Package org.hl7.fhir.r4.fhirpath

Interface IHostApplicationServices

All Known Implementing Classes:
BaseHostServices, LiquidEngine, Runner
public interface IHostApplicationServices
This interface allows the application making use of a FHIRPathEngine to provide additional services that can be used in the FHIRPath statements. The services fall into two categories: extending the FHIRPath engine with types, constants and functions, and performing work that the FHIRPath engine doesn't know how to do itself Functionality: * resolveConstant()/resolveConstantType() - register constants * log() - do something when .log() is used in the FHIRPath statement * resolveFunction() / checkFunction() / executeFunction() - allow the application to define FHIRPath functions of it's own * resolveReference() - called when a FHIRPath statement uses 'resolve()' so the host application can attempt to resolve the reference * resolveValueSet() - called when memberOf() is used * conformsToProfile() - check that the content conforms to the stated profile. Used by the ValidationEngine - not generally suitable for applications to provide their own interface * paramIsType() - used when the FHIRPath statement Note that his used to be called IEvaluationContext in the FHIRPathEngine class, but was renamed due to a broken interface - see comments at https://github.com/hapifhir/org.hl7.fhir.core/releases/tag/6.6.0

  • Method Details

    • resolveConstant

      List<Base> resolveConstant(FHIRPathEngine engine, Object appContext, String name, org.hl7.fhir.utilities.fhirpath.FHIRPathConstantEvaluationMode mode) throws org.hl7.fhir.exceptions.PathEngineException
      A constant reference - e.g. a reference to a name that must be resolved in context. resolveConstant is invoked under 3 different circumstances, which are reflected in the mode parameter: * an explicit constant of the form %{token}, where the token isn't a known internal constant * every evaluation of any expression to allow the Host Application to decide whether to interpret the expression as a constant even if it is not explicitly a constant * at the start of evaluating an expression if the focus provided by the application when invoking the expression is {} The return value is a List - a collection, though most constants are singleton values note that variables created using defineVariable() in the FHIRPath expressions will not be processed by resolveConstant (or resolveConstantType)
      Parameters:
      appContext - - application context passed into the FHIRPath engine when first executed
      name - - name reference to resolve. if mode = EXPLICIT, the % will NOT be in the name
      mode - - what situation the reference comes from - see the documentation for @FHIRPathConstantEvaluationMode
      Returns:
      the value of the constant , or an empty list, though the host application can choose to throw an exception
      Throws:
      org.hl7.fhir.exceptions.PathEngineException

    • resolveConstantType

      TypeDetails resolveConstantType(FHIRPathEngine engine, Object appContext, String name, org.hl7.fhir.utilities.fhirpath.FHIRPathConstantEvaluationMode mode) throws org.hl7.fhir.exceptions.PathEngineException
      Compile time support for a constant reference - e.g. a reference to a name that must be resolved in context. resolveConstant is invoked under 3 different circumstances, which are reflected in the mode parameter: * an explicit constant of the form %{token}, where the token isn't a known internal constant * every evaluation of any expression to allow the Host Application to decide whether to interpret the expression as a constant even if it is not explicitly a constant * at the start of evaluating an expression if the focus provided by the application when invoking the expression is {} The return value is a TypeDetails - a collection, though most constants are singleton values note that variables created using defineVariable() in the FHIRPath expressions will not be processed by resolveConstant (or resolveConstantType)
      Parameters:
      appContext - - application context passed into the FHIRPath engine when first executed
      name - - name reference to resolve. if mode = EXPLICIT, the % will NOT be in the name
      mode - - what situation the reference comes from - see the documentation for @FHIRPathConstantEvaluationMode
      Returns:
      the type of the constant, or null, though the host application can choose to throw an exception
      Throws:
      org.hl7.fhir.exceptions.PathEngineException

    • log

      boolean log(String argument, List<Base> focus)
      when the .log() function is called
      Parameters:
      argument -
      focus -
      Returns:

    • resolveFunction

      FHIRPathUtilityClasses.FunctionDetails resolveFunction(FHIRPathEngine engine, String functionName)
      Parameters:
      functionName -
      Returns:
      null if the function is not known

    • checkFunction

      TypeDetails checkFunction(FHIRPathEngine engine, Object appContext, String functionName, TypeDetails focus, List<TypeDetails> parameters) throws org.hl7.fhir.exceptions.PathEngineException
      Check the function parameters, and throw an error if they are incorrect, or return the type for the function
      Parameters:
      functionName -
      parameters -
      Returns:
      Throws:
      org.hl7.fhir.exceptions.PathEngineException

    • executeFunction

      List<Base> executeFunction(FHIRPathEngine engine, Object appContext, List<Base> focus, String functionName, List<List<Base>> parameters)
      Parameters:
      appContext -
      functionName -
      parameters -
      Returns:

    • resolveReference

      Base resolveReference(FHIRPathEngine engine, Object appContext, String url, Base refContext) throws org.hl7.fhir.exceptions.FHIRException
      Implementation of resolve() function. Passed a string, return matching resource, if one is known - else null
      Parameters:
      url - the reference (Reference.reference or the value of the canonical
      Returns:
      Throws:
      org.hl7.fhir.exceptions.FHIRException

    • conformsToProfile

      boolean conformsToProfile(FHIRPathEngine engine, Object appContext, Base item, String url) throws org.hl7.fhir.exceptions.FHIRException
      Throws:
      org.hl7.fhir.exceptions.FHIRException

    • resolveValueSet

      ValueSet resolveValueSet(FHIRPathEngine engine, Object appContext, String url)

    • paramIsType

      boolean paramIsType(String name, int index)
      For the moment, there can only be one parameter if it's a type parameter
      Parameters:
      name -
      Returns:
      true if it's a type parameter