Validate GsonBuilder.setDateFormat style arguments & extend tests (#…

…2545)

`DateFormat` validates these arguments as well, but it is currently not
documented, see https://bugs.openjdk.org/browse/JDK-8319628.

Also moves the other tests for `setDateFormat(String)` from
DefaultTypeAdaptersTest to GsonBuilderTest.

gson/src/main/java/com/google/gson/GsonBuilder.java

@@ -593,8 +593,10 @@ public GsonBuilder disableHtmlEscaping() {
  * class. See the documentation in {@link java.text.SimpleDateFormat} for more information on
  * valid date and time patterns.
  *
- * @param pattern the pattern that dates will be serialized/deserialized to/from
+ * @param pattern the pattern that dates will be serialized/deserialized to/from; can be {@code
+ * null} to reset the pattern
  * @return a reference to this {@code GsonBuilder} object to fulfill the "Builder" pattern
+ * @throws IllegalArgumentException if the pattern is invalid
  * @since 1.2
  */
  @CanIgnoreReturnValue
@@ -611,6 +613,14 @@ public GsonBuilder setDateFormat(String pattern) {
  return this;
  }
 
+ private static int checkDateFormatStyle(int style) {
+ // Valid DateFormat styles are: 0, 1, 2, 3 (FULL, LONG, MEDIUM, SHORT)
+ if (style < 0 || style > 3) {
+ throw new IllegalArgumentException("Invalid style: " + style);
+ }
+ return style;
+ }
+
  /**
  * Configures Gson to serialize {@code Date} objects according to the style value provided. You
  * can call this method or {@link #setDateFormat(String)} multiple times, but only the last
@@ -623,11 +633,12 @@ public GsonBuilder setDateFormat(String pattern) {
  * @param style the predefined date style that date objects will be serialized/deserialized
  * to/from
  * @return a reference to this {@code GsonBuilder} object to fulfill the "Builder" pattern
+ * @throws IllegalArgumentException if the style is invalid
  * @since 1.2
  */
  @CanIgnoreReturnValue
  public GsonBuilder setDateFormat(int style) {
- this.dateStyle = style;
+ this.dateStyle = checkDateFormatStyle(style);
  this.datePattern = null;
  return this;
  }
@@ -645,12 +656,13 @@ public GsonBuilder setDateFormat(int style) {
  * to/from
  * @param timeStyle the predefined style for the time portion of the date objects
  * @return a reference to this {@code GsonBuilder} object to fulfill the "Builder" pattern
+ * @throws IllegalArgumentException if the style values are invalid
  * @since 1.2
  */
  @CanIgnoreReturnValue
  public GsonBuilder setDateFormat(int dateStyle, int timeStyle) {
- this.dateStyle = dateStyle;
- this.timeStyle = timeStyle;
+ this.dateStyle = checkDateFormatStyle(dateStyle);
+ this.timeStyle = checkDateFormatStyle(timeStyle);
  this.datePattern = null;
  return this;
  }

gson/src/test/java/com/google/gson/GsonBuilderTest.java

@@ -28,6 +28,8 @@
 import java.lang.reflect.Field;
 import java.lang.reflect.Modifier;
 import java.lang.reflect.Type;
+import java.text.DateFormat;
+import java.util.Date;
 import org.junit.Test;
 
 /**
@@ -305,4 +307,88 @@ public void testRegisterTypeHierarchyAdapterJsonElements() {
  // But registering type hierarchy adapter for Object should be allowed
  gsonBuilder.registerTypeHierarchyAdapter(Object.class, NULL_TYPE_ADAPTER);
  }
+
+ @Test
+ public void testSetDateFormatWithInvalidPattern() {
+ GsonBuilder builder = new GsonBuilder();
+ String invalidPattern = "This is an invalid Pattern";
+ IllegalArgumentException e =
+ assertThrows(IllegalArgumentException.class, () -> builder.setDateFormat(invalidPattern));
+ assertThat(e)
+ .hasMessageThat()
+ .isEqualTo("The date pattern '" + invalidPattern + "' is not valid");
+ }
+
+ @Test
+ public void testSetDateFormatWithValidPattern() {
+ GsonBuilder builder = new GsonBuilder();
+ String validPattern = "yyyy-MM-dd";
+ // Should not throw an exception
+ builder.setDateFormat(validPattern);
+ }
+
+ @Test
+ public void testSetDateFormatNullPattern() {
+ GsonBuilder builder = new GsonBuilder();
+ @SuppressWarnings("JavaUtilDate")
+ Date date = new Date(0);
+ String originalFormatted = builder.create().toJson(date);
+
+ String customFormatted = builder.setDateFormat("yyyy-MM-dd").create().toJson(date);
+ assertThat(customFormatted).isNotEqualTo(originalFormatted);
+
+ // `null` should reset the format to the default
+ String resetFormatted = builder.setDateFormat(null).create().toJson(date);
+ assertThat(resetFormatted).isEqualTo(originalFormatted);
+ }
+
+ /**
+ * Tests behavior for an empty date pattern; this behavior is not publicly documented at the
+ * moment.
+ */
+ @Test
+ public void testSetDateFormatEmptyPattern() {
+ GsonBuilder builder = new GsonBuilder();
+ @SuppressWarnings("JavaUtilDate")
+ Date date = new Date(0);
+ String originalFormatted = builder.create().toJson(date);
+
+ String emptyFormatted = builder.setDateFormat(" ").create().toJson(date);
+ // Empty pattern was ignored
+ assertThat(emptyFormatted).isEqualTo(originalFormatted);
+ }
+
+ @Test
+ public void testSetDateFormatValidStyle() {
+ GsonBuilder builder = new GsonBuilder();
+ int[] validStyles = {DateFormat.FULL, DateFormat.LONG, DateFormat.MEDIUM, DateFormat.SHORT};
+
+ for (int style : validStyles) {
+ // Should not throw an exception
+ builder.setDateFormat(style);
+ builder.setDateFormat(style, style);
+ }
+ }
+
+ @Test
+ public void testSetDateFormatInvalidStyle() {
+ GsonBuilder builder = new GsonBuilder();
+
+ IllegalArgumentException e =
+ assertThrows(IllegalArgumentException.class, () -> builder.setDateFormat(-1));
+ assertThat(e).hasMessageThat().isEqualTo("Invalid style: -1");
+
+ e = assertThrows(IllegalArgumentException.class, () -> builder.setDateFormat(4));
+ assertThat(e).hasMessageThat().isEqualTo("Invalid style: 4");
+
+ e =
+ assertThrows(
+ IllegalArgumentException.class, () -> builder.setDateFormat(-1, DateFormat.FULL));
+ assertThat(e).hasMessageThat().isEqualTo("Invalid style: -1");
+
+ e =
+ assertThrows(
+ IllegalArgumentException.class, () -> builder.setDateFormat(DateFormat.FULL, -1));
+ assertThat(e).hasMessageThat().isEqualTo("Invalid style: -1");
+ }
 }

gson/src/test/java/com/google/gson/functional/DefaultTypeAdaptersTest.java

@@ -16,7 +16,6 @@
 package com.google.gson.functional;
 
 import static com.google.common.truth.Truth.assertThat;
-import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.fail;
 
 import com.google.gson.Gson;
@@ -493,6 +492,19 @@ public void testDefaultGregorianCalendarDeserialization() {
  assertThat(cal.get(Calendar.SECOND)).isEqualTo(23);
  }
 
+ @Test
+ public void testDateSerializationWithStyle() {
+ int style = DateFormat.SHORT;
+ Date date = new Date(0);
+ String expectedFormatted = DateFormat.getDateTimeInstance(style, style, Locale.US).format(date);
+
+ Gson gson = new GsonBuilder().setDateFormat(style, style).create();
+ String json = gson.toJson(date);
+ assertThat(json).isEqualTo("\"" + expectedFormatted + "\"");
+ // Verify that custom style is not equal to default style
+ assertThat(json).isNotEqualTo(new Gson().toJson(date));
+ }
+
  @Test
  public void testDateSerializationWithPattern() {
  String pattern = "yyyy-MM-dd";
@@ -738,24 +750,6 @@ public void testStringBufferDeserialization() {
  assertThat(sb.toString()).isEqualTo("abc");
  }
 
- @Test
- public void testSetDateFormatWithInvalidPattern() {
- GsonBuilder builder = new GsonBuilder();
- String invalidPattern = "This is a invalid Pattern";
- assertThrows(
- IllegalArgumentException.class,
- () -> {
- builder.setDateFormat(invalidPattern);
- });
- }
-
- @Test
- public void testSetDateFormatWithValidPattern() {
- GsonBuilder builder = new GsonBuilder();
- String validPattern = "yyyy-MM-dd";
- builder.setDateFormat(validPattern);
- }
-
  private static class MyClassTypeAdapter extends TypeAdapter<Class<?>> {
  @Override
  public void write(JsonWriter out, Class<?> value) throws IOException {