8233272: The Class.forName specification should be updated to match the long-standing implementation with respect to class linking
authorbchristi
Tue, 19 Nov 2019 10:02:46 -0800
changeset 59137 faac483dfb30
parent 59136 fc998c509521
child 59139 302c4d2e7b3a
8233272: The Class.forName specification should be updated to match the long-standing implementation with respect to class linking Reviewed-by: dholmes, mchung
src/java.base/share/classes/java/lang/Class.java
test/jdk/java/lang/Class/forName/NonLinking/Container.java
test/jdk/java/lang/Class/forName/NonLinking/MissingClass.java
test/jdk/java/lang/Class/forName/NonLinking/NonLinking.java
--- 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]);
+        }
+    }
+}