Package org.apache.sis.metadata
Class AbstractMetadata
Object
AbstractMetadata
- All Implemented Interfaces:
- Emptiable,- LenientComparable
- Direct Known Subclasses:
- ModifiableMetadata
Provides basic operations using Java reflection for metadata implementations.
 All 
 
 
AbstractMetadata instances shall be associated to a MetadataStandard.
 The metadata standard is given by the getStandard() 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 providing
 equals(Object), hashCode() and toString() implementations.
 Those methods are implemented using Java reflection for invoking the getter methods
 defined by the MetadataStandard.
AbstractMetadata subclasses may be read-only or read/write, at implementation choice.
 The methods that modify the metadata may throw UnmodifiableMetadataException if the
 metadata does not support the operation. Those methods are:
 | Read-only operations | Read/write operations | 
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Thread safety
Instances 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, another common approach is to use a single lock for the whole metadata tree (including children).- Since:
- 0.3
- See Also:
Defined in the sis-metadata module
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Constructor SummaryConstructors
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Method SummaryModifier and TypeMethodDescriptionasMap()Returns a view of the property values in aMap.Returns the property types and values as a tree table.final booleanPerforms a strict comparison of this metadata with the given object.booleanequals(Object object, ComparisonMode mode) Compares this metadata with the specified object for equality.Class<?>Returns the metadata interface implemented by this class.abstract MetadataStandardReturns the metadata standard implemented by subclasses.intComputes a hash code value for this metadata using Java reflection.booleanisEmpty()voidprune()Removes all references to empty properties.Returns a string representation of this metadata.
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Constructor Details- 
AbstractMetadataprotected AbstractMetadata()Creates an initially empty metadata.
 
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Method Details- 
getStandardReturns 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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getInterfaceReturns 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:
 
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isEmptypublic boolean isEmpty()Returnstrueif 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.
- Another 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.
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prunepublic void prune()Removes all references to empty properties. The default implementation iterates over all non null properties, and sets tonullthe properties for whichisEmpty()returnedtrue.- Throws:
- UnmodifiableMetadataException- if this metadata is not modifiable.
 
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asMapReturns 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 aCollectionbut 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:
 
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asTreeTableReturns 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 TreeTableinstance 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 of- DefaultCitation, 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. Otherwise- null. For example, in a tree table view of- DefaultCitation, if the- "alternateTitle"collection contains two elements, then there is a node with index 0 for the first element and another 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 default- toString()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 crossing the anti-meridian.
 Write operationsOnly theVALUEcolumn may be writable, with one exception: newly created children need to have theirIDENTIFIERset 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:
 
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equalsCompares 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:
- equalsin interface- LenientComparable
- Parameters:
- object- the object to compare with this metadata.
- mode- the strictness level of the comparison.
- Returns:
- trueif the given object is equal to this metadata.
- See Also:
 
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equalsPerforms 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:
- equalsin interface- LenientComparable
- Overrides:
- equalsin class- Object
- Parameters:
- object- the object to compare with this metadata for equality.
- Returns:
- trueif the given object is strictly equals to this metadata.
- See Also:
 
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hashCodepublic 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.
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toStringReturns a string representation of this metadata. The default implementation is as below:
 Note that this make extensive use of Unicode characters and is better rendered with a monospaced font.return asTreeTable().toString(); 
 
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