XMPMeta iteration services. XMPIterator provides a uniform means to iterate over the schema and properties within an XMP object. The iteration over the schema and properties within an XMP object is very complex. It is helpful to have a thorough understanding of the XMP data tree. One way to learn this is to create some complex XMP and examine the output of XMPMeta#toString. This is also described in the XMP Specification, in the XMP Data Model chapter.
The top of the XMP data tree is a single root node. This does not explicitly appear in the dump and is never visited by an iterator (that is, it is never returned from XMPIterator#next()). Beneath the root are schema nodes. These are just collectors for top level properties in the same namespace. They are created and destroyed implicitly. Beneath the schema nodes are the property nodes. The nodes below a property node depend on its type (simple, struct, or array) and whether it has qualifiers.
An XMPIterator is created by XMPMeta#interator() constructor defines a starting point for the iteration and options that control how it proceeds. By default the iteration starts at the root and visits all nodes beneath it in a depth first manner. The root node is not visited, the first visited node is a schema node. You can provide a schema name or property path to select a different starting node. By default this visits the named root node first then all nodes beneath it in a depth first manner.
The XMPIterator#next() method delivers the schema URI, path, and option flags for the node being visited. If the node is simple it also delivers the value. Qualifiers for this node are visited next. The fields of a struct or items of an array are visited after the qualifiers of the parent.
The options to control the iteration are:
next() returns XMPPropertyInfo-objects and throws a NoSuchElementException if there are no more properties to return.
@since 25.01.2006
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