org.apache.lucene.queryparser.flexible.core.processors

## Class QueryNodeProcessorImpl

- java.lang.Object
- - org.apache.lucene.queryparser.flexible.core.processors.QueryNodeProcessorImpl

- All Implemented Interfaces:
    QueryNodeProcessor
  Direct Known Subclasses:
    AllowLeadingWildcardProcessor, AnalyzerQueryNodeProcessor, BooleanModifiersQueryNodeProcessor, BooleanSingleChildOptimizationQueryNodeProcessor, BoostQueryNodeProcessor, DefaultPhraseSlopQueryNodeProcessor, FuzzyQueryNodeProcessor, MatchAllDocsQueryNodeProcessor, MultiFieldQueryNodeProcessor, MultiTermRewriteMethodProcessor, NoChildOptimizationQueryNodeProcessor, OpenRangeQueryNodeProcessor, PhraseSlopQueryNodeProcessor, PointQueryNodeProcessor, PointRangeQueryNodeProcessor, RegexpQueryNodeProcessor, RemoveDeletedQueryNodesProcessor, RemoveEmptyNonLeafQueryNodeProcessor, TermRangeQueryNodeProcessor, WildcardQueryNodeProcessor

      public abstract class QueryNodeProcessorImpl
      extends Object
      implements QueryNodeProcessor

  This is a default implementation for the `QueryNodeProcessor` interface, it's an abstract class, so it should be extended by classes that want to process a `QueryNode` tree.

  This class process `QueryNode`s from left to right in the tree. While it's walking down the tree, for every node, `preProcessNode(QueryNode)` is invoked. After a node's children are processed, `postProcessNode(QueryNode)` is invoked for that node. `setChildrenOrder(List)` is invoked before `postProcessNode(QueryNode)` only if the node has at least one child, in `setChildrenOrder(List)` the implementor might redefine the children order or remove any children from the children list.

  Here is an example about how it process the nodes:

            a
           / \
          b   e
         / \
        c   d

  Here is the order the methods would be invoked for the tree described above:

            preProcessNode( a );
            preProcessNode( b );
            preProcessNode( c );
            postProcessNode( c );
            preProcessNode( d );
            postProcessNode( d );
            setChildrenOrder( bChildrenList );
            postProcessNode( b );
            preProcessNode( e );
            postProcessNode( e );
            setChildrenOrder( aChildrenList );
            postProcessNode( a )

  See Also:
    `QueryNodeProcessor`

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `QueryNodeProcessorImpl()`
    `QueryNodeProcessorImpl(QueryConfigHandler queryConfigHandler)`

  - ### Method Summary

    All Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `QueryConfigHandler` | `getQueryConfigHandler()` For reference about this method check: `QueryNodeProcessor.getQueryConfigHandler()`.
    `protected abstract QueryNode` | `postProcessNode(QueryNode node)` This method is invoked for every node when walking up the tree.
    `protected abstract QueryNode` | `preProcessNode(QueryNode node)` This method is invoked for every node when walking down the tree.
    `QueryNode` | `process(QueryNode queryTree)` Processes a query node tree.
    `protected void` | `processChildren(QueryNode queryTree)` This method is called every time a child is processed.
    `protected abstract List<QueryNode>` | `setChildrenOrder(List<QueryNode> children)` This method is invoked for every node that has at least on child.
    `void` | `setQueryConfigHandler(QueryConfigHandler queryConfigHandler)` For reference about this method check: `QueryNodeProcessor.setQueryConfigHandler(QueryConfigHandler)`.

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

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

- - ### Constructor Detail

    - #### QueryNodeProcessorImpl

          public QueryNodeProcessorImpl()

    - #### QueryNodeProcessorImpl

          public QueryNodeProcessorImpl(QueryConfigHandler queryConfigHandler)

  - ### Method Detail

    - #### process

          public QueryNode process(QueryNode queryTree)
                            throws QueryNodeException

      Description copied from interface: `QueryNodeProcessor`
      Processes a query node tree. It may return the same or another query tree. I should never return `null`.
      Specified by:
        `process` in interface `QueryNodeProcessor`
      Parameters:
        `queryTree` - tree root node
      Returns:
        the processed query tree
      Throws:
        `QueryNodeException`

    - #### processChildren

          protected void processChildren(QueryNode queryTree)
                                  throws QueryNodeException

      This method is called every time a child is processed.
      Parameters:
        `queryTree` - the query node child to be processed
      Throws:
        `QueryNodeException` - if something goes wrong during the query node processing

    - #### setQueryConfigHandler

          public void setQueryConfigHandler(QueryConfigHandler queryConfigHandler)

      For reference about this method check: `QueryNodeProcessor.setQueryConfigHandler(QueryConfigHandler)`.
      Specified by:
        `setQueryConfigHandler` in interface `QueryNodeProcessor`
      Parameters:
        `queryConfigHandler` - the query configuration handler to be set.
      See Also:
        `QueryNodeProcessor.getQueryConfigHandler()`, `QueryConfigHandler`

    - #### getQueryConfigHandler

          public QueryConfigHandler getQueryConfigHandler()

      For reference about this method check: `QueryNodeProcessor.getQueryConfigHandler()`.
      Specified by:
        `getQueryConfigHandler` in interface `QueryNodeProcessor`
      Returns:
        QueryConfigHandler the query configuration handler to be set.
      See Also:
        `QueryNodeProcessor.setQueryConfigHandler(QueryConfigHandler)`, `QueryConfigHandler`

    - #### preProcessNode

          protected abstract QueryNode preProcessNode(QueryNode node)
                                               throws QueryNodeException

      This method is invoked for every node when walking down the tree.
      Parameters:
        `node` - the query node to be pre-processed
      Returns:
        a query node
      Throws:
        `QueryNodeException` - if something goes wrong during the query node processing

    - #### postProcessNode

          protected abstract QueryNode postProcessNode(QueryNode node)
                                                throws QueryNodeException

      This method is invoked for every node when walking up the tree.
      Parameters:
        `node` - node the query node to be post-processed
      Returns:
        a query node
      Throws:
        `QueryNodeException` - if something goes wrong during the query node processing

    - #### setChildrenOrder

          protected abstract List<QueryNode> setChildrenOrder(List<QueryNode> children)
                                                       throws QueryNodeException

      This method is invoked for every node that has at least on child. It's invoked right before `postProcessNode(QueryNode)` is invoked.
      Parameters:
        `children` - the list containing all current node's children
      Returns:
        a new list containing all children that should be set to the current node
      Throws:
        `QueryNodeException` - if something goes wrong during the query node processing

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