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java.lang.Objectjavax.servlet.GenericServlet
javax.servlet.http.HttpServlet
org.mortbay.servlet.ConcatServlet
public class ConcatServlet
Concatenation Servlet This servlet may be used to concatenate multiple resources into a single response. It is intended to be used to load multiple javascript or css files, but may be used for any content of the same mime type that can be meaningfully concatenated.
The servlet uses RequestDispatcher.include(javax.servlet.ServletRequest, javax.servlet.ServletResponse)
to combine the requested content, so dynamically generated content
may be combined (Eg engine.js for DWR).
The servlet uses parameter names of the query string as resource names relative to the context root. So these script tags:
<script type="text/javascript" src="../js/behaviour.js"></script> <script type="text/javascript" src="../js/ajax.js&/chat/chat.js"></script> <script type="text/javascript" src="../chat/chat.js"></script>can be replaced with the single tag (with the ConcatServlet mapped to /concat):
<script type="text/javascript" src="../concat?/js/behaviour.js&/js/ajax.js&/chat/chat.js"></script>The
ServletContext.getMimeType(String)
method is used to determine the
mime type of each resource. If the types of all resources do not match, then a 415
UNSUPPORTED_MEDIA_TYPE error is returned.
If the init parameter "development" is set to "true" then the servlet will run in development mode and the content will be concatenated on every request. Otherwise the init time of the servlet is used as the lastModifiedTime of the combined content and If-Modified-Since requests are handled with 206 NOT Modified responses if appropriate. This means that when not in development mode, the servlet must be restarted before changed content will be served.
Constructor Summary | |
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ConcatServlet()
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Method Summary | |
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protected void |
doGet(HttpServletRequest req,
HttpServletResponse resp)
Called by the server (via the service method) to
allow a servlet to handle a GET request. |
protected long |
getLastModified(HttpServletRequest req)
Returns the time the HttpServletRequest
object was last modified,
in milliseconds since midnight January 1, 1970 GMT. |
void |
init()
A convenience method which can be overridden so that there's no need to call super.init(config) . |
Methods inherited from class javax.servlet.http.HttpServlet |
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doDelete, doHead, doOptions, doPost, doPut, doTrace, service, service |
Methods inherited from class javax.servlet.GenericServlet |
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destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public ConcatServlet()
Method Detail |
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public void init() throws ServletException
GenericServlet
super.init(config)
.
Instead of overriding GenericServlet.init(ServletConfig)
, simply override
this method and it will be called by
GenericServlet.init(ServletConfig config)
.
The ServletConfig
object can still be retrieved via GenericServlet.getServletConfig()
.
init
in class GenericServlet
ServletException
- if an exception occurs that
interrupts the servlet's
normal operationprotected long getLastModified(HttpServletRequest req)
HttpServlet
HttpServletRequest
object was last modified,
in milliseconds since midnight January 1, 1970 GMT.
If the time is unknown, this method returns a negative
number (the default).
Servlets that support HTTP GET requests and can quickly determine their last modification time should override this method. This makes browser and proxy caches work more effectively, reducing the load on server and network resources.
getLastModified
in class HttpServlet
req
- the HttpServletRequest
object that is sent to the servlet
long
integer specifying
the time the HttpServletRequest
object was last modified, in milliseconds
since midnight, January 1, 1970 GMT, or
-1 if the time is not knownprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, java.io.IOException
HttpServlet
service
method) to
allow a servlet to handle a GET request.
Overriding this method to support a GET request also automatically supports an HTTP HEAD request. A HEAD request is a GET request that returns no body in the response, only the request header fields.
When overriding this method, read the request data,
write the response headers, get the response's writer or
output stream object, and finally, write the response data.
It's best to include content type and encoding. When using
a PrintWriter
object to return the response,
set the content type before accessing the
PrintWriter
object.
The servlet container must write the headers before committing the response, because in HTTP the headers must be sent before the response body.
Where possible, set the Content-Length header (with the
ServletResponse.setContentLength(int)
method),
to allow the servlet container to use a persistent connection
to return its response to the client, improving performance.
The content length is automatically set if the entire response fits
inside the response buffer.
When using HTTP 1.1 chunked encoding (which means that the response has a Transfer-Encoding header), do not set the Content-Length header.
The GET method should be safe, that is, without any side effects for which users are held responsible. For example, most form queries have no side effects. If a client request is intended to change stored data, the request should use some other HTTP method.
The GET method should also be idempotent, meaning that it can be safely repeated. Sometimes making a method safe also makes it idempotent. For example, repeating queries is both safe and idempotent, but buying a product online or modifying data is neither safe nor idempotent.
If the request is incorrectly formatted, doGet
returns an HTTP "Bad Request" message.
doGet
in class HttpServlet
req
- an HttpServletRequest
object that
contains the request the client has made
of the servletresp
- an HttpServletResponse
object that
contains the response the servlet sends
to the client
ServletException
- if the request for the GET
could not be handled
java.io.IOException
- if an input or output error is
detected when the servlet handles
the GET requestServletResponse.setContentType(java.lang.String)
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