The Jetty Server 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 the work being done by threads taken from a thread pool.
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While the jetty request/responses are derived from the Servlet API, the full features of the servlet API are only available if the appropriate handlers are configured. 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.
The job of configuring jetty is the job of 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:
deeper ???
deepest this is custom
In code. See the examples in the Jetty 7 Latest Source XRef.
With Jetty XML - dependency injection style XML format.
With your dependency injection framework of choice: Spring or XBean.
Using Jetty WebApp and Context Deployers.
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 AbstractConnector, AbstractHandler and AbstractBuffer.
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The JSR77 inspired life cycle of most jetty components is represented by LifeCycle interface and the AbstractLifeCycle implementation used as the base of many Jetty components.
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.
This diagram is a little out of date, as a Connection interface has been extracted out of HttpConnector to allow support for the AJP protocol.
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:
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SocketConnector - for few busy connections or when NIO is not available
BlockingChannelConnector - for few busy connections when NIO is available
SelectChannelConnector - for many mostly idle connections or asynchronous handling of Ajax requests
SslSocketConnector - SSL without NIO
SslSelectChannelConnector - SSL with non blocking NIO support
AJPConnector AJP protocol support for connections from apache mod_jk or mod_proxy_ajp
The Handler is the component that deals with received requests. The core API of a handler is the handle method:
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public void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
Parameters:
target–The target of the request, either a URI or a name.
baseRequest–The original unwrapped request object.
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.
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.
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:
Coordinating Handlers - Handlers that route requests to other handlers (eg HandlerCollection,
ContextHandlerCollection)
<listitem> Filtering Handlers - Handlers that augment a request and pass it on to other handlers (eg.
HandlerWrapper, ContextHandler, SessionHandler)
<listitem> Generating Handlers - Handlers that produce content (eg ResourceHandler and ServletHandler)
You can combine handlers to handle different aspects of a request by nesting them, calling them in
sequence, or by combining the two models. 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. 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. See also ???.
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. 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. Filters and Servlets can also use a RequestDispatcher to reroute a request to another context or
another servlet in the current context.
Contexts are handlers that group other handlers below a particular URI context path or a virtual
host. Typcially a context can have : A context path that defines which requests are handled by the context (eg /myapp ) A resource base for static content (a docroot) A class loader to obtain classes specific to the context (typically
docroot/WEB-INF/classes) Virtual host names Contexts implementations include: ContextHandler Servlet Context Web Application Context A web application context combines handlers for security, session and servlets in a single unit
that can be configured with a web.xml descriptor.
A Web App 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 web.xml
descriptor normally found in the WEB-INF directory of a webapplication. 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 WebXmlConfiguration.