Package org.apache.lucene.analysis

# Class GraphTokenFilter

java.lang.Object
org.apache.lucene.util.AttributeSource
org.apache.lucene.analysis.TokenStream
org.apache.lucene.analysis.TokenFilter
org.apache.lucene.analysis.GraphTokenFilter

All Implemented Interfaces:
  `Closeable`, `AutoCloseable`, `Unwrappable<TokenStream>`

public abstract class GraphTokenFilter extends TokenFilter
An abstract TokenFilter that exposes its input stream as a graph

Call `incrementBaseToken()` to move the root of the graph to the next position in the TokenStream, `incrementGraphToken()` to move along the current graph, and `incrementGraph()` to reset to the next graph based at the current root.

For example, given the stream 'a b/c:2 d e`, then with the base token at 'a', incrementGraphToken() will produce the stream 'a b d e', and then after calling incrementGraph() will produce the stream 'a c e'.

## Nested Class Summary

## Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource

`AttributeSource.State`

## Field Summary

Fields
Modifier and Type
Field
Description
`static final int`
`MAX_GRAPH_STACK_SIZE`
The maximum permitted number of routes through a graph
`static final int`
`MAX_TOKEN_CACHE_SIZE`
The maximum permitted read-ahead in the token stream

### Fields inherited from class org.apache.lucene.analysis.TokenFilter

`input`

### Fields inherited from class org.apache.lucene.analysis.TokenStream

`DEFAULT_TOKEN_ATTRIBUTE_FACTORY`

## Constructor Summary

Constructors
Constructor
Description
`GraphTokenFilter(TokenStream input)`
Create a new GraphTokenFilter

## Method Summary

Modifier and Type
Method
Description
`void`
`end()`
This method is called by the consumer after the last token has been consumed, after `TokenStream.incrementToken()` returned `false` (using the new `TokenStream` API).
`int`
`getTrailingPositions()`
Return the number of trailing positions at the end of the graph
`protected final boolean`
`incrementBaseToken()`
Move the root of the graph to the next token in the wrapped TokenStream
`protected final boolean`
`incrementGraph()`
Reset to the root token again, and move down the next route through the graph
`protected final boolean`
`incrementGraphToken()`
Move to the next token in the current route through the graph
`void`
`reset()`
This method is called by a consumer before it begins consumption using `TokenStream.incrementToken()`.

### Methods inherited from class org.apache.lucene.analysis.TokenFilter

`close, unwrap`

### Methods inherited from class org.apache.lucene.analysis.TokenStream

`incrementToken`

### Methods inherited from class org.apache.lucene.util.AttributeSource

`addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, endAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, removeAllAttributes, restoreState, toString`

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

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

## Field Details

### MAX_GRAPH_STACK_SIZE

public static final int MAX_GRAPH_STACK_SIZE
The maximum permitted number of routes through a graph

See Also:
  - Constant Field Values

### MAX_TOKEN_CACHE_SIZE

public static final int MAX_TOKEN_CACHE_SIZE
The maximum permitted read-ahead in the token stream

See Also:
  - Constant Field Values

## Constructor Details

### GraphTokenFilter

public GraphTokenFilter(TokenStream input)
Create a new GraphTokenFilter

## Method Details

### incrementBaseToken

protected final boolean incrementBaseToken() throws IOException
Move the root of the graph to the next token in the wrapped TokenStream

Returns:
  `false` if the underlying stream is exhausted
Throws:
  `IOException`

### incrementGraphToken

protected final boolean incrementGraphToken() throws IOException
Move to the next token in the current route through the graph

Returns:
  `false` if there are not more tokens in the current graph
Throws:
  `IOException`

### incrementGraph

protected final boolean incrementGraph() throws IOException
Reset to the root token again, and move down the next route through the graph

Returns:
  false if there are no more routes through the graph
Throws:
  `IOException`

### getTrailingPositions

public int getTrailingPositions()
Return the number of trailing positions at the end of the graph

NB this should only be called after `incrementGraphToken()` has returned `false`

### end

public void end() throws IOException
Description copied from class: `TokenFilter`
This method is called by the consumer after the last token has been consumed, after `TokenStream.incrementToken()` returned `false` (using the new `TokenStream` API). Streams implementing the old API should upgrade to use this feature.

This method can be used to perform any end-of-stream operations, such as setting the final offset of a stream. The final offset of a stream might differ from the offset of the last token eg in case one or more whitespaces followed after the last token, but a WhitespaceTokenizer was used.

Additionally any skipped positions (such as those removed by a stopfilter) can be applied to the position increment, or any adjustment of other attributes where the end-of-stream value may be important.

If you override this method, always call `super.end()`.

NOTE: The default implementation chains the call to the input TokenStream, so be sure to call `super.end()` first when overriding this method.

Overrides:
  `end` in class `TokenFilter`
Throws:
  `IOException` - If an I/O error occurs

### reset

public void reset() throws IOException
Description copied from class: `TokenFilter`
This method is called by a consumer before it begins consumption using `TokenStream.incrementToken()`.

Resets this stream to a clean state. Stateful implementations must implement this method so that they can be reused, just as if they had been created fresh.

If you override this method, always call `super.reset()`, otherwise some internal state will not be correctly reset (e.g., `Tokenizer` will throw `IllegalStateException` on further usage).

NOTE: The default implementation chains the call to the input TokenStream, so be sure to call `super.reset()` when overriding this method.

Overrides:
  `reset` in class `TokenFilter`
Throws:
  `IOException`