Yearmonth support

src/main/java/com/fatboyindustrial/gsonjavatime/Converters.java

@@ -27,15 +27,7 @@
 import com.google.gson.reflect.TypeToken;
 
 import java.lang.reflect.Type;
-import java.time.Duration;
-import java.time.Instant;
-import java.time.LocalDate;
-import java.time.LocalDateTime;
-import java.time.LocalTime;
-import java.time.OffsetDateTime;
-import java.time.OffsetTime;
-import java.time.ZoneId;
-import java.time.ZonedDateTime;
+import java.time.*;
 
 /**
  * The {@code Converters} class contains static methods for registering Java Time converters.
@@ -52,6 +44,9 @@ public class Converters
   /** The specific genericized type for {@code LocalTime}. */
   public static final Type LOCAL_TIME_TYPE = new TypeToken<LocalTime>(){}.getType();
 
+  /** The specific genericized type for {@code YearMonth}. */
+  private static final Type YEAR_MONTH_TYPE = TypeToken.get(YearMonth.class).getType();
+
   /** The specific genericized type for {@code OffsetDateTime}. */
   public static final Type OFFSET_DATE_TIME_TYPE = new TypeToken<OffsetDateTime>(){}.getType();
 
@@ -82,6 +77,7 @@ public static GsonBuilder registerAll(GsonBuilder builder)
     registerLocalDate(builder);
     registerLocalDateTime(builder);
     registerLocalTime(builder);
+    registerYearMonth(builder);
     registerOffsetDateTime(builder);
     registerOffsetTime(builder);
     registerZonedDateTime(builder);
@@ -116,6 +112,18 @@ public static GsonBuilder registerLocalDateTime(GsonBuilder builder)
     return builder;
   }
 
+  /**
+   * Registers the {@link YearMonthConverter} converter.
+   * @param builder The GSON builder to register the converter with.
+   * @return A reference to {@code builder}.
+   */
+  public static GsonBuilder registerYearMonth(GsonBuilder builder)
+  {
+    builder.registerTypeAdapter(YEAR_MONTH_TYPE, new YearMonthConverter());
+
+    return builder;
+  }
+
   /**
    * Registers the {@link LocalTimeConverter} converter.
    * @param builder The GSON builder to register the converter with.

src/main/java/com/fatboyindustrial/gsonjavatime/YearMonthConverter.java

@@ -0,0 +1,59 @@
+package com.fatboyindustrial.gsonjavatime;
+
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonParseException;
+import com.google.gson.JsonPrimitive;
+import com.google.gson.JsonSerializationContext;
+import com.google.gson.JsonSerializer;
+
+
+import java.lang.reflect.Type;
+import java.time.YearMonth;
+
+/**
+ * GSON serialiser/deserialiser for converting {@link YearMonth} objects.
+ */
+public class YearMonthConverter implements JsonSerializer<YearMonth>, JsonDeserializer<YearMonth> {
+
+    /**
+     * Gson invokes this call-back method during serialization when it encounters a field of the
+     * specified type. <p>
+     *
+     * In the implementation of this call-back method, you should consider invoking
+     * {@link JsonSerializationContext#serialize(Object, Type)} method to create JsonElements for any
+     * non-trivial field of the {@code src} object. However, you should never invoke it on the
+     * {@code src} object itself since that will cause an infinite loop (Gson will call your
+     * call-back method again).
+     *
+     * @param src the object that needs to be converted to Json.
+     * @param typeOfSrc the actual type (fully genericized version) of the source object.
+     * @return a JsonElement corresponding to the specified object.
+     */
+    @Override
+    public JsonElement serialize(YearMonth src, Type typeOfSrc, JsonSerializationContext jsonSerializationContext) {
+        return new JsonPrimitive(src.toString());
+    }
+
+    /**
+     * Gson invokes this call-back method during deserialization when it encounters a field of the
+     * specified type. <p>
+     *
+     * In the implementation of this call-back method, you should consider invoking
+     * {@link JsonDeserializationContext#deserialize(JsonElement, Type)} method to create objects
+     * for any non-trivial field of the returned object. However, you should never invoke it on the
+     * same type passing {@code json} since that will cause an infinite loop (Gson will call your
+     * call-back method again).
+     *
+     * @param json The Json data being deserialized
+     * @param typeOfT The type of the Object to deserialize to
+     * @return a deserialized object of the specified type typeOfT which is a subclass of {@code T}
+     * @throws JsonParseException if json is not in the expected format of {@code typeOfT}
+     */
+    @Override
+    public YearMonth deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext jsonDeserializationContext)
+            throws JsonParseException {
+        return YearMonth.parse(json.getAsString());
+    }
+}

src/test/java/com/fatboyindustrial/gsonjavatime/ConvertersTest.java

@@ -29,15 +29,7 @@
 import com.google.gson.JsonPrimitive;
 import org.junit.Test;
 
-import java.time.Instant;
-import java.time.LocalDate;
-import java.time.LocalDateTime;
-import java.time.LocalTime;
-import java.time.OffsetDateTime;
-import java.time.OffsetTime;
-import java.time.ZoneId;
-import java.time.ZoneOffset;
-import java.time.ZonedDateTime;
+import java.time.*;
 
 import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.assertThat;
@@ -59,6 +51,7 @@ public void testSerialisation() throws Exception
     container.ld = LocalDate.of(1969, 7, 21);
     container.lt = LocalTime.of(12, 56, 0);
     container.ldt = LocalDateTime.of(container.ld, container.lt);
+    container.ym = YearMonth.of(2020, 11);
     container.odt = OffsetDateTime.of(container.ld, container.lt, ZoneOffset.ofHours(10));
     container.ot = OffsetTime.of(container.lt, ZoneOffset.ofHours(10));
     container.zdt = ZonedDateTime.of(container.ld, container.lt, ZoneId.of("Australia/Brisbane"));
@@ -71,6 +64,7 @@ public void testSerialisation() throws Exception
     assertThat(json.get("ld").getAsString(), is("1969-07-21"));
     assertThat(json.get("lt").getAsString(), is("12:56:00"));
     assertThat(json.get("ldt").getAsString(), is("1969-07-21T12:56:00"));
+    assertThat(json.get("ym").getAsString(), is("2020-11"));
     assertThat(json.get("odt").getAsString(), is("1969-07-21T12:56:00+10:00"));
     assertThat(json.get("ot").getAsString(), is("12:56:00+10:00"));
     assertThat(json.get("zdt").getAsString(), is("1969-07-21T12:56:00+10:00[Australia/Brisbane]"));
@@ -90,6 +84,7 @@ public void testDeserialisation() throws Exception
     container.ld = LocalDate.of(1969, 7, 21);
     container.lt = LocalTime.of(12, 56, 0);
     container.ldt = LocalDateTime.of(container.ld, container.lt);
+    container.ym = YearMonth.of(2020, 11);
     container.odt = OffsetDateTime.of(container.ld, container.lt, ZoneOffset.ofHours(10));
     container.ot = OffsetTime.of(container.lt, ZoneOffset.ofHours(10));
     container.zdt = ZonedDateTime.of(container.ld, container.lt, ZoneId.of("Australia/Brisbane"));
@@ -100,6 +95,7 @@ public void testDeserialisation() throws Exception
     serialized.add("ld", new JsonPrimitive("1969-07-21"));
     serialized.add("lt", new JsonPrimitive("12:56:00"));
     serialized.add("ldt", new JsonPrimitive("1969-07-21T12:56:00"));
+    serialized.add("ym", new JsonPrimitive("2020-11"));
     serialized.add("odt", new JsonPrimitive("1969-07-21T12:56:00+10:00"));
     serialized.add("ot", new JsonPrimitive("12:56:00+10:00"));
     serialized.add("zdt", new JsonPrimitive("1969-07-21T12:56:00+10:00[Australia/Brisbane]"));
@@ -112,6 +108,7 @@ public void testDeserialisation() throws Exception
     assertThat(deserialised.ld, is(container.ld));
     assertThat(deserialised.ldt, is(container.ldt));
     assertThat(deserialised.lt, is(container.lt));
+    assertThat(deserialised.ym, is(container.ym));
     assertThat(deserialised.odt, is(container.odt));
     assertThat(deserialised.ot, is(container.ot));
     assertThat(deserialised.zdt, is(container.zdt));
@@ -127,6 +124,7 @@ private static class Container
     private LocalDate ld;
     private LocalDateTime ldt;
     private LocalTime lt;
+    private YearMonth ym;
     private OffsetDateTime odt;
     private OffsetTime ot;
     private ZonedDateTime zdt;

src/test/java/com/fatboyindustrial/gsonjavatime/YearMonthConverterTest.java

@@ -0,0 +1,55 @@
+package com.fatboyindustrial.gsonjavatime;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.reflect.TypeToken;
+import org.junit.Test;
+
+import java.lang.reflect.Type;
+import java.time.YearMonth;
+
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+
+public class YearMonthConverterTest {
+
+    /** The specific genericized type for {@code YearMonth}. */
+    private static final Type YEAR_MONTH_TYPE = TypeToken.get(YearMonth.class).getType();
+
+    /**
+     * Tests that serialising to JSON works.
+     */
+    @Test
+    public void testSerialisation(){
+        final Gson gson = registerYearMonth(new GsonBuilder()).create();
+
+        final YearMonth yearMonth = YearMonth.of(2020, 11);
+        final String json = gson.toJson(yearMonth, YearMonth.class);
+
+        assertThat(json, is("\"2020-11\""));
+    }
+
+    /**
+     * Tests that deserialising from JSON works.
+     */
+    @Test
+    public void testDeserialisation(){
+        final Gson gson = registerYearMonth(new GsonBuilder()).create();
+
+        final String json = "\"2020-11\"";
+        final YearMonth yearMonth = gson.fromJson(json, YearMonth.class);
+
+        assertThat(yearMonth, is(YearMonth.of(2020, 11)));
+    }
+
+    /**
+     * Registers the {@link YearMonthConverter} converter.
+     * @param builder The GSON builder to register the converter with.
+     * @return A reference to {@code builder}.
+     */
+    private static GsonBuilder registerYearMonth(GsonBuilder builder){
+        builder.registerTypeAdapter(YEAR_MONTH_TYPE, new YearMonthConverter());
+
+        return builder;
+    }
+}