recursively) examine its contents.


 <P>A constructed <code>DynAny</code> object is a <code>DynAny</code> object associated with
a constructed type.
 There is a different interface, inheriting from the <code>DynAny</code> interface,
associated with
 each kind of constructed type in IDL (fixed, enum, struct, sequence, union, array,
 exception, and value type).  A constructed <code>DynAny</code> object exports operations
that enable the creation of new <code>DynAny</code> objects,
 each of them associated with a component of the constructed data value.
 As an example, a <code>DynStruct</code> is associated with a <code>struct</code> value. This
means that the <code>DynStruct</code>
 may be seen as owning an ordered collection of components, one for each structure member.
 The <code>DynStruct</code> object exports operations that enable the creation of new
<code>DynAny</code> objects,
 each of them associated with a member of the <code>struct</code>.


<P>If a <code>DynAny</code> object has been obtained from another (constructed)
<code>DynAny</code> object,
 such as a <code>DynAny</code> representing a structure member that was created from a
<code>DynStruct</code>,
 the member <code>DynAny</code> is logically contained in the <code>DynStruct</code>.
 Calling an <code>insert</code> or <code>get</code> operation leaves the current position
unchanged.
 Destroying a top-level <code>DynAny</code> object (one that was not obtained as a component
of another <code>DynAny</code>)
 also destroys any component <code>DynAny</code> objects obtained from it.
 Destroying a non-top level <code>DynAny</code> object does nothing.
 Invoking operations on a destroyed top-level <code>DynAny</code> or any of its descendants
raises OBJECT_NOT_EXIST.
 If the programmer wants to destroy a <code>DynAny</code> object but still wants to
manipulate some component
 of the data value associated with it, then he or she should first create a
<code>DynAny</code> for the component
 and, after that, make a copy of the created <code>DynAny</code> object.


<P>The behavior of <code>DynAny</code> objects has been defined in order to enable efficient
implementations
in terms of allocated memory space and speed of access. <code>DynAny</code> objects are
intended to be used
for traversing values extracted from <code>any</code>s or constructing values of
<code>any</code>s at runtime.
Their use for other purposes is not recommended.


 <H2>Handling DynAny objects</H2>

<P><code>Insert</code> and <code>get</code> operations are necessary to handle basic
<code>DynAny</code> objects
 but are also helpful to handle constructed <code>DynAny</code> objects.
 Inserting a basic data type value into a constructed <code>DynAny</code> object
 implies initializing the current component of the constructed data value
 associated with the <code>DynAny</code> object. For example, invoking
<code>insert_boolean</code> on a
 <code>DynStruct</code> implies inserting a <code>boolean</code> data value at the current
position
 of the associated <code>struct</code> data value.
 A type is consistent for inserting or extracting a value if its <code>TypeCode</code> is
equivalent to
 the <code>TypeCode</code> contained in the <code>DynAny</code> or, if the
<code>DynAny</code> has components, is equivalent to the <code>TypeCode</code>
 of the <code>DynAny</code> at the current position.

 <P>Basic operations include:
 <UL>
 	<LI>insert_boolean, get_boolean
 	<LI>insert_char, get_char
 	<LI>insert_short, get_short
 	<LI>insert_ushort, get_ushort
 	<LI>insert_long, get_long
 	<LI>insert_ulong, get_ulong
 	<LI>insert_double, get_double
 	<LI>insert_string, get_string
 	<LI>insert_reference, get_reference
 	<LI>insert_typecode, get_typecode
 	<LI>insert_longlong, get_longlong
 	<LI>insert_ulonglong, get_ulonglong
 	<LI>insert_longdouble, get_longdouble
 	<LI>insert_wchar, get_wchar
 	<LI>insert_wstring, get_wstring
 	<LI>insert_any, get_any
 	<LI>insert_dyn_any, get_dyn_any
 	<LI>insert_val, get_val
 	<LI>insert_octet, get_octet
 	<LI>insert_float, get_float
 	<LI>get_value
 	<LI>get_as_string
 	<LI>get_as_ulong
 	<LI>get_members
 	<LI>get_members_as_dyn_any
 	<LI>get_discriminator
 	<LI>get_length
 	<LI>get_elements
 	<LI>get_elements_as_dyn_any
 	<LI>get_boxed_value
 	<LI>get_boxed_value_as_dyn_any
 </UL>


 <P><code>DynAny</code> and <code>DynAnyFactory</code> objects are intended to be local to
the process in which they are
 created and used. This means that references to <code>DynAny</code> and
<code>DynAnyFactory</code> objects cannot be exported
 to other processes, or externalized with <code>ORB.object_to_string()</code>.
 If any attempt is made to do so, the offending operation will raise a MARSHAL system
exception.
 Since their interfaces are specified in IDL, <code>DynAny</code> objects export operations
defined in the standard
 <code>org.omg.CORBA.Object</code> interface. However, any attempt to invoke operations
exported through the <code>Object</code>
 interface may raise the standard NO_IMPLEMENT exception.
 An attempt to use a <code>DynAny</code> object with the DII may raise the NO_IMPLEMENT
exception.

<H3>Package Specification</H3>

<P>For a precise list of supported sections of official specifications with which
the Java[tm] Platform, Standard Edition 6 ORB complies, see <A
HREF="../CORBA/doc-files/compliance.html">Official Specifications for CORBA
support in Java[tm] SE 6</A>.

@since 1.4
<br>
@serial exclude
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