Author: buildbot
Date: Sat Feb 27 19:19:47 2016
New Revision: 981293
Log:
Production update by buildbot for tapestry
Modified:
websites/production/tapestry/content/cache/main.pageCache
websites/production/tapestry/content/page-life-cycle.html
Modified: websites/production/tapestry/content/cache/main.pageCache
==============================================================================
Binary files - no diff available.
Modified: websites/production/tapestry/content/page-life-cycle.html
==============================================================================
--- websites/production/tapestry/content/page-life-cycle.html (original)
+++ websites/production/tapestry/content/page-life-cycle.html Sat Feb 27
19:19:47 2016
@@ -125,7 +125,7 @@
</div>
</li></ul>
-</div><p>In Tapestry, you are free to develop your presentation objects, page
and components classes, as ordinary objects, complete with instance variables
and so forth.</p><p>This is somewhat revolutionary in terms of web development
in Java. Using traditional servlets, or Struts, your presentation objects
(Servlets, or Struts Actions, or the equivalent in other frameworks) are
<em>stateless singletons</em>. That is, a <em>single</em> instance is created,
and all incoming requests are threaded through that single
instance.</p><p>Because multiple requests are handled by many different
threads, this means that the single instance's variable are useless ... any
value written into an instance variable would immediately be overwritten by a
different thread. Thus, it is necessary to use the Servlet API's
HttpServletRequest object to store per-request data, and the HttpSession object
to store data between requests.</p><p>Tapestry takes a very different
approach.</p><p>In Tapestry, each pa
ge is a singleton, but with a <em>per thread</em> map of field names &
values that Tapestry invisibly manages for you.</p><p>With this approach, all
the difficult, ugly issues related to multi-threading go by the wayside.
Instead, familiar, simple coding practices (using ordinary methods and fields)
can be used.</p><div class="confluence-information-macro
confluence-information-macro-information"><span class="aui-icon aui-icon-small
aui-iconfont-info confluence-information-macro-icon"></span><div
class="confluence-information-macro-body"><p>Tapestry 5.0 and 5.1 used page
pooling, rather than a singleton page with a per-thread map, to achieve the
same effect.</p></div></div><h2 id="PageLifeCycle-PageLifeCycleMethods">Page
Life Cycle Methods</h2><p>There are a few situations where it is useful for a
component to perform some operations, usually some kind of initialization or
caching, based on the life cycle of the page.</p><p>The page life cycle is
quite simple. When first needed,
a page is loaded. Loading a page involves instantiating the components of the
page and connecting them together.</p><p>Once a page is loaded, it is
<em>attached</em> to the current request. Remember that there will be many
threads, each handling its own request to the same page.</p><p>At the end of a
request, after a response has been sent to the client, the page is
<em>detached</em> from the request. This is a chance to perform any cleanup
needed for the page.</p><p>As with <a
href="component-rendering.html">component rendering</a>, you have the ability
to make your components "aware" of these events by identifying methods to be
invoked.</p><p>Page life cycle methods should take no parameters and return
void.</p><p>You have the choice of attaching an annotation to a method, or
simply using the method naming conventions:</p><div class="table-wrap"><table
class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1"
class="confluenceTh"><p>Annotation</p></th><th colspan="1" rowspa
n="1" class="confluenceTh"><p>Method Name</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>When Called</p></th></tr><tr><td colspan="1"
rowspan="1" class="confluenceTd"><p>@<a class="external-link"
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/PageLoaded.html";>PageLoaded</a></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>pageLoaded()</p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>After the page is fully
loaded</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p>@<a
class="external-link"
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/PageAttached.html";>PageAttached</a></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>pageAttached()</p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>After the page is attached to
the request.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd">@<a class="external-link" href="http://tapestry.ap
ache.org/current/apidocs/org/apache/tapestry5/annotations/PageReset.html">PageReset</a></td><td
colspan="1" rowspan="1" class="confluenceTd">pageReset()</td><td colspan="1"
rowspan="1" class="confluenceTd">After the page is <em>activated</em>, except
when requesting the same page</td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>@<a class="external-link"
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/PageDetached.html";>PageDetached</a></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>pageDetached()</p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>AFter the page is detached from
the request.</p></td></tr></tbody></table></div><p>The @PageReset life cycle is
new in Tapestry 5.2. It is invoked on a page render request when linked to from
some <em>other</em> page of the application (but <em>not</em> on a link to the
same page). This is to allow the page to reset its state, if any, when a user
returns to the page fr
om some other part of the application.</p><h2
id="PageLifeCycle-ComparisontoJavaServerPages">Comparison to JavaServer
Pages</h2><p>JSPs also act as singletons. However, the individual JSP tags are
pooled.</p><p>This is one of the areas where Tapestry can significantly
outperform JSPs. Much of the code inside a compiled JSP class concerns getting
tags from a tag pool, configuring the properties of the tag instance, using the
tag instance, then cleaning up the tag instance and putting it back in the
pool.</p><p>The operations Tapestry does once per request are instead executed
dozens or potentially hundreds of times (depending the complexity of the page,
and if any nested loops occur).</p><p>Pooling JSP tags is simply the wrong
granularity.</p><p>Tapestry can also take advantage of its more coarse grained
caching to optimize how data moves, via parameters, between components. This
means that Tapestry pages will actually speed up after they render the first
time.</p><h2 id="PageLifeCyc
le-PagePoolConfiguration">Page Pool Configuration</h2><div
class="confluence-information-macro confluence-information-macro-note"><span
class="aui-icon aui-icon-small aui-iconfont-warning
confluence-information-macro-icon"></span><div
class="confluence-information-macro-body"><p>This related to versions of
Tapestry prior to 5.2. Modern Tapestry uses an alternate approach that allows a
single page instance to be shared across many request processing
threads.</p></div></div><p>In Tapestry 5.0 and 5.1, a page pool is used to
store page instances. The pool is "keyed" on the name of the page (such as
"start") and the <em>locale</em> for the page (such as "en" or
"fr").</p><p>Within each key, Tapestry tracks the number of page instances that
have been created, as well as the number that are in use (currently attached to
a request).</p><p>When a page is first accessed in a request, it is taken from
the pool. Tapestry has some <a href="configuration.html">configuration
values</a> that cont
rol the details of how and when page instances are created.</p><ul><li>If a
free page instance is available, the page is marked in use and attached to the
request.</li><li>If there are fewer page instances than the <em>soft
limit</em>, then a new page instance is simply created and attached to the
request.</li><li>If the soft limit has been reached, Tapestry will wait for a
short period of time for a page instance to become available before creating a
new page instance.</li><li>If the hard limit has been reached, Tapestry will
throw an exception rather than create a new page instance.</li><li>Otherwise,
Tapestry will create a new page instance.<br clear="none"> Thus a busy
application will initially create pages up-to the soft limit (which defaults to
five page instances). If the application continues to be pounded with requests,
it will slow its request processing, using the soft wait time in an attempt to
reuse an existing page instance.</li></ul><p>A truly busy application will c
ontinue to create new page instances as needed until the hard limit is
reached.</p><p>Remember that all these configuration values are per key: the
combination of page name and locale. Thus even with a hard limit of 20, you may
eventually find that Tapestry has created 20 start page instances for locale
"en" <em>and</em> 20 start page instances for locale "fr" (if your application
is configured to support both English and French). Likewise, you may have 20
instances for the start page, and 20 instances for the newaccount
page.</p><p>Tapestry periodically checks its cache for page instances that have
not been used recently (within a configurable window). Unused page instances
are release to the garbage collector.</p><p>The end result is that you have
quite a degree of tuning control over the process. If memory is a limitation
and throughput can be sacrificed, try lowering the soft and hard limit and
increasing the soft wait.</p><p>If performance is absolute and you have lots of
memor
y, then increase the soft and hard limit and reduce the soft wait. This
encourages Tapestry to create more page instances and not wait as long to
re-use existing instances.</p></div>
+</div><div class="confluence-information-macro
confluence-information-macro-note"><span class="aui-icon aui-icon-small
aui-iconfont-warning confluence-information-macro-icon"></span><div
class="confluence-information-macro-body"><p>This is an advanced topic. Most
users won't ever need to know anything about the page life
cycle.</p></div></div><p> </p><p>In Tapestry, you are free to develop your
presentation objects, page and components classes, as ordinary objects,
complete with instance variables and so forth.</p><p>This is somewhat
revolutionary in terms of web development in Java. By comparison, using
traditional servlets, or Struts, your presentation objects (Servlets, or Struts
Actions, or the equivalent in other frameworks) are <em>stateless
singletons</em>. That is, a <em>single</em> instance is created, and all
incoming requests are threaded through that single instance. Because multiple
requests are handled by many different threads, this means that the singleton's
ins
tance variables are useless ... any value written into an instance variable
would immediately be overwritten by a different thread. Thus, it is necessary
to use the Servlet API's HttpServletRequest object to store per-request data,
and the HttpSession object to store data between requests.</p><p>Tapestry takes
a very different approach.</p><p>In Tapestry, each page is a singleton, but
with a <em>per thread</em> map of field names & values that Tapestry
invisibly manages for you.</p><p>With this approach, all the difficult, ugly
issues related to multi-threading go by the wayside. Instead, familiar, simple
coding practices (using ordinary methods and fields) can be used.</p><div
class="confluence-information-macro
confluence-information-macro-information"><span class="aui-icon aui-icon-small
aui-iconfont-info confluence-information-macro-icon"></span><div
class="confluence-information-macro-body"><p>Tapestry 5.0 and 5.1 used page
pooling, rather than a singleton page with a per-t
hread map, to achieve the same effect.</p></div></div><p>The page life cycle
is quite simple:</p><ol><li>When first needed, a page is loaded. Loading a page
involves instantiating the components of the page and connecting them
together.</li><li>Once a page is loaded, it is <em>attached</em> to the current
request. Remember that there will be many threads, each handling its own
request to the same page.</li><li>At the end of a request, after a response has
been sent to the client, the page is <em>detached</em> from the request. This
is a chance to perform any cleanup needed for the page.</li></ol><h2
id="PageLifeCycle-PageLifeCycleMethods">Page Life Cycle Methods</h2><p>There
are rare occasions where it is useful for a component to perform some
operations, usually some kind of initialization or caching, based on the life
cycle of the page.</p><p>As with <a href="component-rendering.html">component
rendering</a>, you have the ability to make your components "aware" of these
events by
telling Tapestry what methods to invoke for each.</p><p>Page life cycle
methods should take no parameters and return void.</p><p>You have the choice of
attaching an annotation to a method, or simply using the method naming
conventions:</p><div class="table-wrap"><table
class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1"
class="confluenceTh"><p>Annotation</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Method Name</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>When Called</p></th></tr><tr><td colspan="1"
rowspan="1" class="confluenceTd"><p>@<a class="external-link"
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/PageLoaded.html";>PageLoaded</a></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>pageLoaded()</p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>After the page is fully
loaded</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p>@<a
class="external-link" href="http://t
apestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/PageAttached.html">PageAttached</a></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>pageAttached()</p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>After the page is attached to
the request.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd">@<a class="external-link"
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/PageReset.html";>PageReset</a></td><td
colspan="1" rowspan="1" class="confluenceTd">pageReset()</td><td colspan="1"
rowspan="1" class="confluenceTd">After the page is <em>activated</em>, except
when requesting the same page</td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>@<a class="external-link"
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/PageDetached.html";>PageDetached</a></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>pageDetached()</p></td><td
colspan="1" rowspan=
"1" class="confluenceTd"><p>AFter the page is detached from the
request.</p></td></tr></tbody></table></div><p>The @PageReset life cycle (only
for Tapestry 5.2 and later) is invoked on a page render request when the page
is linked to from some <em>other</em> page of the application (but <em>not</em>
on a link to the same page), or upon a reload of the page in the browser. This
is to allow the page to reset its state, if any, when a user returns to the
page from some other part of the application.</p><h2
id="PageLifeCycle-ComparisontoJavaServerPages">Comparison to JavaServer
Pages</h2><p>JSPs also act as singletons. However, the individual JSP tags are
pooled.</p><p>This is one of the areas where Tapestry can significantly
outperform JSPs. Much of the code inside a compiled JSP class concerns getting
tags from a tag pool, configuring the properties of the tag instance, using the
tag instance, then cleaning up the tag instance and putting it back in the
pool.</p><p>The operations Tape
stry does once per request are instead executed dozens or potentially hundreds
of times (depending the complexity of the page, and if any nested loops
occur).</p><p>Pooling JSP tags is simply the wrong granularity.</p><p>Tapestry
can also take advantage of its more coarse grained caching to optimize how data
moves, via parameters, between components. This means that Tapestry pages will
actually speed up after they render the first time.</p><h2
id="PageLifeCycle-PagePoolConfiguration">Page Pool Configuration</h2><div
class="confluence-information-macro confluence-information-macro-note"><span
class="aui-icon aui-icon-small aui-iconfont-warning
confluence-information-macro-icon"></span><div
class="confluence-information-macro-body"><p>This related to versions of
Tapestry prior to 5.2. Modern Tapestry uses an alternate approach that allows a
single page instance to be shared across many request processing
threads.</p></div></div><p>In Tapestry 5.0 and 5.1, a page pool is used to
store
page instances. The pool is "keyed" on the name of the page (such as "start")
and the <em>locale</em> for the page (such as "en" or "fr").</p><p>Within each
key, Tapestry tracks the number of page instances that have been created, as
well as the number that are in use (currently attached to a
request).</p><p>When a page is first accessed in a request, it is taken from
the pool. Tapestry has some <a href="configuration.html">configuration
values</a> that control the details of how and when page instances are
created.</p><ul><li>If a free page instance is available, the page is marked in
use and attached to the request.</li><li>If there are fewer page instances than
the <em>soft limit</em>, then a new page instance is simply created and
attached to the request.</li><li>If the soft limit has been reached, Tapestry
will wait for a short period of time for a page instance to become available
before creating a new page instance.</li><li>If the hard limit has been
reached, Tapestry will t
hrow an exception rather than create a new page instance.</li><li>Otherwise,
Tapestry will create a new page instance.<br clear="none"> Thus a busy
application will initially create pages up-to the soft limit (which defaults to
five page instances). If the application continues to be pounded with requests,
it will slow its request processing, using the soft wait time in an attempt to
reuse an existing page instance.</li></ul><p>A truly busy application will
continue to create new page instances as needed until the hard limit is
reached.</p><p>Remember that all these configuration values are per key: the
combination of page name and locale. Thus even with a hard limit of 20, you may
eventually find that Tapestry has created 20 start page instances for locale
"en" <em>and</em> 20 start page instances for locale "fr" (if your application
is configured to support both English and French). Likewise, you may have 20
instances for the start page, and 20 instances for the newaccount page.</
p><p>Tapestry periodically checks its cache for page instances that have not
been used recently (within a configurable window). Unused page instances are
release to the garbage collector.</p><p>The end result is that you have quite a
degree of tuning control over the process. If memory is a limitation and
throughput can be sacrificed, try lowering the soft and hard limit and
increasing the soft wait.</p><p>If performance is absolute and you have lots of
memory, then increase the soft and hard limit and reduce the soft wait. This
encourages Tapestry to create more page instances and not wait as long to
re-use existing instances.</p></div>
</div>
<div class="clearer"></div>
