This server was written with two things in mind:
- Compliance with the specifications, and
- Efficiency: High speed & Low memory usage
Every design decision in this project considered these two points.
Below are listed the notable features and
minor restrictions of this server.
Notable Features
There are a number of features that serparate this server from the pack.
These include:
- Conditionally HTTP/1.1 compilant.
- Servlet 2.2 compilant (minus some minor things specified in
restrictions).
- Persistent connections.
- Understands the "Chunked" transfer-coding.
- Basic and Digest authentication.
- Multiline headers.
- Support for nonstandard HTTP methods.
- URL rewriting for sessions.
- Quoted cookie values.
- Authenticated servlets do not require any change to the code other
than changing the superclass from
HttpServlet to
com.qindesign.servlet.AuthenticatedHttpServlet .
- Remote server shutdown.
- Optional servlet reloading for firmware 1.1 and above.
- Pays attention to
UnavailableException s.
- Template processing.
- The author's goal is compilance with the specifications.
Restrictions
This server was designed explicitly for the TINI, a very powerful,
yet small, embedded device. Hence, there are a few minor restrictions
that must be considered and accounted for in your designs.
Servlet 2.2 Restrictions
- Response buffer size of 0. This means that simply retrieving an
output stream or writer will commit the response.
- The response is not "closed" after
HttpServletResponse.sendError ,
HttpServletResponse.sendRedirect ,
RequestDispatcher.forward , or when the amount of
content specified in the "Content-Length" header has been written to
the response.
Except for the case of exceeding the specified content length,
there are no checks performed that catch a servlet writing out
content after these events.
- No JSP.
- Currently only one
ServletContext for all requested paths.
- Must add cookies and sessions before the response is committed.
- Does not pay attention to the time indicated by
UnavailableException .
A "Retry-After" header is sent when servicing, but the container
does not wait to recreate the servlet for another request during
initialization.
- The
javax.servlet.context.tempdir context attribute is
not set if a valid directory is not specified in the servlet.tempdir
configuration property.
- Any class a servlet uses is a candidate for dynamic classloading,
however, only the servlet class is checked for freshness. In other
words, classes are only reloaded when the servlet class changes.
- When servlet reloading is enabled, servlet authors should take care to
stop all threads and clean up any resources in the
destroy
method. The reason is that TINIClassLoader.unloadClasses
is used when a servlet is reloaded, and this forces all the class
memory to be cleared, potentially causing other objects to point to
invalid references.
- When servlet reloading is not enabled, the
destroy
method is called on a servlet immediately after a permanent
UnavailableException is detected. This means that the
servlet author should take care to properly synchronize and manage any
resources used during the service method.
- There is a similar note for when the server is shut down. When
servlet reloading is not enabled, the
destroy method is
called immediately, and any threads running in the service
method are not given a chance to complete. In other words, the
server defined time limit is zero.
HTTP/1.1 Restrictions
- The "Expect" header is not fully supported: Only a (case-insensitive)
value of "100-continue" is recognized, and if this is encountered,
a 100 (Continue) status is sent right away.
- Persistent connections are not used with the "chunked" transfer
encoding.
Misc. Notes
- If a different crystal is used to drive the TINI, then the server time
will not always be correct. This is because the timekeeping mechanism
relies on
TINIOS.uptimeMillis() and not
System.currentTimeMillis() . The second method uses the
real-time clock and will be correct always, but it is also much
slower.
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