add TtlAttachments

src/main/java/com/alibaba/ttl/TtlCallable.java

 package com.alibaba.ttl;
 
+import com.alibaba.ttl.spi.TtlEnhanced;
+
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import java.util.ArrayList;

src/main/java/com/alibaba/ttl/TtlEnhanced.java

 package com.alibaba.ttl;
 
+import com.alibaba.ttl.spi.TtlAttachments;
+
 /**
- * a Ttl marker/tag interface, for ttl enhanced class, for example {@code TTL wrapper}.
+ * @see TtlAttachments
+ * @deprecated Use {@link com.alibaba.ttl.spi.TtlEnhanced} instead.
  */
+@Deprecated
 public interface TtlEnhanced {
 }

src/main/java/com/alibaba/ttl/TtlRecursiveAction.java

 package com.alibaba.ttl;
 
+import com.alibaba.ttl.spi.TtlEnhanced;
+
 import java.util.concurrent.ForkJoinTask;
 
 import static com.alibaba.ttl.TransmittableThreadLocal.Transmitter.*;

src/main/java/com/alibaba/ttl/TtlRecursiveTask.java

 package com.alibaba.ttl;
 
+import com.alibaba.ttl.spi.TtlEnhanced;
+
 import java.util.concurrent.ForkJoinTask;
 
 import static com.alibaba.ttl.TransmittableThreadLocal.Transmitter.*;

src/main/java/com/alibaba/ttl/TtlRunnable.java

 package com.alibaba.ttl;
 
+import com.alibaba.ttl.spi.TtlEnhanced;
+
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import java.util.ArrayList;

src/main/java/com/alibaba/ttl/TtlTimerTask.java

 package com.alibaba.ttl;
 
+import com.alibaba.ttl.spi.TtlEnhanced;
+
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import java.util.*;

src/main/java/com/alibaba/ttl/spi/TtlAttachments.java

+package com.alibaba.ttl.spi;
+
+/**
+ * The TTL attachments for TTL tasks, eg: {@link com.alibaba.ttl.TtlRunnable}, {@link com.alibaba.ttl.TtlCallable}.
+ */
+public interface TtlAttachments extends TtlEnhanced {
+    void setTtlAttachment(String key, Object value);
+
+    <T> T getTtlAttachment(String key);
+}

src/main/java/com/alibaba/ttl/spi/TtlEnhanced.java

+package com.alibaba.ttl.spi;
+
+/**
+ * a Ttl marker/tag interface, for ttl enhanced class, for example {@code TTL wrapper}.
+ *
+ * @see TtlAttachments
+ */
+public interface TtlEnhanced {
+}

src/main/java/com/alibaba/ttl/threadpool/ExecutorServiceTtlWrapper.java

@@ -2,7 +2,7 @@ package com.alibaba.ttl.threadpool;
 
 import com.alibaba.ttl.TransmittableThreadLocal;
 import com.alibaba.ttl.TtlCallable;
-import com.alibaba.ttl.TtlEnhanced;
+import com.alibaba.ttl.spi.TtlEnhanced;
 import com.alibaba.ttl.TtlRunnable;
 
 import javax.annotation.Nonnull;

src/main/java/com/alibaba/ttl/threadpool/ExecutorTtlWrapper.java

 package com.alibaba.ttl.threadpool;
 
 import com.alibaba.ttl.TransmittableThreadLocal;
-import com.alibaba.ttl.TtlEnhanced;
+import com.alibaba.ttl.spi.TtlEnhanced;
 import com.alibaba.ttl.TtlRunnable;
 
 import javax.annotation.Nonnull;

src/main/java/com/alibaba/ttl/threadpool/ScheduledExecutorServiceTtlWrapper.java

@@ -2,7 +2,7 @@ package com.alibaba.ttl.threadpool;
 
 import com.alibaba.ttl.TransmittableThreadLocal;
 import com.alibaba.ttl.TtlCallable;
-import com.alibaba.ttl.TtlEnhanced;
+import com.alibaba.ttl.spi.TtlEnhanced;
 import com.alibaba.ttl.TtlRunnable;
 
 import javax.annotation.Nonnull;

src/main/java/com/alibaba/ttl/threadpool/TtlExecutors.java

 package com.alibaba.ttl.threadpool;
 
 import com.alibaba.ttl.TransmittableThreadLocal;
-import com.alibaba.ttl.TtlEnhanced;
+import com.alibaba.ttl.spi.TtlEnhanced;
 import com.alibaba.ttl.threadpool.agent.TtlAgent;
 
 import javax.annotation.Nullable;

src/main/java/com/alibaba/ttl/threadpool/agent/internal/transformlet/impl/TtlForkJoinTransformlet.java

 package com.alibaba.ttl.threadpool.agent.internal.transformlet.impl;
 
-import com.alibaba.ttl.TtlEnhanced;
+import com.alibaba.ttl.spi.TtlEnhanced;
 import com.alibaba.ttl.threadpool.agent.internal.logging.Logger;
 import com.alibaba.ttl.threadpool.agent.internal.transformlet.JavassistTransformlet;
 import javassist.*;

src/main/java/com/alibaba/ttl/threadpool/agent/internal/transformlet/impl/Utils.java

 package com.alibaba.ttl.threadpool.agent.internal.transformlet.impl;
 
 import com.alibaba.ttl.TransmittableThreadLocal;
-import com.alibaba.ttl.TtlEnhanced;
+import com.alibaba.ttl.spi.TtlEnhanced;
 import com.alibaba.ttl.threadpool.agent.internal.logging.Logger;
 import javassist.*;