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From "Nick Williams (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LOG4J2-242) Make Messages more fluent
Date Thu, 30 May 2013 15:36:20 GMT

    [ https://issues.apache.org/jira/browse/LOG4J2-242?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13670414#comment-13670414

Nick Williams commented on LOG4J2-242:

Ralph, I think a fluent API does not require some of the tricks you think it does.

Consider the code example you demonstrated:


The {{message}} method wouldn't return the {{log}} it was called on. It would return a {{new
MessageBuilder}} (or whatever you want to call it). The message builder would hold a reference
to the {{Logger}} it was created from. Each method call on the message builder would return
the message builder again. Then when {{info}}, {{warn}}, {{error}}, etc. are called on the
message builder, it would in turn call the corresponding method on the underlying {{Logger}}
that it's holding on to. No properties held on to in the {{Logger}}, no {{ThreadLocal}} s

I actually really like this idea. Fluent APIs are much more natural to some types of people
(I think EasyMock's fluent API is one of its greatest strengths), and this would be a feature
that would help Log4j 2 stand out among other logging APIs.
> Make Messages more fluent
> -------------------------
>                 Key: LOG4J2-242
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-242
>             Project: Log4j 2
>          Issue Type: Improvement
>          Components: API
>    Affects Versions: 2.0-beta5
>            Reporter: Bruce Brouwer
> I really like the feature were we can pass in a Message object into the logger methods.
However, it bugs me that some of the implementations of Message provide vararg constructors,
and others only provide an Object[] parameter. I really would like to write this code:
>     log.info(new ParameterizedMessage("abc: {} xyz: {}", abc, xyz), throwable);
> I realize that this particular example would work with this code by default:
>     log.info("abc: {} xyz: {}", abc, xyz, throwable);
> But the other Message implementations don't provide a vararg constructor, nor do they
try to detect the last parameter as a Throwable.
> [LOG4J2-48] addresses some of the complexity of having varargs with the last vararg being
an implicit final parameter, but again, this only works with ParameterizedMessage. But I would
like this to be more consistent across the board. One idea that I had was this:
>     log.info(new ParameterizedMessage("abc: {} xyz: {}", abc, xyz).throwing(throwable));
> Now all of the message constructors (not just ParameterizedMessage) could have varargs
with none of them providing a Throwable parameter in the constructor, but provided through
a more fluent API. I don't know that it would warrant adding it to the Message interface,
but we could go further with it by adding these methods:
>     Message withParameters(Object... parameters);
>     Message throwing(Throwable throwable);
> It wouldn't be absolutely necessary as the concrete implementations could define that
and work in my case.
> Another idea that I had was maybe a bit more impactful to the Logger API. What if I wrote
my code like this:
>     log.with(exception).info("abc: {} xyz: {}", abc, xyz);
>     // or maybe this
>     log.message("abc: {} xyz: {}", abc, xyz).with(exception).info();
> That would necessitate something like a LogBuilder interface, maybe tie it into the MessageFactory
classes. This LogBuilder interface could have these methods:
>     LogBuilder message(String pattern, Object... params);
>     LogBuilder with(Throwable t);
>     LogBuilder marker(Marker marker);
>     LogBuilder level(Level level);
>     void info(); // and others like it
>     void info(String pattern, Object... params); // and others like it
> I'm not exactly sure what the best way would be to go and implement this as I'm sure
you don't want to have objects created all over the place. 
> Is this an idea worth pursuing a bit further?

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