Package org.apache.lucene.util

Class AttributeSource

java.lang.Object
org.apache.lucene.util.AttributeSource
Direct Known Subclasses:
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.

  • Constructor Details

  • Method Details

    • getAttributeFactory

      public final AttributeFactory getAttributeFactory()
      returns the used AttributeFactory.

    • getAttributeClassesIterator

      public final Iterator<Class<? extends Attribute>> getAttributeClassesIterator()
      Returns a new iterator that iterates the attribute classes in the same order they were added in.

    • getAttributeImplsIterator

      public final 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 final void addAttributeImpl(AttributeImpl att)
      Expert: Adds a custom AttributeImpl instance with one or more Attribute interfaces.

      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<T>) after adding with this method and cast to your class. The recommended way to use custom implementations is using an AttributeFactory.

      This method will only add the Attribute interfaces directly implemented by the class and its super classes.

    • addAttribute

      public final <T extends Attribute> T addAttribute(Class<T> 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 final boolean hasAttributes()
      Returns true, iff this AttributeSource has any attributes

    • hasAttribute

      public final 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 final <T extends Attribute> T getAttribute(Class<T> attClass)
      Returns the instance of the passed in Attribute contained in this AttributeSource

      The caller must pass in a Class<? extends Attribute> value.

      Returns:
      instance of the passed in Attribute, or null if this AttributeSource does not contain the Attribute. It is recommended to always use addAttribute(java.lang.Class<T>) even in consumers of TokenStreams, because you cannot know if a specific TokenStream really uses a specific Attribute. addAttribute(java.lang.Class<T>) 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 final void clearAttributes()
      Resets all Attributes in this AttributeSource by calling AttributeImpl.clear() on each Attribute implementation.

    • endAttributes

      public final void endAttributes()
      Resets all Attributes in this AttributeSource by calling AttributeImpl.end() on each Attribute implementation.

    • removeAllAttributes

      public final void removeAllAttributes()
      Removes all attributes and their implementations from this AttributeSource.

    • captureState

      public final 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.

      Be careful, this method comes with a cost of deep copying all attributes in the source.

    • restoreState

      public final 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

    • 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

      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:

    • cloneAttributes

      public final 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 AttributeFactory. You can use this method as a replacement for restoreState(org.apache.lucene.util.AttributeSource.State), if you use cloneAttributes() instead of captureState().

    • toString

      public String toString()
      Returns a string consisting of the class's simple name, the hex representation of the identity hash code, and the current reflection of all attributes.
      Overrides:
      toString in class Object
      See Also: