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From Josh Canfield <joshcanfi...@gmail.com>
Subject Re: [CONF] Apache Tapestry > Developer Bible
Date Fri, 01 Oct 2010 01:27:01 GMT
Ah. I thought I needed my Apache account. I'm signed up for cwiki now and
I'll just fix it next time! :)
On Sep 30, 2010 5:58 PM, "Kalle Korhonen" <kalle.o.korhonen@gmail.com>
> I see - but cwiki accounts are separate from Apache accounts, so just sign
> Kalle
> On Thu, Sep 30, 2010 at 5:52 PM, Josh Canfield <joshcanfield@gmail.com>
>> Yep, but I'm still waiting for my account...
>> On Sep 30, 2010 4:52 PM, "Kalle Korhonen" <kalle.o.korhonen@gmail.com>
>> wrote:
>>> Fixed. Faster to fix yourself than send an email, no?
>>> Kalle
>>> On Thu, Sep 30, 2010 at 3:31 PM, Josh Canfield <joshcanfield@gmail.com>
>> wrote:
>>>> typo in Copyright section:  "try to check the coyright date"
>>>> On Thu, Sep 30, 2010 at 2:49 PM, <confluence@apache.org> wrote:
>>>>>    Developer Bible<
>> https://cwiki.apache.org/confluence/display/TAPESTRY/Developer+Bible>
>>>>> *added* by Howard M. Lewis Ship<
>> https://cwiki.apache.org/confluence/display/~hlship>
>>>>> This is a semi-random outpouring of thoughts related to being a
>>>>> committer.
>>>>> IDE IntelliJ
>>>>> It's a free license for all committers and it's just better. Yes, the
>> first
>>>>> few days
>>>>> can be an unpleasant fumble because everything is almost, but not
>>>>> familiar. Pretty soon you'll love IDEA and
>>>>> recognize that Eclipse has been bending you over and doing unspeakable
>>>>> things.
>>>>> There are shared code formatting settings in
>> *<support/idea-settings.jar*>.
>>>>> This will prevent
>>>>> unexpected conflicts due to formatting.
>>>>> Eclipse
>>>>> Howard uses this ... because he can't manage to switch IDEs constantly
>> (he
>>>>> uses Eclipse for training). Lately
>>>>> its gotten better.
>>>>> Copyrights
>>>>> All source files should have a copyright comment on top, except where
>> such
>>>>> a comment
>>>>> would interfere with its behavior. For example, component template
>>>>> omit the comment.
>>>>> The year on the copyright should be updated as a file changes. As you
>> are
>>>>> reviewing your changes
>>>>> before checking them in, try to check the coyright date, and add the
>>>>> current year to the list if not
>>>>> present.
>>>>> Commit Messages
>>>>> Always provide a commit message. I generally try to work off the JIRA,
>> so
>>>>> my commit message is often:
>>>>> TAP5-1234: Make the Foo Widget more Ajax-tastic!
>>>>> It is *very important* to include the JIRA issue id in the commit.
>> is
>>>>> used in many places:
>>>>> JIRA links issues to the SVN commits for that issue (very handy for
>> seeing
>>>>> what changed
>>>>> as part of a bug fix). The Hudson CI server does as well, and will
>> actually
>>>>> link SVN commits to issues after
>>>>> succesfully building.
>>>>> JIRA Procedures
>>>>> All Tapestry committers should be registerred with JIRA and part of
>>>>> tapestry-developers JIRA group.
>>>>> I work the following JIRA list: JIRA Work Queue<
>>>>> .
>>>>> Ideally, we would always work top priortity to low priority. I
>>>>> sometimes jump out of order,
>>>>> if there's something cool to work on that fits in an available time
>> slot.
>>>>> Alternately, you are always
>>>>> allowed to change the priority of a bug before or as you work it.
>>>>> Starting work
>>>>> When you start to work on an issue, make sure it is *assigned to you*
>> and
>>>>> use the *start progress*
>>>>> option.
>>>>> I often add comments about the state of the fix, or the challenges in
>>>>> creating a fix. This often spurs the Issue's adder to
>>>>> provide more details.
>>>>> I often update the issue description to make it more legible and more
>>>>> precise, i.e., "NPE in CheckUpdates"
>>>>> might become "NullPointerException when checking for updates to files
>> that
>>>>> have been deleted". Verbose is good.
>>>>> Closing bugs
>>>>> Is it a bug fix without tests? *No.* In some cases, I write new tests
>>>>> prove that an issue is not valid and
>>>>> then leave the tests in place – then close the bug as invalid.
>>>>> A good plan is to write a test that fails then work the code until the
>> test
>>>>> passes.
>>>>> I'm also surprised by how often code works in a unit test but fails
>>>>> unexpectedly in an integration test.
>>>>> As the G-Man says *"Expect unforseen consequences"*.
>>>>> When you check in a fix, you should *close* the issue and make sure
>> *fix
>>>>> release* is correct.
>>>>> We're playing fast and loose – a better procedure would be to mark
>> bug
>>>>> resolved and verify
>>>>> the fix before closing it. That's ok, we have a community to double
>> check
>>>>> our work .
>>>>> For anything non-trivial, wait for the Hudson CI server to build. It
>>>>> catches a lot of things ... such as
>>>>> files that were not added to SVN. And even IntelliJ has a bit of
>>>>> with wildly refactored code.
>>>>> Hudson will catch all that.
>>>>> Invalid issues and duplicates
>>>>> Always provide comments about why_ an issue is invalid (*"A Ruby
>>>>> implementation of Tapestry is out of scope for the project."*), or at
>>>>> least, a link to the duplicate issues.
>>>>> Close the issue but *make sure the fix release is blank*. Otherwise,
>>>>> issue _will be listed
>>>>> in the release notes_, which we don't want.
>>>>> Copyrights
>>>>> The ASF copyright must appear on all Java source files. Technically it
>>>>> should appear on all non-binary
>>>>> files in the repository.
>>>>> As you make changes to files, update the copyright to add the current
>> year
>>>>> to the list. The goal is that the copyright
>>>>> notice includes the year in which files change. When creating a new
>> file,
>>>>> don't back date the copyright year ... starwith the current year. Try
>> not to
>>>>> change the copyright year on files that haven't actually changed.
>>>>> IntelliJ has a great comparison view: Cmd-9 to see the local changes,
>> the
>>>>> Cmd-D to see the differences.
>>>>> I whip through the changes (using Cmd-forward arrow) and make sure
>>>>> copyrights are up to date as I review the changes
>>>>> prior to a commit.
>>>>> Public vs. Private/Internal
>>>>> This is a real big deal. As long as code is in the internal package,
>>>>> have a high degree of carte-blanche
>>>>> to change it. As soon as code is public, we become handcuffed to
>> backwards
>>>>> compatibility.
>>>>> *Interfaces are public, implementations are private*. You can see this
>> is
>>>>> the bulk of the code, where
>>>>> org.apache.tapestry5.services is almost all interfaces and the
>>>>> implementations are
>>>>> in org.apache.tapestry5.internal.services.
>>>>> Many more services have both the interface and the implementation in
>>>>> org.apache.tapestry5.internal.services.
>>>>> We absolutely *do not* want to make Page or ComponentPageElement
>>>>> You will often see
>>>>> public service facades that take a page name as a method parameter,
>>>>> and convert it to a page instance before invoking methods
>>>>> on internal services.
>>>>> Evolving Components
>>>>> We do not have a specific plan for this yet. Future Tapestry 5 will
>>>>> features to allow clean renames
>>>>> of parameters, and a way to deprecated and eventually remove
>>>>> Evolving Interfaces
>>>>> Tapestry uses interfaces quite extensively.
>>>>> Interfaces fall into two categories: service interfaces called by user
>>>>> code, and interfaces implemented by user code.
>>>>> Internal interfaces may be changed at any time. That's why so much is
>> kept
>>>>> internal.
>>>>> Service Interfaces
>>>>> New methods may be added if absolutely necessary, but this should be
>>>>> avoided if at all possible. Don't forget
>>>>> the @since Javadoc annotation.
>>>>> Consider having a stable public facade service whose implementation
>> calls
>>>>> into one or more internal service.
>>>>> User Interfaces
>>>>> These should be frozen, no changes once released. Failure to do so
>> causes
>>>>> *non-backwards compatible upgrade problems*;
>>>>> that is, classes that implement the (old) interface are suddenly
>> invalid,
>>>>> missing methods from the (new) interface.
>>>>> Consider introducing a new interface that extends the old one and adds
>> new
>>>>> methods. Make sure you support both.
>>>>> You can see this with ServiceDef and ServiceDef2 (which extends
>>>>> ServiceDef). Yes this can be a bit ugly.
>>>>> I actually have utility methods that convert from ServiceDef to
>>>>> ServiceDef2, adding a wrapper implementation around
>>>>> a ServiceDef instance if necessary:
>>>>>  Use of @since
>>>>> When adding new classes or interface, or adding new methods to
>>>>> types, add an @since Javadoc comment.
>>>>> Use the complete version number of the release in which the type or
>> method
>>>>> was added: i.e., *@since*.
>>>>> Code Style
>>>>> Yes, at one time I (Howard) used leading underscores for field names.
>> I've
>>>>> since changed my mind, but
>>>>> I unfortunately infected other people; please try to make your code
>> blend
>>>>> in when modifying existing source.
>>>>> Long ago, Tapestry (3) code used the regrettable
>> "leading-I-on-interfaces"
>>>>> style. Don't do that. Everything's an interface.
>>>>> I prefer braces on a new line (and thus, open braces lined up with
>>>>> braces), so that's what the default
>>>>> code formatting is set up for. I sometimes omit braces for trivial if
>>>>> statements, such as {{ if (!test) return; }}.
>>>>> I use a lot of vertical whitespace to break methods into logical
>> sections.
>>>>> We're coding Java, not Pascal; I'd much rather see a few checks early
>>>>> with quick returns or exceptions than
>>>>> have ten-levels deep block nesting just so a method can have a single
>>>>> return statement. In other words,
>>>>> *else considered harmful*. Low code complexity is better, more
>>>>> more maintainable code.
>>>>> I don't bother alphabetizing things, because I have an IDE that lets
>>>>> jump around easily.
>>>>> *Final is the new private.* Final fields are great for multi-threaded
>>>>> code. Especially when creating
>>>>> service implementations with dependencies, store those dependencies
>>>>> final fields. Once we're all running
>>>>> on 100 core workstations, you'll thank me. Seriously, Java's memory
>> model
>>>>> is seriously twisted stuff, and
>>>>> assigning to a non-final field from a constructor opens up a tiny
>> of
>>>>> non-thread safety.
>>>>> Comments
>>>>> Comments are overwhelmingly important. Try to capture the *why* of a
>> class
>>>>> or method. Add lots
>>>>> of links, to code that will be invoked by the method, to related
>> or
>>>>> classes, and so forth. For instance,
>>>>> I'll often have an annotation, a worker class for the annotation, and
>>>>> related service all cross-linked.
>>>>> Comment the *interfaces* and don't get worked up on the
>> *implementations*.
>>>>> Javadoc does a perfectly
>>>>> good job of copying interface comments to implementations, so this
>>>>> under the *Dont Repeat Yourself*
>>>>> guideline.
>>>>> Be very careful about documenting what methods can accept null, and
>>>>> methods may return null. Generally
>>>>> speaking, people will assume that null is not allowed for parameter
>>>>> method will never return null, unless
>>>>> it is explicitly documented that null is allowed (or potentially
>> returned).
>>>>> Documentation
>>>>> Try and keep the documentation up-to date as you make changes; it is
>> *much
>>>>> * harder to do so later. This is now much easier using the Confluence
>> wiki
>>>>> (you're reading it ).
>>>>> Documentation is the *#1 criticism* of Tapestry!
>>>>> Class and Method Naming Conventions
>>>>> aming things is hard. Names that make sense to one person won't to
>> another.
>>>>> hat being said, I've tried to be somewhat consistent with naming. Not
>>>>> perfectly.
>>>>> Factory, Creator
>>>>> A factory class creates new objects. Methods will often be prefixed
>>>>> "create"
>>>>> or "new". Don't expect a Factory to cache anything, it just creates
>>>>> things.
>>>>> Source
>>>>> A source is a level up from a Factory. It *may* combine multiple
>> factories
>>>>> together.
>>>>> It *usually* will cache the result. Method are often prefixed with
>> "get".
>>>>> Find vs. Get
>>>>> For methods: A "find" prefix indicates that a non-match is valid and
>> null
>>>>> may be returned.
>>>>> A "get" prefix indicates that a non-match is invalid and an exception
>> will
>>>>> be thrown
>>>>> in that case (and null will never be returned).
>>>>> Contribution
>>>>> A data object usually associated with a Tapestry IoC service's
>>>>> configuration.
>>>>> Filter
>>>>> Part of a pipeline, where there's an associated main interface,
>>>>> and the Filter wraps around that main interface. Each main interface
>>>>> method is duplicated in the Filter, with an extra parameter used
>>>>> to chain the interface.
>>>>> Manager
>>>>> Often a wrapper around a service configuration, it provides access
>>>>> to the contributed values (possibly after some transformation).
>>>>> To
>>>>> A method prefix that indicates a conversion or coersion from one type
>>>>> another. I.e., toUserPresentable().
>>>>> Worker
>>>>> An object that peforms a specific job. Workers will be stateless, but
>> will
>>>>> be passed
>>>>> a stateful object to perform some operation upon.
>>>>> Builder
>>>>> An object whose job is to create other objects, typically in the
>> of
>>>>> creating a core service implementation for a Tapestry IoC service
>> as
>>>>> PipelineBuilder
>>>>> or ChainBuilder).
>>>>> Support
>>>>> An object that provides supporting operations to other objects; this
>> a
>>>>> kind of "loose aggregation".
>>>>> Parameters
>>>>> A data object that holds a number of related values that would
>> be
>>>>> separate
>>>>> parameter values to a method. This tends to streamline code
>>>>> when using
>>>>> a Filter interface) and allows the parameters to be evolved without
>>>>> changing the method signature.
>>>>> Strategy
>>>>> An object that "plugs into" some other code, allowing certain
>> to
>>>>> be deferred
>>>>> to the Strategy. Often a Strategy is selected based on the type of
>>>>> object
>>>>> being operated upon.
>>>>> Context
>>>>> Captures some stateful information that may be passed around between
>>>>> stateless services.
>>>>> Constants
>>>>> A non-instantiable class that contains public static fields that are
>>>>> referenced in multiple places.
>>>>> Hub
>>>>> An object that allows listeners to be registered. Often includes a
>> method
>>>>> prefixed with "trigger"
>>>>> that will send notifications to listeners.
>>>>> Implement toString()
>>>>> Objects that are exposed to user code should generally implement a
>>>>> meaningful toString() method.
>>>>> And that method should be tested.
>>>>> Subclassing
>>>>> You'll notice there isn't a lot of inheritance in Tapestry. Given the
>>>>> function of the IoC container,
>>>>> it is much more common to use some variation of *aggregation* rather
>> than
>>>>> *inheritance*.
>>>>> Where subclassing exists, the guideline for constructor parameters is:
>> the
>>>>> subclass should include all
>>>>> the constructor parameters of the superclass, in the same positions.
>> Thus
>>>>> subclass constructor parameters
>>>>> are appended to the list of super-class constructor parameters.
>>>>>   Change Notification Preferences<
>> https://cwiki.apache.org/confluence/users/viewnotifications.action>
>>>>> View Online<
>> https://cwiki.apache.org/confluence/display/TAPESTRY/Developer+Bible>
>>>> --
>>>> --
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>>>> health and fitness facility.
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>> reasonable
>>>> price!
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