it's a nested class, but it's loaded with the same class loader as the toplevel. which is what i thought you thought was the problem when
you wrote: > this test loads a nested type into a different classloader to its enclosing type and: > it is a requirement that all nest members be defined in the same > package - which implies the same classloader On Mon, Mar 25, 2019 at 11:40 PM David Holmes <david.hol...@oracle.com> wrote: > On 26/03/2019 1:06 pm, seth lytle wrote: > > i still get the same stack trace after breaking the example out into two > > files. does that sufficiently address the nesting issue ? > > ?? > > public static class MyCode ... > > is still a nested class. > > David > > > file: SerializedLambdaTest > > package test; > > > > import java.io.ByteArrayInputStream; > > import java.io.ByteArrayOutputStream; > > import java.io.IOException; > > import java.io.ObjectInputStream; > > import java.io.ObjectOutputStream; > > import java.io.Serializable; > > > > // from: https://bugs.openjdk.java.net/browse/JDK-8008770 > > public class SerializedLambdaTest implements Runnable { > > public void run() { new MyCode().run(); } > > public interface SerializableRunnable extends Runnable,Serializable > { > > } > > public static class MyCode implements SerializableRunnable { > > SerializableRunnable runnable2 = () > > -> { > > System.out.println("HELLO"+this.getClass()); > > }; > > private byte[] serialize(Object o) { > > ByteArrayOutputStream baos; > > try ( > > ObjectOutputStream oos > > = new ObjectOutputStream(baos = new > > ByteArrayOutputStream())) { > > oos.writeObject(o); > > } catch (IOException e) { > > throw new RuntimeException(e); > > } > > return baos.toByteArray(); > > } > > private <T> T deserialize(byte[] bytes) { > > try ( > > ObjectInputStream ois > > = new ObjectInputStream(new > > ByteArrayInputStream(bytes))) { > > return (T) ois.readObject(); > > } catch (IOException|ClassNotFoundException e) { > > throw new RuntimeException(e); > > } > > } > > @Override > > public void run() { > > System.out.println(" this: "+this); > > SerializableRunnable deSerializedThis > > = deserialize(serialize(this)); > > System.out.println(" deSerializedThis: " > > +deSerializedThis); > > > > SerializableRunnable runnable = runnable2; > > System.out.println(" runnable: "+runnable); > > SerializableRunnable deSerializedRunnable > > = deserialize(serialize(runnable)); > > System.out.println("deSerializedRunnable: " > > +deSerializedRunnable); > > } > > } > > } > > > > > > file: MyClassLoader > > package test; > > > > import java.io.IOException; > > import java.io.InputStream; > > > > class MyClassLoader extends ClassLoader { > > MyClassLoader(ClassLoader parent) { > > super(parent); > > } > > @Override > > protected Class<?> loadClass(String name,boolean resolve) throws > > ClassNotFoundException { > > if (name.startsWith("test.")) > > synchronized (getClassLoadingLock(name)) { > > Class<?> c = findLoadedClass(name); > > if (c==null) c = findClass(name); > > if (resolve) resolveClass(c); > > return c; > > } > > else return super.loadClass(name,resolve); > > } > > @Override > > protected Class<?> findClass(String name) throws > > ClassNotFoundException { > > String path = name.replace('.','/').concat(".class"); > > try (final InputStream is = getResourceAsStream(path)) { > > if (is!=null) { > > byte[] bytes = is.readAllBytes(); > > return defineClass(name,bytes,0,bytes.length); > > } > > else throw new ClassNotFoundException(name); > > } catch (IOException e) { > > throw new ClassNotFoundException(name,e); > > } > > } > > public static void main(String[] args) throws Exception { > > ClassLoader myCl = new MyClassLoader( > > MyClassLoader.class.getClassLoader() > > ); > > Class<?> myCodeClass = Class.forName( > > "test.SerializedLambdaTest", > > true, > > myCl > > ); > > Runnable myCode = (Runnable) myCodeClass.newInstance(); > > myCode.run(); > > } > > } > > > > > > > > > > On Mon, Mar 25, 2019 at 10:34 PM David Holmes <david.hol...@oracle.com > > <mailto:david.hol...@oracle.com>> wrote: > > > > Hi Seth, > > > > On 26/03/2019 12:16 pm, seth lytle wrote: > > > i haven't changed the assignment from the original test case > > (which was > > > accepted as valid at the time). i haven't gone through it in > > depth, but > > > assume that it's ok and used it since people are already familiar > > with > > > it. it appears to me that that example uses reflection to > > allocate an > > > instance using a definitive class loader and then uses a runnable > > for > > > the serialization/deserialization cycle > > > > > > the class cast exception happens not at the example level, but > deep > > > inside `readObject` when it's doing an internal assignment > > > > > > perhaps my choice of words "into a new classloader" was > > insufficient or > > > misleading. in both examples that i've come up with so far, the > > class > > > loader calls defineClass directly without first delegating to > > super (for > > > a subset of the classes). so "into a definitive classloader" > > might have > > > been a better choice > > > > I think the basic problem is that this test loads a nested type into > a > > different classloader to its enclosing type. I can easily imagine > this > > messing up the code that gets generated to implement the lambda > > expression - but I'd need to examine that code in detail to see > exactly > > why (others may know this more readily than I do). It's unclear to me > > whether this would be considered a bug or a "don't do that" > situation. > > As of JDK 11, nested types define "nests" at the VM level (see > JEP-181) > > and it is a requirement that all nest members be defined in the same > > package - which implies the same classloader. > > > > David > > > > > > > > > > > > > > > > > > > > On Mon, Mar 25, 2019 at 9:34 PM David Holmes > > <david.hol...@oracle.com <mailto:david.hol...@oracle.com> > > > <mailto:david.hol...@oracle.com > > <mailto:david.hol...@oracle.com>>> wrote: > > > > > > Hi Seth, > > > > > > On 26/03/2019 11:22 am, seth lytle wrote: > > > > if a lambda is a field and captures `this`, and it's > > deserialized > > > into a > > > > new class loader, it throws a ClassCastException. > > > > > > Not sure I follow. If you load a class into a different > > classloader > > > then > > > you get a different type. It might appear the same to you but > > it is a > > > distinct type, so you can't assign across different instances > > loaded by > > > different classloaders. > > > > > > Cheers, > > > David > > > ----- > > > > > > > i came across this bug > > > > independently while writing a test, but then found an old > > openjdk > > > bug with > > > > a similar issue and tweaked the test case (source below). > > my version > > > > differs only in > > > > 1. moved the lambda to a field > > > > 2. reference `this` in it > > > > 3. uses readAllBytes instead of the internal method > > > > 4. formatting > > > > > > > > running with java 11 or 12 (or java 8 using a substitute > for > > > readAllBytes) > > > > results in: > > > > this: > > test.SerializedLambdaTest$MyCode@8efb846 > > > > deSerializedThis: > > test.SerializedLambdaTest$MyCode@2b71fc7e > > > > runnable: > > > > > > > > > > test.SerializedLambdaTest$MyCode$$Lambda$1/0x0000000801188440@37bba400 > > > > Exception in thread "main" java.lang.ClassCastException: > > cannot > > > assign > > > > instance of java.lang.invoke.SerializedLambda to field > > > > test.SerializedLambdaTest$MyCode.runnable2 of type > > > > test.SerializedLambdaTest$SerializableRunnable in instance > of > > > > test.SerializedLambdaTest$MyCode > > > > at > > > > java.base/java.io <http://java.io> > > > > > <http://java.io > >.ObjectStreamClass$FieldReflector.setObjFieldValues(ObjectStreamClass.java:2190) > > > > at > > > > java.base/java.io <http://java.io> > > > > > <http://java.io > >.ObjectStreamClass$FieldReflector.checkObjectFieldValueTypes(ObjectStreamClass.java:2153) > > > > at > > > > java.base/java.io <http://java.io> > > > > > <http://java.io > >.ObjectStreamClass.checkObjFieldValueTypes(ObjectStreamClass.java:1407) > > > > at > > > > java.base/java.io <http://java.io> > > > > > <http://java.io > >.ObjectInputStream.defaultCheckFieldValues(ObjectInputStream.java:2371) > > > > at > > > > java.base/java.io <http://java.io> > > > > > <http://java.io > >.ObjectInputStream.readSerialData(ObjectInputStream.java:2278) > > > > at > > > > java.base/java.io <http://java.io> > > > > > <http://java.io > >.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2087) > > > > at > > > > java.base/java.io <http://java.io> > > > > > <http://java.io > >.ObjectInputStream.readObject0(ObjectInputStream.java:1594) > > > > at > > > > java.base/java.io <http://java.io> > > > > > <http://java.io > >.ObjectInputStream.readArray(ObjectInputStream.java:1993) > > > > at > > > > java.base/java.io <http://java.io> > > > > > <http://java.io > >.ObjectInputStream.readObject0(ObjectInputStream.java:1588) > > > > at > > > > java.base/java.io <http://java.io> > > > > > <http://java.io > >.ObjectInputStream.defaultReadFields(ObjectInputStream.java:2355) > > > > at > > > > java.base/java.io <http://java.io> > > > > > <http://java.io > >.ObjectInputStream.readSerialData(ObjectInputStream.java:2249) > > > > at > > > > java.base/java.io <http://java.io> > > > > > <http://java.io > >.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2087) > > > > at > > > > java.base/java.io <http://java.io> > > > > > <http://java.io > >.ObjectInputStream.readObject0(ObjectInputStream.java:1594) > > > > at > > > > java.base/java.io <http://java.io> > > > > > <http://java.io > >.ObjectInputStream.readObject(ObjectInputStream.java:430) > > > > at > > > > > > > > > > test.SerializedLambdaTest$MyCode.deserialize(SerializedLambdaTest.java:35) > > > > at > > test.SerializedLambdaTest$MyCode.run(SerializedLambdaTest.java:51) > > > > at > > test.SerializedLambdaTest.main(SerializedLambdaTest.java:66) > > > > > > > > > > > > > > > > https://bugs.openjdk.java.net/browse/JDK-8008770 > > > > > > > > > > > > package test; > > > > > > > > import java.io.ByteArrayInputStream; > > > > import java.io.ByteArrayOutputStream; > > > > import java.io.IOException; > > > > import java.io.InputStream; > > > > import java.io.ObjectInputStream; > > > > import java.io.ObjectOutputStream; > > > > import java.io.Serializable; > > > > > > > > // from: https://bugs.openjdk.java.net/browse/JDK-8008770 > > > > public class SerializedLambdaTest { > > > > public interface SerializableRunnable extends > > > Runnable,Serializable { > > > > } > > > > public static class MyCode implements > > SerializableRunnable { > > > > SerializableRunnable runnable2 = () > > > > -> { > > > > System.out.println("HELLO"+this.getClass()); > > > > }; > > > > private byte[] serialize(Object o) { > > > > ByteArrayOutputStream baos; > > > > try ( > > > > ObjectOutputStream oos > > > > = new ObjectOutputStream(baos = new > > > > ByteArrayOutputStream())) { > > > > oos.writeObject(o); > > > > } catch (IOException e) { > > > > throw new RuntimeException(e); > > > > } > > > > return baos.toByteArray(); > > > > } > > > > private <T> T deserialize(byte[] bytes) { > > > > try ( > > > > ObjectInputStream ois > > > > = new ObjectInputStream(new > > > > ByteArrayInputStream(bytes))) { > > > > return (T) ois.readObject(); > > > > } catch (IOException|ClassNotFoundException > e) { > > > > throw new RuntimeException(e); > > > > } > > > > } > > > > @Override > > > > public void run() { > > > > System.out.println(" this: > > "+this); > > > > SerializableRunnable deSerializedThis > > > > = deserialize(serialize(this)); > > > > System.out.println(" deSerializedThis: " > > > > +deSerializedThis); > > > > > > > > SerializableRunnable runnable = runnable2; > > > > System.out.println(" runnable: > > "+runnable); > > > > SerializableRunnable deSerializedRunnable > > > > = deserialize(serialize(runnable)); > > > > System.out.println("deSerializedRunnable: " > > > > +deSerializedRunnable); > > > > } > > > > } > > > > public static void main(String[] args) throws > Exception { > > > > ClassLoader myCl = new MyClassLoader( > > > > > SerializedLambdaTest.class.getClassLoader() > > > > ); > > > > Class<?> myCodeClass = Class.forName( > > > > > > SerializedLambdaTest.class.getName()+"$MyCode", > > > > true, > > > > myCl > > > > ); > > > > Runnable myCode = (Runnable) > > myCodeClass.newInstance(); > > > > myCode.run(); > > > > } > > > > static class MyClassLoader extends ClassLoader { > > > > MyClassLoader(ClassLoader parent) { > > > > super(parent); > > > > } > > > > @Override > > > > protected Class<?> loadClass(String name,boolean > > resolve) > > > > throws ClassNotFoundException { > > > > if (name.startsWith("test.")) > > > > synchronized (getClassLoadingLock(name)) { > > > > Class<?> c = findLoadedClass(name); > > > > if (c==null) > > > > c = findClass(name); > > > > if (resolve) > > > > resolveClass(c); > > > > return c; > > > > } > > > > else > > > > return super.loadClass(name,resolve); > > > > } > > > > @Override > > > > protected Class<?> findClass(String name) throws > > > > ClassNotFoundException { > > > > String path = > > name.replace('.','/').concat(".class"); > > > > try ( InputStream is = > > getResourceAsStream(path)) { > > > > if (is!=null) { > > > > byte[] bytes = is.readAllBytes(); > > > > return > > defineClass(name,bytes,0,bytes.length); > > > > } else > > > > throw new > ClassNotFoundException(name); > > > > } catch (IOException e) { > > > > throw new ClassNotFoundException(name,e); > > > > } > > > > } > > > > } > > > > } > > > > > > > > > >
