[Feature #10] Implement and use custom deserializers for date values.

Simplify literal value presence validation.

src/main/java/cz/cvut/kbss/jsonld/deserialization/CommonValueDeserializers.java

@@ -26,6 +26,8 @@ private void initBuiltInDeserializers() {
         deserializers.put(Date.class, new DateDeserializer(coreDatetimeDeserializer));
         deserializers.put(OffsetTime.class, coreTimeDeserializer);
         deserializers.put(LocalTime.class, new LocalTimeDeserializer(coreTimeDeserializer));
+        deserializers.put(LocalDate.class, new LocalDateDeserializer());
+        // TODO Period, Duration
     }
 
     @Override

src/main/java/cz/cvut/kbss/jsonld/deserialization/datetime/LocalDateDeserializer.java

@@ -0,0 +1,28 @@
+package cz.cvut.kbss.jsonld.deserialization.datetime;
+
+import cz.cvut.kbss.jopa.datatype.xsd.XsdDateMapper;
+import cz.cvut.kbss.jsonld.JsonLd;
+import cz.cvut.kbss.jsonld.deserialization.DeserializationContext;
+import cz.cvut.kbss.jsonld.deserialization.ValueDeserializer;
+
+import java.time.LocalDate;
+import java.util.Map;
+
+import static cz.cvut.kbss.jsonld.deserialization.datetime.OffsetDateTimeDeserializer.missingValueException;
+
+/**
+ * Deserializes values to {@link LocalDate}.
+ * <p>
+ * The values are expected to be String in the ISO date format.
+ */
+public class LocalDateDeserializer implements ValueDeserializer<LocalDate> {
+
+    @Override
+    public LocalDate deserialize(Map<?, ?> jsonNode, DeserializationContext<LocalDate> ctx) {
+        final Object value = jsonNode.get(JsonLd.VALUE);
+        if (value == null) {
+            throw missingValueException(jsonNode);
+        }
+        return XsdDateMapper.map(value.toString());
+    }
+}

src/main/java/cz/cvut/kbss/jsonld/deserialization/datetime/OffsetDateTimeDeserializer.java

@@ -27,12 +27,16 @@ public class OffsetDateTimeDeserializer implements ValueDeserializer<OffsetDateT
     public OffsetDateTime deserialize(Map<?, ?> jsonNode, DeserializationContext<OffsetDateTime> ctx) {
         final Object value = jsonNode.get(JsonLd.VALUE);
         if (value == null) {
-            throw new JsonLdDeserializationException("Cannot deserialize node " + jsonNode + "as date time. " +
-                    "It is missing attribute " + JsonLd.VALUE + ".");
+            throw missingValueException(jsonNode);
         }
         return value instanceof Long ? epochResolver.resolve((Long) value) : stringResolver.resolve(value.toString());
     }
 
+    static JsonLdDeserializationException missingValueException(Map<?, ?> jsonNode) {
+        return new JsonLdDeserializationException("Cannot deserialize node " + jsonNode + "as literal. " +
+                "It is missing attribute " + JsonLd.VALUE + ".");
+    }
+
     @Override
     public void configure(Configuration config) {
         stringResolver.configure(config);

src/main/java/cz/cvut/kbss/jsonld/deserialization/datetime/OffsetTimeDeserializer.java

@@ -4,11 +4,12 @@
 import cz.cvut.kbss.jsonld.JsonLd;
 import cz.cvut.kbss.jsonld.deserialization.DeserializationContext;
 import cz.cvut.kbss.jsonld.deserialization.ValueDeserializer;
-import cz.cvut.kbss.jsonld.exception.JsonLdDeserializationException;
 
 import java.time.OffsetTime;
 import java.util.Map;
 
+import static cz.cvut.kbss.jsonld.deserialization.datetime.OffsetDateTimeDeserializer.missingValueException;
+
 /**
  * Deserializes values to {@link OffsetTime}.
  * <p>
@@ -20,8 +21,7 @@ public class OffsetTimeDeserializer implements ValueDeserializer<OffsetTime> {
     public OffsetTime deserialize(Map<?, ?> jsonNode, DeserializationContext<OffsetTime> ctx) {
         final Object value = jsonNode.get(JsonLd.VALUE);
         if (value == null) {
-            throw new JsonLdDeserializationException("Cannot deserialize node " + jsonNode + "as time. " +
-                    "It is missing attribute " + JsonLd.VALUE + ".");
+            throw missingValueException(jsonNode);
         }
         return XsdTimeMapper.map(value.toString());
     }

src/test/java/cz/cvut/kbss/jsonld/deserialization/datetime/LocalDateDeserializerTest.java

@@ -0,0 +1,40 @@
+package cz.cvut.kbss.jsonld.deserialization.datetime;
+
+import cz.cvut.kbss.jsonld.JsonLd;
+import cz.cvut.kbss.jsonld.exception.JsonLdDeserializationException;
+import org.junit.jupiter.api.Test;
+
+import java.time.LocalDate;
+import java.time.OffsetTime;
+import java.time.format.DateTimeFormatter;
+import java.util.Collections;
+import java.util.Map;
+
+import static cz.cvut.kbss.jsonld.deserialization.datetime.OffsetDateTimeDeserializerTest.deserializationContext;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.containsString;
+import static org.junit.jupiter.api.Assertions.*;
+
+class LocalDateDeserializerTest {
+
+    private final LocalDateDeserializer sut = new LocalDateDeserializer();
+
+    @Test
+    void deserializeDeserializesSpecifiedIsoFormattedDateString() {
+        final LocalDate value = LocalDate.now();
+        final Map<String, Object> input = Collections.singletonMap(JsonLd.VALUE, value.format(DateTimeFormatter.ISO_DATE));
+
+        final LocalDate result = sut.deserialize(input, deserializationContext(LocalDate.class));
+        assertEquals(value, result);
+    }
+
+    @Test
+    void deserializeThrowsJsonLdDeserializationExceptionWhenInputIsMissingValueAttribute() {
+        final Map<String, Object> input = Collections.singletonMap("notValue", LocalDate.now().format(DateTimeFormatter.ISO_DATE));
+
+        final JsonLdDeserializationException ex = assertThrows(JsonLdDeserializationException.class,
+                () -> sut.deserialize(input, deserializationContext(LocalDate.class)));
+        assertThat(ex.getMessage(), containsString(JsonLd.VALUE));
+        assertThat(ex.getMessage(), containsString("missing"));
+    }
+}