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/*
* Copyright (c) 2023, 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.
*/
/*
* @test
* @bug 8291065
* @summary Checks interaction of static field VarHandle with class
* initialization mechanism..
* @run junit LazyInitializingTest
* @run junit/othervm -Djava.lang.invoke.VarHandle.VAR_HANDLE_IDENTITY_ADAPT=true LazyInitializingTest
* @run junit/othervm -Djava.lang.invoke.VarHandle.VAR_HANDLE_GUARDS=false LazyInitializingTest
* @run junit/othervm -Djava.lang.invoke.VarHandle.VAR_HANDLE_IDENTITY_ADAPT=true
* -Djava.lang.invoke.VarHandle.VAR_HANDLE_GUARDS=false LazyInitializingTest
*/
import org.junit.jupiter.api.Test;
import java.io.IOException;
import java.lang.constant.ConstantDescs;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
import java.util.Objects;
import static org.junit.jupiter.api.Assertions.*;
public class LazyInitializingTest {
record SampleData(Runnable callback, int initialValue) {
private static final Runnable FAIL_ON_CLINIT_CALLBACK = () -> {
throw new AssertionError("Class shouldn't be initialized");
};
static final SampleData FAIL_ON_CLINIT = new SampleData();
SampleData() {
this(FAIL_ON_CLINIT_CALLBACK, 0);
}
}
record ClassInfo(MethodHandles.Lookup definingLookup, VarHandle vh) {}
private static final MethodHandles.Lookup LOOKUP = MethodHandles.lookup();
/**
* Meta test to ensure the testing mechanism to check initialization is correct.
*/
@Test
public void testMeta() throws IllegalAccessException {
boolean[] val = new boolean[1];
var v0 = createSampleClass(new SampleData(() -> val[0] = true, 0));
assertFalse(val[0], "callback run before class init");
v0.definingLookup.ensureInitialized(v0.definingLookup.lookupClass());
assertTrue(val[0], "callback not run at class init");
}
@Test
public void testUninitializedOperations() {
var ci = createSampleClass(SampleData.FAIL_ON_CLINIT);
var vh = ci.vh;
vh.describeConstable();
vh.isAccessModeSupported(VarHandle.AccessMode.GET_AND_BITWISE_XOR_ACQUIRE);
vh.withInvokeExactBehavior();
vh.withInvokeBehavior();
vh.toMethodHandle(VarHandle.AccessMode.GET_AND_BITWISE_XOR_ACQUIRE);
vh.hasInvokeExactBehavior();
vh.accessModeType(VarHandle.AccessMode.GET_AND_BITWISE_XOR_ACQUIRE);
}
@Test
public void testInitializationOnVarHandleUse() {
var initialized = new boolean[1];
var ci = createSampleClass(new SampleData(() -> initialized[0] = true, 42));
var vh = ci.vh;
assertEquals(42, (int) vh.get(), "VH does not read value set in class initializer");
assertTrue(initialized[0], "class initialization not captured");
}
@Test
public void testInitializationOnToMethodHandleUse() throws Throwable {
var initialized = new boolean[1];
var ci = createSampleClass(new SampleData(() -> initialized[0] = true, 42));
var mh = ci.vh.toMethodHandle(VarHandle.AccessMode.GET);
assertEquals(42, (int) mh.invokeExact(), "VH does not read value set in class initializer");
assertTrue(initialized[0], "class initialization not captured");
}
@Test
public void testParentChildLoading() throws Throwable {
// ChildSample: ensure only ParentSample (field declarer) is initialized
var l = new ParentChildLoader();
var childSampleClass = l.childClass();
var lookup = MethodHandles.privateLookupIn(childSampleClass, LOOKUP);
var childVh = lookup.findStaticVarHandle(childSampleClass, "f", int.class);
assertEquals(3, (int) childVh.get(), "Child class initialized unnecessarily");
lookup.ensureInitialized(childSampleClass);
assertEquals(6, (int) childVh.get(), "Child class was not initialized");
}
static ClassInfo createSampleClass(SampleData sampleData) {
try {
var lookup = LOOKUP.defineHiddenClassWithClassData(sampleClassBytes(), sampleData, false);
var vh = lookup.findStaticVarHandle(lookup.lookupClass(), "f", int.class);
return new ClassInfo(lookup, vh);
} catch (IllegalAccessException | NoSuchFieldException ex) {
throw new AssertionError(ex);
}
}
private static byte[] sampleClassBytes;
private static byte[] sampleClassBytes() {
var bytes = sampleClassBytes;
if (bytes != null)
return bytes;
try (var in = LazyInitializingTest.class.getResourceAsStream("LazyInitializingSample.class")) {
if (in == null)
throw new AssertionError("class file not found");
return sampleClassBytes = in.readAllBytes();
} catch (IOException ex) {
throw new AssertionError(ex);
}
}
}
// This is used as a template class, whose bytes are used to define
// hidden classes instead
class LazyInitializingSample {
static int f;
static {
try {
var data = MethodHandles.classData(MethodHandles.lookup(), ConstantDescs.DEFAULT_NAME,
LazyInitializingTest.SampleData.class);
Objects.requireNonNull(data);
data.callback().run();
f = data.initialValue();
} catch (IllegalAccessException e) {
throw new ExceptionInInitializerError(e);
}
}
}
class ParentChildLoader extends ClassLoader {
ParentChildLoader() {
super(LazyInitializingTest.class.getClassLoader().getParent());
}
Class<?> parentClass() {
try {
return loadClass("ParentSample");
} catch (ClassNotFoundException e) {
throw new AssertionError(e);
}
}
Class<?> childClass() {
try {
return loadClass("ChildSample");
} catch (ClassNotFoundException e) {
throw new AssertionError(e);
}
}
@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {
try (var stream = switch (name) {
case "ParentSample", "ChildSample" -> LazyInitializingTest.class.getResourceAsStream(name + ".class");
default -> throw new ClassNotFoundException(name);
}) {
if (stream == null)
throw new AssertionError();
var b = stream.readAllBytes();
return defineClass(name, b, 0, b.length);
} catch (IOException ex) {
throw new AssertionError(ex);
}
}
}
class ParentSample {
static int f;
static {
f = 3;
}
}
class ChildSample extends ParentSample {
static {
f = 6;
}
}
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