add FlexIDKeyGenerator

mybatis-flex-core/src/main/java/com/mybatisflex/core/keygen/KeyGeneratorFactory.java

@@ -15,6 +15,7 @@
  */
 package com.mybatisflex.core.keygen;
 
+import com.mybatisflex.core.keygen.impl.FlexIDKeyGenerator;
 import com.mybatisflex.core.keygen.impl.UUIDKeyGenerator;
 
 import java.util.HashMap;
@@ -28,6 +29,7 @@ public class KeyGeneratorFactory {
          * {@link com.mybatisflex.annotation.Id}
          */
         register("uuid", new UUIDKeyGenerator());
+        register("flex", new FlexIDKeyGenerator());
     }
 
 

mybatis-flex-core/src/main/java/com/mybatisflex/core/keygen/impl/FlexIDKeyGenerator.java

@@ -0,0 +1,97 @@
+/**
+ * Copyright (c) 2022-2023, Mybatis-Flex (fuhai999@gmail.com).
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.mybatisflex.core.keygen.impl;
+
+import com.mybatisflex.core.keygen.IKeyGenerator;
+
+import java.util.concurrent.ThreadLocalRandom;
+
+/**
+ * 独创的 FlexID 算法（简单、好用）:
+ * <p>
+ * 特点：
+ * 1、保证 id 生成的顺序为时间顺序，越往后生成的 ID 值越大；
+ * 2、运行时，单台机器并发量在每秒钟 10w 以内；
+ * 3、运行时，无视时间回拨；
+ * 4、最大支持 99 台机器；
+ * 5、够用大概 300 年左右的时间；
+ * <p>
+ * 缺点：
+ * 1、每台机器允许最大的并发量为 10w/s。
+ * 2、出现时间回拨，重启机器时，在时间回拨未恢复的情况下，可能出现 id 重复。
+ * <p>
+ * ID组成：时间（7+）| 毫秒内的时间自增 （00~99：2）| 机器ID（01 ~ 99：2）| 随机数（000~999：3）用于分库分表时，通过 id 取模，保证分布均衡。
+ */
+public class FlexIDKeyGenerator implements IKeyGenerator {
+
+    private static final long INITIAL_TIMESTAMP = 1680411660000L;
+    private static final long MAX_CLOCK_SEQ = 99;
+
+    private long lastTimeMillis = 0;//最后一次生成 ID 的时间
+    private long clockSeq = 0;      //时间序列
+    private long workId = 1;        //机器 ID
+
+    public FlexIDKeyGenerator() {
+    }
+
+    public FlexIDKeyGenerator(long workId) {
+        this.workId = workId;
+    }
+
+    @Override
+    public Object generate(Object entity, String keyColumn) {
+        return nextId();
+    }
+
+    private synchronized long nextId() {
+
+        //当前时间
+        long currentTimeMillis = System.currentTimeMillis();
+
+        if (currentTimeMillis == lastTimeMillis) {
+            clockSeq++;
+            if (clockSeq > MAX_CLOCK_SEQ) {
+                clockSeq = 0;
+                currentTimeMillis++;
+            }
+        }
+
+        //出现时间回拨
+        else if (currentTimeMillis < lastTimeMillis) {
+            currentTimeMillis = lastTimeMillis;
+            clockSeq++;
+
+            if (clockSeq > MAX_CLOCK_SEQ) {
+                clockSeq = 0;
+                currentTimeMillis++;
+            }
+        } else {
+            clockSeq = 0;
+        }
+
+        lastTimeMillis = currentTimeMillis;
+
+        long diffTimeMillis = currentTimeMillis - INITIAL_TIMESTAMP;
+        return diffTimeMillis * 1000000 + clockSeq * 10000 + workId * 1000 + getRandomInt();
+    }
+
+
+    private int getRandomInt() {
+        return ThreadLocalRandom.current().nextInt(1000);
+    }
+
+
+}