java-topology/test/jdk/java/lang/reflect/Proxy/ProtectedObjectMethodsTest.java

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import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.reflect.Proxy;
import java.util.concurrent.atomic.AtomicInteger;

import org.junit.jupiter.api.Test;

import static org.junit.jupiter.api.Assertions.*;

/*
 * @test
 * @bug 8370839
 * @summary Behavior of protected methods in java.lang.Object
 * @modules java.base/java.lang:+open
 * @run junit ProtectedObjectMethodsTest
 */
public class ProtectedObjectMethodsTest {

    static final MethodHandle OBJECT_CLONE;
    static final MethodHandle OBJECT_FINALIZE;

    static {
        try {
            var lookup = MethodHandles.privateLookupIn(Object.class, MethodHandles.lookup());
            OBJECT_CLONE = lookup.findVirtual(Object.class, "clone", MethodType.methodType(Object.class));
            OBJECT_FINALIZE = lookup.findVirtual(Object.class, "finalize", MethodType.methodType(void.class));
        } catch (ReflectiveOperationException ex) {
            throw new ExceptionInInitializerError(ex);
        }
    }

    interface FakeClone {
        // This method is not related to Object::clone in the JVM, but most
        // implementations in the Java Language override Object::clone as
        // covariant overrides
        FakeClone clone();
    }

    interface TrueClone {
        // This method is identical to Object::clone in the JVM, that calls
        // to Object::clone can always call an implementation of this method
        // if it exists
        Object clone();
    }

    interface PrimitiveClone {
        // This method is not related to Object::clone in the JVM, but it can't
        // be implemented in the Java Language unless using a lambda expression,
        // due to the Java language covariant override restrictions.
        int clone();
    }

    // Does not duplicate with Object::clone so it is not proxied
    @Test
    void testDistinctClone() throws Throwable {
        {
            // This proxy declares FakeClone clone(); which cannot be
            // invoked through Object::clone.
            var fake = (FakeClone) Proxy.newProxyInstance(FakeClone.class.getClassLoader(), new Class[] { FakeClone.class }, (p, _, _) -> p);
            assertSame(fake, fake.clone());
            // Verify the default Object::clone behavior (this is not Cloneable)
            assertThrows(CloneNotSupportedException.class, () -> {
                var _ = (Object) OBJECT_CLONE.invoke((Object) fake);
            });
        }

        {
            // This proxy declares FakeClone clone(); which cannot be
            // invoked through Object::clone.
            var fake = (FakeClone) Proxy.newProxyInstance(FakeClone.class.getClassLoader(), new Class[] { FakeClone.class, Cloneable.class }, (p, _, _) -> p);
            assertSame(fake, fake.clone());
            // Verify the default Object::clone behavior (this is Cloneable)
            var fakeClone = (Object) OBJECT_CLONE.invoke((Object) fake);
            assertNotSame(fake, fakeClone);
            assertSame(fake.getClass(), fakeClone.getClass());
            assertSame(fakeClone, ((FakeClone) fakeClone).clone());
        }

        {
            // This proxy declares int clone(); which cannot be
            // invoked through Object::clone.
            var instance = (PrimitiveClone) Proxy.newProxyInstance(PrimitiveClone.class.getClassLoader(), new Class[] { PrimitiveClone.class }, (_, _, _) -> 42);
            assertEquals(42, instance.clone());
            // Verify the default Object::clone behavior (this is not Cloneable)
            assertThrows(CloneNotSupportedException.class, () -> {
                var _ = (Object) OBJECT_CLONE.invoke((Object) instance);
            });
        }

        {
            // This proxy declares int clone(); which cannot be
            // invoked through Object::clone
            var instance = (PrimitiveClone) Proxy.newProxyInstance(PrimitiveClone.class.getClassLoader(), new Class[] { PrimitiveClone.class, Cloneable.class }, (_, _, _) -> 76);
            assertEquals(76, instance.clone());
            // Verify the default Object::clone behavior (this is Cloneable)
            var clone = (Object) OBJECT_CLONE.invoke((Object) instance);
            assertNotSame(instance, clone);
            assertSame(instance.getClass(), clone.getClass());
            assertEquals(76, ((PrimitiveClone) clone).clone());
        }
    }

    // Duplicates with Object::clone so it is proxied
    @Test
    void testDuplicateClone() throws Throwable {
        {
            // This proxy declares Object clone();, which
            // accidentally overrides Object::clone
            var instance = (TrueClone) Proxy.newProxyInstance(TrueClone.class.getClassLoader(), new Class[] { TrueClone.class }, (p, _, _) -> p);
            assertSame(instance, instance.clone());
            // Verify Object::clone is overridden
            assertSame(instance, (Object) OBJECT_CLONE.invoke((Object) instance));
        }

        {
            // This proxy declares Object clone(); and FakeClone clone();.
            // They are considered duplicate methods and dispatched equivalently.
            // Object clone() accidentally overrides Object::clone, so now
            // FakeClone clone() can be called through Object::clone
            var instance = Proxy.newProxyInstance(TrueClone.class.getClassLoader(), new Class[] { TrueClone.class, FakeClone.class }, (p, _, _) -> p);
            assertSame(instance, ((FakeClone) instance).clone());
            assertSame(instance, ((TrueClone) instance).clone());
            // Verify Object::clone is overridden
            assertSame(instance, (Object) OBJECT_CLONE.invoke((Object) instance));
        }
    }

    interface FalseFinalize {
        // This method is not related to Object::finalize in the JVM, but it can't
        // be implemented in the Java Language unless using a lambda expression,
        // due to the Java language covariant override restrictions.
        int finalize();
    }

    interface TrueFinalize {
        // This method is identical to Object::finalize in the JVM, that calls
        // to Object::finalize can always call an implementation of this method
        // if it exists
        void finalize();
    }

    @Test
    void testDistinctFinalize() throws Throwable {
        AtomicInteger invokeCount = new AtomicInteger();
        // This proxy declares int finalize(), which cannot be
        // invoked through Object::finalize.
        var instance = Proxy.newProxyInstance(FalseFinalize.class.getClassLoader(), new Class[] { FalseFinalize.class }, (_, _, _) -> invokeCount.incrementAndGet());
        // Verify the default Object::finalize behavior
        OBJECT_FINALIZE.invoke(instance);
        assertEquals(0, invokeCount.get());
        assertEquals(1, ((FalseFinalize) instance).finalize());
    }

    @Test
    void testDuplicateFinalize() throws Throwable {
        AtomicInteger invokeCount = new AtomicInteger();
        // This proxy declares void finalize(), which can be
        // invoked through Object::finalize.
        var instance = Proxy.newProxyInstance(TrueFinalize.class.getClassLoader(), new Class[] { TrueFinalize.class }, (_, _, _) -> invokeCount.incrementAndGet());
        // Verify the overridden Object::finalize behavior
        OBJECT_FINALIZE.invoke(instance);
        assertEquals(1, invokeCount.get());
        ((TrueFinalize) instance).finalize();
        assertEquals(2, invokeCount.get());
    }
}