Package org.frankframework.functional

Class FunctionalUtil

java.lang.Object
org.frankframework.functional.FunctionalUtil
public class FunctionalUtil extends Object
Static utility class with helper functions for functional programming and using lambdas.

  • Method Summary

    Modifier and Type
    Method
    Description
    static <T, R> Function<T,R>
    function(Function<T,R> f)
    Helper function to cast parameter as Function when the compiler cannot work it out by itself.
    static <T> org.apache.logging.log4j.util.Supplier<T>
    logMethod(Supplier<T> method)
    Helper function to create a Log4J Supplier to be able to use a method as supplier in a row of mixed arguments.
    static <T> org.apache.logging.log4j.util.Supplier<T>
    logValue(T value)
    Helper function to create a Log4J Supplier to supply a single constant argument value.
    static <T> Supplier<T>
    supplier(Supplier<T> s)
    Helper function to cast parameter as a Supplier when the compiler cannot work it out by itself.
    static <T> Supplier<T>
    supply(T value)
    Helper function to create a Supplier to supply the single constant argument value.

    Methods inherited from class java.lang.Object

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

  • Method Details

    • supply

      public static <T> Supplier<T> supply(T value)
      Helper function to create a Supplier to supply the single constant argument value.

      This function is useful to disambiguate method-overloads when an array of mixed arguments should be passed all as type Supplier to a function that takes a number of Object parameters, such as Log4J log methods (in particular the methods where an exception is passed as last argument). For example: 

      
         log.error("{} Error with message id [{}]", supplier(this::getLogPrefix), supply(messageId), e);

      Type Parameters:
      T - Type of the value to be supplied.
      Parameters:
      value - Value to be supplied. NB: This should be a constant, otherwise its value is instantly computed instead of being delayed on-demand!
      Returns:
      Supplier that will return the value parameter.

    • logValue

      public static <T> org.apache.logging.log4j.util.Supplier<T> logValue(T value)
      Helper function to create a Log4J Supplier to supply a single constant argument value.

      This function is useful when you need to pass a variable as constant which is not effectively final, or to disambiguate method-overloads when an array of mixed arguments should be passed all as type Supplier to a logger method (in particular the methods where an exception is passed as last argument). For example: 

      
         String messageId = null;
         if (true) messageId = "msg id";
         log.error("{} Error with message id [{}]", supplier(this::getLogPrefix), logValue(messageId), e);

      Type Parameters:
      T - Type of the value to be supplied.
      Parameters:
      value - Value to be supplied. NB: This should be a constant, otherwise its value is instantly computed instead of being delayed on-demand!
      Returns:
      Supplier that will return the value parameter.

    • logMethod

      public static <T> org.apache.logging.log4j.util.Supplier<T> logMethod(Supplier<T> method)
      Helper function to create a Log4J Supplier to be able to use a method as supplier in a row of mixed arguments.

      This function is useful when you need to pass a variable as constant which is not effectively final, or to disambiguate method-overloads when an array of mixed arguments should be passed all as type Supplier to a logger method (in particular the methods where an exception is passed as last argument). For example: 

      
         log.error("Error with message id [{}]", logMethod(this::getLogPrefix), logValue(v), e);

      Type Parameters:
      T - Type of the value of the method argument.
      Parameters:
      method - Single-argument Method to be invoked.
      Returns:
      Supplier that will return the method parameter.

    • supplier

      public static <T> Supplier<T> supplier(Supplier<T> s)
      Helper function to cast parameter as a Supplier when the compiler cannot work it out by itself.

      This function is useful to disambiguate method-overloads when an array of mixed arguments should be passed all as type Supplier to a function that takes a number of Object parameters, such as Log4J log methods (in particular the methods where an exception is passed as last argument).

      For example: 

      
         log.error("{} Error with message id [{}]", supplier(this::getLogPrefix), e);
      This can also be useful when for instance a no-arguments function should be passed to a JUnit arguments supplier for a parameterized unit test: 
      
 	    public static Stream<Arguments> transactionManagers() {
 		    return Stream.of(
 			    Arguments.of(supplier(ReceiverTest::buildNarayanaTransactionManager))
 		    );
      }

      Type Parameters:
      T - Return type of the Supplier function.
      Parameters:
      s - Supplier lambda or function reference.
      Returns:
      The same Supplier but now type verified by the compiler.

    • function

      public static <T, R> Function<T,R> function(Function<T,R> f)
      Helper function to cast parameter as Function when the compiler cannot work it out by itself.

      This function is useful when a single-argument function needs to be passed to a method where the compiler cannot determine correct argument types due to method overloads of methods that take generic object parameters, such as JUnit Arguments.of().

      For Example:

      
  public static Stream<Arguments> transactionManagers() {
 		return Stream.of(
 			Arguments.of(function(ReceiverTest::buildNarayanaTransactionManager))
 		);
  }
      Type Parameters:
      T - Type of the argument to the function parameter.
      R - Return type of the function parameter.
      Parameters:
      f - Lambda or function reference that takes a single parameter and returns a value.
      Returns:
      Same lambda or function reference but now type verified by the compiler.