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| </p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="architecture"></a>Chapter 32. Architecture</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="architecture.html#basic-architecture">Jetty Architecture</a></span></dt><dt><span class="section"><a href="jetty-classloading.html">Jetty Classloading</a></span></dt><dt><span class="section"><a href="1xx-responses.html">Managing 1xx Responses</a></span></dt><dt><span class="section"><a href="creating-custom-protocol.html">Creating a Custom Protocol</a></span></dt></dl></div><p>General items related to the architecture of jetty and how it deals with certain design decisions.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="basic-architecture"></a>Jetty Architecture</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="architecture.html#d0e22453">View from 20,000 feet</a></span></dt><dt><span class="section"><a href="architecture.html#d0e22492">Patterns</a></span></dt><dt><span class="section"><a href="architecture.html#d0e22523">Connectors</a></span></dt><dt><span class="section"><a href="architecture.html#d0e22571">Handlers</a></span></dt><dt><span class="section"><a href="architecture.html#what-is-a-context">Contexts</a></span></dt><dt><span class="section"><a href="architecture.html#d0e22684">Web Application</a></span></dt></dl></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="d0e22453"></a>View from 20,000 feet</h3></div></div></div><p>The Jetty <a class="link" href="http://download.eclipse.org/jetty/stable-9/apidocs/org/eclipse/jetty/server/Server.html" target="_top">Server</a> |
| is the plumbing between a collection of Connectors that accept HTTP |
| connections and a collection of Handlers that service requests from the |
| connections and produce responses, with threads from a thread pool doing |
| the work.</p><div class="mediaobject" align="center"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr><td align="center"><img src="images/jetty-high-level-architecture.png" align="middle" width="540"></td></tr></table></div><p>While the Jetty request/responses are derived from the Servlet API, |
| the full features of the Servlet API are only available if you configure |
| the appropriate handlers. For example, the session API on the request is |
| inactive unless the request has been passed to a Session Handler. The |
| concept of a servlet itself is implemented by a Servlet Handler. If |
| servlets are not required, there is very little overhead in the use of the |
| servlet request/response APIs. Thus you can build a Jetty server using |
| only connectors and handlers, without using servlets.</p><p>The job of configuring Jetty is building a network of connectors and |
| handlers and providing their individual configurations. As Jetty |
| components are simply Plain Old Java Objects (POJOs), you can accomplish |
| this assembly and configuration of components by a variety of |
| techniques:</p><p>deeper <a class="xref" href="">???</a></p><p>deepest <a class="link" href="">this is custom</a></p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>In code. See the examples in the Jetty 7 Latest Source |
| XRef.</p></li><li class="listitem"><p>Using Jetty XML–dependency injection style XML format.</p></li><li class="listitem"><p>With your dependency injection framework of choice: Spring or |
| XBean.</p></li><li class="listitem"><p>Using Jetty WebApp and Context Deployers.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="d0e22492"></a>Patterns</h3></div></div></div><p>The implementation of Jetty follows some fairly standard patterns. |
| Most abstract concepts such as Connector, Handler and Buffer are captured |
| by interfaces. Generic handling for those interfaces is then provided in |
| an Abstract implementation such as <code class="code">AbstractConnector</code>, |
| <code class="code">AbstractHandler</code> and <code class="code"> AbstractBuffer</code>.</p><div class="mediaobject" align="center"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr><td align="center"><img src="images/basic-architecture-patterns.png" align="middle" width="540"></td></tr></table></div><p>The JSR77 inspired life cycle of most Jetty components is |
| represented by the <code class="code">LifeCycle</code> interface and the |
| <code class="code">AbstractLifeCycle</code> implementation used as the base of many |
| Jetty components.</p><p>Jetty provides its own IO Buffering abstract over String, byte |
| arrays and NIO buffers. This allows for greater portability of Jetty as |
| well as hiding some of the complexity of the NIO layer and its advanced |
| features.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="d0e22523"></a>Connectors</h3></div></div></div><p>This diagram is a little out of date, as a Connection interface has |
| been extracted out of <code class="code"> HttpConnector</code> to allow support for the |
| AJP protocol.</p><p>The connectors represent the protocol handlers that accept |
| connections, parse requests and generate responses. The different types of |
| connectors available are based on the protocols, scheduling model, and IO |
| APIs used:</p><div class="mediaobject" align="center"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr><td align="center"><img src="images/basic-architecture-connectors.png" align="middle" width="540"></td></tr></table></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="code">SocketConnector</code> –for few busy connections or when |
| NIO is not available</p></li><li class="listitem"><p><code class="code">BlockingChannelConnector</code> –for few busy connections |
| when NIO is available</p></li><li class="listitem"><p><code class="code">SelectChannelConnector</code> –for many mostly idle |
| connections or asynchronous handling of Ajax requests</p></li><li class="listitem"><p><code class="code">SslSocketConnector</code> –SSL without NIO</p></li><li class="listitem"><p><code class="code">SslSelectChannelConnector</code> –SSL with non blocking |
| NIO support</p></li><li class="listitem"><p><code class="code">AJPConnector</code> –AJP protocol support for connections |
| from apache mod_jk or mod_proxy_ajp</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="d0e22571"></a>Handlers</h3></div></div></div><p>The Handler is the component that deals with received requests. The |
| core API of a handler is the handle method:</p><div class="mediaobject" align="center"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr><td align="center"><img src="images/basic-architecture-handlers.png" align="middle" width="540"></td></tr></table></div><div class="informalexample"><script type="syntaxhighlighter" class="brush: java;toolbar: false"> |
| <![CDATA[ |
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| public void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException |
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| |
| ]]> |
| </script></div><p>Parameters:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>target–The target of the request, either a URI or a name.</p></li><li class="listitem"><p>baseRequest–The original unwrapped request object.</p></li><li class="listitem"><p>request–The request either as the Request object or a wrapper of |
| that request. You can use the HttpConnection.getCurrentConnection() |
| method to access the Request object if required.</p></li><li class="listitem"><p>response–The response as the Response object or a wrapper of |
| that request. You can use the HttpConnection.getCurrentConnection() |
| method to access the Response object if required.</p></li></ul></div><p>An implementation of this method can handle the request, pass the |
| request onto another handler (or servlet) or it might modify and/or wrap |
| the request and then pass it on. This gives three styles of |
| Handler:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Coordinating Handlers–Handlers that route requests to other |
| handlers (HandlerCollection, ContextHandlerCollection)</p></li><li class="listitem"><p>Filtering Handlers–Handlers that augment a request and pass it |
| on to other handlers (HandlerWrapper, ContextHandler, |
| SessionHandler)</p></li><li class="listitem"><p>Generating Handlers–Handlers that produce content |
| (ResourceHandler and ServletHandler)</p></li></ul></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a name="d0e22613"></a>Nested Handlers and Handlers Called Sequentially</h4></div></div></div><p>You can combine handlers to handle different aspects of a request |
| by nesting them, calling them in sequence, or by combining the two |
| models.</p><div class="mediaobject" align="center"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr><td align="center"><img src="images/basic-architecture-nested-handlers.png" align="middle" width="540"></td></tr></table></div><p>Handlers called in sequence perform actions that do not depend on |
| the next invocation, nor on the handler order. They handle a request and |
| generate the response without interacting with other handlers. The main |
| class for this model is Handler Collection.</p><p>Nested handlers are called according to a before/invokeNext/after |
| pattern. The main class for nested handlers is Handler Wrapper. Nested |
| handlers are much more common than those called in sequence.</p><p>See also <a class="xref" href="jetty-handlers.html#writing-custom-handlers" title="Writing Custom Handlers">Writing Custom Handlers</a>.</p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a name="d0e22633"></a>Servlet Handler</h4></div></div></div><p>The ServletHandler is a Handler that generates content by passing |
| the request to any configured filters and then to a Servlet mapped by a |
| URI pattern.</p><div class="mediaobject" align="center"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr><td align="center"><img src="images/basic-architecture-servlet-handler.png" align="middle" width="540"></td></tr></table></div><p>A ServletHandler is normally deployed within the scope of a |
| servlet Context, which is a ContextHandler that provides convenience |
| methods for mapping URIs to servlets.</p><p>Filters and Servlets can also use a RequestDispatcher to reroute a |
| request to another context or another servlet in the current |
| context.</p></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="what-is-a-context"></a>Contexts</h3></div></div></div><p>Contexts are handlers that group other handlers below a particular |
| URI context path or a virtual host. Typcially a context can have :</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>A context path that defines which requests are handled by the |
| context (eg /myapp )</p></li><li class="listitem"><p>A resource base for static content (a docroot)</p></li><li class="listitem"><p>A class loader to obtain classes specific to the context |
| (typically docroot/WEB-INF/classes)</p></li><li class="listitem"><p>Virtual host names</p></li></ul></div><p>Contexts implementations include:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>ContextHandler</p></li><li class="listitem"><p>Servlet Context</p></li><li class="listitem"><p>Web Application Context</p></li></ul></div><p>A web application context combines handlers for security, session |
| and servlets in a single unit that you can configure with a |
| <code class="filename">web.xml</code> descriptor.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="d0e22684"></a>Web Application</h3></div></div></div><p>A WebApp Context is a derivation of the servlet Context that |
| supports the standardized layout of a web application and configuration of |
| session, security, listeners, filter, servlets, and JSP via a <code class="filename"> |
| web.xml</code> descriptor normally found in the |
| <code class="filename">WEB-INF</code> directory of a webapplication.</p><div class="mediaobject" align="center"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr><td align="center"><img src="images/basic-architecture-web-application.png" align="middle" width="540"></td></tr></table></div><p>Essentially the WebAppContext is a convenience class that assists |
| the construction and configuration of other handlers to achieve a standard |
| web application configuration. Configuration is actually done by pluggable |
| implementations of the Configuration class and the prime among these is |
| <code class="code">WebXmlConfiguration.</code></p></div></div></div><script type="text/javascript"> |
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