Package org.apache.lucene.index

# Class FilterDirectoryReader.DelegatingCacheHelper

java.lang.Object
org.apache.lucene.index.FilterDirectoryReader.DelegatingCacheHelper

All Implemented Interfaces:
  `IndexReader.CacheHelper`

Enclosing class:
  `FilterDirectoryReader`

protected static class FilterDirectoryReader.DelegatingCacheHelper extends Object implements IndexReader.CacheHelper
A DelegatingCacheHelper is a CacheHelper specialization for implementing long-lived caching behaviour for FilterDirectoryReader subclasses. It uses a unique CacheKey for the purpose of implementing the onClose listener delegation for the reader.

## Constructor Summary

Constructors
Modifier
Constructor
Description
`protected`
`DelegatingCacheHelper(IndexReader.CacheHelper delegate)`
Create a new DelegatingCacheHelper that delegates the cache onClose listener to another CacheHelper, but with its own unique CacheKey.

## Method Summary

Modifier and Type
Method
Description
`void`
`addClosedListener(IndexReader.ClosedListener listener)`
Add a `IndexReader.ClosedListener` which will be called when the resource guarded by `IndexReader.CacheHelper.getKey()` is closed.
`IndexReader.CacheKey`
`getKey()`
Get a key that the resource can be cached on.

### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

## Constructor Details

### DelegatingCacheHelper

protected DelegatingCacheHelper(IndexReader.CacheHelper delegate)
Create a new DelegatingCacheHelper that delegates the cache onClose listener to another CacheHelper, but with its own unique CacheKey.

Parameters:
  `delegate` - the CacheHelper to delegate the close listener to

## Method Details

### getKey

public IndexReader.CacheKey getKey()
Description copied from interface: `IndexReader.CacheHelper`
Get a key that the resource can be cached on. The given entry can be compared using identity, ie. `Object.equals(java.lang.Object)` is implemented as `==` and `Object.hashCode()` is implemented as `System.identityHashCode(java.lang.Object)`.

Specified by:
  `getKey` in interface `IndexReader.CacheHelper`

### addClosedListener

public void addClosedListener(IndexReader.ClosedListener listener)
Description copied from interface: `IndexReader.CacheHelper`
Add a `IndexReader.ClosedListener` which will be called when the resource guarded by `IndexReader.CacheHelper.getKey()` is closed.

Specified by:
  `addClosedListener` in interface `IndexReader.CacheHelper`