refactor: 雪花ID生成器发生时间回退时不拒绝生成ID

hsweb-core/src/main/java/org/hswebframework/web/id/SnowflakeIdGenerator.java

@@ -51,7 +51,7 @@ public class SnowflakeIdGenerator {
         return create(ThreadLocalRandom.current().nextInt(31), ThreadLocalRandom.current().nextInt(31));
     }
 
-    private SnowflakeIdGenerator(long workerId, long dataCenterId) {
+    public SnowflakeIdGenerator(long workerId, long dataCenterId) {
         // sanity check for workerId
         if (workerId > maxWorkerId || workerId < 0) {
             throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
@@ -66,10 +66,11 @@ public class SnowflakeIdGenerator {
 
     public synchronized long nextId() {
         long timestamp = timeGen();
-
+        //时间回退
         if (timestamp < lastTimestamp) {
-            log.error("clock is moving backwards.  Rejecting requests until {}.", lastTimestamp);
-            throw new UnsupportedOperationException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
+            //发生回退时不拒绝,有可能出现重复数据?
+            log.warn("clock is moving backwards {}.", lastTimestamp);
+//            throw new UnsupportedOperationException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
         }
 
         if (lastTimestamp == timestamp) {

hsweb-core/src/test/java/org/hswebframework/web/id/SnowflakeIdGeneratorTest.java

@@ -0,0 +1,35 @@
+package org.hswebframework.web.id;
+
+import org.junit.Test;
+
+import java.util.concurrent.atomic.AtomicLong;
+
+import static org.junit.Assert.*;
+
+public class SnowflakeIdGeneratorTest {
+
+
+    @Test
+    public void test(){
+
+        AtomicLong time = new AtomicLong(System.currentTimeMillis());
+
+
+        SnowflakeIdGenerator generator = new SnowflakeIdGenerator(0,1){
+            @Override
+            protected long timeGen() {
+                return time.get();
+            }
+        };
+
+        System.out.println(generator.nextId());
+        //回退1秒
+        time.addAndGet(-1000);
+        System.out.println(generator.nextId());
+
+        time.addAndGet(2000);
+        System.out.println(generator.nextId());
+
+    }
+
+}