Add additional methods to interact with an ArgumentValue

Author: James Bodkin

spring-graphql/src/main/java/org/springframework/graphql/data/ArgumentValue.java

@@ -18,6 +18,7 @@
 
 
 import java.util.Optional;
+import java.util.function.Consumer;
 
 import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
@@ -69,6 +70,14 @@ public boolean isPresent() {
 		return (this.value != null);
 	}
 
+	/**
+	 * Return {@code true} if the input value was present in the input but the value was {@code null},
+	 * and {@code false} otherwise.
+	 */
+	public boolean isEmpty() {
+		return !this.omitted;
+	}
+
 	/**
 	 * Return {@code true} if the input value was omitted altogether from the
 	 * input, and {@code false} if it was provided, but possibly set to the
@@ -93,6 +102,33 @@ public Optional<T> asOptional() {
 		return Optional.ofNullable(this.value);
 	}
 
+	/**
+	 * If a value is present, performs the given action with the value, otherwise does nothing.
+	 * @param action the action to be performed, if a value is present
+	 * @throws NullPointerException if value is present and the given action is {@code null}
+	 */
+	public void ifPresent(Consumer<? super T> action) {
+		if (this.value != null) {
+			action.accept(value);
+		}
+	}
+
+	/**
+	 * If the value is present, performs the given action with the value, otherwise if the value is empty
+	 * performs the given empty-based action. If the value is omitted, do nothing.
+	 * @param action the action to be performed, if the value is present
+	 * @param emptyAction the empty-based action to be performed, if the value is empty
+	 * @throws NullPointerException if a value is present and the given action is {@code null}, or no value is present
+	 * and the given empty-based action is {@code null}
+	 */
+	public void ifPresentOrEmpty(Consumer<? super T> action, Runnable emptyAction) {
+		if (value != null) {
+			action.accept(value);
+		} else if (!omitted) {
+			emptyAction.run();
+		}
+	}
+
 	@Override
 	public boolean equals(Object other) {
 		// This covers OMITTED constant