add javadoc and prepend license header

sentinel-core/src/main/java/com/alibaba/csp/sentinel/annotation/SentinelResource.java

@@ -79,6 +79,13 @@
      */
     String defaultFallback() default "";
 
+
+    /**
+     * The {@code globalFallback} is used as the global fallback handler class.
+     * The returned class should implement the {@link IGlobalFallback} interface.
+     * If no specific global fallback handler is provided, the default {@link DefaultGlobalFallback} class will be used.
+     * @return The class that serves as the global fallback handler.
+     */
     Class<? extends IGlobalFallback> globalFallback() default DefaultGlobalFallback.class;
 
 

sentinel-core/src/main/java/com/alibaba/csp/sentinel/fallback/DefaultGlobalFallback.java

@@ -1,3 +1,18 @@
+/*
+ * Copyright 1999-2018 Alibaba Group Holding Ltd.
+ *
+ * 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
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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.alibaba.csp.sentinel.fallback;
 
 import java.lang.reflect.Method;

sentinel-core/src/main/java/com/alibaba/csp/sentinel/fallback/IGlobalFallback.java

@@ -1,3 +1,18 @@
+/*
+ * Copyright 1999-2018 Alibaba Group Holding Ltd.
+ *
+ * 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
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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.alibaba.csp.sentinel.fallback;
 
 import java.lang.reflect.Method;
@@ -9,7 +24,14 @@
  */
 public interface IGlobalFallback {
 
-
+     /**
+      *
+      * @param originalMethod the original method called
+      * @param args The parameters of the method that was originally called
+      * @param t The exception thrown by the method originally called
+      * @return The result of the global fallback handler execution
+      * @throws Throwable
+      */
      Object handle(Method originalMethod, Object[] args, Throwable t) throws Throwable;
 
 }