On Sun, 17 Apr 2022 16:17:30 GMT, liach <d...@openjdk.java.net> wrote:
> Convert dynamic proxies to hidden classes. Modifies the serialization of > proxies (requires change in "Java Object Serialization Specification"). Makes > the proxies hidden in stack traces. Removes duplicate logic in proxy building. > > The main compatibility changes and their rationales are: > 1. Modification to the serialization specification: In the "An instance of > the class is allocated... The contents restored appropriately" section, I > propose explicitly state that handling of proxies are unspecified as to allow > implementation freedom, though I've seen deliberate attempts for proxies to > implement interfaces with `readResolve` in order to control their > serialization behavior. > - This is for the existing generated constructor accessor is > bytecode-based, which cannot refer to hidden classes. > - An alternative is to preserve the behavior, where the serialization > constructor calls `invokespecial` on the closest serializable superclass' > no-arg constructor, like in #1830 by @DasBrain. > - My rationale against preservation is such super calls are unsafe and > should be discouraged in the long term. Calling the existing constructor with > a dummy argument, as in my implementation, would be more safe. > 2. The disappearance of proxies in stack traces. > - Same behavior exists in lambda expressions: For instance, in > `((Runnable) () -> { throw new Error(); }).run();`, the `run` method, > implemented by the lambda, will not appear in the stack trace, and isn't too > problematic. > > A summary of the rest of the changes: > 1. Merged the two passes of determining module and package of the proxy into > one. This reduced a lot of code and allowed anchor class (for hidden class > creation) selection be done together as well. > 2. Exposed internal API for obtaining a full-privileged lookup to the rest of > `java.base`. This API is intended for implementation of legacy (pre > `MethodHandles.Lookup`) caller sensitive public APIs so they don't need more > complex tricks to obtain proper permissions as lookups. > 3. Implements [8229959](https://bugs.openjdk.java.net/browse/JDK-8229959): > passes methods computed by proxy generator as class data to the hidden proxy > class to reduce generated proxy class size and improve performance. > > In addition, since this change is somewhat large, should we keep the old > proxy generator as well and have it toggled through a command-line flag (like > the old v49 proxy generator or the old reflection implementation)? > > Please feel free to comment or review. This change definitely requires a CSR, > but I have yet to determine what specifications should be changed. Fixing deserialization is not particularly hard. A longer term goal is to declare a readResolve for proxies (presumably by extra methods on invocation handlers) to convert serialization result to something else ------------- PR: https://git.openjdk.java.net/jdk/pull/8278