Use recommanded finalize chain pattern when override finalize() method (#16212)

laosijikaichele · web-flow · commit 3007ba9d2853 · 2026-02-04T09:07:01.000+01:00
According to the java docs of [Object.finalize()](https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/Object.html#finalize()), when override `finalize()` method, the `super.finalize()` should be placed in the `finally` block: > Finalizer invocations are not automatically chained, unlike constructors. If a subclass overrides finalize it must invoke the superclass finalizer explicitly. To guard against exceptions prematurely terminating the finalize chain, the subclass should use a try-finally block to ensure super.finalize() is always invoked. For example, ``` @OverRide protected void finalize() throws Throwable { try { ... // cleanup subclass state } finally { super.finalize(); } } ``` As we know, the [constructor chaining](https://docs.oracle.com/javase/tutorial/java/IandI/super.html) order is: First the superclass constructor, then the subclass constructor. The destruction order has not been explained well in java docs, but we can take C++ docs as reference: https://isocpp.org/wiki/faq/dtors#order-dtors-for-members So when doing finalize(), the order should be reversed: First the subclass, then the superclass. This pattern has also been stated in the book [<Effective Java, 2nd Edition>](https://www.oreilly.com/library/view/effective-java-2nd/9780137150021/)(Item 7): > You should finalize the subclass in a try block and invoke the superclass finalizer in the corresponding finally block. By doing so, it should make the code less error prone, for example: https://issues.apache.org/jira/browse/AXIS2-4163 Co-authored-by: lao <none>
diff --git a/buffer/src/main/java/io/netty/buffer/AdaptivePoolingAllocator.java b/buffer/src/main/java/io/netty/buffer/AdaptivePoolingAllocator.java
@@ -345,9 +345,9 @@ long usedMemory() {
     @Override
     protected void finalize() throws Throwable {
         try {
-            super.finalize();
-        } finally {
             free();
+        } finally {
+            super.finalize();
         }
     }
 
diff --git a/buffer/src/main/java/io/netty/buffer/PoolArena.java b/buffer/src/main/java/io/netty/buffer/PoolArena.java
@@ -640,10 +640,10 @@ private static void appendPoolSubPages(StringBuilder buf, PoolSubpage<?>[] subpa
     @Override
     protected final void finalize() throws Throwable {
         try {
-            super.finalize();
-        } finally {
             destroyPoolSubPages(smallSubpagePools);
             destroyPoolChunkLists(qInit, q000, q025, q050, q075, q100);
+        } finally {
+            super.finalize();
         }
     }
 
diff --git a/buffer/src/main/java/io/netty/buffer/PoolThreadCache.java b/buffer/src/main/java/io/netty/buffer/PoolThreadCache.java
@@ -484,15 +484,15 @@ private FreeOnFinalize(PoolThreadCache cache) {
         @Override
         protected void finalize() throws Throwable {
             try {
-                super.finalize();
-            } finally {
                 PoolThreadCache cache = this.cache;
                 // this can race with a non-finalizer thread calling free: regardless who wins, the cache will be
                 // null out
                 this.cache = null;
                 if (cache != null) {
                     cache.free(true);
                 }
+            } finally {
+                super.finalize();
             }
         }
     }
diff --git a/common/src/main/java/io/netty/util/HashedWheelTimer.java b/common/src/main/java/io/netty/util/HashedWheelTimer.java
@@ -322,13 +322,13 @@ public HashedWheelTimer(
     @Override
     protected void finalize() throws Throwable {
         try {
-            super.finalize();
-        } finally {
             // This object is going to be GCed and it is assumed the ship has sailed to do a proper shutdown. If
             // we have not yet shutdown then we want to make sure we decrement the active instance count.
             if (WORKER_STATE_UPDATER.getAndSet(this, WORKER_STATE_SHUTDOWN) != WORKER_STATE_SHUTDOWN) {
                 INSTANCE_COUNTER.decrementAndGet();
             }
+        } finally {
+            super.finalize();
         }
     }
 
diff --git a/common/src/test/java/io/netty/util/RecyclerFastThreadLocalTest.java b/common/src/test/java/io/netty/util/RecyclerFastThreadLocalTest.java
@@ -56,8 +56,11 @@ public void run() {
         }) {
             @Override
             protected void finalize() throws Throwable {
-                super.finalize();
-                collected.set(true);
+                try {
+                    collected.set(true);
+                } finally {
+                    super.finalize();
+                }
             }
         };
         assertFalse(collected.get());
diff --git a/common/src/test/java/io/netty/util/RecyclerTest.java b/common/src/test/java/io/netty/util/RecyclerTest.java
@@ -185,8 +185,11 @@ public void run() {
         }) {
             @Override
             protected void finalize() throws Throwable {
-                super.finalize();
-                collected.set(true);
+                try {
+                    collected.set(true);
+                } finally {
+                    super.finalize();
+                }
             }
         };
         assertFalse(collected.get());
diff --git a/handler/src/main/java/io/netty/handler/ssl/OpenSslContext.java b/handler/src/main/java/io/netty/handler/ssl/OpenSslContext.java
@@ -60,7 +60,10 @@ final SSLEngine newEngine0(ByteBufAllocator alloc, String peerHost, int peerPort
     @Override
     @SuppressWarnings("FinalizeDeclaration")
     protected final void finalize() throws Throwable {
-        super.finalize();
-        OpenSsl.releaseIfNeeded(this);
+        try {
+            OpenSsl.releaseIfNeeded(this);
+        } finally {
+            super.finalize();
+        }
     }
 }
diff --git a/handler/src/main/java/io/netty/handler/ssl/OpenSslEngine.java b/handler/src/main/java/io/netty/handler/ssl/OpenSslEngine.java
@@ -39,7 +39,10 @@ public final class OpenSslEngine extends ReferenceCountedOpenSslEngine {
     @Override
     @SuppressWarnings("FinalizeDeclaration")
     protected void finalize() throws Throwable {
-        super.finalize();
-        OpenSsl.releaseIfNeeded(this);
+        try {
+            OpenSsl.releaseIfNeeded(this);
+        } finally {
+            super.finalize();
+        }
     }
 }

Original file line number	Diff line number	Diff line change
`@@ -345,9 +345,9 @@ long usedMemory() {`
`345`	`345`	`@Override`
`346`	`346`	`protected void finalize() throws Throwable {`
`347`	`347`	`try {`
`348`		`- super.finalize();`
`349`		`- } finally {`
`350`	`348`	`free();`
	`349`	`+ } finally {`
	`350`	`+ super.finalize();`
`351`	`351`	`}`
`352`	`352`	`}`
`353`	`353`
Original file line number	Diff line number	Diff line change
`@@ -640,10 +640,10 @@ private static void appendPoolSubPages(StringBuilder buf, PoolSubpage<?>[] subpa`
`640`	`640`	`@Override`
`641`	`641`	`protected final void finalize() throws Throwable {`
`642`	`642`	`try {`
`643`		`- super.finalize();`
`644`		`- } finally {`
`645`	`643`	`destroyPoolSubPages(smallSubpagePools);`
`646`	`644`	`destroyPoolChunkLists(qInit, q000, q025, q050, q075, q100);`
	`645`	`+ } finally {`
	`646`	`+ super.finalize();`
`647`	`647`	`}`
`648`	`648`	`}`
`649`	`649`
Original file line number	Diff line number	Diff line change
`@@ -484,15 +484,15 @@ private FreeOnFinalize(PoolThreadCache cache) {`
`484`	`484`	`@Override`
`485`	`485`	`protected void finalize() throws Throwable {`
`486`	`486`	`try {`
`487`		`- super.finalize();`
`488`		`- } finally {`
`489`	`487`	`PoolThreadCache cache = this.cache;`
`490`	`488`	`// this can race with a non-finalizer thread calling free: regardless who wins, the cache will be`
`491`	`489`	`// null out`
`492`	`490`	`this.cache = null;`
`493`	`491`	`if (cache != null) {`
`494`	`492`	`cache.free(true);`
`495`	`493`	`}`
	`494`	`+ } finally {`
	`495`	`+ super.finalize();`
`496`	`496`	`}`
`497`	`497`	`}`
`498`	`498`	`}`
Original file line number	Diff line number	Diff line change
`@@ -322,13 +322,13 @@ public HashedWheelTimer(`
`322`	`322`	`@Override`
`323`	`323`	`protected void finalize() throws Throwable {`
`324`	`324`	`try {`
`325`		`- super.finalize();`
`326`		`- } finally {`
`327`	`325`	`// This object is going to be GCed and it is assumed the ship has sailed to do a proper shutdown. If`
`328`	`326`	`// we have not yet shutdown then we want to make sure we decrement the active instance count.`
`329`	`327`	`if (WORKER_STATE_UPDATER.getAndSet(this, WORKER_STATE_SHUTDOWN) != WORKER_STATE_SHUTDOWN) {`
`330`	`328`	`INSTANCE_COUNTER.decrementAndGet();`
`331`	`329`	`}`
	`330`	`+ } finally {`
	`331`	`+ super.finalize();`
`332`	`332`	`}`
`333`	`333`	`}`
`334`	`334`
Original file line number	Diff line number	Diff line change
`@@ -60,7 +60,10 @@ final SSLEngine newEngine0(ByteBufAllocator alloc, String peerHost, int peerPort`
`60`	`60`	`@Override`
`61`	`61`	`@SuppressWarnings("FinalizeDeclaration")`
`62`	`62`	`protected final void finalize() throws Throwable {`
`63`		`- super.finalize();`
`64`		`- OpenSsl.releaseIfNeeded(this);`
	`63`	`+ try {`
	`64`	`+ OpenSsl.releaseIfNeeded(this);`
	`65`	`+ } finally {`
	`66`	`+ super.finalize();`
	`67`	`+ }`
`65`	`68`	`}`
`66`	`69`	`}`
Original file line number	Diff line number	Diff line change
`@@ -39,7 +39,10 @@ public final class OpenSslEngine extends ReferenceCountedOpenSslEngine {`
`39`	`39`	`@Override`
`40`	`40`	`@SuppressWarnings("FinalizeDeclaration")`
`41`	`41`	`protected void finalize() throws Throwable {`
`42`		`- super.finalize();`
`43`		`- OpenSsl.releaseIfNeeded(this);`
	`42`	`+ try {`
	`43`	`+ OpenSsl.releaseIfNeeded(this);`
	`44`	`+ } finally {`
	`45`	`+ super.finalize();`
	`46`	`+ }`
`44`	`47`	`}`
`45`	`48`	`}`