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 `AttributeImpl`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 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.State` This class holds the state of an AttributeSource.

  - ### Constructor Summary

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

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `<T extends Attribute> T` | `addAttribute(Class<T> 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 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`.
    `void` | `endAttributes()` Resets all Attributes in this AttributeSource by calling `AttributeImpl.end()` on each Attribute implementation.
    `boolean` | `equals(Object obj)`
    `<T extends Attribute> T` | `getAttribute(Class<T> attClass)` Returns the instance of the passed in Attribute contained in this AttributeSource
    `Iterator<Class<? extends Attribute>>` | `getAttributeClassesIterator()` Returns a new iterator that iterates the attribute classes in the same order they were added in.
    `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 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` | `removeAllAttributes()` Removes all attributes and their implementations from this AttributeSource.
    `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 consisting of the class's simple name, the hex representation of the identity hash code, and the current reflection of all attributes.

    - ### 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 `AttributeFactory.DEFAULT_ATTRIBUTE_FACTORY`.

    - #### AttributeSource

          public AttributeSource(AttributeSource input)

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

    - #### AttributeSource

          public AttributeSource(AttributeFactory factory)

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

  - ### Method Detail

    - #### 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`.

    - #### 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.

    - #### 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(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 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 `Attribute`s 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:
        `reflectAsString(boolean)`

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