| org.vfny.geoserver.Response
All known Subclasses: org.vfny.geoserver.wms.responses.GetLegendGraphicResponse, org.vfny.geoserver.wms.responses.featureInfo.GetFeatureInfoDelegate, org.vfny.geoserver.wms.responses.GetMapResponse, org.vfny.geoserver.wcs.responses.WCSCapabilitiesResponse, org.vfny.geoserver.sld.responses.PutStylesResponse, org.vfny.geoserver.wms.responses.DescribeLayerResponse, org.vfny.geoserver.wms.responses.WMSCapabilitiesResponse, org.vfny.geoserver.wcs.responses.CoverageResponse, org.vfny.geoserver.wms.responses.GetFeatureInfoResponse, org.vfny.geoserver.wcs.responses.DescribeResponse,
| Response | | public interface Response (Code) | | The Response interface serves as a common denominator for all service
operations that generates content.
The work flow for this kind of objects is divided in two parts: the first is
executing a request and the second writing the result to an OuputStream.
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Execute: execute(Request)
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Executing the request means taking a Request object and, based on it's set
of request parameters, do any heavy processing necessary to produce the
response.
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Once the execution has been made, the Response object should be ready to
send the response content to an output stream with minimal risk of
generating an exception.
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Anyway, it is not required, even recomended, that the execution process
generates the response content itself; just that it performs any query or
processing that should generate a trapable error.
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Execute may throw a ServiceException if they wish to supply a specific
response in error. As an example the WFSTransaction process has a defined
Transaction Document with provisions for reporting error information.
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ContentType: getContentType()
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Called to set the response type. Depending on the stratagy used by
AbstractService the framework may be commited to returning this type.
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Writing: writeTo(OutputStream)
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Write the response to the provided output stream.
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Any exceptions thrown by this writeTo method may never reach the end user in
useable form. You should assume you are writing directly to the client.
Note: abort() will be called as part of error handling giving your
response subclass a chance to clean up any temporary resources it may have
required in execute() for use in writeTo().
This is specially usefull for streamed responses such as wfs GetFeature or
WMS GetMap, where the execution process can be used to parse parameters,
execute queries upon the corresponding data sources and leave things ready
to generate a streamed response when the consumer calls writeTo.
author:
Gabriel Rold?n
version:
$Id: Response.java 6326 2007-03-15 18:36:40Z jdeolive $ |
| Method Summary | |
| public void | abort(Service gs)
Called when things go horriably wrong.
Used try and restore application state when things go wrong. | | public void | execute(Request request)
Excecutes a request. | | public String | getContentDisposition()
| | public String | getContentEncoding()
| | public String | getContentType(GeoServer gs)
MIME type of this Response - example "text/xml".
thinked to be called after excecute(), this method must return the MIME
type of the response content that will be writen when writeTo were
called
an implementation of this interface is required to throw an
IllegalStateException if execute has not been called yet, to indicate
that an inconsistence in the work flow that may result in an
inconsistence between the response content and the content type
declared for it, if such an implementation can return different
contents based on the request that has originated it. | | public HashMap | getResponseHeaders()
Returns any extra headers that this Response might wish to have set in the
HTTP response object. | | public void | writeTo(OutputStream out)
Writes this respone to the provided output stream.
To implememt streaming, execution is sometimes delayed until the write
opperation (for example of this see FeatureResponse). |
| abort | | public void abort(Service gs)(Code) | | Called when things go horriably wrong.
Used try and restore application state when things go wrong. This is
called by AbstractAction to try and recover when sending out a
ServiceException.
Allows a Response a chance to clean up after its self when
AbstractionAction is error handling.
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| execute | | public void execute(Request request) throws ServiceException(Code) | | Excecutes a request. If this method finalizes without throwing an
Exception, the Response instance should be ready to write the response
content through the writeTo method with the minimal posible risk of
failure other than not beeing able to write to the output stream due to
external reassons
We should clarify when a ServiceException is thrown? I would assume that
a "failed" request should still result in a Response that we could
write out.
Parameters:
request - a Request object that implementations should cast to it'sRequest specialization, wich must contain the parsed and readyto use parameters sent by the calling client. In general, such aRequest will be created by either a KVP or XML request reader;resulting in a Request object more usefull than a set of rawparameters, as can be the list of feature types requested as aset of FeatureTypeInfo objects rather than just a list of Stringtype names
throws:
ServiceException - |
| getContentDisposition | | public String getContentDisposition()(Code) | | Returns any special content disposition this response will encode its
contents to, such as "filename" and "attachement"
the content disposition writeTo will encode with, or null if none |
| getContentEncoding | | public String getContentEncoding()(Code) | | Returns any special content encoding this response will encode its
contents to, such as "gzip" or "deflate"
the content encoding writeTo will encode with, or null if none |
| getContentType | | public String getContentType(GeoServer gs) throws IllegalStateException(Code) | | MIME type of this Response - example "text/xml".
thinked to be called after excecute(), this method must return the MIME
type of the response content that will be writen when writeTo were
called
an implementation of this interface is required to throw an
IllegalStateException if execute has not been called yet, to indicate
that an inconsistence in the work flow that may result in an
inconsistence between the response content and the content type
declared for it, if such an implementation can return different
contents based on the request that has originated it. i.e. a WMS GetMap
response will return different content encodings based on the FORMAT
requested, so it would be impossible to it knowing the exact MIME
response type if it has not processed the request yet.
There is some MIME stuff in JDK for reference:
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java.awt.datatransfer package
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javax.mail.internet
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and a few other places as well.
the MIME type of the generated or ready to generate responsecontent
throws:
IllegalStateException - if this method is called and execute hasnot been called yet |
| getResponseHeaders | | public HashMap getResponseHeaders()(Code) | | Returns any extra headers that this Response might wish to have set in the
HTTP response object.
In particular, a WMS might wish to have some external caching information added
to the HTTP response, so that caches can hang onto this map for a while and ligten
the load on geoserver.
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| writeTo | | public void writeTo(OutputStream out) throws ServiceException, IOException(Code) | | Writes this respone to the provided output stream.
To implememt streaming, execution is sometimes delayed until the write
opperation (for example of this see FeatureResponse). Hopefully this is
okay? GR:the idea for minimize risk error at writing time, is that
execute performs any needed query/processing, leaving to this method
just the risk of encountering an uncaught or IO exception. i.e.
FeatureResponse should execute the queries inside the execute method,
and have a set of FeatureReader's (or results) ready to be streamed
here. This approach fits well with the Chirs' idea of configuring
geoserver for speed or full conformance, wich ends in just writing
directly to the http response output stream or to a
ByteArrayOutputStream
JG: Consider using a Writer here? GR: I don't think so, because not all
responses will be char sequences, such as an image in a WMS GetImage
response.
Parameters:
out -
throws:
ServiceException - wrapping of any unchecked exception or otherpredictable exception except an IO error while writing toout
throws:
IOException - ONLY if an error occurs trying to write content tothe passed OutputStream. By this way, we'll can control thevery common situation of a java.net.SocketException product ofthe client closing the connection (like a user pressing it'srefresh browser button many times) |
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