Package org.apache.nifi.util

Class EqualsWrapper<T>

java.lang.Object
org.apache.nifi.util.EqualsWrapper<T>
Type Parameters:
T - The type of object to wrap
public class EqualsWrapper<T> extends Object
Wraps an object to be able to check equality conveniently, even if it doesn't have meaningful equals() implementation or it's not appropriate for a given context. This is achieved by providing a list of transformer functions that usually extract properties of the object (and maybe transform them) and do equality checks on those.

Also provides a convenient toString() which can help identifying differences of expected and actual objects during unit tests.

Here's an example of a typical use-case: 
 
 @Test
 public void testPersonEquals() throws Exception {
     // GIVEN
     Person expected = new Person();
     expected.setName("Joe");
     expected.setStuff(Arrays.asList(1, 2, 3));

     Person actual = new Person();
     actual.setName("Joe");
     actual.setStuff(Arrays.asList(1, 2, 3));

     // WHEN
     List<Function<Person, Object>> equalsProperties = Arrays.asList(
         Person::getName,
         Person::getStuff
     );

     EqualsWrapper expectedWrapper = new EqualsWrapper(expected, equalsProperties);
     EqualsWrapper actualWrapper = new EqualsWrapper(actual, equalsProperties);

     // THEN
     assertEquals(expectedWrapper, actualWrapper);
 }

 private class Person {
     private String name;
     private List<Object> stuff = new ArrayList<>();

     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }

     public List<Object> getStuff() {
         return stuff;
     }
     public void setStuff(List<Object> stuff) {
         this.stuff = stuff;
     }
 }

  • Field Details

    • item

      private final T item

    • propertyProviders

      private final List<Function<T,Object>> propertyProviders

  • Constructor Details

    • EqualsWrapper

      public EqualsWrapper(T item, List<Function<T,Object>> propertyProviders)
      Wraps an object and primes it for equality checks.
      Parameters:
      item - The item to be wrapped
      propertyProviders - List of functions with which to extract properties to use for equality checks

  • Method Details

    • wrapList

      public static <T> List<EqualsWrapper<T>> wrapList(Collection<T> items, List<Function<T,Object>> propertyProviders)
      Wraps multiple objects and primes them for equality checks.
      Type Parameters:
      T - The type of the objects to be wrapped
      Parameters:
      items - The items to be wrapped
      propertyProviders - List of functions with with to extract properties to use for equality checks
      Returns:
      A list of wrapped objects

    • equals

      public boolean equals(Object o)
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • toString

      public String toString()
      Overrides:
      toString in class Object