Provides basic operations using Java reflection for metadata implementations.
Enumeration of some metadata standards.
Provides convenience methods for support of modifiable properties in metadata implementations.
The name of the keys included in a
The kind of values in the
Thrown when a metadata is in a invalid state, usually because a mandatory property is missing.
Thrown on attempt to set a read-only value in a metadata object.
javax.imageio.metadata. The SIS implementation focuses on ISO 19115 (including its ISO 19115-2 extension), but the classes are designed in a way that allow the usage of different standards. This genericity goal should be keep in mind in the discussion below.
org.opengis.metadatapackage and sub-packages. That standard is identified in SIS by the
MetadataStandard.ISO_19115constant. Other standards are defined as well, for example the
MetadataStandard.ISO_19123constant stands for the standards defined by the interfaces in the
org.opengis.coveragepackage and sub-packages.
For each interface, the collection of declared getter methods defines its properties
(or attributes). If a
UML annotation is attached to the getter method,
the identifier declared in that annotation is taken as the property name. This is typically the name defined by the
International Standard from which the interface is derived. Otherwise (if there is no
the property name is inferred from the method name like what the Java Beans framework does.
The implementation classes, if they exist, are defined in different packages than the interfaces.
For example the ISO 19115 interfaces, declared in
org.opengis.metadata, are implemented by
org.apache.sis.metadata.iso. The sub-packages hierarchy is the same, and the names
of implementation classes are the name of the implemented interfaces prefixed with
Abstractprefix means that the class is abstract in the sense of the implemented standard. It it not necessarily abstract in the sense of Java. Because incomplete metadata are common in practice, sometime we wish to instantiate an "abstract" class despite the lack of knowledge about the exact sub-type.
Proxy. This is the approach taken by the
org.apache.sis.metadata.sqlpackage for generating metadata implementations backed by the content of a database.
titleproperty of a
Citationobject), but provide few logic. The package
org.apache.sis.metadata.isoand its sub-packages are the main examples of such containers.
In addition, the metadata modules provide support methods for handling the metadata objects through Java Reflection. This is an approach similar to Java Beans, in that users are encouraged to use directly the API of Plain Old Java objects (actually interfaces) every time their type is known at compile time, and fallback on the reflection technic when the type is known only at runtime.
Using Java reflection, a metadata can be viewed in many different ways:
MetadataStandardclass provides various methods returning a view of an arbitrary metadata implementation as a
Map, where the key are the property names and the values are the return values, types or descriptions of getter methods. The map is writable if the underlying metadata implementation has setter methods, otherwise attempts to set a value throw an
Citationmetadata contains one or many
ResponsiblePartyelements, each of them containing a
Contactelement, which contains a
Telephoneelement, etc. For each node, there is many information that can be displayed in columns:
Only the implementation classes defined in the
org.apache.sis.metadata.iso packages and sub-packages
are annotated for JAXB marshalling. If a metadata is implemented by an other package (for example
org.apache.sis.metadata.sql), then it shall be converted to an annotated class before to be marshalled.
All SIS annotated classes provide a copy constructor for this purpose. A shallow copy is sufficient;
JAXB adapters will convert the elements on-the-fly when needed.
The annotated classes can be given to a JAXB
Marshaller. For best results, it shall be a marshaller
obtained from the
MarshallerPool, otherwise some XML outputs may be incomplete
(missing namespaces for instance). The
XML class provides convenience methods
for this purpose.
Defined in the
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