Author: hlship
Date: Sat Oct 28 10:21:51 2006
New Revision: 468706
URL: http://svn.apache.org/viewvc?view=rev&rev=468706
Log:
Fill out some details about the development process, and add some comments to
ConcurrentBarrier.
Modified:
tapestry/tapestry5/tapestry-core/trunk/src/main/java/org/apache/tapestry/internal/util/ConcurrentBarrier.java
tapestry/tapestry5/tapestry-core/trunk/src/site/resources/tap5devwiki.html
tapestry/tapestry5/tapestry-core/trunk/src/site/resources/tap5devwiki.xml
Modified:
tapestry/tapestry5/tapestry-core/trunk/src/main/java/org/apache/tapestry/internal/util/ConcurrentBarrier.java
URL:
http://svn.apache.org/viewvc/tapestry/tapestry5/tapestry-core/trunk/src/main/java/org/apache/tapestry/internal/util/ConcurrentBarrier.java?view=diff&rev=468706&r1=468705&r2=468706
==============================================================================
---
tapestry/tapestry5/tapestry-core/trunk/src/main/java/org/apache/tapestry/internal/util/ConcurrentBarrier.java
(original)
+++
tapestry/tapestry5/tapestry-core/trunk/src/main/java/org/apache/tapestry/internal/util/ConcurrentBarrier.java
Sat Oct 28 10:21:51 2006
@@ -18,7 +18,10 @@
import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
- * A barrier used to execute code in a context where it is guarded by
read/write locks.
+ * A barrier used to execute code in a context where it is guarded by
read/write locks. In addition,
+ * handles upgrading read locks to write locks (and vice versa). Execution of
code within a lock is
+ * in terms of a [EMAIL PROTECTED] Runnable} object (that returns no value),
or a [EMAIL PROTECTED] Invokable} object
+ * (which does return a value).
*/
public class ConcurrentBarrier
{
@@ -49,7 +52,9 @@
* the lock has already been acquired, then the status of the lock is not
changed.
* <p>
* TODO: Check to see if the write lock is acquired and <em>not</em>
acquire the read lock in
- * that situation.
+ * that situation. Currently this code is not re-entrant. If a write lock
is already acquired
+ * and the thread attempts to get the read lock, then the thread will
hang. For the moment, all
+ * the uses of ConcurrentBarrier are coded in such a way that reentrant
locks are not a problem.
*
* @param <T>
* @param invokable
@@ -81,6 +86,10 @@
}
}
+ /**
+ * As with [EMAIL PROTECTED] #withRead(Invokable)}, creating an [EMAIL
PROTECTED] Invokable} wrapper around the
+ * runnable object.
+ */
public void withRead(final Runnable runnable)
{
Invokable<Void> invokable = new Invokable<Void>()
@@ -97,9 +106,16 @@
}
/**
- * Acquires the single write lock before invoking the Invokable. If the
current thread has a
- * read lock, it is released before attempting to acquire the write lock,
and re-acquired after
- * the write lock is released.
+ * Acquires the exclusive write lock before invoking the Invokable. The
code will be executed
+ * exclusively, no other reader or writer threads will exist (they will be
blocked waiting for
+ * the lock). If the current thread has a read lock, it is released before
attempting to acquire
+ * the write lock, and re-acquired after the write lock is released. Note
that in that short
+ * window, between releasing the read lock and acquiring the write lock,
it is entirely possible
+ * that some other thread will sneak in and do some work, so the [EMAIL
PROTECTED] Invokable} object should
+ * be prepared for cases where the state has changed slightly, despite
holding the read lock.
+ * This usually manifests as race conditions where either a) some parallel
unrelated bit of work
+ * has occured or b) duplicate work has occured. The latter is only
problematic if the operation
+ * is very expensive.
*
* @param <T>
* @param invokable
@@ -138,6 +154,10 @@
}
}
+ /**
+ * As with [EMAIL PROTECTED] #withWrite(Invokable)}, creating an [EMAIL
PROTECTED] Invokable} wrapper around the
+ * runnable object.
+ */
public void withWrite(final Runnable runnable)
{
Invokable<Void> invokable = new Invokable<Void>()
Modified:
tapestry/tapestry5/tapestry-core/trunk/src/site/resources/tap5devwiki.html
URL:
http://svn.apache.org/viewvc/tapestry/tapestry5/tapestry-core/trunk/src/site/resources/tap5devwiki.html?view=diff&rev=468706&r1=468705&r2=468706
==============================================================================
--- tapestry/tapestry5/tapestry-core/trunk/src/site/resources/tap5devwiki.html
(original)
+++ tapestry/tapestry5/tapestry-core/trunk/src/site/resources/tap5devwiki.html
Sat Oct 28 10:21:51 2006
@@ -5169,6 +5169,7 @@
<div tiddler="ComponentEvent" modifier="HowardLewisShip"
modified="200610081359" created="200610081351" tags="requests events">Component
events represent the way in which incoming requests are routed to user-supplied
Java methods.\n\nComponent events //primarily// originate as a result of a
ComponentActionRequest, though certain other LifecycleEvents will also
originate component events.\n\nEach component event contains:\n* An event type;
a string that identifies the type of event\n* An event source; a component that
orginates the event (where applicable)\n* A context; an array of strings
associated with the event\n\nEvent processing starts with the component that
originates the event.\n\nHandler methods for the event within the component are
invoked.\n\nIf no handler method aborts the event, then handlers for the
originating component's container are invoked.\n\nThis containues until
handlers for the page (the root component) are invoked, or until some handler
method aborts
the event.\n\nThe event is aborted when a handler method returns a non-null,
non-void value. The interpretation of that value varies based on the type of
event.\n\nEvents are routed to handler methods using the @~OnEvent
annotation.\n\nThis annotation is attached to a method within a component
class. This method becomes a handler method for an event.\n\nThe annotation
allows events to be filtered by event type or by originating
component.\n\n{{{\n @OnEvent(value="submit",
component="form")\n String handleSubmit()\n {\n // . . .\n\n
return "PostSubmit";\n }\n}}}\n\nIn the above hypothetical example,
a handler method is attached to a particular component's submit event. After
processing the data in the form, the LogicalPageName of another page within the
application is returned. The client browser will be redirected to that
page.\n\nHandler methods need not be public; they are most often package
private (which facilitated UnitTesting
of the component class).\n\nHandler methods may take parameters. This is most
useful with handler methods related to links, rather than forms.\n\nAssociated
with each event is the context, a set of strings defined by the application
programmer.\n\nParameters are coerced (see TypeCoercion) from these strings.
Alternately, a parameter of type String[] receives the set of strings.\n\n{{{\n
@OnEvent(component="delete")\n String deleteAccount(long
accountId)\n {\n // . . .\n\n return "AccountPage";\n
}\n}}}\n\nHere, ther first context value has been coerced to a long and passed
to the deleteAccount() method. Presemuable, an action link on the page, named
"delete", is the source of this event.\n\n</div>
<div tiddler="ComponentMixins" modifier="HowardLewisShip"
modified="200610051243" created="200610051234" tags="mixins">One of the more
exciting ideas in Tapestry 5 is //mixins//; the ability to add behavior to a
component without writing code. \n\nIt is expected that much common behavior,
especially for form control components, will be provided by mixins. Further,
many Ajax techniques will take the form of mixins applied to otherwise ordinary
components.\n\nA mixin is an additional component class that operates //with//
the main component. For a component element within the page, the functionality
is provided by the main component class and by\nthe mixin. \n\nMixins are
primarily about rendering. Mixin render methods are //mixed in// to the
components' render methods. In effect, the different rendering phases of a
component are different AOP-like //joinpoints//, and the mixins can provide
//before advice//.\n\nMixins can be specified for an //instance// of a
component, or c
an be specified as part of the //implementation// of a component.\n\nIn the
former case, the @Component annotation will be supplemented with a @Mixin
annotation. The @Mixin is a list of one or more mixin classes for that
component.\n\n''Todo: Template syntax for mixins?''\n\nIn the latter case, the
@ComponentClass annotation will be supplemented with a @Mixin
annotation.\n\nMixins can be configured. They can have parameters, just like
ordinary components. When a formal parameter name is ambiguous, it will be
prefixed with the unqualified class name. Thus, you might have to say,
"MyMixin.parameterName=someProperty" if "parameterName" is
ambiguous (by ambiguous, we mean, a parameter of more than one mixin or of the
component itself). \n\nThis disambiguation is //simple//. It is assumed that
the unqualified class name will be sufficient to uniquely identify a mixin.
That is, it is expected that you will not have the same class name even in
different packag
es (as mixins, on a single component). In a //degenerate case// where this is
not so, it will be necessary to disambiguate the mixin name by create a
subclass of the mixin with a new name.\n\n''Todo: how are mixins on a component
implementation configured?''\n\nMixins may have persistent state, just as with
ordinary components.\n\n</div>
<div tiddler="ComponentTemplates" modifier="HowardLewisShip"
modified="200610201807" created="200610201801" tags="">There are some issues
related to component templates.\n\nFirstly, people are really interested in
seeing the return of InvisibleInstrumentation. That is coming.\n\nSecondly,
the idea that templates are well-formed XML documents is causing some
issues.\n\nThe problem is related to entities and doctypes.\n\nUnless you
provide a doctype for the template,
[[entities|http://www.htmlhelp.com/reference/html40/entities/]] don't work;
they result in template parse errors.\n\nIf you provide a standard doctype,
say\n{{{\n <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0
Transitional//EN"\n
"http://www.w3.org/TR/REC-html40/loose.dtd">\n}}}\n\nYou also get
parse errors, because the DTD does some odd things with comments that the Java
SAX parser doesn't seem to understand.\n\nI've had better luck with the XHTML
doctype:\n{{{\n<!DOCTYPE htm
l PUBLIC "-//W3C//DTD XHTML 1.0
Transitional//EN"\n"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">\n}}}\n\nBut
this doesn't render quite the way I want it to.\n\nFurther, entities in the
text are converted to unicode by the parser, then converted to <numeric>
entities on output. Not quite WYSIWYG and potentially confusing.\n\nIt may be
necessary to discard SAX and build a limited XML parser that allows entities to
be passed through unchanged (they would become a special type of document
token).\n\nLastly, the question is how to get the correct DOCTYPE into the
rendered output, espcially in the common case that a Border component provides
the outer tags, as is common in Tapestry 4. This may have to be configured as
a annotation on page classes.</div>
+<div tiddler="DeveloperProcedures" modifier="HowardLewisShip"
modified="200610281525" created="200610281524" tags="">Tapestry is a big chunk
of code, growing every day. We need to not step on each other's toes.\n\n//At
this time, Tapestry is pretty single threaded, with Howard setting up the main
infrastructure. Soon there's going to be a crowd of folks working on it, and
we need to coordinate on this ahead of time.//\n\nBasic guidelines:\n\n*
WorkInYourOwnBranch\n* WatchCodeCoverage\n* FocusOnTesting\n*
DontTouchInternals\n</div>
<div tiddler="DynamicPageState" modifier="HowardLewisShip"
modified="200609211635" created="200609211610" tags="">Tapestry 4 has left
tracking of dynamic page state as an exercise to the developer. Mostly, this
is done using the ''parameters'' parameter of the ~DirectLink
component.\n\nDynamic page state is anything that isn't inside a persistent
page property. For the most part, this includes page properties updated by a
For component\n\nIt seems likely that this information could be automatically
encoded into ~URLs. \n\nI'm envisioning a service that accumulates a series of
//commands//. Each command is used to store a bit of page state. The commands
are serializable. The commands are ultimately serialized into a MIME string
and attached as a query parameter to each URL.\n\nWhen such a link is
triggered, the commands are de-serialized and each executed in turn. Only when
that is finished is any further event processing executed, including calling
into to user code.\n\nM
y outline for this is to store a series of tuples; each tuple is a component
id plus the command to execute.\n\n{{{\npublic interface
ComponentCommand<T>\n{\n void execute(T component);\n}\n}}}\n\nThese
commands should be immutable.\n\nSo a component, such as a For loop component,
could provide itself and a ComponentCommand instance (probably a static inner
class) to some kind of PageStateTracker service.\n\n{{{\npublic interface
PageStateTracker\n{\n void <T> addCommand(T component,
ComponentCommand<T> command);\n}\n}}}\n\nThe commands are kept in the
order that they are added, except that new commands for the same component
//replace// previous commands for that component.\n\nAs with the Tapestry 4 For
component, some mechanism will be needed to store object ids inside the URLs
(that is, inside the commands serialized into URL query parameters) and
translate back to //equivalent// objects when the link is triggered.\n\nDynamic
page state outside of a Fo
rm will overlap with some of the FormProcessing inside the form.</div>
<div tiddler="EditTemplate" modifier="HowardLewisShip" modified="200609210649"
created="200609210648" tags=""><div class='toolbar' macro='toolbar
+saveTiddler -cancelTiddler deleteTiddler'></div>\n<div
class='title' macro='view title'></div>\n<div class='editor'
macro='edit title'></div>\n<div class='editor' macro='edit
text'></div>\n<div class='editor' macro='edit
tags'></div><div class='editorFooter'><span macro='message
views.editor.tagPrompt'></span><span
macro='tagChooser'></span></div></div>
<div tiddler="EnvironmentalServices" modifier="HowardLewisShip"
modified="200609260145" created="200609251547" tags="">Frequently, different
components need to //cooperate// during the rendering process.\n\nThis is an
established pattern from Tapestry 4, which an enclosing component provides
services to the components it encloses. By //encloses// we mean, any components
that are rendered as part of the Form's body; give the use of the
Block/~RenderBlock components, this can not be determined statically, but is
instead determined dynamically, as part of the rendering process.\n\nThe
canoncial example of this pattern is Form component, and the complex
relationship it has with each form element component it encloses.\n\nIn
Tapestry 4, this mechanism was based on the ~IRequestCycle which could store
named attributes. The service providing component would store itself into the
cycle using a well known name, and service consuming components would retrieve
the service using the sam
e well known name.\n\nFor Tapestry 5, this will be formalized. A new service
will be used to manage this information:\n\n{{{\npublic interface
Enviroment\n{\n <T> T push(Class<T> type, T instance);\n\n
<T> peek(Class<T> type);\n\n <T> T pop(Class<T>
type);\n}\n}}}\n\nThe Environment is unique to a request.</div>
@@ -5176,7 +5177,7 @@
<div tiddler="InvisibleInstrumentation" modifier="HowardLewisShip"
modified="200610201803" created="200610201802" tags="">A feature of Tapestry 4
where the component id, type and parameters were "hidden" inside
ordinary HTML tags.\n\nThis will show up inside Tapestry 5 pretty soon, and
look something like:\n{{{\n<span t:type="If"
t:test="prop:showWarning" class="warning"> \n . .
.\n</span>\n}}}</div>
<div tiddler="LogicalPageName" modifier="HowardLewisShip"
modified="200610081330" created="200610081330" tags="">A logical page name is
the name of a page as it is represented in a URI.\n\nInternally, Tapestry
operates on pages using full qualified class names. Technically, the FQCN is
the class of the page's root element, but from an end developer point of view,
the root element is the page.\n\nThe logical page name must be converted to a
fully qualified class name.\n\nA set of LibraryMappings are used. Each library
mapping is used to express a folder name, such as "core", with a Java
package name, such as org.apache.tapestry.corelib. For pages, the page name is
searched for in the pages sub-package (i.e.,
org.apache.tapestry.corelib.pages). Component libraries have unique folder
names mapped to root packages that contain the pages (and components, and
mixins) of that library.\n\nWhen there is no folder name, the page is expected
to be part of the application,
under the pages sub-package of the application's root package.\n\nIf not found
there, as a special case, the name is treated as if it were prefixed with
"core/". This allows access to the core pages (and more importantly,
components -- the search algorithm is the same).\n\nFinally, pages may be
organized into folders. These folders become further sub-packages. Thus as
page name of "admin/EditUsers" may be resolved to class
org.example.myapp.pages.admin.EditUsers.\n\n</div>
<div tiddler="MainMenu" modifier="HowardLewisShip" modified="200609210701"
created="200609210643" tags="">MasterIndex\n[[RSS
feed|tap5devwiki.xml]]\n\n[[Tapestry 5
Home|http://tapestry.apache.org/tapestry5/]]\n[[Howard's
Blog|http://howardlewisship.com/blog/]]\n\n[[Formatting
Help|http://www.blogjones.com/TiddlyWikiTutorial.html#EasyToEdit%20Welcome%20NewFeatures%20WhereToFindHelp]]</div>
-<div tiddler="MasterIndex" modifier="HowardLewisShip" modified="200610201757"
created="200609202214" tags="">Top level concepts within Tapestry 5.\n\n*
PropBinding -- Notes on the workhorse "prop:" binding prefix\n*
TypeCoercion -- How Tapestry 5 extensibly addresses type conversion\n*
FormProcessing\n* DynamicPageState -- tracking changes to page state during the
render\n* EnvironmentalServices -- how components cooperate during page
render\n* ComponentMixins -- A new fundamental way to build web
functionality\n* RequestTypes -- Requests, request processing, URL formats\n*
ComponentTemplates -- Issues about Component Templates</div>
+<div tiddler="MasterIndex" modifier="HowardLewisShip" modified="200610281524"
created="200609202214" tags="">Top level concepts within Tapestry 5.\n\nA
//meta-note//: This is where new ideas are first explained, usually before
being implemented. In many cases, the final implementation is\nnot a perfect
match for the notes. That's OK ... as long as the official Maven documentation
does a good job. It's not reasonable to expect developers to jump back in here
and dot every i and cross every t if they're already expected to generate good
Maven documentation.\n\n* PropBinding -- Notes on the workhorse
"prop:" binding prefix\n* TypeCoercion -- How Tapestry 5 extensibly
addresses type conversion\n* FormProcessing\n* DynamicPageState -- tracking
changes to page state during the render\n* EnvironmentalServices -- how
components cooperate during page render\n* ComponentMixins -- A new fundamental
way to build web functionality\n* RequestTypes -- Requests, request processing
, URL formats\n* ComponentTemplates -- Issues about Component Templates\n*
DeveloperProcedures -- Your a Tapestry committer ... how do you makes
changes?</div>
<div tiddler="OGNL" modifier="HowardLewisShip" modified="200610071249"
created="200609202254" tags="">The [[Object Graph Navigation
Library|http://ognl.org]] was an essential part of Tapestry 4.\n\nOGNL is both
exceptionally powerful (especially the higher order things it can do, such as
list selections and projections). However, for the highest\nend sites, it is
also a performance problem, both because of its heavy use of reflection, and
because it uses a lot of code inside synchronized blocks.\n\nIt will be
optional in Tapestry 5. I believe it will not be part of the tapestry-core, but
may be packaged as tapestry-ognl.\n\nThe "prop:" binding prefix is an
effective replacement for OGNL in Tapestry 5. See PropBinding.\n</div>
<div tiddler="PageRenderRequest" modifier="HowardLewisShip"
modified="200610081333" created="200610071313" tags="">Page render requests are
requests used to render a specific page. //render// is the term meaning to
compose the HTML response to be sent to the client. Note: HTML is used here
only as the most common case, other markups are entirely possible.\n\nIn many
cases, pages are stand-alone. No extra information in the URL is necesarry to
render them. PersistentProperties of the page will factor in to the rendering
of the page.\n\nIn specific cases, a page needs to render within a particular
context. The most common example of this is a page that is used to present a
specific instance of a database persistent entity. In such a case, the page
must be combined with additional data, in the URL, to identify the specific
entity to access and render.\n\n! URI
Format\n\n{{{\n/page-name.html/id\n}}}\n\nHere "page-name" is the
LogicalPageName for the page. \n\nThe &q
uot;.html" file extension is used as a delimiter between the page name
portion of the URI, and the context portion of the URI. This is necessary
because it is not possible (given the plethora of libraries and folders) to
determine how many slashes will appear in the URI.\n\nThe context consists of
one ore more ids (though a single id is the normal case). The id is used to
identify the specific data to be displayed. Further, a page may require
multiple ids, which will separated with slashes. Example:
/admin/DisplayDetail.html/loginfailures/2006\n\nNote that these context values,
the ids, are simply //strings//. Tapestry 4 had a mechanism, the DataSqueezer,
that would encode the type of object with its value, as a single string, and
convert it back. While seemingly desirable, this facility was easy to abuse,
resulting in long and extremely ugly URIs.\n\nAny further information needed by
Tapestry will be added to the URI as query parameters. This may include things
like us
er locale, persistent page properties, applicaition flow identifiers, or
anything else we come up with.\n\n! Request Processing\n\nOnce the page and id
parameters are identified, the corresponding page will be loaded.\n\nTapestry
will fire two events before rendering the page.\n\nThe first event is of type
"setupPageRender". This allows the page to process the context (the
set of ids). This typically involves reading objects from an external
persistent store (a database)\nand storing those objects into transient page
properties, in expectaion of the render.\n\nThe @SetupPageRender annotation
marks a method to be invoked when this event is triggered. The method may take
one or more strings, or an array of strings, as parameters; these will be\nthe
context values. The method will normally return void. Other values are
''TBD''. It may also take other simple types, which will be coerced from the
string [EMAIL PROTECTED] setup(long id)\n{\n . .
.\n}\n}}}\n\n\n\nThe second event is of type "pageValidate". It
allows the page to decide whether the page is valid for rendering at this time.
This most often involves a check to see if the user is logged into the
application, and has the necessary privileges to display the contents of the
page. User identity and privileges are //not// concepts built into Tapestry,
but are fundamental to the majority of Tapestry applications.</div>
<div tiddler="PropBinding" modifier="HowardLewisShip" modified="200610201450"
created="200609202203" tags="bindings">The "prop:" binding prefix is
the default in a lot of cases, i.e., in any Java code (annotations).\n\nThis
binding prefix supports several common idioms even though they are not,
precisely, the names of properties. In many cases, this will save developers
the bother of using a "literal:" prefix.\n\nThe goal of the
"prop:" prefix is to be highly efficient and useful in 90%+ of the
cases. [[OGNL]], or synthetic properties in the component class, will pick up
the remaining cases.\n\n!Numeric literals\n\nSimple numeric literals should be
parsed into read-only, invariant
bindings.\n{{{\nprop:5\n\nprop:-22.7\n}}}\n\nThe resulting objects will be of
type Long or type Double. TypeCoercion will ensure that component parameters
get values (say, int or float) of the correct type.\n\n!Range
literals\n\nExpresses a range of integer values,
either ascending or descending.\n{{{\nprop:1..10\n\nprop:100..-100\n}}}\n\nThe
value of such a binding is Iterable; it can be used by the Loop
component.\n\n!Boolean literals\n\n"true" and "false"
should also be converted to invariant
bindings.\n{{{\nprop:true\n\nprop:false\n}}}\n\n!String literals\n\n//Simple//
string literals, enclosed in single quotes. Example:\n{{{\nprop:'Hello
World'\n}}}\n\n//Remember that the binding expression will always be enclosed
in double quotes.//\n\n!This literal\n\nIn some cases, it is useful to be able
to identify the current component:\n{{{\nprop:this\n}}}\n\nEven though a
component is not immutable, the value of //this// does not ever change,\nand
this binding is also invariant.\n\n!Null literal\n\n{{{\nprop:null\n}}}\n\nThis
value is always exactly null. This can be used to set a parameter who'se
default value is non-null to the explicit value null.\n\n!Property
paths\n\nMulti-step property paths are extremely importa
nt.\n\n{{{\nprop:poll.title\n\nprop:identity.user.name\n}}}\n\nThe initial
terms need to be readable, they are never updated. Only the final property name
must be read/write, and in fact, it is valid to be read-only or
write-only.\n\nThe prop: binding factory builds a Java expression to read and
update properties. It does not use reflection at runtime. Therefore, the
properties of the //declared// type are used. By contrast, [[OGNL]] uses the
//actual// type, which is reflection-intensive. Also, unlike OGNL, errors (such
as missing properties in the property path) are identified when the page is
loaded, rather than when the expression is evaluated.\n</div>
@@ -5187,6 +5188,7 @@
<div tiddler="SiteUrl" modifier="HowardLewisShip" modified="200609210703"
created="200609210641"
tags="">http://tapestry.apache.org/tapestry5/tap5devwiki.html</div>
<div tiddler="TabAll" modifier="HowardLewisShip" modified="200609210650"
created="200609210650" tags=""><<list all>></div>
<div tiddler="TypeCoercion" modifier="HowardLewisShip" modified="200610051240"
created="200609202217" tags="parameters types">Automatic coercion of types is
essential. This primarily applies to component parameters.\n\nParameters are
tied to the
[[Binding|http://tapestry.apache.org/tapestry5/apidocs/org/apache/tapestry/Binding.html]]
interface.\n\nTapestry component parameters look like simple instance
variables, but Tapestry's RuntimeTransformation of component classes means that
reading the value of a parameter instance variable //may// invoke
Binding.get(), and changing the value of a parameter instance variable will
invoke Binding.set().\n\n!Reading From Parameters\n\nReading a parameter value
involves two steps:\n* Invoking Binding.get()\n* Converting the result to the
type of the parameter (where different)\n\nWhen reading parameters, the binding
will provide an object of the type of the bound property. Various kinds of
invariant bindings will returned a fixed type,
typically a String.\n\nThe parameter will be assigned to a variable that has a
known type, possibly a primtive type (int, boolean) or an object type (Map,
Date).\n\n!Writing To Parameters\n\nWriting to, or updating, a parameter is in
two steps:\n* Converting the new value into a type appropriate for the
binding\n* Invoking Binding.set()\n\nWe will be adding a getPropertyType()
method to the Binding interface, that will identify the property type of the
property bound to the parameter.\n\nThe component will be responsible for
performing a coercion from the value provided to the proper type, before
invoking Binding.set().\n\n!Coercion Tuples\n\nAt the core of this will be a
service that performs type coercions.\n\nCoercions are based on //coercion
tuples// that define:\n* A source type\n* A target type\n* An object to perform
the coercion from source to target\n* A "cost" for the conversion
(possibly, but usually with a standard default value) ''(not yet implemented)
''\n\nAs a special case, the type of null will be treated as type void (i.e.,
void.class). Thus we can use the same mechanism to identify how to convert
from null to other types, such as Boolean or Integer.\n\nThere should be a
large number of these tuples available. The most common tuples may be
conversions between various types and String.\n\n!Coercion Algorithm\n*
Determine the source type (treating null as void.class)\n* Determine the target
type (converting primitive types to equivalent wrapper types)\n* If the source
type is assignable to the target type, then the input value is valid and the
process is complete\n* Find a converter that converts between the source type
and the target type, pass the source value through the converter to get a
target value\n\nThat last part needs a bit of expansion.\n\nFirst off, there
will often ''not'' be a tuple for coercing directly form the source type to the
target type.\n\nIn that scenario, the conversion will involve a search
to find a sequence of tuples that will perform the coercion. This will take
the form a breadth-first search where we look for tuples that coerce from the
source type to an intermediate type, then search for tuples from the
intermediate type to the target type. This may involve more than two
coercions.\n\nYou can think of the set of tuples as a kind of directed graph.
Each type is a node on the graph, and each tuple represents a connection
between one type and another type (say, from String to Double). What we're
trying to do is find a path form a source type (or some super-class or
super-interface of the source type) to some target type (or sub-class or
sub-interface of the target type).\n\nMay need to express a "cost" of
the coercion from start type to target type; this might be useful if there are
multiple paths for the conversion. Cost may factor in both the computing
expense, and any loss of detail. Basic cost is established in terms of the
number of steps
and enforced by the order in which tuples are considered and combined.\n\nFor
example, a coercion tuple from Number to Float may be represented as the
tuple:\n(Number, Float, {{{ return new Float(input.floatValue());
}}})\n\n{{{\npublic interface Coercion<S,T>\n{\n T coerce(S
input);\n}\n}}}\n\nIf the input type is an Integer, then a search for
Integer->Float will find no entries. At that point, it will be necessary to
"climb" the inheritance tree and look for coercions from Number (the
super class of Integer); this will find the Number->Float tuple.\n\nAgain,
in terms of cost, we might also find a pair of tuples: Object->String and
String->Float. This will have a higher cost than the Number->Float tuple
and should be rejected in favor of the lower cost coercion.\n\n//Note: cost
hasn't been implemented, and likely won't be, unless and until the algorithm as
it stands is shown to provide less than optimal results.//\n\nThe algorithm
caches t
he result of this search, with proper guards for concurrent access. The cache
is cleared when an invalidation of the component class loader
occurs.\n\n!Configuring the service\n\nThis has been implemented as service
tapestry.TypeCoercer.\n\nThe configuration of this service is an unordered
collection of CoercionTuple.</div>
+<div tiddler="WorkInYourOwnBranch" modifier="HowardLewisShip"
modified="200610281536" created="200610281528" tags="">Working in the trunk can
be a problem. ''The SVN trunk is where merges happen, not where development
happens.''\n\nFor any bit of code change you make, you want to do the
following:\n\n* Branch trunk to form your own sandbox\n* Work in the sandbox\n*
Ensure high quality: high code coverage, unit and integration tests, up-to-date
documentation\n* Announce (on the developer mailing list) that you are
committing to trunk\n* Switch your workspace back to trunk\n* Tag trunk as
premerge\n* Merge from your sandbox\n* Ensure a good merge (including
documentation, tests, and code coverage)\n* Commit your merge to trunk\n* Tag
trunk as postmerge\n\n!Branch names\n\nBranch names should consist of your user
id, the current date as YYYYMMDD, and a short mneumonic, such as a bug id.
Example: {{{hlship-20061027-removeaspectj}}}.\n\nThere's a branches folder for
tapestry5/t
apestry-core, i.e.
[http://svn.apache.org/viewvc/tapestry/tapestry5/tapestry-core/branches/]\n\n!Tag
names\n\nPrefix the branch name with "premerge" or
"postmerge". i.e.
[http://svn.apache.org/viewvc/tapestry/tapestry5/tapestry-core/tags/]\n\nThese
are really important when trying to back out a change, the pre and the post
give a lot of context to see what actually changed.\n\n!Announcing\n\nMerging
is hard enough, it's worse if two people are making possibly conflicting
changes at the same time. A little coordination goes a long way.\n\n!Small
increments are ''Good''\n\nThis looks like a lot of overhead, but thanks to
Subversion, it really isn't. It's still better to do small increments of work.
Don't go away for six months and expect an easy job of committing changes. You
can do this style of work several times a day (Subversion was created
specifically to make tagging, branching, and merging fast).</div>
</div>
<!--POST-BODY-START-->
Modified:
tapestry/tapestry5/tapestry-core/trunk/src/site/resources/tap5devwiki.xml
URL:
http://svn.apache.org/viewvc/tapestry/tapestry5/tapestry-core/trunk/src/site/resources/tap5devwiki.xml?view=diff&rev=468706&r1=468705&r2=468706
==============================================================================
--- tapestry/tapestry5/tapestry-core/trunk/src/site/resources/tap5devwiki.xml
(original)
+++ tapestry/tapestry5/tapestry-core/trunk/src/site/resources/tap5devwiki.xml
Sat Oct 28 10:21:51 2006
@@ -6,27 +6,39 @@
<description>The quick and dirty one-stop shopping of random ideas for
Tapestry 5.</description>
<language>en-us</language>
<copyright>Copyright 2006 HowardLewisShip</copyright>
-<pubDate>Fri, 20 Oct 2006 18:07:34 GMT</pubDate>
-<lastBuildDate>Fri, 20 Oct 2006 18:07:34 GMT</lastBuildDate>
+<pubDate>Sat, 28 Oct 2006 15:36:05 GMT</pubDate>
+<lastBuildDate>Sat, 28 Oct 2006 15:36:05 GMT</lastBuildDate>
<docs>http://blogs.law.harvard.edu/tech/rss</docs>
<generator>TiddlyWiki 2.0.11</generator>
<item>
+<title>WorkInYourOwnBranch</title>
+<description>Working in the trunk can be a problem. ''The SVN trunk is where
merges happen, not where development happens.''<br /><br />For any
bit of code change you make, you want to do the following:<br /><br
/>* Branch trunk to form your own sandbox<br />* Work in the
sandbox<br />* Ensure high quality: high code coverage, unit and
integration tests, up-to-date documentation<br />* Announce (on the
developer mailing list) that you are committing to trunk<br />* Switch
your workspace back to trunk<br />* Tag trunk as premerge<br />*
Merge from your sandbox<br />* Ensure a good merge (including
documentation, tests, and code coverage)<br />* Commit your merge to
trunk<br />* Tag trunk as postmerge<br /><br />!Branch
names<br /><br />Branch names should consist of your user id, the
current date as YYYYMMDD, and a short mneumonic, such as a bug id. Example:
{{{hlship-20061
027-removeaspectj}}}.<br /><br />There's a branches folder for
tapestry5/tapestry-core, i.e.
[http://svn.apache.org/viewvc/tapestry/tapestry5/tapestry-core/branches/]<br
/><br />!Tag names<br /><br />Prefix the branch name with
"premerge" or "postmerge". i.e.
[http://svn.apache.org/viewvc/tapestry/tapestry5/tapestry-core/tags/]<br
/><br />These are really important when trying to back out a change,
the pre and the post give a lot of context to see what actually changed.<br
/><br />!Announcing<br /><br />Merging is hard enough,
it's worse if two people are making possibly conflicting changes at the same
time. A little coordination goes a long way.<br /><br />!Small
increments are ''Good''<br /><br />This looks like a lot of
overhead, but thanks to Subversion, it really isn't. It's still better to do
small increments of work. Don't go away for six months and exp
ect an easy job of committing changes. You can do this style of work several
times a day (Subversion was created specifically to make tagging, branching,
and merging fast).</description>
+<link>http://tapestry.apache.org/tapestry5/tap5devwiki.html#WorkInYourOwnBranch</link>
+<pubDate>Sat, 28 Oct 2006 15:36:05 GMT</pubDate>
+</item>
+<item>
+<title>DeveloperProcedures</title>
+<description>Tapestry is a big chunk of code, growing every day. We need to
not step on each other's toes.<br /><br />//At this time, Tapestry
is pretty single threaded, with Howard setting up the main infrastructure.
Soon there's going to be a crowd of folks working on it, and we need to
coordinate on this ahead of time.//<br /><br />Basic
guidelines:<br /><br />* WorkInYourOwnBranch<br />*
WatchCodeCoverage<br />* FocusOnTesting<br />*
DontTouchInternals<br /></description>
+<link>http://tapestry.apache.org/tapestry5/tap5devwiki.html#DeveloperProcedures</link>
+<pubDate>Sat, 28 Oct 2006 15:25:11 GMT</pubDate>
+</item>
+<item>
+<title>MasterIndex</title>
+<description>Top level concepts within Tapestry 5.<br /><br />A
//meta-note//: This is where new ideas are first explained, usually before
being implemented. In many cases, the final implementation is<br />not a
perfect match for the notes. That's OK ... as long as the official Maven
documentation does a good job. It's not reasonable to expect developers to jump
back in here and dot every i and cross every t if they're already expected to
generate good Maven documentation.<br /><br />* PropBinding --
Notes on the workhorse "prop:" binding prefix<br />*
TypeCoercion -- How Tapestry 5 extensibly addresses type conversion<br
/>* FormProcessing<br />* DynamicPageState -- tracking changes to page
state during the render<br />* EnvironmentalServices -- how components
cooperate during page render<br />* ComponentMixins -- A new fundamental
way to build web functionality<br />* RequestTypes -- Requests, requ
est processing, URL formats<br />* ComponentTemplates -- Issues about
Component Templates<br />* DeveloperProcedures -- Your a Tapestry
committer ... how do you makes changes?</description>
+<link>http://tapestry.apache.org/tapestry5/tap5devwiki.html#MasterIndex</link>
+<pubDate>Sat, 28 Oct 2006 15:24:18 GMT</pubDate>
+</item>
+<item>
<title>ComponentTemplates</title>
<description>There are some issues related to component templates.<br
/><br />Firstly, people are really interested in seeing the return of
InvisibleInstrumentation. That is coming.<br /><br />Secondly, the
idea that templates are well-formed XML documents is causing some issues.<br
/><br />The problem is related to entities and doctypes.<br
/><br />Unless you provide a doctype for the template,
[[entities|http://www.htmlhelp.com/reference/html40/entities/]] don't work;
they result in template parse errors.<br /><br />If you provide a
standard doctype, say<br />{{{<br /> <!DOCTYPE HTML PUBLIC
"-//W3C//DTD HTML 4.0 Transitional//EN"<br />
"http://www.w3.org/TR/REC-html40/loose.dtd"><br />}}}<br
/><br />You also get parse errors, because the DTD does some odd
things with comments that the Java SAX parser doesn't seem to understand.<br
/>&l
t;br />I've had better luck with the XHTML doctype:<br />{{{<br
/><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
Transitional//EN"<br
/>"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><br
/>}}}<br /><br />But this doesn't render quite the way I want
it to.<br /><br />Further, entities in the text are converted to
unicode by the parser, then converted to <numeric> entities on output.
Not quite WYSIWYG and potentially confusing.<br /><br />It may be
necessary to discard SAX and build a limited XML parser that allows entities to
be passed through unchanged (they would become a special type of document
token).<br /><br />Lastly, the question is how to get the correct
DOCTYPE into the rendered output, espcially in the common case that a Border
component provides the outer tags, as is common in Tapestry 4. This may have
to be configured as a annotation on page class
es.</description>
<link>http://tapestry.apache.org/tapestry5/tap5devwiki.html#ComponentTemplates</link>
-<pubDate>Fri, 20 Oct 2006 18:07:34 GMT</pubDate>
+<pubDate>Fri, 20 Oct 2006 18:07:00 GMT</pubDate>
</item>
<item>
<title>InvisibleInstrumentation</title>
<description>A feature of Tapestry 4 where the component id, type and
parameters were "hidden" inside ordinary HTML tags.<br /><br
/>This will show up inside Tapestry 5 pretty soon, and look something
like:<br />{{{<br /><span t:type="If"
t:test="prop:showWarning" class="warning"> <br />
. . .<br /></span><br />}}}</description>
<link>http://tapestry.apache.org/tapestry5/tap5devwiki.html#InvisibleInstrumentation</link>
-<pubDate>Fri, 20 Oct 2006 18:03:21 GMT</pubDate>
-</item>
-<item>
-<title>MasterIndex</title>
-<description>Top level concepts within Tapestry 5.<br /><br />*
PropBinding -- Notes on the workhorse "prop:" binding prefix<br
/>* TypeCoercion -- How Tapestry 5 extensibly addresses type
conversion<br />* FormProcessing<br />* DynamicPageState --
tracking changes to page state during the render<br />*
EnvironmentalServices -- how components cooperate during page render<br
/>* ComponentMixins -- A new fundamental way to build web
functionality<br />* RequestTypes -- Requests, request processing, URL
formats<br />* ComponentTemplates -- Issues about Component
Templates</description>
-<link>http://tapestry.apache.org/tapestry5/tap5devwiki.html#MasterIndex</link>
-<pubDate>Fri, 20 Oct 2006 17:57:13 GMT</pubDate>
+<pubDate>Fri, 20 Oct 2006 18:03:00 GMT</pubDate>
</item>
<item>
<title>PropBinding</title>
@@ -125,18 +137,6 @@
<description><<tabs txtMainTab Timeline Timeline TabTimeline All 'All
tiddlers' TabAll Tags 'All tags' TabTags More 'More lists'
TabMore>><br /></description>
<link>http://tapestry.apache.org/tapestry5/tap5devwiki.html#SideBarTabs</link>
<pubDate>Thu, 21 Sep 2006 06:52:00 GMT</pubDate>
-</item>
-<item>
-<title>TabAll</title>
-<description><<list all>></description>
-<link>http://tapestry.apache.org/tapestry5/tap5devwiki.html#TabAll</link>
-<pubDate>Thu, 21 Sep 2006 06:50:00 GMT</pubDate>
-</item>
-<item>
-<title>EditTemplate</title>
-<description><div class='toolbar' macro='toolbar +saveTiddler
-cancelTiddler deleteTiddler'></div><br /><div class='title'
macro='view title'></div><br /><div class='editor'
macro='edit title'></div><br /><div class='editor'
macro='edit text'></div><br /><div class='editor' macro='edit
tags'></div><div class='editorFooter'><span macro='message
views.editor.tagPrompt'></span><span
macro='tagChooser'></span></div></description>
-<link>http://tapestry.apache.org/tapestry5/tap5devwiki.html#EditTemplate</link>
-<pubDate>Thu, 21 Sep 2006 06:49:00 GMT</pubDate>
</item>
</channel>
</rss>
