Get a JSON Value as Optional

This enables further filtering and mapping of a JSON Value.

acme4j-client/src/main/java/org/shredzone/acme4j/toolbox/JSON.java

@@ -35,6 +35,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.NoSuchElementException;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.Set;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
@@ -264,6 +265,16 @@ public final class JSON implements Serializable {
             this.val = val;
         }
 
+        /**
+         * Returns this value as {@link Optional}, for further mapping and filtering.
+         *
+         * @return {@link Optional} of this value, or {@link Optional#empty()} if this
+         *         value is {@code null}.
+         */
+        public Optional<Value> optional() {
+            return val != null ? Optional.of(this) : Optional.empty();
+        }
+
         /**
          * Checks if the value is present. An {@link AcmeProtocolException} is thrown if
          * the value is {@code null}.

acme4j-client/src/test/java/org/shredzone/acme4j/toolbox/JSONTest.java

@@ -201,6 +201,8 @@ public class JSONTest {
         assertThat(json.get("status").asStatusOrElse(Status.INVALID), is(Status.VALID));
         assertThat(json.get("binary").asBinary(), is("Chainsaw".getBytes()));
 
+        assertThat(json.get("text").optional().isPresent(), is(true));
+
         JSON.Array array = json.get("array").asArray();
         assertThat(array.get(0).asString(), is("foo"));
         assertThat(array.get(1).asInt(), is(987));
@@ -241,6 +243,8 @@ public class JSONTest {
         assertThat(json.get("none").orElse(42).asInt(), is(42));
         assertThat(json.get("none").orElse(true).asBoolean(), is(true));
 
+        assertThat(json.get("none").optional().isPresent(), is(false));
+
         try {
             json.get("none").asInt();
             fail("asInt did not fail");