org.apache.lucene.util

Class AttributeSource

java.lang.Object

org.apache.lucene.util.AttributeSource

Direct Known Subclasses:

AbstractQueryConfig, TokenStream

public class AttributeSource
extends Object

An AttributeSource contains a list of different AttributeImpls, 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 the addAttribute(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.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AttributeSource.AttributeFactory An AttributeFactory creates instances of AttributeImpls.
static class	AttributeSource.State This class holds the state of an AttributeSource.

Constructor Summary

Constructors

Constructor and Description
AttributeSource() An AttributeSource using the default attribute factory AttributeSource.AttributeFactory.DEFAULT_ATTRIBUTE_FACTORY.
AttributeSource(AttributeSource.AttributeFactory factory) An AttributeSource using the supplied AttributeSource.AttributeFactory for creating new Attribute instances.
AttributeSource(AttributeSource input) An AttributeSource that uses the same attributes as the supplied one.

Method Summary

Methods

Modifier and Type	Method and Description
<A extends Attribute> A	addAttribute(Class<A> attClass) The caller must pass in a Class<?
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 calling AttributeImpl.clear() on each Attribute implementation.
AttributeSource	cloneAttributes() Performs a clone of all AttributeImpl instances returned in a new AttributeSource instance.
void	copyTo(AttributeSource target) Copies the contents of this AttributeSource to the given target AttributeSource.
boolean	equals(Object obj)
<A extends Attribute> A	getAttribute(Class<A> attClass) The caller must pass in a Class<?
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<?
boolean	hasAttributes() Returns true, iff this AttributeSource has any attributes
int	hashCode()
String	reflectAsString(boolean prependAttClass) This method returns the current attribute values as a string in the following format by calling the reflectWith(AttributeReflector) method: iff prependAttClass=true: "AttributeClass#key=value,AttributeClass#key=value" iff prependAttClass=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 given AttributeReflector.
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.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

AttributeSource

public AttributeSource()

An AttributeSource using the default attribute factory AttributeSource.AttributeFactory.DEFAULT_ATTRIBUTE_FACTORY.

AttributeSource

public AttributeSource(AttributeSource input)

An AttributeSource that uses the same attributes as the supplied one.

AttributeSource

public AttributeSource(AttributeSource.AttributeFactory factory)

An AttributeSource using the supplied AttributeSource.AttributeFactory for creating new Attribute instances.

Method Detail

getAttributeFactory

public AttributeSource.AttributeFactory getAttributeFactory()

returns the used AttributeFactory.

getAttributeClassesIterator

public Iterator<Class<? extends Attribute>> getAttributeClassesIterator()

Returns a new iterator that iterates the attribute classes in the same order they were added in.

getAttributeImplsIterator

public Iterator<AttributeImpl> getAttributeImplsIterator()

Returns a new iterator that iterates all unique Attribute implementations. This iterator may contain less entries that getAttributeClassesIterator(), if one instance implements more than one Attribute interface.

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 the AttributeSource, because the provided attributes may already exist. You should always retrieve the wanted attributes using getAttribute(java.lang.Class<A>) after adding with this method and cast to your class. The recommended way to use custom implementations is using an AttributeSource.AttributeFactory.

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.

hasAttributes

public boolean hasAttributes()

Returns true, iff this AttributeSource has any attributes

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.

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 use addAttribute(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), use hasAttribute(java.lang.Class<? extends org.apache.lucene.util.Attribute>).

clearAttributes

public void clearAttributes()

Resets all Attributes in this AttributeSource by calling AttributeImpl.clear() on each Attribute implementation.

captureState

public AttributeSource.State captureState()

Captures the state of all Attributes. The return value can be passed to restoreState(org.apache.lucene.util.AttributeSource.State) to restore the state of this or another AttributeSource.

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.

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

toString

public String toString()

Returns a string representation of the object. In general, the toString 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) or reflectWith(org.apache.lucene.util.AttributeReflector) to get a well-defined output of AttributeSource's internals.

Overrides:

toString in class Object

reflectAsString

public final String reflectAsString(boolean prependAttClass)

This method returns the current attribute values as a string in the following format by calling the reflectWith(AttributeReflector) method:

• iff prependAttClass=true: "AttributeClass#key=value,AttributeClass#key=value"
• iff prependAttClass=false: "key=value,key=value"

See Also:

reflectWith(AttributeReflector)

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 given AttributeReflector.

This method iterates over all Attribute implementations and calls the corresponding AttributeImpl.reflectWith(org.apache.lucene.util.AttributeReflector) method.

See Also:

AttributeImpl.reflectWith(org.apache.lucene.util.AttributeReflector)

cloneAttributes

public AttributeSource cloneAttributes()

Performs a clone of all AttributeImpl instances returned in a new AttributeSource instance. This method can be used to e.g. create another TokenStream with exactly the same attributes (using AttributeSource(AttributeSource)). You can also use it as a (non-performant) replacement for captureState(), if you need to look into / modify the captured state.

copyTo

public final void copyTo(AttributeSource target)

Copies the contents of this AttributeSource to the given target AttributeSource. The given instance has to provide all Attributes this instance contains. The actual attribute implementations must be identical in both AttributeSource instances; ideally both AttributeSource instances should use the same AttributeSource.AttributeFactory. You can use this method as a replacement for restoreState(org.apache.lucene.util.AttributeSource.State), if you use cloneAttributes() instead of captureState().