8278065: Refactor subclassAudits to use ClassValue

src/java.base/share/classes/java/io/ClassCache.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package java.io;
+
+import java.lang.ref.Reference;
+import java.lang.ref.ReferenceQueue;
+import java.lang.ref.SoftReference;
+
+// Maps Class instances to values of type T. Under memory pressure, the
+// mapping is released (under soft references GC policy) and would be
+// recomputed the next time it is queried. The mapping is bound to the
+// lifetime of the class: when the class is unloaded, the mapping is
+// removed too.
+abstract class ClassCache<T> {
+
+    private static class CacheRef<T> extends SoftReference<T> {
+        private final Class<?> type;
+
+        CacheRef(T referent, ReferenceQueue<T> queue, Class<?> type) {
+            super(referent, queue);
+            this.type = type;
+        }
+
+        Class<?> getType() {
+            return type;
+        }
+    }
+
+    private final ReferenceQueue<T> queue;
+    private final ClassValue<SoftReference<T>> map;
+
+    protected abstract T computeValue(Class<?> cl);
+
+    protected ClassCache() {
+        queue = new ReferenceQueue<>();
+        map = new ClassValue<>() {
+            @Override
+            protected SoftReference<T> computeValue(Class<?> type) {
+                return new CacheRef<>(ClassCache.this.computeValue(type), queue, type);
+            }
+        };
+    }
+
+    T get(Class<?> cl) {
+        processQueue();
+        T val;
+        do {
+            SoftReference<T> ref = map.get(cl);
+            val = ref.get();
+            if (val == null) {
+                map.remove(cl);
+            }
+        } while (val == null);
+        return val;
+    }
+
+    private void processQueue() {
+        Reference<? extends T> ref;
+        while((ref = queue.poll()) != null) {
+            CacheRef<? extends T> cacheRef = (CacheRef<? extends T>)ref;
+            map.remove(cacheRef.getType());
+        }
+    }
+}

src/java.base/share/classes/java/io/ObjectInputStream.java

@@ -25,9 +25,7 @@
 
 package java.io;
 
-import java.io.ObjectStreamClass.WeakClassKey;
 import java.lang.System.Logger;
-import java.lang.ref.ReferenceQueue;
 import java.lang.reflect.Array;
 import java.lang.reflect.InvocationHandler;
 import java.lang.reflect.Modifier;
@@ -40,10 +38,6 @@
 import java.util.Arrays;
 import java.util.Map;
 import java.util.Objects;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
-
-import static java.io.ObjectStreamClass.processQueue;
 
 import jdk.internal.misc.SharedSecrets;
 import jdk.internal.misc.Unsafe;
@@ -256,12 +250,13 @@ public class ObjectInputStream
 
     private static class Caches {
         /** cache of subclass security audit results */
-        static final ConcurrentMap<WeakClassKey,Boolean> subclassAudits =
-            new ConcurrentHashMap<>();
-
-        /** queue for WeakReferences to audited subclasses */
-        static final ReferenceQueue<Class<?>> subclassAuditsQueue =
-            new ReferenceQueue<>();
+        static final ClassValue<Boolean> subclassAudits =
+            new ClassValue<>() {
+                @Override
+                protected Boolean computeValue(Class<?> type) {
+                    return auditSubclass(type);
+                }
+            };
 
         /**
          * Property to permit setting a filter after objects
@@ -1554,13 +1549,7 @@ private void verifySubclass() {
         if (sm == null) {
             return;
         }
-        processQueue(Caches.subclassAuditsQueue, Caches.subclassAudits);
-        WeakClassKey key = new WeakClassKey(cl, Caches.subclassAuditsQueue);
-        Boolean result = Caches.subclassAudits.get(key);
-        if (result == null) {
-            result = auditSubclass(cl);
-            Caches.subclassAudits.putIfAbsent(key, result);
-        }
+        boolean result = Caches.subclassAudits.get(cl);
         if (!result) {
             sm.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
         }

src/java.base/share/classes/java/io/ObjectOutputStream.java

@@ -25,17 +25,12 @@
 
 package java.io;
 
-import java.io.ObjectStreamClass.WeakClassKey;
-import java.lang.ref.ReferenceQueue;
 import java.security.AccessController;
 import java.security.PrivilegedAction;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.StringJoiner;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
-import static java.io.ObjectStreamClass.processQueue;
 import sun.reflect.misc.ReflectUtil;
 
 /**
@@ -166,12 +161,13 @@ public class ObjectOutputStream
 
     private static class Caches {
         /** cache of subclass security audit results */
-        static final ConcurrentMap<WeakClassKey,Boolean> subclassAudits =
-            new ConcurrentHashMap<>();
-
-        /** queue for WeakReferences to audited subclasses */
-        static final ReferenceQueue<Class<?>> subclassAuditsQueue =
-            new ReferenceQueue<>();
+        static final ClassValue<Boolean> subclassAudits =
+            new ClassValue<>() {
+                @Override
+                protected Boolean computeValue(Class<?> type) {
+                    return auditSubclass(type);
+                }
+            };
     }
 
     /** filter stream for handling block data conversion */
@@ -1049,13 +1045,7 @@ private void verifySubclass() {
         if (sm == null) {
             return;
         }
-        processQueue(Caches.subclassAuditsQueue, Caches.subclassAudits);
-        WeakClassKey key = new WeakClassKey(cl, Caches.subclassAuditsQueue);
-        Boolean result = Caches.subclassAudits.get(key);
-        if (result == null) {
-            result = auditSubclass(cl);
-            Caches.subclassAudits.putIfAbsent(key, result);
-        }
+        boolean result = Caches.subclassAudits.get(cl);
         if (!result) {
             sm.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
         }