Fix #78: allow configuring UUIDClock to use for epoch-based UUID generation (#80)

Author: cowtowncoder

pom.xml

@@ -15,7 +15,7 @@
     -->
   <packaging>bundle</packaging>
   <name>Java UUID Generator</name>
-  <version>4.2.1-SNAPSHOT</version>
+  <version>4.3.0-SNAPSHOT</version>
   <description>
 Java UUID Generator (JUG) is a Java library for generating
 Universally Unique IDentifiers, UUIDs (see http://en.wikipedia.org/wiki/UUID).

release-notes/VERSION

@@ -4,6 +4,11 @@ Project: java-uuid-generator
 Releases
 ============================================================================
 
+4.3.0 (23-Aug-2023)
+
+#78: TimeBasedEpochGenerator (UUIDv7) can't be provided a `UUIDClock`
+ (reported by @Frozenlock)
+
 4.2.0 (14-May-2023)
 
 #73: Add `Generators.defaultTimeBasedGenerator()` to use "default" interface

src/main/java/com/fasterxml/uuid/Generators.java

@@ -141,7 +141,23 @@ public static TimeBasedEpochGenerator timeBasedEpochGenerator(Random random)
     {
         return new TimeBasedEpochGenerator(random);
     }
-    
+
+    /**
+     * Factory method for constructing UUID generator that generates UUID using
+     * version 7 (time+random based), using specified Ethernet address
+     * as the location part of UUID.
+     * Timestamp to use is access using specified {@link UUIDClock}
+     *
+     * No additional external synchronization is used.
+     *
+     * @since 4.3
+     */
+    public static TimeBasedEpochGenerator timeBasedEpochGenerator(Random random,
+            UUIDClock clock)
+    {
+        return new TimeBasedEpochGenerator(random, clock);
+    }
+
     // // Time+location-based generation
 
     /**

src/main/java/com/fasterxml/uuid/UUIDClock.java

@@ -26,6 +26,15 @@
  */
 public class UUIDClock
 {
+    private final static UUIDClock DEFAULT = new UUIDClock();
+
+    /**
+     * @since 4.3
+     */
+    public final static UUIDClock systemTimeClock() {
+        return DEFAULT;
+    }
+
     /**
      * Returns the current time in milliseconds.
      */

src/main/java/com/fasterxml/uuid/UUIDTimer.java

@@ -169,7 +169,7 @@ public class UUIDTimer
 
     public UUIDTimer(Random rnd, TimestampSynchronizer sync) throws IOException
     {
-        this(rnd, sync, new UUIDClock());
+        this(rnd, sync, UUIDClock.systemTimeClock());
     }
 
     /**

src/main/java/com/fasterxml/uuid/impl/TimeBasedEpochGenerator.java

@@ -7,6 +7,7 @@
 import java.util.concurrent.locks.ReentrantLock;
 
 import com.fasterxml.uuid.NoArgGenerator;
+import com.fasterxml.uuid.UUIDClock;
 import com.fasterxml.uuid.UUIDType;
 
 /**
@@ -37,6 +38,15 @@ public class TimeBasedEpochGenerator extends NoArgGenerator
      * Random number generator that this generator uses.
      */
     protected final Random _random;
+
+    /**
+     * Underlying {@link UUIDClock} used for accessing current time, to use for
+     * generation.
+     *
+     * @since 4.3
+     */
+    protected final UUIDClock _clock;
+
     private long _lastTimestamp = -1;
     private final byte[] _lastEntropy  = new byte[ENTROPY_BYTE_LENGTH];
     private final Lock lock = new ReentrantLock();
@@ -53,13 +63,24 @@ public class TimeBasedEpochGenerator extends NoArgGenerator
      *   use a <b>good</b> (pseudo) random number generator; for example, JDK's
      *   {@link SecureRandom}.
      */
-    
-    public TimeBasedEpochGenerator(Random rnd)
+    public TimeBasedEpochGenerator(Random rnd) {
+        this(rnd, UUIDClock.systemTimeClock());
+    }
+
+    /**
+     * @param rnd Random number generator to use for generating UUIDs; if null,
+     *   shared default generator is used. Note that it is strongly recommend to
+     *   use a <b>good</b> (pseudo) random number generator; for example, JDK's
+     *   {@link SecureRandom}.
+     * @param clock clock Object used for accessing current time to use for generation
+     */
+    public TimeBasedEpochGenerator(Random rnd, UUIDClock clock)
     {
         if (rnd == null) {
             rnd = LazyRandom.sharedSecureRandom(); 
         }
         _random = rnd;
+        _clock = clock;
     }
 
     /*
@@ -82,7 +103,7 @@ public UUID generate()
     {
         lock.lock();
         try { 
-            long rawTimestamp = System.currentTimeMillis();
+            long rawTimestamp = _clock.currentTimeMillis();
             if (rawTimestamp == _lastTimestamp) {
                 boolean c = true;
                 for (int i = ENTROPY_BYTE_LENGTH - 1; i >= 0; i--) {

src/test/java/com/fasterxml/uuid/UUIDGeneratorTest.java

@@ -17,6 +17,8 @@
 
 package com.fasterxml.uuid;
 
+import static org.junit.Assert.assertNotEquals;
+
 import java.nio.ByteBuffer;
 import java.security.MessageDigest;
 import java.util.*;
@@ -26,7 +28,6 @@
 import junit.framework.TestSuite;
 import junit.textui.TestRunner;
 
-
 import com.fasterxml.uuid.impl.UUIDUtil;
 import com.fasterxml.uuid.impl.NameBasedGenerator;
 import com.fasterxml.uuid.impl.RandomBasedGenerator;
@@ -38,6 +39,7 @@
  * JUnit Test class for the com.fasterxml.uuid.UUIDGenerator class.
  *
  * @author Eric Bie
+ * @author Tatu Saloranta
  */
 public class UUIDGeneratorTest extends TestCase
 {
@@ -254,7 +256,7 @@ public void testGenerateTimeBasedEpochUUID() throws Exception
     {
         // this test will attempt to check for reasonable behavior of the
         // generateTimeBasedUUID method
-        
+
         Random entropy = new Random(0x666);
 
         // we need a instance to use
@@ -296,6 +298,38 @@ public void testGenerateTimeBasedEpochUUID() throws Exception
         // check that all uuids have timestamps between the start and end time
         checkUUIDArrayForCorrectCreationTimeEpoch(uuid_array, start_time, end_time);
     }
+
+    // [#70]: allow use of custom UUIDClock
+    public void testGenerateTimeBasedEpochUUIDWithFixedClock() throws Exception
+    {
+        final UUIDClock fixedClock = new UUIDClock() {
+            @Override
+            public long currentTimeMillis() {
+                return 123L;
+            }
+        };
+        // we need a instance to use
+        TimeBasedEpochGenerator gen = Generators.timeBasedEpochGenerator(new Random(123),
+                fixedClock);
+
+        UUID uuid1 = gen.generate();
+        UUID uuid2 = gen.generate();
+        UUID uuid3 = gen.generate();
+
+        // Alas! Was thinking of comparing fixed value, but even Epoch-based generator
+        // forces uniqueness by default. So instead will only test that generation
+        // works and produces unique instances
+
+        // First: should be unique (diff contents)
+        assertNotEquals(uuid1, uuid2);
+        assertNotEquals(uuid2, uuid3);
+        assertNotEquals(uuid3, uuid1);
+
+        // Second: should not be same instances either:
+        assertNotSame(uuid1, uuid2);
+        assertNotSame(uuid2, uuid3);
+        assertNotSame(uuid3, uuid1);
+    }
 
     /**
      * Test of generateNameBasedUUID(UUID, String)