JEP 102 Process Updates revised API draft

[Roger Riggs]

Hi,

Just a thought, it might be useful to introduce a public subtype of 
Process that is
returned from ProcessBuilder for which the guarantees about behavior 
could be
tighter  (no UOEs).  It would also provide a place to document the 
behaviors
now spread across ProcessBuilder and Process.

$.02, Roger


On 3/12/15 9:09 AM, Chris Hegarty wrote:
> This is looking good, still looking at the detail… just a quick comment.
>
> It may be possible to remove the UOE from Process.onExit, if you implement the “never to be used” default without using ProcessHandle?
>
> diff --git a/src/java.base/share/classes/java/lang/Process.java b/src/java.base/share/classes/java/lang/Process.java
> --- a/src/java.base/share/classes/java/lang/Process.java
> +++ b/src/java.base/share/classes/java/lang/Process.java
> @@ -360,20 +360,20 @@
>        * a unique instance is returned for each call to {@code onExit}.
>        *
>        * @throws IllegalStateException if the process is the current process
> -     * @throws UnsupportedOperationException if the Process implementation
> -     *         does not support this operation
> -     * @implSpec
> -     * The Process instances created by {@link ProcessBuilder ProcessBuilder} return
> -     * a {@code ComputableFuture<Process>} equivalent
> -     * to {@code toHandle().onExit().thenApply(ph -> this)}.
>        *
> -     * @implNote
> -     * The implementation of this method is {@link #toHandle toHandle().onExit().thenApply(ph -> this)}.
> -     * Override to provide more specific onExit behavior.
>        * @since 1.9
>        */
>       public CompletableFuture<Process> onExit() {
> -        return toHandle().onExit().thenApply((ph) -> this);
> +        return CompletableFuture.supplyAsync(this::wait0);
> +    }
> +
> +    private Process wait0() {
> +        while(true) {
> +            try {
> +                waitFor();
> +                return this;
> +            } catch (InterruptedException x) {}
> +        }
>       }
>   
>       /**
>
> -Chris.
>
> On 11 Mar 2015, at 19:58, Roger Riggs <Roger.Riggs at oracle.com> wrote:
>
>> Hi,
>>
>> The recommendations have been applied to the javadoc and the sandbox JDK-8046092-branch.
>>
>>     http://cr.openjdk.java.net/~rriggs/ph-apidraft/
>>
>> Some operations on a Process take an extra dereference due to the delegation to ProcessHandle.
>> For example, getting the cputime or startTime of the process:
>>     Process p = ...
>>     Duration d = p.toHandle().info().totalCpuDuration();
>>     Instant start = p.toHandle().info().startInstant();
>>
>> As do the listing of children; convenience methods could be introduced with the UOE possibility
>> but that is a risk only for externally defined Process subtypes.
>> Developers working with Processes should not have to deal with ProcessHandle
>> to get information about the processes they spawn.
>>
>> Comments appreciated, Roger
>>