8233272: The Class.forName specification should be updated to match the long-standing implementation with respect to class linking
Reviewed-by: dholmes, mchung
--- a/src/java.base/share/classes/java/lang/Class.java Fri Nov 15 11:05:03 2019 +0100
+++ b/src/java.base/share/classes/java/lang/Class.java Tue Nov 19 10:02:46 2019 -0800
@@ -325,6 +325,10 @@
* @throws ExceptionInInitializerError if the initialization provoked
* by this method fails
* @throws ClassNotFoundException if the class cannot be located
+ *
+ * @jls 12.2 Loading of Classes and Interfaces
+ * @jls 12.3 Linking of Classes and Interfaces
+ * @jls 12.4 Initialization of Classes and Interfaces
*/
@CallerSensitive
public static Class<?> forName(String className)
@@ -339,7 +343,7 @@
* interface with the given string name, using the given class loader.
* Given the fully qualified name for a class or interface (in the same
* format returned by {@code getName}) this method attempts to
- * locate, load, and link the class or interface. The specified class
+ * locate and load the class or interface. The specified class
* loader is used to load the class or interface. If the parameter
* {@code loader} is null, the class is loaded through the bootstrap
* class loader. The class is initialized only if the
@@ -374,7 +378,7 @@
* is accessible to its caller.
*
* @param name fully qualified name of the desired class
- * @param initialize if {@code true} the class will be initialized.
+ * @param initialize if {@code true} the class will be initialized (which implies linking).
* See Section 12.4 of <em>The Java Language Specification</em>.
* @param loader class loader from which the class must be loaded
* @return class object representing the desired class
@@ -392,6 +396,10 @@
*
* @see java.lang.Class#forName(String)
* @see java.lang.ClassLoader
+ *
+ * @jls 12.2 Loading of Classes and Interfaces
+ * @jls 12.3 Linking of Classes and Interfaces
+ * @jls 12.4 Initialization of Classes and Interfaces
* @since 1.2
*/
@CallerSensitive
@@ -427,9 +435,9 @@
* Returns the {@code Class} with the given <a href="ClassLoader.html#binary-name">
* binary name</a> in the given module.
*
- * <p> This method attempts to locate, load, and link the class or interface.
- * It does not run the class initializer. If the class is not found, this
- * method returns {@code null}. </p>
+ * <p> This method attempts to locate and load the class or interface.
+ * It does not link the class, and does not run the class initializer.
+ * If the class is not found, this method returns {@code null}. </p>
*
* <p> If the class loader of the given module defines other modules and
* the given name is a class defined in a different module, this method
@@ -465,6 +473,8 @@
* in a module.</li>
* </ul>
*
+ * @jls 12.2 Loading of Classes and Interfaces
+ * @jls 12.3 Linking of Classes and Interfaces
* @since 9
* @spec JPMS
*/
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/java/lang/Class/forName/NonLinking/Container.java Tue Nov 19 10:02:46 2019 -0800
@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2019, 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.
+ *
+ * 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.
+ */
+
+public class Container {
+
+ public Container(MissingClass m) {}
+
+ public Container() {
+ this(new MissingClass() {});
+ }
+}
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/java/lang/Class/forName/NonLinking/MissingClass.java Tue Nov 19 10:02:46 2019 -0800
@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2019, 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.
+ *
+ * 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.
+ */
+
+public class MissingClass {}
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/java/lang/Class/forName/NonLinking/NonLinking.java Tue Nov 19 10:02:46 2019 -0800
@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2019, 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.
+ *
+ * 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.
+ */
+
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+/*
+ * @test
+ * @bug 8231924 8233091 8233272
+ * @summary Confirm load (but not link) behavior of Class.forName()
+ * @library /test/lib
+ *
+ * @compile MissingClass.java Container.java
+ *
+ * @run driver ClassFileInstaller -jar classes.jar Container Container$1
+ *
+ * @run main/othervm NonLinking init
+ * @run main/othervm NonLinking load
+ */
+/*
+ * The @compile and '@main ClassFileInstaller' tasks above create a classes.jar
+ * file containing the .class file for Container, but not MissingClass.
+ */
+
+public class NonLinking {
+ public static void main(String[] args) throws Throwable {
+ Path jarPath = Paths.get("classes.jar");
+ URL url = jarPath.toUri().toURL();
+ URLClassLoader ucl1 = new URLClassLoader("UCL1",
+ new URL[] { url },
+ null); // Don't delegate
+ switch(args[0]) {
+ case "init":
+ try {
+ // Trying to initialize Container without MissingClass -> NCDFE
+ Class.forName("Container", true, ucl1);
+ throw new RuntimeException("Missed expected NoClassDefFoundError");
+ } catch (NoClassDefFoundError expected) {
+ final String CLASSNAME = "MissingClass";
+ Throwable cause = expected.getCause();
+ if (!cause.getMessage().contains(CLASSNAME)) {
+ throw new RuntimeException("Cause of NoClassDefFoundError does not contain \"" + CLASSNAME + "\"", cause);
+ }
+ }
+ break;
+ case "load":
+ // Loading (but not linking) Container will succeed.
+ // Before 8233091, this fails with NCDFE due to linking.
+ Class.forName("Container", false, ucl1);
+ break;
+ default:
+ throw new RuntimeException("Unknown command: " + args[0]);
+ }
+ }
+}