Package org.apache.lucene.util

Class AttributeSource

  • Direct Known Subclasses:
    TokenStream
    public class AttributeSource
extends java.lang.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.

    • Method Detail

      • getAttributeClassesIterator

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

      • getAttributeImplsIterator

        public final java.util.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.

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

      • addAttribute

        public final <T extends Attribute> T addAttribute​(java.lang.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​(java.lang.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​(java.lang.Class<T> attClass)
        The caller must pass in a Class<? extends Attribute> value. Returns the instance of the passed in Attribute contained in this AttributeSource
        Throws:
        java.lang.IllegalArgumentException - 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.

      • 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 java.lang.Object

      • equals

        public boolean equals​(java.lang.Object obj)
        Overrides:
        equals in class java.lang.Object

      • reflectAsString

        public final java.lang.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)

      • 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.

      • toString

        public java.lang.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 java.lang.Object
        See Also:
        reflectAsString(boolean)