Package org.apache.sis.metadata
Class AbstractMetadata
- Object
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- AbstractMetadata
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- All Implemented Interfaces:
Emptiable
,LenientComparable
- Direct Known Subclasses:
ModifiableMetadata
public abstract class AbstractMetadata extends Object implements LenientComparable, Emptiable
Provides basic operations using Java reflection for metadata implementations. AllAbstractMetadata
instances shall be associated to aMetadataStandard
. The metadata standard is given by thegetStandard()
method and is typically a constant fixed by the subclass.There is a large number of
AbstractMetadata
subclasses (not necessarily as direct children) for the same standard, where each subclass implement one Java interface defined by the metadata standard. This base class reduces the effort required to implement those metadata interfaces by providingequals(Object)
,hashCode()
andtoString()
implementations. Those methods are implemented using Java reflection for invoking the getter methods defined by theMetadataStandard
.AbstractMetadata
subclasses may be read-only or read/write, at implementation choice. The methods that modify the metadata may throwUnmodifiableMetadataException
if the metadata does not support the operation. Those methods are:Metadata operations Read-only operations Read/write operations isEmpty()
asMap()
withget
operationsasTreeTable()
withgetValue
operationsequals(Object, ComparisonMode)
prune()
asMap()
withput
operationsasTreeTable()
withsetValue
operations
Thread safetyInstances of this class are not synchronized for multi-threading. Synchronization, if needed, is caller's responsibility. Note that synchronization locks are not necessarily the metadata instances. For example an other common approach is to use a single lock for the whole metadata tree (including children).- Since:
- 0.3
- See Also:
MetadataStandard
Defined in the
sis-metadata
module
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Constructor Summary
Constructors Modifier Constructor Description protected
AbstractMetadata()
Creates an initially empty metadata.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description Map<String,Object>
asMap()
Returns a view of the property values in aMap
.TreeTable
asTreeTable()
Returns the property types and values as a tree table.boolean
equals(Object object)
Performs a strict comparison of this metadata with the given object.boolean
equals(Object object, ComparisonMode mode)
Compares this metadata with the specified object for equality.Class<?>
getInterface()
Returns the metadata interface implemented by this class.abstract MetadataStandard
getStandard()
Returns the metadata standard implemented by subclasses.int
hashCode()
Computes a hash code value for this metadata using Java reflection.boolean
isEmpty()
void
prune()
Removes all references to empty properties.String
toString()
Returns a string representation of this metadata.
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Method Detail
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getStandard
public abstract MetadataStandard getStandard()
Returns the metadata standard implemented by subclasses. Subclasses will typically return a hard-coded constant such asMetadataStandard.ISO_19115
.Note for implementersImplementation of this method shall not depend on the object state, since this method may be indirectly invoked by copy constructors.- Returns:
- the metadata standard implemented.
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getInterface
public Class<?> getInterface()
Returns the metadata interface implemented by this class. It should be one of the interfaces defined in the metadata standard implemented by this class.- Returns:
- the standard interface implemented by this implementation class.
- See Also:
MetadataStandard.getInterface(Class)
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isEmpty
public boolean isEmpty()
Returnstrue
if this metadata contains onlynull
, nil or empty properties. A non-null and non-nil property is considered empty in any of the following cases:- An empty character sequences.
- An empty collection or an empty array.
- A collection or array containing only
null
, nil or empty elements. - An other metadata object containing only
null
, nil or empty properties.
prune()
method.Note for implementersThe default implementation uses Java reflection indirectly, by iterating over all entries returned byMetadataStandard.asValueMap(Object, Class, KeyNamePolicy, ValueExistencePolicy)
. Subclasses that override this method should usually not invokesuper.isEmpty()
, because the Java reflection will discover and process the properties defined in the subclasses - which is usually not the intent when overriding a method.- Specified by:
isEmpty
in interfaceEmptiable
- Returns:
true
if this metadata is empty.- See Also:
DefaultGeographicBoundingBox.isEmpty()
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prune
public void prune()
Removes all references to empty properties. The default implementation iterates over all non null properties, and sets tonull
the properties for whichisEmpty()
returnedtrue
.- Throws:
UnmodifiableMetadataException
- if this metadata is not modifiable.
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asMap
public Map<String,Object> asMap()
Returns a view of the property values in aMap
. The map is backed by this metadata object, so changes in the underlying metadata object are immediately reflected in the map and conversely.Supported operationsThe map supports theput(…)
andremove(…)
operations if the underlying metadata object contains setter methods. Theremove(…)
method is implemented by a call toput(…, null)
.Keys and valuesThe keys are case-insensitive and can be either the JavaBeans property name, the getter method name or the UML identifier. The value given to a call to theput(…)
method shall be an instance of the type expected by the corresponding setter method, or an instance of a type convertible to the expected type.Multi-values entriesCalls toput(…)
replace the previous value, with one noticeable exception: if the metadata property associated to the given key is aCollection
but the given value is a single element (not a collection), then the given value is added to the existing collection. In other words, the returned map behaves as a multi-values map for the properties that allow multiple values. If the intent is to unconditionally discard all previous values, then make sure that the given value is a collection when the associated metadata property expects such collection.Default implementationThe default implementation is equivalent to the following method call:return getStandard().asValueMap(this, null, KeyNamePolicy.JAVABEANS_PROPERTY, ValueExistencePolicy.NON_EMPTY);
- Returns:
- a view of this metadata object as a map.
- See Also:
MetadataStandard.asValueMap(Object, Class, KeyNamePolicy, ValueExistencePolicy)
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asTreeTable
public TreeTable asTreeTable()
Returns the property types and values as a tree table. The tree table is backed by the metadata object using Java reflection, so changes in the underlying metadata object are immediately reflected in the tree table and conversely.The returned
TreeTable
instance contains the following columns:TableColumn.IDENTIFIER
The UML identifier if any, or the Java Beans property name otherwise, of a metadata property. For example in a tree table view ofDefaultCitation
, there is a node having the"title"
identifier.TableColumn.INDEX
If the metadata property is a collection, then the zero-based index of the element in that collection. Otherwisenull
. For example in a tree table view ofDefaultCitation
, if the"alternateTitle"
collection contains two elements, then there is a node with index 0 for the first element and an other node with index 1 for the second element.Note: The(IDENTIFIER, INDEX)
pair can be used as a primary key for uniquely identifying a node in a list of children. That uniqueness is guaranteed only for the children of a given node; the same keys may appear in the children of any other nodes.TableColumn.NAME
A human-readable name for the node, derived from the identifier and the index. This is the column shown in the defaulttoString()
implementation and may be localizable.TableColumn.TYPE
The base type of the value (usually an interface).TableColumn.VALUE
The metadata value for the node. Values in this column are writable if the underlying metadata class have a setter method for the property represented by the node.TableColumn.REMARKS
Remarks or warning on the property value. This is rarely present. It is provided when the value may look surprising, for example the longitude values in a geographic bounding box spanning the anti-meridian.
Write operationsOnly theVALUE
column may be writable, with one exception: newly created children need to have theirIDENTIFIER
set before any other operation. For example the following code adds a title to a citation:
Nodes can be removed by invoking theTreeTable.Node node = ...; // The node for a DefaultCitation. TreeTable.Node child = node.newChild(); child.setValue(TableColumn.IDENTIFIER, "title"); child.setValue(TableColumn.VALUE, "Le petit prince"); // Nothing else to do - the child node has been added.
Iterator.remove()
method on the children iterator.Default implementationThe default implementation is equivalent to the following method call:return getStandard().asTreeTable(this, null, ValueExistencePolicy.COMPACT);
- Returns:
- a tree table representation of the specified metadata.
- See Also:
MetadataStandard.asTreeTable(Object, Class, ValueExistencePolicy)
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equals
public boolean equals(Object object, ComparisonMode mode)
Compares this metadata with the specified object for equality. The default implementation uses Java reflection. Subclasses may override this method for better performances, or for comparing "hidden" properties not specified by the GeoAPI (or other standard) interface.- Specified by:
equals
in interfaceLenientComparable
- Parameters:
object
- the object to compare with this metadata.mode
- the strictness level of the comparison.- Returns:
true
if the given object is equal to this metadata.- See Also:
Utilities.deepEquals(Object, Object, ComparisonMode)
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equals
public final boolean equals(Object object)
Performs a strict comparison of this metadata with the given object. This method is implemented as below:
If a subclass needs to override the behavior of this method, then overridepublic final boolean equals(final Object object) { return equals(object, ComparisonMode.STRICT); }
equals(Object, ComparisonMode)
instead.- Specified by:
equals
in interfaceLenientComparable
- Overrides:
equals
in classObject
- Parameters:
object
- the object to compare with this metadata for equality.- Returns:
true
if the given object is strictly equals to this metadata.- See Also:
ComparisonMode.STRICT
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hashCode
public int hashCode()
Computes a hash code value for this metadata using Java reflection. The hash code is defined as the sum of hash code values of all non-empty properties, excluding cyclic dependencies. For acyclic metadata, this method contract is compatible with theSet.hashCode()
one and ensures that the hash code value is insensitive to the ordering of properties.Implementation note: This method does not cache the value because current implementation has no notification mechanism for tracking changes in children properties. If this metadata is known to be immutable, then subclasses may consider caching the hash code value if performance is important.- Overrides:
hashCode
in classObject
- See Also:
MetadataStandard.hashCode(Object)
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