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Subject cvs commit: xml-axis/proposals/arch/docs architecture-guide.html
Date Fri, 28 Jun 2002 12:53:28 GMT
glyn        2002/06/28 05:53:28

  Modified:    java/docs architecture-guide.html chainclasses.jpg
                        engineclasses.jpg messagecontext.jpg
               proposals/arch/docs architecture-guide.html
  Tidy up architecture guide and improve UML notation in certain diagrams.
  Revision  Changes    Path
  1.14      +23 -20    xml-axis/java/docs/architecture-guide.html
  Index: architecture-guide.html
  RCS file: /home/cvs/xml-axis/java/docs/architecture-guide.html,v
  retrieving revision 1.13
  retrieving revision 1.14
  diff -u -r1.13 -r1.14
  --- architecture-guide.html	15 May 2002 13:03:56 -0000	1.13
  +++ architecture-guide.html	28 Jun 2002 12:53:27 -0000	1.14
  @@ -58,7 +58,7 @@
   Handlers and the Message Path in Axis</h3>
   Put simply, Axis is all about processing Messages. When the central Axis
   processing logic runs, a series of <b>Handlers</b> are each invoked in
  -order. The particular oder is determined by two factors - deployment configuration
  +order. The particular order is determined by two factors - deployment configuration
   and whether the engine is a client or a server. The object which is passed
   to each Handler invocation is a <b>MessageContext</b>. A MessageContext
   is a structure which contains several important parts: 1) a "request" message,
  @@ -75,14 +75,16 @@
   model of Axis) will generate a MessageContext and invoke the Axis processing
   In either case, the Axis framework's job is simply to pass the resulting
  -MessageContext through a configurable set of Handlers, each of which has
  +MessageContext through the configured set of Handlers, each of which has
   an opportunity to do whatever it is designed to do with the MessageContext.
   Message Path on the Server</h3>
   The server side message path is shown in the following diagram. The small
   cylinders represent Handlers and the larger, enclosing cylinders represent
  +<b>Chains</b> (ordered collections of Handlers which will be described
   <br><img SRC="ServerMessagePath.jpg" VSPACE=30 height=282 width=602>
   <br>A message arrives (in some protocol-specific manner) at a Transport
   Listener. In this case, let's assume the Listener is a HTTP servlet. It's
  @@ -102,8 +104,7 @@
   the invoke() method. This will result in calling all the Handlers specified
   in the request Chain configuration.
   <p>After the transport request Handler, the engine locates a global request
  -Chain, if configured (in the &lt;requestFlow> element of the WSDD &lt;globalConfiguration>,
  -as explained in the WSDD deployment section later in this document), and
  +Chain, if configured, and
   then invokes any Handlers specified therein.
   <p>At some point during the processing up until now, some Handler has hopefully
   set the <b>serviceHandler</b> field of the MessageContext (this is usually
  @@ -116,7 +117,7 @@
   what we saw at the transport and global levels), and must contain a <b>provider</b>,
   which is simply a Handler responsible for implementing the actual back
   end logic of the service.
  -<p>In typical RPC examples, the provider is the
  +<p>For RPC-style requests, the provider is the
   class. This is just another Handler that, when invoked, attempts to call
   a backend Java object whose class is determined by the "className" parameter
   specified at deployment time. It uses the SOAP RPC convention for determining
  @@ -130,7 +131,7 @@
   <br>The <b>service</b> Handler, if any, is called first - on the client
   side, there is no "provider" since the service is being provided by a remote
   node, but there is still the possibility of request and response Chains.
  -The service request and response Chains serve to do any service-specific
  +The service request and response Chains perform any service-specific
   processing of the request message on its way out of the system, and also
   of the response message on its way back to the caller.
   <p>After the service request Chain, the global request Chain, if any, is
  @@ -153,6 +154,13 @@
   example, the HTTP and SMTP transports are independent of each other but
   may be used together.
   <p><img SRC="subsystems.jpg">
  +In fact, the Axis source code is not as cleanly separated into subsystems
  +as the above diagram might imply. Some subsystems are spread over
  +several packages and some packages overlap more than one subsystem.
  +Proposals to improve the code structure and make it
  +conform more accurately to the notional Axis subsystems will be considered
  +after v1.0 of Axis is complete.
   <a NAME="Message Flow"></a>Message Flow Subsystem</h2>
  @@ -175,8 +183,8 @@
   timers, clean up resources, etc.
   <p>A Chain is a composite Handler, i.e. it aggregates a collection of Handlers
   as well as implementing the Handler interface as shown in the following
  -<br><img SRC="chainclasses.jpg" height=297 width=267>
  +UML diagram:
  +<br><img SRC="chainclasses.jpg">
   <p>A Chain also has similarities to the Chain of Responsibility design pattern
   in which a request flows along a sequence of Handlers until it is processed.
   Although an Axis Chain may process a request in stages over a succession of
  @@ -186,7 +194,7 @@
   the appropriate Chains. A message context is used to pass the message and
   associated environment through the sequence of Handlers. The model is that
   Axis Chains are constructed offline by having Handlers added to them one
  -at a time. Then they are made online and message contexts start to flow
  +at a time. Then they are turned online and message contexts start to flow
   through the Chains. Multiple message contexts may flow through a single
   Chain concurrently. Handlers are never added to a Chain once it goes online.
   If a Handler needs to be added or removed, the Chain must be 'cloned',
  @@ -200,7 +208,7 @@
   and Chains can be defined to have 'per-access', 'per-request', or 'singleton'
   scope although the registry currently only distinguishes between these
   by constructing non-singleton scope objects when requested and constructing
  -'singleton scope objects once and holding on to them for use on subsequent
  +singleton scope objects once and holding on to them for use on subsequent
   creation requests.
   Targeted Chains</h4>
  @@ -209,7 +217,7 @@
   following class diagram shows how Targeted Chains relate to Chains. Note
   that a Targeted Chain is an aggregation of Handlers by virtue of extending
   the Chain interface which is an aggregation of Handlers.
  -<p><img SRC="targetedchainclasses.jpg" height=288 width=253>
  +<p><img SRC="targetedchainclasses.jpg">
   <p>A service is a special kind of Targeted Chain in which the pivot Handler
   is known as a "provider".
  @@ -227,25 +235,20 @@
   context may be associated with a request Message and/or a response Message.
   Each Message has a SOAPPart and an Attachments object, both of which implement
   the Part interface.
  -<br><img SRC="messagecontext.jpg" height=140 width=597>
  +<br><img SRC="messagecontext.jpg">
   <br>The typing of Message Contexts needs to be carefully considered in
   relation to the Axis architecture. Since a Message Context appears on the
   Handler interface, it should not be tied to or biassed in favour of&nbsp;
   SOAP. The current implementation is marginally biassed towards SOAP in
   that the setServiceHandler method narrows the specified Handler to a SOAPService.
  -But if we were to factor out a more abstract Message Context interface,
  -we would then be then faced with a problem. Some Handlers, most likely
  -in the global layer, would need to accept a Message Context with a particular
  -concete type (e.g. for a HTTP transport) and produce a Message Context
  -of a different concrete type (e.g. for a SOAP service) and so Handler.invoke
  -would need a more complex signature.
   <a NAME="Engine"></a>Engine</h3>
   Axis has an abstract AxisEngine class with two concrete subclasses: AxisClient
   drives the client side handler chains and AxisServer drives the server
   side handler chains. The relationships between these classes is fairly
  -<br><img SRC="engineclasses.jpg" height=242 width=169>
  +<br><img SRC="engineclasses.jpg">
   <h4>Engine Configuration</h3>
   The EngineConfiguration interface is the means of configuring the Handler
   factories and global options of an engine instance. An instance of a
  1.2       +37 -48    xml-axis/java/docs/chainclasses.jpg
  	<<Binary file>>
  1.2       +48 -46    xml-axis/java/docs/engineclasses.jpg
  	<<Binary file>>
  1.2       +30 -60    xml-axis/java/docs/messagecontext.jpg
  	<<Binary file>>
  1.2       +45 -52    xml-axis/java/docs/targetedchainclasses.jpg
  	<<Binary file>>
  1.3       +12 -1     xml-axis/proposals/arch/docs/architecture-guide.html
  Index: architecture-guide.html
  RCS file: /home/cvs/xml-axis/proposals/arch/docs/architecture-guide.html,v
  retrieving revision 1.2
  retrieving revision 1.3
  diff -u -r1.2 -r1.3
  --- architecture-guide.html	20 Jun 2002 07:48:36 -0000	1.2
  +++ architecture-guide.html	28 Jun 2002 12:53:28 -0000	1.3
  @@ -127,6 +127,17 @@
   The alternative of an abstract Marker class extending the
   javax.xml.soap.SOAPMessage abstract class would limit Axis to SOAP
   messages and bias the flow subsystem towards the SAAJ interface style.
  +<b>Note:</b>The Axis Architecture Guide used to argue that if we were to
  +factor out an
  +abstract Message Context interface, we would then be then faced with a
  +problem. Some Handlers, most likely
  +in the global layer, would need to accept a Message Context with a particular
  +concete type (e.g. for a HTTP transport) and produce a Message Context
  +of a different concrete type (e.g. for a SOAP service) and so Handler.invoke
  +would need a more complex signature.
  +However, this argument seems flawed as it would clearly be possible to make
  +the existing MessageContext class inherit a more abstract Message Context
  +interface without the need to change the signature of invoke.

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