RFR: 8283660: Convert com/sun/jndi/ldap/AbstractLdapNamingEnumeration.java finalizer to Cleaner

[Brent Christian]

On Wed, 20 Apr 2022 13:48:21 GMT, Daniel Fuchs <dfuchs at openjdk.org> wrote:

>> Please review this change to replace the finalizer in `AbstractLdapNamingEnumeration` with a Cleaner.
>> 
>> The pieces of state required for cleanup (`LdapCtx homeCtx`, `LdapResult res`, and `LdapClient enumClnt`) are moved to a static inner class . From there, the change is fairly mechanical.
>> 
>> Details of note: 
>> 1. Some operations need to change the state values (the update() method is probably the most interesting).
>> 2. Subclasses need to access `homeCtx`; I added a `homeCtx()` method to read `homeCtx` from the superclass's `state`.
>> 
>> The test case is based on a copy of `com/sun/jndi/ldap/blits/AddTests/AddNewEntry.java`. A more minimal test case might be possible, but this was done for expediency.
>> 
>> The test only confirms that the new Cleaner use does not keep the object reachable. It only tests `LdapSearchEnumeration` (not `LdapNamingEnumeration` or `LdapBindingEnumeration`, though all are subclasses of `AbstractLdapNamingEnumeration`). 
>> 
>> Thanks.
>
> src/java.naming/share/classes/com/sun/jndi/ldap/AbstractLdapNamingEnumeration.java line 73:
> 
>> 71:         public void run() {
>> 72:             if (enumClnt != null) {
>> 73:                 enumClnt.clearSearchReply(res, homeCtx.reqCtls);
> 
> It's a bit strange to see that there is no guard here to verify that `homeCtx != null`, when line 76 implies that it might. My reading is that `homeCtxt` is not supposed to be `null` when `enumClnt` is not `null`. That could be explained in a comment, or alternatively asserted just before line 73 (`assert homeCtx != null;`)

Yes, it is strange -- that code came from the finalizer. I will add an assert.

> src/java.naming/share/classes/com/sun/jndi/ldap/AbstractLdapNamingEnumeration.java line 83:
> 
>> 81:     }
>> 82: 
>> 83:     private CleaningAction state;
> 
> I wonder if state should be final?

Makes sense to me. `cleanable` can be final, too.

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PR: https://git.openjdk.java.net/jdk/pull/8311