diff --git a/src/main/java/org/springframework/data/util/Lazy.java b/src/main/java/org/springframework/data/util/Lazy.java
index 4634fa0640..c0be59c8a5 100644
--- a/src/main/java/org/springframework/data/util/Lazy.java
+++ b/src/main/java/org/springframework/data/util/Lazy.java
@@ -25,8 +25,10 @@
/**
* Simple value type to delay the creation of an object using a {@link Supplier} returning the produced object for
- * subsequent lookups. Note, that no concurrency control is applied during the lookup of {@link #get()}, which means in
- * concurrent access scenarios, the provided {@link Supplier} can be called multiple times.
+ * subsequent lookups.
+ *
+ * Note, that no concurrency control is applied during the lookup of {@link #get()}, which means in concurrent access
+ * scenarios, the provided {@link Supplier} can be called multiple times.
*
* @author Oliver Gierke
* @author Mark Paluch
@@ -45,17 +47,12 @@ public class Lazy implements Supplier {
private @Nullable T value;
private volatile boolean resolved;
- /**
- * Creates a new {@link Lazy} instance for the given supplier.
- *
- * @param supplier
- */
private Lazy(Supplier extends T> supplier) {
this(supplier, null, false);
}
/**
- * Creates a new {@link Lazy} for the given {@link Supplier}, value and whether it has been resolved or not.
+ * Creates a new {@code Lazy} for the given {@link Supplier}, value and whether it has been resolved or not.
*
* @param supplier must not be {@literal null}.
* @param value can be {@literal null}.
@@ -69,22 +66,22 @@ private Lazy(Supplier extends T> supplier, @Nullable T value, boolean resolved
}
/**
- * Creates a new {@link Lazy} to produce an object lazily.
+ * Creates a new {@code Lazy} to produce an object lazily.
*
* @param the type of which to produce an object of eventually.
* @param supplier the {@link Supplier} to create the object lazily.
- * @return
+ * @return a {@code Lazy} wrapping the given {@link Supplier}.
*/
public static Lazy of(Supplier extends T> supplier) {
return new Lazy<>(supplier);
}
/**
- * Creates a new {@link Lazy} to return the given value.
+ * Creates a new {@code Lazy} to return the given value.
*
* @param the type of the value to return eventually.
* @param value the value to return.
- * @return
+ * @return a {@code Lazy} wrapping {@code value}.
*/
public static Lazy of(T value) {
@@ -94,9 +91,9 @@ public static Lazy of(T value) {
}
/**
- * Creates a pre-resolved empty {@link Lazy}.
+ * Creates a pre-resolved empty {@code Lazy}.
*
- * @return
+ * @return an empty {@code Lazy}.
* @since 2.1
*/
@SuppressWarnings("unchecked")
@@ -105,11 +102,12 @@ public static Lazy empty() {
}
/**
- * Returns the value created by the configured {@link Supplier}. Will return the calculated instance for subsequent
- * lookups.
+ * Returns the value created by the configured {@link Supplier}. Will return the same instance for subsequent lookups.
*
- * @return
+ * @return the value created by the configured {@link Supplier}. Will return the same instance for subsequent lookups.
+ * @throws IllegalStateException if the resolved value is {@literal null}.
*/
+ @Override
public T get() {
T value = getNullable();
@@ -121,63 +119,84 @@ public T get() {
return value;
}
+ /**
+ * Returns the value of the lazy evaluation.
+ *
+ * @return the value of the lazy evaluation, can be {@literal null}.
+ * @since 2.2
+ */
+ @Nullable
+ public T getNullable() {
+
+ if (resolved) {
+ return value;
+ }
+
+ this.value = supplier.get();
+ this.resolved = true;
+
+ return value;
+ }
+
/**
* Returns the {@link Optional} value created by the configured {@link Supplier}, allowing the absence of values in
* contrast to {@link #get()}. Will return the calculated instance for subsequent lookups.
*
- * @return
+ * @return an {@link Optional} value created by the configured {@link Supplier} or an empty {@link Optional} if the
+ * resolved value is {@literal null}.
*/
public Optional getOptional() {
return Optional.ofNullable(getNullable());
}
/**
- * Returns a new Lazy that will consume the given supplier in case the current one does not yield in a result.
+ * Returns a new {@code Lazy} that will return the given value in case the current one does not yield in a result.
*
- * @param supplier must not be {@literal null}.
- * @return
+ * @param other must not be {@literal null}.
+ * @return a new {@code Lazy} that will yield its value if present, otherwise {@code other}.
*/
- public Lazy or(Supplier extends T> supplier) {
+ public Lazy or(T other) {
- Assert.notNull(supplier, "Supplier must not be null");
+ Assert.notNull(other, "Other value must not be null");
- return Lazy.of(() -> orElseGet(supplier));
+ return Lazy.of(() -> orElse(other));
}
/**
- * Returns a new Lazy that will return the given value in case the current one does not yield in a result.
+ * Returns a new {@code Lazy} that will consume the given supplier in case the current one does not yield in a result.
*
- * @param value must not be {@literal null}.
- * @return
+ * @param supplier the supplying function that produces a value to be returned, must not be {@literal null}.
+ * @return a new {@code Lazy} that will yield its value if present, otherwise the result produced by the supplying
+ * function.
*/
- public Lazy or(T value) {
+ public Lazy or(Supplier extends T> supplier) {
- Assert.notNull(value, "Value must not be null");
+ Assert.notNull(supplier, "Supplier must not be null");
- return Lazy.of(() -> orElse(value));
+ return Lazy.of(() -> orElseGet(supplier));
}
/**
* Returns the value of the lazy computation or the given default value in case the computation yields
* {@literal null}.
*
- * @param value
- * @return
+ * @param other the value to be returned, if no value is present. May be {@literal null}.
+ * @return the value, if present, otherwise {@code other}.
*/
@Nullable
- public T orElse(@Nullable T value) {
+ public T orElse(@Nullable T other) {
T nullable = getNullable();
- return nullable == null ? value : nullable;
+ return nullable == null ? other : nullable;
}
/**
* Returns the value of the lazy computation or the value produced by the given {@link Supplier} in case the original
* value is {@literal null}.
*
- * @param supplier must not be {@literal null}.
- * @return
+ * @param supplier the supplying function that produces a value to be returned, must not be {@literal null}.
+ * @return the value, if present, otherwise the result produced by the supplying function.
*/
@Nullable
public T orElseGet(Supplier extends T> supplier) {
@@ -190,10 +209,11 @@ public T orElseGet(Supplier extends T> supplier) {
}
/**
- * Creates a new {@link Lazy} with the given {@link Function} lazily applied to the current one.
+ * Creates a new {@code Lazy} with the given {@link Function} lazily applied to the current one.
*
* @param function must not be {@literal null}.
- * @return
+ * @return an {@code Lazy} describing the result of applying a mapping function to the value of this {@code Lazy} or
+ * throwing {@link IllegalStateException} if the {@code Lazy} is empty.
*/
public Lazy map(Function super T, ? extends S> function) {
@@ -203,10 +223,11 @@ public Lazy map(Function super T, ? extends S> function) {
}
/**
- * Creates a new {@link Lazy} with the given {@link Function} lazily applied to the current one.
+ * Creates a new {@code Lazy} with the given {@link Function} lazily applied to the current one.
*
* @param function must not be {@literal null}.
- * @return
+ * @return the result of applying an {@code Lazy}-bearing mapping function to the value of this {@code Lazy} or a
+ * {@code Lazy} throwing {@link IllegalStateException} if the {@code Lazy} is empty.
*/
public Lazy flatMap(Function super T, Lazy extends S>> function) {
@@ -215,50 +236,6 @@ public Lazy flatMap(Function super T, Lazy extends S>> function) {
return Lazy.of(() -> function.apply(get()).get());
}
- /**
- * Returns the {@link String} representation of the already resolved value or the one provided through the given
- * {@link Supplier} if the value has not been resolved yet.
- *
- * @param fallback must not be {@literal null}.
- * @return will never be {@literal null}.
- * @since 3.0.1
- */
- public String toString(Supplier fallback) {
-
- Assert.notNull(fallback, "Fallback must not be null!");
-
- return resolved ? toString() : fallback.get();
- }
-
- /**
- * Returns the value of the lazy evaluation.
- *
- * @return
- * @since 2.2
- */
- @Nullable
- public T getNullable() {
-
- if (resolved) {
- return value;
- }
-
- this.value = supplier.get();
- this.resolved = true;
-
- return value;
- }
-
- @Override
- public String toString() {
-
- if (!resolved) {
- return UNRESOLVED;
- }
-
- return value == null ? "null" : value.toString();
- }
-
@Override
public boolean equals(@Nullable Object o) {
@@ -291,4 +268,29 @@ public int hashCode() {
return result;
}
+
+ @Override
+ public String toString() {
+
+ if (!resolved) {
+ return UNRESOLVED;
+ }
+
+ return value == null ? "null" : value.toString();
+ }
+
+ /**
+ * Returns the {@link String} representation of the already resolved value or the one provided through the given
+ * {@link Supplier} if the value has not been resolved yet.
+ *
+ * @param fallback must not be {@literal null}.
+ * @return will never be {@literal null}.
+ * @since 3.0.1
+ */
+ public String toString(Supplier fallback) {
+
+ Assert.notNull(fallback, "Fallback must not be null!");
+
+ return resolved ? toString() : fallback.get();
+ }
}
diff --git a/src/test/java/org/springframework/data/util/LazyUnitTests.java b/src/test/java/org/springframework/data/util/LazyUnitTests.java
index 37c10c5283..b40344d503 100755
--- a/src/test/java/org/springframework/data/util/LazyUnitTests.java
+++ b/src/test/java/org/springframework/data/util/LazyUnitTests.java
@@ -70,7 +70,7 @@ void returnsLastValueInChain() {
@Test
void returnsCachedInstanceOnMultipleAccesses() {
- var lazy = Lazy.of(() -> new Object());
+ var lazy = Lazy.of(Object::new);
assertThat(lazy.get()).isSameAs(lazy.get());
}
@@ -113,6 +113,7 @@ void returnsElseValue() {
var empty = Lazy.of(() -> null);
assertThat(empty.orElse(reference)).isEqualTo(reference);
+ assertThat(empty.orElseGet(() -> reference)).isEqualTo(reference);
assertThat(empty.or(reference).get()).isEqualTo(reference);
assertThat(empty.or(() -> reference).get()).isEqualTo(reference);
}