Class AttributeSource
- java.lang.Object
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- org.apache.lucene.util.AttributeSource
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- Direct Known Subclasses:
AbstractQueryConfig
,TokenStream
public class AttributeSource extends Object
An AttributeSource contains a list of differentAttributeImpl
s, and methods to add and get them. There can only be a single instance of an attribute in the same AttributeSource instance. This is ensured by passing in the actual type of the Attribute (Class<Attribute>) to theaddAttribute(Class)
, which then checks if an instance of that type is already present. If yes, it returns the instance, otherwise it creates a new instance and returns it.
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
AttributeSource.AttributeFactory
An AttributeFactory creates instances ofAttributeImpl
s.static class
AttributeSource.State
This class holds the state of an AttributeSource.
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Constructor Summary
Constructors Constructor Description AttributeSource()
An AttributeSource using the default attribute factoryAttributeSource.AttributeFactory.DEFAULT_ATTRIBUTE_FACTORY
.AttributeSource(AttributeSource input)
An AttributeSource that uses the same attributes as the supplied one.AttributeSource(AttributeSource.AttributeFactory factory)
An AttributeSource using the suppliedAttributeSource.AttributeFactory
for creating newAttribute
instances.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description <A extends Attribute>
AaddAttribute(Class<A> attClass)
The caller must pass in a Class<? extends Attribute> value.void
addAttributeImpl(AttributeImpl att)
Expert: Adds a custom AttributeImpl instance with one or more Attribute interfaces.AttributeSource.State
captureState()
Captures the state of all Attributes.void
clearAttributes()
Resets all Attributes in this AttributeSource by callingAttributeImpl.clear()
on each Attribute implementation.AttributeSource
cloneAttributes()
Performs a clone of allAttributeImpl
instances returned in a newAttributeSource
instance.void
copyTo(AttributeSource target)
Copies the contents of thisAttributeSource
to the given targetAttributeSource
.boolean
equals(Object obj)
<A extends Attribute>
AgetAttribute(Class<A> attClass)
The caller must pass in a Class<? extends Attribute> value.Iterator<Class<? extends Attribute>>
getAttributeClassesIterator()
Returns a new iterator that iterates the attribute classes in the same order they were added in.AttributeSource.AttributeFactory
getAttributeFactory()
returns the used AttributeFactory.Iterator<AttributeImpl>
getAttributeImplsIterator()
Returns a new iterator that iterates all unique Attribute implementations.boolean
hasAttribute(Class<? extends Attribute> attClass)
The caller must pass in a Class<? extends Attribute> value.boolean
hasAttributes()
Returns true, iff this AttributeSource has any attributesint
hashCode()
String
reflectAsString(boolean prependAttClass)
This method returns the current attribute values as a string in the following format by calling thereflectWith(AttributeReflector)
method: iffprependAttClass=true
:"AttributeClass#key=value,AttributeClass#key=value"
iffprependAttClass=false
:"key=value,key=value"
void
reflectWith(AttributeReflector reflector)
This method is for introspection of attributes, it should simply add the key/values this AttributeSource holds to the givenAttributeReflector
.void
restoreState(AttributeSource.State state)
Restores this state by copying the values of all attribute implementations that this state contains into the attributes implementations of the targetStream.String
toString()
Returns a string representation of the object.
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Constructor Detail
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AttributeSource
public AttributeSource()
An AttributeSource using the default attribute factoryAttributeSource.AttributeFactory.DEFAULT_ATTRIBUTE_FACTORY
.
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AttributeSource
public AttributeSource(AttributeSource input)
An AttributeSource that uses the same attributes as the supplied one.
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AttributeSource
public AttributeSource(AttributeSource.AttributeFactory factory)
An AttributeSource using the suppliedAttributeSource.AttributeFactory
for creating newAttribute
instances.
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Method Detail
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getAttributeFactory
public AttributeSource.AttributeFactory getAttributeFactory()
returns the used AttributeFactory.
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getAttributeClassesIterator
public Iterator<Class<? extends Attribute>> getAttributeClassesIterator()
Returns a new iterator that iterates the attribute classes in the same order they were added in.
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getAttributeImplsIterator
public Iterator<AttributeImpl> getAttributeImplsIterator()
Returns a new iterator that iterates all unique Attribute implementations. This iterator may contain less entries thatgetAttributeClassesIterator()
, if one instance implements more than one Attribute interface.
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addAttributeImpl
public void addAttributeImpl(AttributeImpl att)
Expert: Adds a custom AttributeImpl instance with one or more Attribute interfaces.Please note: It is not guaranteed, that
att
is added to theAttributeSource
, because the provided attributes may already exist. You should always retrieve the wanted attributes usinggetAttribute(java.lang.Class<A>)
after adding with this method and cast to your class. The recommended way to use custom implementations is using anAttributeSource.AttributeFactory
.
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addAttribute
public <A extends Attribute> A addAttribute(Class<A> attClass)
The caller must pass in a Class<? extends Attribute> value. This method first checks if an instance of that class is already in this AttributeSource and returns it. Otherwise a new instance is created, added to this AttributeSource and returned.
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hasAttributes
public boolean hasAttributes()
Returns true, iff this AttributeSource has any attributes
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hasAttribute
public boolean hasAttribute(Class<? extends Attribute> attClass)
The caller must pass in a Class<? extends Attribute> value. Returns true, iff this AttributeSource contains the passed-in Attribute.
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getAttribute
public <A extends Attribute> A getAttribute(Class<A> attClass)
The caller must pass in a Class<? extends Attribute> value. Returns the instance of the passed in Attribute contained in this AttributeSource- Throws:
IllegalArgumentException
- if this AttributeSource does not contain the Attribute. It is recommended to always useaddAttribute(java.lang.Class<A>)
even in consumers of TokenStreams, because you cannot know if a specific TokenStream really uses a specific Attribute.addAttribute(java.lang.Class<A>)
will automatically make the attribute available. If you want to only use the attribute, if it is available (to optimize consuming), usehasAttribute(java.lang.Class<? extends org.apache.lucene.util.Attribute>)
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clearAttributes
public void clearAttributes()
Resets all Attributes in this AttributeSource by callingAttributeImpl.clear()
on each Attribute implementation.
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captureState
public AttributeSource.State captureState()
Captures the state of all Attributes. The return value can be passed torestoreState(org.apache.lucene.util.AttributeSource.State)
to restore the state of this or another AttributeSource.
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restoreState
public void restoreState(AttributeSource.State state)
Restores this state by copying the values of all attribute implementations that this state contains into the attributes implementations of the targetStream. The targetStream must contain a corresponding instance for each argument contained in this state (e.g. it is not possible to restore the state of an AttributeSource containing a TermAttribute into a AttributeSource using a Token instance as implementation).Note that this method does not affect attributes of the targetStream that are not contained in this state. In other words, if for example the targetStream contains an OffsetAttribute, but this state doesn't, then the value of the OffsetAttribute remains unchanged. It might be desirable to reset its value to the default, in which case the caller should first call
clearAttributes()
on the targetStream.
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toString
public String toString()
Returns a string representation of the object. In general, thetoString
method returns a string that "textually represents" this object.WARNING: For backwards compatibility this method is implemented as in Lucene 2.9/3.0. In Lucene 4.0 this default implementation will be removed.
It is recommeneded to use
reflectAsString(boolean)
orreflectWith(org.apache.lucene.util.AttributeReflector)
to get a well-defined output of AttributeSource's internals.
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reflectAsString
public final String reflectAsString(boolean prependAttClass)
This method returns the current attribute values as a string in the following format by calling thereflectWith(AttributeReflector)
method:- iff
prependAttClass=true
:"AttributeClass#key=value,AttributeClass#key=value"
- iff
prependAttClass=false
:"key=value,key=value"
- See Also:
reflectWith(AttributeReflector)
- iff
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reflectWith
public final void reflectWith(AttributeReflector reflector)
This method is for introspection of attributes, it should simply add the key/values this AttributeSource holds to the givenAttributeReflector
.This method iterates over all Attribute implementations and calls the corresponding
AttributeImpl.reflectWith(org.apache.lucene.util.AttributeReflector)
method.
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cloneAttributes
public AttributeSource cloneAttributes()
Performs a clone of allAttributeImpl
instances returned in a newAttributeSource
instance. This method can be used to e.g. create another TokenStream with exactly the same attributes (usingAttributeSource(AttributeSource)
). You can also use it as a (non-performant) replacement forcaptureState()
, if you need to look into / modify the captured state.
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copyTo
public final void copyTo(AttributeSource target)
Copies the contents of thisAttributeSource
to the given targetAttributeSource
. The given instance has to provide allAttribute
s this instance contains. The actual attribute implementations must be identical in bothAttributeSource
instances; ideally both AttributeSource instances should use the sameAttributeSource.AttributeFactory
. You can use this method as a replacement forrestoreState(org.apache.lucene.util.AttributeSource.State)
, if you usecloneAttributes()
instead ofcaptureState()
.
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