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Posted to dev@tapestry.apache.org by hl...@apache.org on 2006/11/24 21:03:48 UTC
svn commit: r478972 [1/2] - in
/tapestry/tapestry5/tapestry-project/trunk/src/site/resources:
tap5devwiki.html tap5devwiki.xml
Author: hlship
Date: Fri Nov 24 12:03:47 2006
New Revision: 478972
URL: http://svn.apache.org/viewvc?view=rev&rev=478972
Log:
More random thoughts ...
Modified:
tapestry/tapestry5/tapestry-project/trunk/src/site/resources/tap5devwiki.html
tapestry/tapestry5/tapestry-project/trunk/src/site/resources/tap5devwiki.xml
Modified: tapestry/tapestry5/tapestry-project/trunk/src/site/resources/tap5devwiki.html
URL: http://svn.apache.org/viewvc/tapestry/tapestry5/tapestry-project/trunk/src/site/resources/tap5devwiki.html?view=diff&rev=478972&r1=478971&r2=478972
==============================================================================
--- tapestry/tapestry5/tapestry-project/trunk/src/site/resources/tap5devwiki.html (original)
+++ tapestry/tapestry5/tapestry-project/trunk/src/site/resources/tap5devwiki.html Fri Nov 24 12:03:47 2006
@@ -5165,31 +5165,38 @@
<div id="saveTest"></div>
<div id="contentWrapper"></div>
<div id="contentStash"></div>
- <div id="storeArea"><div tiddler="ComponentActionRequest" modifier="HowardLewisShip" modified="200610081335" created="200610080113" tags="">Component actions are actions that reflect user interaction with a component within a page. Again, this falls into several broad categories:\n\n* Links that perform a server-side action, and result in a page refresh, or a new page being displayed.\n* Ajax style links, which perform a server-side action, and refresh only part of the page.\n* Forms which perform a server-side action, followed by a page refresh (or new page being displayed).\n* Ajax style forms, which trigger an action, followed by a refresh of part of the page.\n* Other user interactions, which result in a server side action, and a partial page refresh.\n\nIn all of these cases, one or more ComponentEvents is fired. The result of ComponentEvent determines whether a partial page render or a full page render occurs.\n\nIn the later case, a client side redirect is sent, to f
orce the browser to initial a new PageRenderRequest. This addresses an issue in Tapestry 4, in that following a link or form submission, the URL would indicate details about the previous page, not the newly displayed page, and clicking the browser refresh button could cause a server side operation to occur again (which would often be quite undersirable).\n\n!URI Format\n\n{{{\n/page-name.event-type/component-id-path/id\n}}}\n\nHere page-name is the LogicalPageName. The event-type is a string that identifies the type of event (and will ultimately be used to select an event handler method). \n\nThe component-id-path is a dot-separated series of component ids, used to identify a specific component within the overall page.\n\nThe id is optional, and may be repeated. The id value or values will be provided to the event handler method.\n\nExample: /Login.submit/form (the URI for a form component on page Login).\n\nExample: /admin/UserProfile/action/menu.delete/37 (component m
enu.delete of the UserProfile page, with an id of 37).\n</div>
+ <div id="storeArea"><div tiddler="Assets" modifier="HowardLewisShip" modified="200611241951" created="200611241951" tags="">The concept of Assets is unchanged from Tapestry 4.\n\nThere will be an "exclusion list" of file name extensions. Files with that extension will require an md5sum as part of the URI. The default exclusion list with be ".class". For other file types (particularily .js, .css, etc.) the file will be the file, and relative file names will work.\n\nSome kind of hook will be necessary to support schemes like Akamai, where assets are stored externally. This should also take into account localization.\n\nSome kind of folder aliasing will be necessary. I may want "/assets/dojo/" to map on the classpath to "/org/apache/tapestry/dojo/dojo_0_0_4/". When handling updates to big packages such as Dojo, I don't want to have to sort through some ungodly number of changes between 0.0.4 and 0.0.5, I want to create a new dojo_0_0
_5 folder, drop the contents in, delete the dojo_0_0_4 folder, and update the mapping of "/assets/dojo/".</div>
+<div tiddler="ComponentActionRequest" modifier="HowardLewisShip" modified="200610081335" created="200610080113" tags="">Component actions are actions that reflect user interaction with a component within a page. Again, this falls into several broad categories:\n\n* Links that perform a server-side action, and result in a page refresh, or a new page being displayed.\n* Ajax style links, which perform a server-side action, and refresh only part of the page.\n* Forms which perform a server-side action, followed by a page refresh (or new page being displayed).\n* Ajax style forms, which trigger an action, followed by a refresh of part of the page.\n* Other user interactions, which result in a server side action, and a partial page refresh.\n\nIn all of these cases, one or more ComponentEvents is fired. The result of ComponentEvent determines whether a partial page render or a full page render occurs.\n\nIn the later case, a client side redirect is sent, to force the browser to i
nitial a new PageRenderRequest. This addresses an issue in Tapestry 4, in that following a link or form submission, the URL would indicate details about the previous page, not the newly displayed page, and clicking the browser refresh button could cause a server side operation to occur again (which would often be quite undersirable).\n\n!URI Format\n\n{{{\n/page-name.event-type/component-id-path/id\n}}}\n\nHere page-name is the LogicalPageName. The event-type is a string that identifies the type of event (and will ultimately be used to select an event handler method). \n\nThe component-id-path is a dot-separated series of component ids, used to identify a specific component within the overall page.\n\nThe id is optional, and may be repeated. The id value or values will be provided to the event handler method.\n\nExample: /Login.submit/form (the URI for a form component on page Login).\n\nExample: /admin/UserProfile/action/menu.delete/37 (component menu.delete of the Use
rProfile page, with an id of 37).\n</div>
+<div tiddler="ComponentDocumentation" modifier="HowardLewisShip" modified="200611231534" created="200611231533" tags="parameters">Tapestry needs a JavaDoc-like, or JavaDoc-based tool to extract documentation about component parameters (and mixins) and present it in a useable format. In Tapestry 4, you could document the public getters and setters, but in Tapestry 5, the annotations are on the private instance variables, which are generally not documented.</div>
<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="DontTouchInternals" modifier="HowardLewisShip" modified="200611241953" created="200611241953" tags="">Very few of the Tapestry committers will need to touch anything inside the internals package. When this occurs, some online discussion may be mandated. The goal of Tapestry is to ensure that most work for commiters and for developers is in the domain of creating components, not tinkering with internals.</div>
+<div tiddler="DynamicPageState" modifier="HowardLewisShip" modified="200611241832" 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\n''Update: As I've thought this one through, I don't think it is viable outside of Forms. It will end up with long URLs and a constant ambiguity about whether each link should include or exclude the page state. So this one is unlikely to get implemented.''\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 M
IME 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\nMy 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 Form 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>
+<div tiddler="FocusOnTesting" modifier="HowardLewisShip" modified="200611241954" created="200611241954" tags="">I'm still not at the stage of test first, but with every line of code I write, I am thiking about how I will test that line of code. Tapestry uses EasyMock extensively, and there's lots of existing code examples to work with.\n\n!Dont Despair\n\nI occasionally get exhausted by the amount of test code I write for simple chunks of code. And I inevitably find a broken line of code that would be a major pain to locate inside a running application, but easy inside a unit test. Keep your eyes on the big picture.</div>
<div tiddler="FormProcessing" modifier="HowardLewisShip" modified="200609211540" created="200609210203" tags="forms">Form processing in Tapestry 4 had certain strengths and limitations.\n\nBasically, any action framework that can do a simple mapping from query parameters to bean property names has advantages in terms of simple forms, and Tapestry 4's approach has huge advantages on more complex forms (with some considerable developer and framework overhead).\n\nWith a direct mapping of query parameter names to bean names, each query parameter becomes self describing. You map query parameters to property of some well known bean. You do simple conversions from strings to other types (typically, ints and dates and the like). You drop query parameters that don't match up. You leave a lot of validation and other plumbing (such as getting those values into your DataTransferObjects) to the developer.\n\nBut you never see a ~StaleLinkException.\n\nYou also have some unwanted loophol
es in your application in that //any// property can be updated through the URL. This is //one step// towards a security hole.\n\n!Tapestry 4 Approach\n\nEvery form component, as it renders, asks the Form that encloses it to provide a client id. The terminology is a little messed; client id is the unique (within the form) name for //one rendering// of the component. If the component renders multiple times, because of loops, each rendering gets a unique name. This becomes the <input>'s name attribute, and ultimately, the query parameter name.\n\nTapestry attempts to make the client id match the (user provided) component id. This is not always possible, especially in a loop, in which case a numeric suffix may be appended to the id to (help) ensure uniqueness.\n\nOn render, a sequence of //component activations// occur, guided by the normal render sequence. The exact sequence of activations guides\nthe production of client ids.\n\nUsing more advanced Tapestry techniques,
including loops, conditionals and the Block/RenderBlock combo, the exact set of components and\ncomponent activations that will occur for a given rendering of a given form can not be predicted statically. Tapestry must actually render out the form\nto discover all of these.\n\nIn fact, while the Form component is producing this series of client ids, it builds up the list and stores it into the rendered page as a hidden form field. It will need it later, when the client-side form is submitted back to the server.\n\nAn advantage of this approach is the disconnect between the query parameter names (the client ids) and the objects and properties being editted. Often the client ids will be //mneumonic// for the properties, but aren't directly mapped to them. Only the components responsible for each query parameter know how to validate the submitted value, and what property of which object will need to be updated.\n\nWhen a form submission occurs, we want to ensure that each quer
y parameter value read out of the request is applied to the correct property of the correct object. There's a limit to how much Tapestry can help here (because it has only a casual knowledge of this aspect of the application structure).\n\nDuring this submission process, which endded up with the curious name, //rewind phase//, Tapestry must do two things:\n* Activate each component, such that the component may re-determine its client id, read its parameter, and update its page property\n* Validate that the process has not been comprimised by a change of server side state\n\nThat second element is a tricky one; things can go wonky if a race condition occurs between two users. For example, lets take a simple invoice and line item model. If users A and B both read the same invoice, user A adds a line item, and user B changes a line item ... we can have a problem when user B submits the form. Now that there are three line items (not two) in the form, there will be extra componen
t activations to process query parameters that don't exist in the request. \n\nThis scenario can occur whenever the processing of the form submission is driven by server-side data that can change between request.\n\nTapestry detects this as a difference in the sequence of client ids allocated, and throws a ~StaleLinkException, which is very frustrating for developers to comprehend and fix.\n\nThere are also other edge cases for different race conditions where data is applied to the wrong server-side objects.\n\nThe Tapestry 3 ~ListEdit component, which evolved into the Tapestry 4 For component, attempts to address this by serializing a series of //object ids// into the form (as a series of hidden fields). This requires a bit of work on the part of the developer to provide an ~IPrimaryKeyConverter that can help convert objects to ids (when rendering) and ids back to objects (during form submission).\n\nGenerally speaking, the Tapestry 4 approach represents layers of kludge o
n layers of kludge. It works, it gets the job done, it can handle some very complex situations, but it is less than ideal.\n\n!Tapestry 5\n\nThe goal here is to capture the series of //component activations//, along with any significant page state changes, during the render.\n\nThese activations will be a series of //commands//. For each component activation there will be two commands: the first command will be used to inform the component of its client id (this command executes during render and during form submission). The second command will request that the client handle the form submission (this command executes only during form submission).\n\nThe serialized series of commands is stored as a hidden form field.\n\nThere's a lot of API to be figured out, especially the relationship between the form components and the form itself.\n\nFurther, a lot of what the Tapestry 4 For component does, in terms of serializing dynamic page state, will need to fold into this as well.
\n\nThe end result will be a single hidden field with a big MIME string inside it ... but compared to the Tapestry 4 Form component (which has to write out many hidden fields) the whole will be less than the sum of the parts ... due to the overhead of serialization and gzip compression.\n\n\n\n\n\n\n</div>
<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="200611040038" 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?\n* SmartDefaults -- do even more with event less\n* RandomIdeas -- stuff that doesn't fit elsewhere</div>
+<div tiddler="MasterIndex" modifier="HowardLewisShip" modified="200611241944" 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?\n* SmartDefaults -- do even more with event less\n* RandomIdeas -- stuff that doesn't fit elsewhere\n* ProblemsNeedingSolutions\n* ComponentDocumentation -- Generating Documentation about Components\n* TapestryLookAndFeel -- Default CSS\n* [[Assets]]\n\n</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 values.\n\n{{{\n@SetupPageRender\nvoid 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="ProblemsNeedingSolutions" modifier="HowardLewisShip" modified="200611230401" created="200611230401" tags="">There are a few things that I'm concerned about.\n\n!Render Complexity\n\nAll those states in the render component state machine may be a little much, especially ~PreBeginRender, ~BeginRender and ~PostBeginRender. In addition, it doesn't work for a case I'm interested in ... for link components, I'd like to use the RenderInformals mixin, but also support a disable parameter that turns off the <a> tag (but still renders the body). The state machine currently is set up so that returning false in any of the ~BeginRender states skips all the way to ~AfterRender, bypassing the template and/or body.</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>
-<div tiddler="RandomIdeas" modifier="HowardLewisShip" modified="200611041749" created="200611040039" tags="">!HTML / XHTML DTDs\n\nThe template parser should include local (in JAR) copies of the HTML and XHTML DTDs and redirect the parser to use the local copies. This can be a huge performance boost when parsing a template.\n\n!final should imply @Retain\n\nFinal fields should be treated as if they have the @Retain annotation\n\n! Exceptions from event handler / phase render methods\n\nTapestry should wrap non-runtime exceptions from these methods. I think today, if you declare that such a method throws an exception, you'll get a runtime exception out of Javassist.\n\n! SubForms\n\nPerhaps one way to approach highly dynamic, Ajax pages with forms is to have a logical "sub form" concept. A sub form would work inside an existing form, and organize a group of fields within that form. Processing of the fields would occur only if the sub form was active, which itself\nw
ould be tracked based on visibility of the sub form (a sub form in an invisible panel would not be processed on the server side). This idea needs a lot of fleshing out, even to see if it is viable.\n\n! Ajax Constraints\n\nThe best way to tackle Ajax features, especially w.r.t. forms, is to put some sensible constraints on what the user can do, then make it easy to implement those things.\n\nBasically ... never delete! Deletions are a real pain to handle, unless I suddenly get much smarter. Allow things to be hidden on the client side,\nand for the corresponding fields to do nothing on the server side, but don't allow them to full out delete. \n\nAllow new things to be added, preferable only at the "tail end" of the form. </div>
+<div tiddler="RandomIdeas" modifier="HowardLewisShip" modified="200611230501" created="200611040039" tags="">!HTML / XHTML DTDs\n\nThe template parser should include local (in JAR) copies of the HTML and XHTML DTDs and redirect the parser to use the local copies. This can be a huge performance boost when parsing a template.\n\n!final should imply @Retain\n\nFinal fields should be treated as if they have the @Retain annotation\n\n! Exceptions from event handler / phase render methods\n\nTapestry should wrap non-runtime exceptions from these methods. I think today, if you declare that such a method throws an exception, you'll get a runtime exception out of Javassist.\n\n! SubForms\n\nPerhaps one way to approach highly dynamic, Ajax pages with forms is to have a logical "sub form" concept. A sub form would work inside an existing form, and organize a group of fields within that form. Processing of the fields would occur only if the sub form was active, which itself\nw
ould be tracked based on visibility of the sub form (a sub form in an invisible panel would not be processed on the server side). This idea needs a lot of fleshing out, even to see if it is viable.\n\n! Ajax Constraints\n\nThe best way to tackle Ajax features, especially w.r.t. forms, is to put some sensible constraints on what the user can do, then make it easy to implement those things.\n\nBasically ... never delete! Deletions are a real pain to handle, unless I suddenly get much smarter. Allow things to be hidden on the client side,\nand for the corresponding fields to do nothing on the server side, but don't allow them to full out delete. \n\nAllow new things to be added, preferable only at the "tail end" of the form. \n\n! SPI Package\n\nA number of interfaces, such as Binding, probably belong in a SPI (Service Provider Interface) package, since they will generally only be used by authors of Tapestry extensions. Perhaps we should just use the oat.services
package as the SPI package?</div>
<div tiddler="RequestTypes" modifier="HowardLewisShip" modified="200610081334" created="200610071243" tags="request">There are three broad categories of user requests (requests from the client web browser):\n\n* PageRenderRequest -- requests to render a specific page, possibly with some configuration\n* ComponentActionRequest -- requests that trigger behaivor within a specific component\n* ResourceRequest -- requests that access a resource file within the classpath\n\nEach of these requests has a specific URI format.</div>
<div tiddler="SideBarTabs" modifier="HowardLewisShip" modified="200609210652" created="200609210651" tags=""><<tabs txtMainTab Timeline Timeline TabTimeline All 'All tiddlers' TabAll Tags 'All tags' TabTags More 'More lists' TabMore>>\n</div>
<div tiddler="SiteSubtitle" modifier="HowardLewisShip" modified="200609202249" created="200609202155" tags="">\nThe quick and dirty one-stop shopping of random ideas for Tapestry 5.</div>
<div tiddler="SiteTitle" modifier="HowardLewisShip" modified="200609202249" created="200609202155" tags="">Tapestry 5 Brain Dump</div>
<div tiddler="SiteUrl" modifier="HowardLewisShip" modified="200609210703" created="200609210641" tags="">http://tapestry.apache.org/tapestry5/tap5devwiki.html</div>
-<div tiddler="SmartDefaults" modifier="HowardLewisShip" modified="200611032359" created="200611032344" tags="">As great as the annotations are, allowing things to work without the annotations could be even better.\n\n!Event handler methods\n\nMethods with the prefix "on" could automatically be considered event handler methods. The string after the prefix, converted to lower case, would be the event type. We could even add "from//~ComponentId//" to the end. Examples (with annotation equivalents):\n\n* onSubmit --> @~OnEvent("submit")\n* onSubmitFromForm --> @~OnEvent(value="submit", component="form")\n* onUpdateFromSelect --> @~OnEvent(value="update", component="select")\n\n!Render phase methods\n\nNaming a method the same as the render phase (with the first character lower case). Again, Tapestry could deduce the phase from the method name, as if the annotation were present:\n\n* beforeRender
() --> @~BeforeRender\n* beforeRenderBody() --> @~BeforeRenderBody\n\netc. Again, the methods don't have to be public, they just have to have the correct name. In every other way they are the same as annotated render phase methods except that they don't have the annotation.\n\nThere may be some minor implications w.r.t. render phase method ordering.\n\netc.\n\n!Other Ideas\n\nThis gets more component specific. I had the idea that a ~TextField whose id was "userId" might want to edit a property named "userId" as the default for when its value parameter is unbound. I think to accomplish this, we need the concept of computed bindings for unbound parameters ... perhaps in the form of methods that return a Binding with a name and/or annotation, for example:\n\n{{{\n\n @Inject\n private ComponentResources _resources;\n\n @Inject("infrastructure:bindingSource")\n private BindingSource _source;\n\n @Parameter\n private Object _value;\n\n B
inding valueDefault()\n {\n ComponentResources containerResources = _resources.getContainer().getComponentResources();\n return _source.newBinding("default value", containerResources, "prop", _resources.getId(), null); \n }\n}}}\n\nSo valueDefault() is invoked if the value parameter is not bound. The component uses its own immediate id ("userId") as the name of a property of its container (typically, the page). ~ComponentResources does not yet implement getContainer(), but the rest would work.\n\nIf this was widespread, there could be even better optimizations for it. Perhaps container resources could just be passed into the method as a parameter, to save the code to find it. Ditto with BindingSource. Once again, rather than come up with complex XML-ese to come up with defaults, we're trying to work //with// Java code.\n</div>
+<div tiddler="SmartDefaults" modifier="HowardLewisShip" modified="200611231535" created="200611032344" tags="">As great as the annotations are, allowing things to work without the annotations could be even better.\n\n!Event handler methods\n\nMethods with the prefix "on" could automatically be considered event handler methods. The string after the prefix, converted to lower case, would be the event type. We could even add "from//~ComponentId//" to the end. Examples (with annotation equivalents):\n\n* onSubmit --> @~OnEvent("submit")\n* onSubmitFromForm --> @~OnEvent(value="submit", component="form")\n* onUpdateFromSelect --> @~OnEvent(value="update", component="select")\n\n!Render phase methods\n\nNaming a method the same as the render phase (with the first character lower case). Again, Tapestry could deduce the phase from the method name, as if the annotation were present:\n\n* beforeRender
() --> @~BeforeRender\n* beforeRenderBody() --> @~BeforeRenderBody\n\netc. Again, the methods don't have to be public, they just have to have the correct name. In every other way they are the same as annotated render phase methods except that they don't have the annotation.\n\nThere may be some minor implications w.r.t. render phase method ordering.\n\netc.\n\n!Other Ideas\n\nThis gets more component specific. I had the idea that a ~TextField whose id was "userId" might want to edit a property named "userId" as the default for when its value parameter is unbound. I think to accomplish this, we need the concept of computed bindings for unbound parameters ... perhaps in the form of methods that return a Binding with a name and/or annotation, for example:\n\n{{{\n\n @Inject\n private ComponentResources _resources;\n\n @Inject("infrastructure:bindingSource")\n private BindingSource _source;\n\n @Parameter\n private Object _value;\n\n B
inding valueDefault()\n {\n ComponentResources containerResources = _resources.getContainer().getComponentResources();\n return _source.newBinding("default value", containerResources, "prop", _resources.getId(), null); \n }\n}}}\n\nSo valueDefault() is invoked if the value parameter is not bound. The component uses its own immediate id ("userId") as the name of a property of its container (typically, the page). ~ComponentResources does not yet implement getContainer(), but the rest would work.\n\nIf this was widespread, there could be even better optimizations for it. Perhaps container resources could just be passed into the method as a parameter, to save the code to find it. Ditto with BindingSource. Once again, rather than come up with complex XML-ese to come up with defaults, we're trying to work //with// Java code.\n</div>
<div tiddler="TabAll" modifier="HowardLewisShip" modified="200609210650" created="200609210650" tags=""><<list all>></div>
+<div tiddler="TapestryLookAndFeel" modifier="HowardLewisShip" modified="200611241943" created="200611241943" tags="">I think it would be very compelling to create a reasonably sharp default CSS for Tapestry applications. Something pretty, standards based, Web-2.0-ish, that would make even the simplest apps stand out.\n\nOf course, the Tapestry default CSS would be the first stylesheet, and could be overridden by additional stylesheets or inline styles.</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="WatchCodeCoverage" modifier="HowardLewisShip" modified="200611241957" created="200611241956" tags="">The code coverage tools built into ''mvn site'' are quite useful. Right now, overall coverage is at 93%. Keep an eye on code coverage, including branch coverage (do you test both outcomes of an if statement?). Use unexecuted code to target your efforts.\n\nI often do a cursory unit test for "normal behavior", plus more exaustive unit tests for error conditions. I then "back the test up" using an integration test (build with [[Selenium]]) to prove that the normal behavior case really works.</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>
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