Add support for ISO8601 to java.time.Instant serialization/deserialization

elide-core/src/main/java/com/yahoo/elide/utils/coerce/converters/InstantSerde.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2020, Yahoo Inc.
+ * Licensed under the Apache License, Version 2.0
+ * See LICENSE file in project root for terms.
+ */
+package com.yahoo.elide.utils.coerce.converters;
+
+import java.time.Instant;
+import java.time.format.DateTimeFormatter;
+
+/**
+ * Convert an Instant to/from an ISO-8601 string representation.
+ *
+ * Uses the semantics of {@link java.time.format.DateTimeFormatter#ISO_INSTANT}
+ */
+@ElideTypeConverter(type = Instant.class, name = "Instant")
+public class InstantSerde implements Serde<String, Instant> {
+    @Override
+    public Instant deserialize(final String value) {
+        return Instant.from(
+            // NB. ideally we would use ISO_INSTANT here but there is a bug in JDK-8 that
+            // means that parsing an ISO offset time doesn't work :-(
+            // https://bugs.openjdk.java.net/browse/JDK-8166138
+            DateTimeFormatter.ISO_OFFSET_DATE_TIME.parse(value)
+        );
+    }
+
+    @Override
+    public String serialize(final Instant value) {
+        return DateTimeFormatter.ISO_INSTANT.format(value);
+    }
+}

elide-core/src/test/java/com/yahoo/elide/utils/coerce/converters/InstantSerdeTest.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2018, Yahoo Inc.
+ * Licensed under the Apache License, Version 2.0
+ * See LICENSE file in project root for terms.
+ */
+package com.yahoo.elide.utils.coerce.converters;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+import java.time.Instant;
+
+public class InstantSerdeTest {
+    private final Serde<String, Instant> serde = new InstantSerde();
+
+    @Test
+    public void canDeserializeUtcIsoString() {
+        final Instant instant = serde.deserialize("2019-06-01T09:42:55Z");
+
+        assertEquals(1559382175, instant.getEpochSecond());
+        assertEquals(0, instant.getNano());
+    }
+
+    @Test
+    public void canDeserializeOffsetIsoString() {
+        final Instant instant = serde.deserialize("2019-06-01T10:42:55+01:00");
+
+        assertEquals(1559382175, instant.getEpochSecond());
+        assertEquals(0, instant.getNano());
+    }
+
+    @Test
+    public void canDeserializeSubSecondPrecisionUtcIsoString() {
+        final Instant instant = serde.deserialize("2019-06-01T09:42:55.123Z");
+
+        assertEquals(1559382175, instant.getEpochSecond());
+        assertEquals(123000000, instant.getNano());
+    }
+
+    @Test
+    public void canSerialize() {
+        assertEquals(
+            "2019-06-01T09:42:55Z",
+            serde.serialize(Instant.ofEpochSecond(1559382175))
+        );
+    }
+
+    @Test
+    public void canSerializeSubSecondPrecision() {
+        assertEquals(
+            "2019-06-01T09:42:55.123Z",
+            serde.serialize(Instant.ofEpochMilli(1559382175123L))
+        );
+    }
+}