fix: optimize code and comment (#989)

hippo4j-core/src/main/java/cn/hippo4j/core/executor/ExtensibleThreadPoolExecutor.java

@@ -17,7 +17,11 @@
 
 package cn.hippo4j.core.executor;
 
-import cn.hippo4j.core.plugin.*;
+import cn.hippo4j.core.plugin.ExecuteAwarePlugin;
+import cn.hippo4j.core.plugin.RejectedAwarePlugin;
+import cn.hippo4j.core.plugin.ShutdownAwarePlugin;
+import cn.hippo4j.core.plugin.TaskAwarePlugin;
+import cn.hippo4j.core.plugin.ThreadPoolPlugin;
 import cn.hippo4j.core.plugin.manager.ThreadPoolPluginManager;
 import cn.hippo4j.core.plugin.manager.ThreadPoolPluginSupport;
 import lombok.AllArgsConstructor;
@@ -28,7 +32,14 @@ import lombok.Setter;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
-import java.util.concurrent.*;
+import java.util.Objects;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.Callable;
+import java.util.concurrent.RejectedExecutionHandler;
+import java.util.concurrent.RunnableFuture;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
 
 /**
  * <p>Extensible thread-pool executor. <br />
@@ -96,13 +107,10 @@ public class ExtensibleThreadPoolExecutor extends ThreadPoolExecutor implements
                                         @NonNull ThreadFactory threadFactory,
                                         @NonNull RejectedExecutionHandler handler) {
         super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);
-        // Pool extended info.
+        // pool extended info.
         this.threadPoolId = threadPoolId;
         this.threadPoolPluginManager = threadPoolPluginManager;
-        // Proxy handler to support Aware callback.
-        while (handler instanceof RejectedAwareHandlerWrapper) {
-            handler = ((RejectedAwareHandlerWrapper) handler).getHandler();
-        }
+        // proxy handler to support callback, repeated packaging of the same rejection policy should be avoided here.
         this.handlerWrapper = new RejectedAwareHandlerWrapper(threadPoolPluginManager, handler);
         super.setRejectedExecutionHandler(handlerWrapper);
     }
@@ -124,7 +132,9 @@ public class ExtensibleThreadPoolExecutor extends ThreadPoolExecutor implements
     /**
      * {@inheritDoc}
      *
-     * <p><b>Before calling the superclass method, {@link TaskAwarePlugin#beforeTaskExecute} will be called first.
+     * <p>Before calling the superclass method, {@link TaskAwarePlugin#beforeTaskExecute} will be called first. <br />
+     * If the task becomes null after being processed by the {@link TaskAwarePlugin#beforeTaskExecute},
+     * the task will not be submitted.
      *
      * @param runnable the task to execute
      */
@@ -133,6 +143,9 @@ public class ExtensibleThreadPoolExecutor extends ThreadPoolExecutor implements
         Collection<TaskAwarePlugin> taskAwarePluginList = threadPoolPluginManager.getTaskAwarePluginList();
         for (TaskAwarePlugin taskAwarePlugin : taskAwarePluginList) {
             runnable = taskAwarePlugin.beforeTaskExecute(runnable);
+            if (Objects.isNull(runnable)) {
+                return;
+            }
         }
         super.execute(runnable);
     }
@@ -251,9 +264,6 @@ public class ExtensibleThreadPoolExecutor extends ThreadPoolExecutor implements
      */
     @Override
     public void setRejectedExecutionHandler(@NonNull RejectedExecutionHandler handler) {
-        while (handler instanceof RejectedAwareHandlerWrapper) {
-            handler = ((RejectedAwareHandlerWrapper) handler).getHandler();
-        }
         handlerWrapper.setHandler(handler);
     }
 

hippo4j-core/src/main/java/cn/hippo4j/core/plugin/TaskAwarePlugin.java

@@ -17,6 +17,9 @@
 
 package cn.hippo4j.core.plugin;
 
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
 import java.util.concurrent.Callable;
 import java.util.concurrent.ThreadPoolExecutor;
 
@@ -30,9 +33,13 @@ public interface TaskAwarePlugin extends ThreadPoolPlugin {
      *
      * @param executor executor
      * @param runnable original task
-     * @return Tasks that really need to be performed
+     * @param value    the default value for the returned future
+     * @param <V>      value type
+     * @return Tasks that really need to be performed, if the return task is null,
+     * terminate the execution of the next plugin immediately.
      * @see ThreadPoolExecutor#newTaskFor(Runnable, Object)
      */
+    @Nullable
     default <V> Runnable beforeTaskCreate(ThreadPoolExecutor executor, Runnable runnable, V value) {
         return runnable;
     }
@@ -42,9 +49,12 @@ public interface TaskAwarePlugin extends ThreadPoolPlugin {
      *
      * @param executor executor
      * @param future   original task
-     * @return Tasks that really need to be performed
+     * @param <V>      value type
+     * @return Tasks that really need to be performed, if the return task is null,
+     * terminate the execution of the next plugin immediately.
      * @see ThreadPoolExecutor#newTaskFor(Callable)
      */
+    @Nullable
     default <V> Callable<V> beforeTaskCreate(ThreadPoolExecutor executor, Callable<V> future) {
         return future;
     }
@@ -53,10 +63,12 @@ public interface TaskAwarePlugin extends ThreadPoolPlugin {
      * Callback when task is execute.
      *
      * @param runnable runnable
-     * @return tasks to be execute
+     * @return task to be executed, if the return task is null,
+     * terminate the execution of the next plug-in immediately.
      * @see ThreadPoolExecutor#execute
      */
-    default Runnable beforeTaskExecute(Runnable runnable) {
+    @Nullable
+    default Runnable beforeTaskExecute(@NonNull Runnable runnable) {
         return runnable;
     }
 }

hippo4j-core/src/main/java/cn/hippo4j/core/plugin/impl/TaskDecoratorPlugin.java

@@ -48,7 +48,7 @@ public class TaskDecoratorPlugin implements TaskAwarePlugin {
      * @see ExtensibleThreadPoolExecutor#execute
      */
     @Override
-    public Runnable beforeTaskExecute(Runnable runnable) {
+    public Runnable beforeTaskExecute(@NonNull Runnable runnable) {
         for (TaskDecorator decorator : decorators) {
             runnable = decorator.decorate(runnable);
         }

hippo4j-core/src/test/java/cn/hippo4j/core/executor/ExtensibleThreadPoolExecutorTest.java

@@ -25,6 +25,8 @@ import cn.hippo4j.core.plugin.TaskAwarePlugin;
 import cn.hippo4j.core.plugin.manager.DefaultThreadPoolPluginManager;
 import cn.hippo4j.core.plugin.manager.ThreadPoolPluginManager;
 import lombok.Getter;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
@@ -101,6 +103,13 @@ public class ExtensibleThreadPoolExecutorTest {
         });
         ThreadUtil.sleep(500L);
         Assert.assertEquals(2, plugin.getInvokeCount().get());
+
+        // no task will be executed because it has been replaced with null
+        executor.register(new TestTaskToNullAwarePlugin());
+        executor.execute(() -> {
+        });
+        ThreadUtil.sleep(500L);
+        Assert.assertEquals(2, plugin.getInvokeCount().get());
     }
 
     @Test
@@ -148,6 +157,14 @@ public class ExtensibleThreadPoolExecutorTest {
         }
     }
 
+    private final static class TestTaskToNullAwarePlugin implements TaskAwarePlugin {
+
+        @Override
+        public @Nullable Runnable beforeTaskExecute(@NonNull Runnable runnable) {
+            return null;
+        }
+    }
+
     @Getter
     private final static class TestTaskAwarePlugin implements TaskAwarePlugin {
 
@@ -164,7 +181,7 @@ public class ExtensibleThreadPoolExecutorTest {
             return TaskAwarePlugin.super.beforeTaskCreate(executor, future);
         }
         @Override
-        public Runnable beforeTaskExecute(Runnable runnable) {
+        public Runnable beforeTaskExecute(@NonNull Runnable runnable) {
             invokeCount.incrementAndGet();
             return TaskAwarePlugin.super.beforeTaskExecute(runnable);
         }