Adds `Timestamps.now()`.

PiperOrigin-RevId: 526160914

java/util/src/main/java/com/google/protobuf/util/Timestamps.java

@@ -42,6 +42,7 @@ import com.google.j2objc.annotations.J2ObjCIncompatible;
 import com.google.protobuf.Duration;
 import com.google.protobuf.Timestamp;
 import java.io.Serializable;
+import java.lang.reflect.Method;
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
 import java.util.Comparator;
@@ -49,6 +50,7 @@ import java.util.Date;
 import java.util.GregorianCalendar;
 import java.util.Locale;
 import java.util.TimeZone;
+import javax.annotation.Nullable;
 
 /**
  * Utilities to help create/manipulate {@code protobuf/timestamp.proto}. All operations throw an
@@ -117,8 +119,8 @@ public final class Timestamps {
 
   /**
    * Returns a {@link Comparator} for {@link Timestamp Timestamps} which sorts in increasing
-   * chronological order. Nulls and invalid {@link Timestamp Timestamps} are not allowed (see
-   * {@link #isValid}). The returned comparator is serializable.
+   * chronological order. Nulls and invalid {@link Timestamp Timestamps} are not allowed (see {@link
+   * #isValid}). The returned comparator is serializable.
    */
   public static Comparator<Timestamp> comparator() {
     return TimestampComparator.INSTANCE;
@@ -281,7 +283,8 @@ public final class Timestamps {
     try {
       return normalizedTimestamp(seconds, nanos);
     } catch (IllegalArgumentException e) {
-      ParseException ex = new ParseException(
+      ParseException ex =
+          new ParseException(
               "Failed to parse timestamp " + value + " Timestamp is out of range.", 0);
       ex.initCause(e);
       throw ex;
@@ -307,6 +310,39 @@ public final class Timestamps {
     }
   }
 
+  // the following 3 constants contain references to java.time.Instant methods (if that class is
+  // available at runtime); otherwise, they are null.
+  @Nullable private static final Method INSTANT_NOW = instantMethod("now");
+
+  @Nullable private static final Method INSTANT_GET_EPOCH_SECOND = instantMethod("getEpochSecond");
+
+  @Nullable private static final Method INSTANT_GET_NANO = instantMethod("getNano");
+
+  @Nullable
+  private static Method instantMethod(String methodName) {
+    try {
+      return Class.forName("java.time.Instant").getMethod(methodName);
+    } catch (Exception e) {
+      return null;
+    }
+  }
+
+  /** Create a Timestamp using the best-available system clock. */
+  public static Timestamp now() {
+    if (INSTANT_NOW != null) {
+      try {
+        Object now = INSTANT_NOW.invoke(null);
+        long epochSecond = (long) INSTANT_GET_EPOCH_SECOND.invoke(now);
+        int nanoAdjustment = (int) INSTANT_GET_NANO.invoke(now);
+        return normalizedTimestamp(epochSecond, nanoAdjustment);
+      } catch (Throwable fallThrough) {
+        throw new AssertionError(fallThrough);
+      }
+    }
+    // otherwise, fall back on millisecond precision
+    return fromMillis(System.currentTimeMillis());
+  }
+
   /** Create a Timestamp from the number of seconds elapsed from the epoch. */
   @SuppressWarnings("GoodTime") // this is a legacy conversion API
   public static Timestamp fromSeconds(long seconds) {
@@ -333,7 +369,7 @@ public final class Timestamps {
   }
 
   /**
-   * Create a Timestamp from a java.util.Date. If the java.util.Date is a java.sql.Timestamp,
+   * Create a Timestamp from a {@link Date}. If the {@link Date} is a {@link java.sql.Timestamp},
    * full nanonsecond precision is retained.
    *
    * @throws IllegalArgumentException if the year is before 1 CE or after 9999 CE
@@ -344,7 +380,10 @@ public final class Timestamps {
     if (date instanceof java.sql.Timestamp) {
       java.sql.Timestamp sqlTimestamp = (java.sql.Timestamp) date;
       long time = sqlTimestamp.getTime();
-      long integralSeconds = (time < 0 && time % 1000 != 0) ? time / 1000L - 1 : time / 1000L ; // truncate the fractional seconds
+      long integralSeconds =
+          (time < 0 && time % 1000 != 0)
+              ? time / 1000L - 1
+              : time / 1000L; // truncate the fractional seconds
       return Timestamp.newBuilder()
           .setSeconds(integralSeconds)
           .setNanos(sqlTimestamp.getNanos())

java/util/src/test/java/com/google/protobuf/util/TimestampsTest.java

@@ -73,13 +73,41 @@ public class TimestampsTest {
   private static final Timestamp INVALID_MIN =
       Timestamp.newBuilder().setSeconds(Long.MIN_VALUE).setNanos(Integer.MIN_VALUE).build();
 
+  @Test
+  public void testNow() {
+    Timestamp now = Timestamps.now();
+    long epochSeconds = System.currentTimeMillis() / 1000;
+    assertThat(now.getSeconds()).isAtLeast(epochSeconds - 1);
+    assertThat(now.getSeconds()).isAtMost(epochSeconds + 1);
+  }
+
+  @Test
+  public void testNowWithSubMillisecondPrecision() {
+    try {
+      // throws if we're not on Java9+
+      Class.forName("java.lang.Runtime$Version");
+    } catch (ClassNotFoundException e) {
+      // ignored; we're not on Java 9+
+      return;
+    }
+
+    // grab 100 timestamps, and ensure that at least 1 of them has sub-millisecond precision
+    for (int i = 0; i < 100; i++) {
+      Timestamp now = Timestamps.now();
+      Timestamp nowWithMilliPrecision = Timestamps.fromMillis(Timestamps.toMillis(now));
+      if (!now.equals(nowWithMilliPrecision)) {
+        return;
+      }
+    }
+    assertWithMessage("no timestamp had sub-millisecond precision").fail();
+  }
+
   @Test
   public void testMinMaxAreValid() {
     assertThat(Timestamps.isValid(Timestamps.MAX_VALUE)).isTrue();
     assertThat(Timestamps.isValid(Timestamps.MIN_VALUE)).isTrue();
   }
 
-
   @Test
   public void testIsValid_false() {
     assertThat(Timestamps.isValid(0L, -1)).isFalse();
@@ -615,6 +643,7 @@ public class TimestampsTest {
     } catch (IllegalArgumentException expected) {
     }
   }
+
   @Test
   public void testInvalidMaxMicrosecondsOverflow() {
     try {
@@ -693,7 +722,6 @@ public class TimestampsTest {
     }
   }
 
-
   @Test
   public void testIllegalArgumentExceptionForMaxMilliseconds() {
     try {
@@ -718,7 +746,6 @@ public class TimestampsTest {
     }
   }
 
-
   @Test
   public void testIllegalArgumentExceptionForMinMilliseconds() {
     try {