BAEL-6716 - Storing UUID as Base64 String in Java

core-java-modules/core-java-uuid/pom.xml

@@ -29,6 +29,16 @@
             <artifactId>tsid-creator</artifactId>
             <version>5.2.3</version>
         </dependency>
+        <dependency>
+            <groupId>commons-codec</groupId>
+            <artifactId>commons-codec</artifactId>
+            <version>1.16.0</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>3.14.0</version>
+        </dependency>
     </dependencies>
 
     <build>

core-java-modules/core-java-uuid/src/test/java/com/baeldung/uuid/DecodeUUIDStringFromBase64Test.java

@@ -0,0 +1,61 @@
+package com.baeldung.uuid;
+
+import static org.apache.commons.codec.binary.Base64.decodeBase64;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.nio.ByteBuffer;
+import java.util.Base64;
+import java.util.UUID;
+
+import org.apache.commons.lang3.Conversion;
+import org.junit.jupiter.api.Test;
+
+public class DecodeUUIDStringFromBase64Test {
+    private final UUID originalUUID = UUID.fromString("cc5f93f7-8cf1-4a51-83c6-e740313a0c6c");
+
+    @Test
+    public void shouldDecodeUUIDUsingByteArrayAndBase64Decoder() {
+        byte[] decodedBytes = Base64.getDecoder()
+          .decode("UUrxjPeTX8xsDDoxQOfGgw");
+        UUID uuid = convertToUUID(decodedBytes);
+        assertEquals(originalUUID, uuid);
+    }
+
+    @Test
+    public void shouldDecodeUUIDUsingByteBufferAndBase64UrlDecoder() {
+        byte[] decodedBytes = Base64.getUrlDecoder()
+          .decode("zF-T94zxSlGDxudAMToMbA");
+        ByteBuffer byteBuffer = ByteBuffer.wrap(decodedBytes);
+        long mostSignificantBits = byteBuffer.getLong();
+        long leastSignificantBits = byteBuffer.getLong();
+        UUID uuid = new UUID(mostSignificantBits, leastSignificantBits);
+        assertEquals(originalUUID, uuid);
+    }
+
+    @Test
+    public void shouldDecodeUUIDUsingApacheUtils() {
+        byte[] decodedBytes = decodeBase64("UUrxjPeTX8xsDDoxQOfGgw");
+        UUID uuid = Conversion.byteArrayToUuid(decodedBytes, 0);
+        assertEquals(originalUUID, uuid);
+    }
+
+    private UUID convertToUUID(byte[] src) {
+        long mostSignificantBits = convertBytesToLong(src, 0);
+        long leastSignificantBits = convertBytesToLong(src, 8);
+
+        return new UUID(mostSignificantBits, leastSignificantBits);
+    }
+
+    private long convertBytesToLong(byte[] uuidBytes, int start) {
+        long result = 0;
+
+        for(int i = 0; i < 8; i++) {
+            int shift = i * 8;
+            long bits = (255L & (long)uuidBytes[i + start]) << shift;
+            long mask = 255L << shift;
+            result = result & ~mask | bits;
+        }
+
+        return result;
+    }
+}

core-java-modules/core-java-uuid/src/test/java/com/baeldung/uuid/EncodeUUIDToBase64StringTest.java

@@ -0,0 +1,59 @@
+package com.baeldung.uuid;
+
+import static org.apache.commons.codec.binary.Base64.encodeBase64URLSafeString;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.nio.ByteBuffer;
+import java.util.Base64;
+import java.util.UUID;
+
+import org.apache.commons.lang3.Conversion;
+import org.junit.jupiter.api.Test;
+
+public class EncodeUUIDToBase64StringTest {
+    private final UUID originalUUID = UUID.fromString("cc5f93f7-8cf1-4a51-83c6-e740313a0c6c");
+
+    @Test
+    public void shouldEncodeUUIDUsingByteArrayAndBase64Encoder() {
+        byte[] uuidBytes = convertToByteArray(originalUUID);
+        String encodedUUID = Base64.getEncoder().withoutPadding()
+          .encodeToString(uuidBytes);
+        assertEquals("UUrxjPeTX8xsDDoxQOfGgw", encodedUUID);
+    }
+
+    @Test
+    public void shouldEncodeUUIDUsingByteBufferAndBase64UrlEncoder() {
+        ByteBuffer byteBuffer = ByteBuffer.wrap(new byte[16]);
+        byteBuffer.putLong(originalUUID.getMostSignificantBits());
+        byteBuffer.putLong(originalUUID.getLeastSignificantBits());
+        String encodedUUID = Base64.getUrlEncoder().withoutPadding()
+          .encodeToString(byteBuffer.array());
+        assertEquals("zF-T94zxSlGDxudAMToMbA", encodedUUID);
+    }
+
+    @Test
+    public void shouldEncodeUUIDUsingApacheUtils() {
+        byte[] bytes = Conversion.uuidToByteArray(originalUUID, new byte[16], 0, 16);
+        String encodedUUID = encodeBase64URLSafeString(bytes);
+        assertEquals("UUrxjPeTX8xsDDoxQOfGgw", encodedUUID);
+    }
+
+    private byte[] convertToByteArray(UUID uuid) {
+        byte[] result = new byte[16];
+
+        long mostSignificantBits = uuid.getMostSignificantBits();
+        fillByteArray(0, 8, result, mostSignificantBits);
+
+        long leastSignificantBits = uuid.getLeastSignificantBits();
+        fillByteArray(8, 16, result, leastSignificantBits);
+
+        return result;
+    }
+
+    private static void fillByteArray(int start, int end, byte[] result, long bits) {
+        for (int i = start; i < end; i++) {
+            int shift = i * 8;
+            result[i] = (byte) ((int) (255L & bits >> shift));
+        }
+    }
+}