Package org.apache.uima.cas.impl

Class FeatureValuePathImpl

java.lang.Object
org.apache.uima.cas.impl.FeatureValuePathImpl
All Implemented Interfaces:
FeatureValuePath
public class FeatureValuePathImpl extends 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 Details

    • getFeaturePath

      public static FeatureValuePathImpl getFeaturePath(String featurePath) throws CASRuntimeException
      Throws:
      CASRuntimeException

    • evaluate

      public Object evaluate(int currentFS, LowLevelCAS cas)
      Specified by:
      evaluate in interface FeatureValuePath

    • evaluateAsFloat

      public Float evaluateAsFloat(int currentFS, LowLevelCAS cas)
      Specified by:
      evaluateAsFloat in interface FeatureValuePath

    • evaluateAsFloatArray

      public Float[] evaluateAsFloatArray(int currentFS, LowLevelCAS cas)
      Specified by:
      evaluateAsFloatArray in interface FeatureValuePath

    • evaluateAsInt

      public Integer evaluateAsInt(int currentFS, LowLevelCAS cas)
      Specified by:
      evaluateAsInt in interface FeatureValuePath

    • evaluateAsIntArray

      public Integer[] evaluateAsIntArray(int currentFS, LowLevelCAS cas)
      Specified by:
      evaluateAsIntArray in interface FeatureValuePath

    • evaluateAsString

      public 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.

    • evaluateAsStringArray

      public String[] evaluateAsStringArray(int currentFS, LowLevelCAS cas)
      Specified by:
      evaluateAsStringArray in interface FeatureValuePath

    • 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 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 String toString()
      Overrides:
      toString in class Object

    • typeSystemInit

      public void typeSystemInit(int fsType, LowLevelTypeSystem ts) throws CASRuntimeException
      Specified by:
      typeSystemInit in interface FeatureValuePath
      Throws:
      CASRuntimeException