RFR: 8283660: Convert com/sun/jndi/ldap/AbstractLdapNamingEnumeration.java finalizer to Cleaner [v12]

[Roger Riggs]

On Mon, 6 Jun 2022 21:59:56 GMT, Brent Christian <bchristi 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.
>
> Brent Christian has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Restore EnumCtx to being an inner class, to keep all the state together in the code

trivial comments.
The commented out printf/println's should be removed before committing.

src/java.naming/share/classes/com/sun/jndi/ldap/AbstractLdapNamingEnumeration.java line 152:

> 150:             // Ensures that context won't get closed from underneath us
> 151:             this.enumCtx.homeCtx.incEnumCount();
> 152:             this.cleanable = LDAP_CLEANER.register(this, enumCtx);

Use  `enumCtx.getHomeCts()` above.
Use `this.enumCtx` in call to `register`.
For consistency.

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Marked as reviewed by rriggs (Reviewer).

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