Package org.apache.uima.cas.impl

Class FeatureValuePathImpl

  • All Implemented Interfaces:
    FeatureValuePath
    public class FeatureValuePathImpl
extends java.lang.Object
implements FeatureValuePath
    Contains CAS Type and Feature objects to represent a feature path of the form feature1/.../featureN. Each part that is enclosed within / is referred to as "path snippet" below. Also contains the necessary evaluation logic to yield the value of the feature path. For leaf snippets, the following "special features" are defined:
    • coveredText() can be accessed using evaluateAsString
    • typeName() can be accessed using evaluateAsString
    • fsId() can be accessed using evaluateAsInt. Its result can be used to retrieve an FS from the current LowLevel-CAS.
    • uniqueId() can be accessed using evaluateAsInt. Its result can be used to uniquely identify an FS for a document (even if the document is split over several CAS chunks)
    Handling of Arrays
    • A feature path may contain 0 or more features of type FSArray, but not as the last path snippet. The next path snippet must contain the fully qualified type name, example: family/members[0]/somepackage.Person:name
    • A feature path may also contain 0 or 1 feature of type IntArray, StringArray, FloatArray, but only as the last path snippet.
    For array-valued features, the following access operators are defined:
    • [index] returns the array entry at index
    • [last] returns the last entry of the array
    • [] returns an array of values. [] is only allowed 0 or 1 time in a feature path. If it is used, getValueType will return one of the following: CAS.TYPE_NAME_STRING_ARRAY ,CAS.TYPE_NAME_INTEGER_ARRAY,CAS.TYPE_NAME_FLOAT_ARRAY.
    If the feature path is defined directly for an FSArray, an actual feature name can be omitted, and only the array access operator can be used. Examples: 
                            
                         
                          
                           
                            
                             
                              
                               
                                
                                 
                                                                            []/somepackage.Person:coveredText()
                                                                             [last]/somepackage.Person:fsId()

    Usage
    • To create the feature path, use FeaturePath.getFeaturePath. Note that the client code needs to keep track of the "start type" of the feature path, that is, the type that contains the attribute used in the first snippet of the path.
    • At typeSystemInit of your component (CAS consumer or TAE), call typeSystemInit of the feature path.
    • Call getValueType to find out whether the feature path evaluates to a String, and int, a float, or their array counterparts.
    • Depending on the leaf type, call the appropriate evaluateAs methods

    • Method Detail

      • evaluateAsString

        public java.lang.String evaluateAsString​(int currentFS,
                                         LowLevelCAS cas)
        Evaluates each snippet of the feature path. Returns a String representation of the leaf value of the path. Returns null if some feature within the path is not set. If the leaf snippet is COVERED_TEXT, returns the covered text of currentFS.
        Specified by:
        evaluateAsString in interface FeatureValuePath
        Parameters:
        currentFS - the current Feature Structure
        cas - CAS
        Returns:
        A string representation of the leaf value.

      • getFSType

        public int getFSType()
        Returns the type for which the last feature in the feature path is defined. Assumes that typeSystemInit has been called prior to this method.
        • For a feature path feature1/.../featureN-1/featureN, returns the type of featureN.
        • For a feature path feature1/.../featureN-1/typeN:featureN, returns the type code for typeN. (For example, if the range type of featureN-1 is FSList or FSArray)
        • For a feature path feature1, where feature1 is simple-valued, returns the type that was used in typeSystemInit
        Specified by:
        getFSType in interface FeatureValuePath
        Returns:
        the type for which the last feature in the feature path is defined.

      • getValueType

        public java.lang.String getValueType()
        Returns the type that this feature path will evaluate to. Can be used to select the correct "evaluateAs" method.
        Specified by:
        getValueType in interface FeatureValuePath
        Returns:
        String the type that this feature path will evaluate to. Will be one of the following:
        • CAS.TYPE_NAME_STRING
        • CAS.TYPE_NAME_STRING_ARRAY
        • CAS.TYPE_NAME_INTEGER
        • CAS.TYPE_NAME_INTEGER_ARRAY
        • CAS.TYPE_NAME_FLOAT
        • CAS.TYPE_NAME_FLOAT_ARRAY

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object