8365400: enhance JFR to emit file and module metadata for class loading

src/java.base/share/classes/java/security/SecureClassLoader.java

@@ -31,6 +31,8 @@
 import java.util.function.Function;
 import jdk.internal.misc.CDS;
 
+import jdk.internal.event.ClassFileDefineEvent;
+
 /**
  * This class extends {@code ClassLoader} with additional support for defining
  * classes with an associated code source and permissions.
@@ -138,11 +140,16 @@ protected SecureClassLoader(String name, ClassLoader parent) {
      *             a different set of certificates than this class, or if
      *             the class name begins with "java.".
      */
-    protected final Class<?> defineClass(String name,
-                                         byte[] b, int off, int len,
-                                         CodeSource cs)
-    {
-        return defineClass(name, b, off, len, getProtectionDomain(cs));
+    protected final Class<?> defineClass(String name, byte[] b, int off, int len, CodeSource cs) {
+        final var cls = defineClass(name, b, off, len, getProtectionDomain(cs));
+
+        final var evt = new ClassFileDefineEvent();
+
+        evt.definedClass = cls;
+        evt.path         = cs.getLocation().toExternalForm();
+        evt.commit();
+
+        return cls;
     }
 
     /**
@@ -171,10 +178,17 @@ protected final Class<?> defineClass(String name,
      *
      * @since  1.5
      */
-    protected final Class<?> defineClass(String name, java.nio.ByteBuffer b,
-                                         CodeSource cs)
+    protected final Class<?> defineClass(String name, java.nio.ByteBuffer b, CodeSource cs)
     {
-        return defineClass(name, b, getProtectionDomain(cs));
+        final var cls = defineClass(name, b, getProtectionDomain(cs));
+
+        final var evt = new ClassFileDefineEvent();
+
+        evt.definedClass = cls;
+        evt.path         = cs.getLocation().toExternalForm();
+        evt.commit();
+
+        return cls;
     }
 
     /**

src/java.base/share/classes/jdk/internal/event/ClassFileDefineEvent.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2025, 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 jdk.internal.event;
+
+import java.net.URL;
+
+/**
+ * Event recording that a Class has been loaded and defined by a ClassLoader.
+ */
+public final class ClassFileDefineEvent extends Event {
+    public Class<?> definedClass;
+    public String   path;
+}

src/jdk.jfr/share/classes/jdk/jfr/events/ClassFileDefineEvent.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2025, 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 jdk.jfr.events;
+
+import jdk.jfr.Category;
+import jdk.jfr.Description;
+import jdk.jfr.Label;
+import jdk.jfr.Name;
+import jdk.jfr.internal.MirrorEvent;
+import jdk.jfr.internal.Type;
+
+@Category("Java Virtual Machine, Class Loading")
+@Label("ClassFile Define")
+@Name("jdk.ClassFileDefine")
+public final class ClassFileDefineEvent extends MirrorEvent {
+    @Label("Defined Class Name")
+    public Class<?> definedClass;
+
+    @Label("Path")
+    @Description("The path/url location of the classfile loaded")
+    public String   path;
+}

src/jdk.jfr/share/classes/jdk/jfr/internal/JDKEvents.java

@@ -35,6 +35,7 @@
 import jdk.jfr.Event;
 import jdk.jfr.events.ActiveRecordingEvent;
 import jdk.jfr.events.ActiveSettingEvent;
+import jdk.jfr.events.ClassFileDefineEvent;
 import jdk.jfr.events.ContainerCPUThrottlingEvent;
 import jdk.jfr.events.ContainerCPUUsageEvent;
 import jdk.jfr.events.ContainerConfigurationEvent;
@@ -56,6 +57,7 @@ public final class JDKEvents {
         ActiveRecordingEvent.class,
         // jdk.internal.event.* classes need their mirror
         // event class to be listed in the MirrorEvents class.
+        jdk.internal.event.ClassFileDefineEvent.class,
         jdk.internal.event.DeserializationEvent.class,
         jdk.internal.event.ErrorThrownEvent.class,
         jdk.internal.event.ExceptionStatisticsEvent.class,

src/jdk.jfr/share/classes/jdk/jfr/internal/MirrorEvents.java

@@ -27,6 +27,7 @@
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
+import jdk.jfr.events.ClassFileDefineEvent;
 import jdk.jfr.events.DeserializationEvent;
 import jdk.jfr.events.ErrorThrownEvent;
 import jdk.jfr.events.ExceptionStatisticsEvent;
@@ -57,6 +58,7 @@ final class MirrorEvents {
 
     // Add mirror event mapping here. See MirrorEvent class for details.
     static {
+        register("jdk.internal.event.ClassFileDefineEvent", ClassFileDefineEvent.class);
         register("jdk.internal.event.DeserializationEvent", DeserializationEvent.class);
         register("jdk.internal.event.FileForceEvent", FileForceEvent.class);
         register("jdk.internal.event.FileReadEvent", FileReadEvent.class);

src/jdk.jfr/share/conf/jfr/default.jfc

@@ -166,6 +166,10 @@
       <setting name="stackTrace">true</setting>
     </event>
 
+    <event name="jdk.ClassFileDefine">
+      <setting name="enabled" control="class-loading">false</setting>
+    </event>
+
     <event name="jdk.RedefineClasses">
       <setting name="enabled">true</setting>
       <setting name="stackTrace">true</setting>