OPeNDAP Hyrax Back End Server (BES)  Updated for version 3.8.3
BESInterface Class Referenceabstract

Entry point into BES, building responses to given requests. More...

#include <BESInterface.h>

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Public Member Functions

virtual void dump (ostream &strm) const
 dumps information about this object More...
 
virtual int execute_request (const string &from)
 Executes the given request to generate a specified response object. More...
 
virtual int finish_with_error (int status)
 

Static Public Member Functions

static void add_end_callback (p_bes_end end)
 
static void add_init_callback (p_bes_init init)
 

Protected Member Functions

 BESInterface (ostream *strm)
 
virtual void build_data_request_plan ()=0
 Build the data request plan. More...
 
virtual void clean ()
 Clean up after the request. More...
 
virtual void end_request ()
 End the BES request. More...
 
virtual int exception_manager (BESError &e)
 Manage any exceptions thrown during the whole process. More...
 
virtual void execute_data_request_plan ()
 Execute the data request plan. More...
 
virtual int finish (int status)
 
virtual void initialize ()
 Initialize the BES object. More...
 
virtual void invoke_aggregation ()
 Aggregate the resulting response object. More...
 
virtual void log_status ()
 Log the status of the request. More...
 
virtual void report_request ()
 Report the request and status of the request to BESReporterList::TheList() More...
 
virtual void transmit_data ()
 Transmit the resulting response object. More...
 
virtual void validate_data_request ()
 Validate the incoming request information. More...
 
virtual ~BESInterface ()
 

Protected Attributes

BESDataHandlerInterface_dhi
 
BESTransmitter_transmitter
 

Detailed Description

Entry point into BES, building responses to given requests.

BESInterface is an abstract class providing the entry point into the retrieval of information using the BES framework. There are eight steps to retrieving a response to a given request:

  1. initialize the BES environment
  2. validate the incoming information to make sure that all information is available to perform the query
  3. build the request plan to retrieve the information. A response can be generated for multiple files using multiple server types (cedar, cdf, netcdf, etc...)
  4. execute the request plan and build the response object
  5. transmit the response object
  6. log the status of the request
  7. send out report information that can be reported on by any number of reporters registered with the system.
  8. end the request

The way in which the response is generated is as follows. A BESResponseHandler is found that knows how to build the requested response object. The built-in response handlers are for the response objects das, dds, ddx, data, help, version. These response handlers are added to a response handler list during initialization. Additional response handlers can be added to this list. For example, in Cedar, response handlers are registered to build flat, tab, info, and stream responses.

To build the response objects a user can make many requests. For example, a das object can be built using as many different files as is requested, say for file1,file2,file3,file4. And each of these files could be of a different data type. For example, file1 and file3 could be cedar files, file2 could be cdf file and file4 could be a netcdf file.

The structure that holds all of the requested information is the BESDataHandlerInterface. It holds on to a list of containers, each of which has the data type (cedar, cdf, nph, etc...) and the file to be read. The BESDataHandlerInterface is built in the build request method.

The response handlers know how to build the specified response object, such as DAS, DDS, help, status, version, etc...

For each container in the BESDataHandlerInterface find the request handler (BESRequestHandler) for the containers data type. Each request handler registers functions that know how to fill in a certain type of response (DAS, DDS, etc...). Find that function and invoke it. So, for example, there is a CedarRequestHandler class that registers functions that knows how to fill in the different response objects from cedar files.

Once the response object is filled it is transmitted using a specified BESTransmitter.

The status is then logged (default is to not log any status. It is up to derived classes of BESInterface to implement the log_status method.)

The request and status are then reported. The default action is to pass off the reporting to BESReporterList::TheList(), which has a list of registered reporters and passes off the information to each of those reporters. For example, if the Cedar project wants to report on any cedar access then it can register a reporter with BESReporterList::TheList().

See also
BESGlobalInit
BESKeys
BESResponseHandler
BESRequestHandler
BESTransmitter
BESLog
BESReporter

Definition at line 123 of file BESInterface.h.

Constructor & Destructor Documentation

BESInterface::BESInterface ( ostream *  strm)
protected

Definition at line 69 of file BESInterface.cc.

BESInterface::~BESInterface ( )
protectedvirtual

Definition at line 80 of file BESInterface.cc.

Member Function Documentation

void BESInterface::add_end_callback ( p_bes_end  end)
static

Definition at line 467 of file BESInterface.cc.

void BESInterface::add_init_callback ( p_bes_init  init)
static

Definition at line 281 of file BESInterface.cc.

virtual void BESInterface::build_data_request_plan ( )
protectedpure virtual

Build the data request plan.

It is the responsibility of the derived class to build the request plan. In other words, the container list must be filled in and the action set in the BESDataHandlerInterface structure.

See also
BESDataHandlerInterface

Implemented in BESBasicInterface, and BESXMLInterface.

Referenced by execute_request().

void BESInterface::clean ( )
protectedvirtual

Clean up after the request.

Reimplemented in BESBasicInterface, and BESXMLInterface.

Definition at line 503 of file BESInterface.cc.

References _dhi, and BESDataHandlerInterface::clean().

Referenced by BESBasicInterface::clean().

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void BESInterface::dump ( ostream &  strm) const
virtual

dumps information about this object

Displays the pointer value of this instance along with information about BESDataHandlerInterface, the BESTransmitter being used, and the number of initialization and termimation callbacks.

Parameters
strmC++ i/o stream to dump the information to

Implements BESObj.

Reimplemented in BESBasicInterface, and BESXMLInterface.

Definition at line 536 of file BESInterface.cc.

References _dhi, _transmitter, BESTransmitter::dump(), BESDataHandlerInterface::dump(), BESIndent::Indent(), BESIndent::LMarg(), and BESIndent::UnIndent().

Referenced by BESBasicInterface::dump().

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void BESInterface::end_request ( )
protectedvirtual

End the BES request.

This method allows developers to add callbacks at the end of a request, to do any cleanup or do any extra work at the end of a request

Definition at line 478 of file BESInterface.cc.

References _dhi, BESDEBUG, BESDataHandlerInterface::container, BESDataHandlerInterface::data, DATA_REQUEST, BESDataHandlerInterface::first_container(), BESDataHandlerInterface::next_container(), and BESContainer::release().

Referenced by finish().

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int BESInterface::exception_manager ( BESError e)
protectedvirtual

Manage any exceptions thrown during the whole process.

Specific responses are generated given a specific Exception caught. If additional exceptions are thrown within derived systems then implement those in the derived exception_manager methods. This is a catch-all manager and should be called once derived methods have caught their exceptions.

Parameters
eBESError to be managed
Returns
status after exception is handled
See also
BESError

Definition at line 522 of file BESInterface.cc.

References _dhi, BESExceptionManager::handle_exception(), and BESExceptionManager::TheEHM().

Referenced by execute_request(), finish(), and finish_with_error().

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void BESInterface::execute_data_request_plan ( )
protectedvirtual

Execute the data request plan.

Given the information in the BESDataHandlerInterface, execute the request. To do this we simply find the response handler given the action in the BESDataHandlerInterface and tell it to execute.

If no BESResponseHandler can be found given the action then an exception is thrown.

See also
BESDataHandlerInterface
BESResponseHandler
BESResponseObject

Reimplemented in BESBasicInterface, and BESXMLInterface.

Definition at line 337 of file BESInterface.cc.

References _dhi, BESDataHandlerInterface::action, BESDEBUG, BESDataHandlerInterface::data, DATA_REQUEST, BESResponseHandler::execute(), invoke_aggregation(), BESDataHandlerInterface::response_handler, and transmit_data().

Referenced by BESBasicInterface::execute_data_request_plan(), and execute_request().

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int BESInterface::execute_request ( const string &  from)
virtual

Executes the given request to generate a specified response object.

Execute the request by:

  1. initializing BES
  2. validating the request, make sure all elements are present
  3. build the request plan (ie filling in the BESDataHandlerInterface)
  4. execute the request plan using the BESDataHandlerInterface
  5. transmit the resulting response object
  6. log the status of the execution
  7. notify the reporters of the request
  8. end the request, which allows developers to add callbacks to notify them of the end of the request

If an exception is thrown in any of these steps the exception is handed over to the exception manager in order to generate the proper response. Control is returned back to the calling method if an exception is thrown and it is the responsibility of the calling method to call finish_with_error in order to transmit the error message back to the client.

Returns
status of the execution of the request, 0 if okay, !0 otherwise
See also
initialize()
validate_data_request()
build_data_request_plan()
execute_data_request_plan()
finish_no_error()
finish_with_error()
transmit_data()
log_status()
report_request()
end_request()
exception_manager()

Reimplemented in BESBasicInterface, and BESXMLInterface.

Definition at line 117 of file BESInterface.cc.

References _dhi, build_data_request_plan(), BESDataHandlerInterface::data, exception_manager(), execute_data_request_plan(), BESDataHandlerInterface::executed, finish(), initialize(), REQUEST_FROM, SERVER_PID, BESDataHandlerInterface::set_output_stream(), BESLog::TheLog(), and validate_data_request().

Referenced by BESBasicInterface::execute_request().

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int BESInterface::finish ( int  status)
protectedvirtual
int BESInterface::finish_with_error ( int  status)
virtual

Definition at line 267 of file BESInterface.cc.

References _dhi, BESDataHandlerInterface::error_info, exception_manager(), and finish().

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void BESInterface::initialize ( )
protectedvirtual

Initialize the BES object.

This method must be called by all derived classes as it will initialize the environment

Reimplemented in BESBasicInterface, and BESXMLInterface.

Definition at line 292 of file BESInterface.cc.

References _dhi, BESDEBUG, BESDataHandlerInterface::data, and DATA_REQUEST.

Referenced by execute_request(), and BESBasicInterface::initialize().

void BESInterface::invoke_aggregation ( )
protectedvirtual

Aggregate the resulting response object.

Reimplemented in BESBasicInterface, and BESXMLInterface.

Definition at line 364 of file BESInterface.cc.

References _dhi, AGG_CMD, AGG_HANDLER, BESAggregationServer::aggregate(), BESDEBUG, BESDataHandlerInterface::data, BESAggFactory::find_handler(), and BESAggFactory::TheFactory().

Referenced by execute_data_request_plan(), and BESBasicInterface::invoke_aggregation().

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void BESInterface::log_status ( )
protectedvirtual

Log the status of the request.

Reimplemented in BESBasicInterface, and BESXMLInterface.

Definition at line 440 of file BESInterface.cc.

Referenced by finish().

void BESInterface::report_request ( )
protectedvirtual

Report the request and status of the request to BESReporterList::TheList()

If interested in reporting the request and status of the request then one must register a BESReporter with BESReporterList::TheList().

If no BESReporter objects are registered then nothing happens.

See also
BESReporterList
BESReporter

Reimplemented in BESXMLInterface.

Definition at line 456 of file BESInterface.cc.

References _dhi, BESDEBUG, BESDataHandlerInterface::data, DATA_REQUEST, BESReporterList::report(), and BESReporterList::TheList().

Referenced by finish(), and BESXMLInterface::report_request().

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void BESInterface::transmit_data ( )
protectedvirtual

Transmit the resulting response object.

The derived classes are responsible for specifying a transmitter object for use in transmitting the response object. Again, the BESResponseHandler knows how to transmit itself.

If no response handler or no response object or no transmitter is specified then do nothing here.

See also
BESResponseHandler
BESResponseObject
BESTransmitter

Reimplemented in BESBasicInterface, and BESXMLInterface.

Definition at line 400 of file BESInterface.cc.

References _dhi, _transmitter, BESDEBUG, BESDataHandlerInterface::data, DATA_REQUEST, BESDataHandlerInterface::error_info, BESInfo::print(), BESDataHandlerInterface::response_handler, BESLog::TheLog(), BESInfo::transmit(), and BESResponseHandler::transmit().

Referenced by execute_data_request_plan(), finish(), and BESBasicInterface::transmit_data().

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void BESInterface::validate_data_request ( )
protectedvirtual

Validate the incoming request information.

Reimplemented in BESBasicInterface, and BESXMLInterface.

Definition at line 319 of file BESInterface.cc.

Referenced by execute_request(), and BESBasicInterface::validate_data_request().

Member Data Documentation


The documentation for this class was generated from the following files: