bes  Updated for version 3.19.1
BESInterface Class Referenceabstract

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

#include <BESInterface.h>

Inheritance diagram for BESInterface:
Inheritance graph

Public Member Functions

virtual void dump (ostream &strm) const
 dumps information about this object More...
 
virtual int execute_request (const string &from)
 The entry point for command execution; called by BESServerHandler::execute() More...
 
virtual int finish_with_error (int status)
 

Protected Member Functions

 BESInterface (ostream *strm)
 
virtual void build_data_request_plan ()=0
 
virtual void clean ()=0
 
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 ()=0
 
virtual void finish ()
 
virtual void log_status ()=0
 
virtual void transmit_data ()=0
 

Protected Attributes

BESDataHandlerInterfaced_dhi_ptr
 Allocated by the child class. More...
 
BESTransmitterd_transmitter
 The Transmitter to use for the result. More...
 

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 115 of file BESInterface.h.

Member Function Documentation

◆ dump()

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 termination callbacks.

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

Implements BESObj.

Reimplemented in BESXMLInterface.

Definition at line 501 of file BESInterface.cc.

◆ end_request()

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 465 of file BESInterface.cc.

◆ exception_manager()

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 488 of file BESInterface.cc.

◆ execute_request()

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

The entry point for command execution; called by BESServerHandler::execute()

Execute the request by:

  1. initializing BES
  2. build the request plan (i.e., filling in the BESDataHandlerInterface)
  3. execute the request plan using the BESDataHandlerInterface
  4. transmit the resulting response object
  5. log the status of the execution
  6. 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.

Parameters
fromA string that tells where this request came from. Literally, the IP and port number or the string 'standalone'. See void BESServerHandler::execute(Connection *c) or void StandAloneClient::executeCommand(const string & cmd, int repeat)
Returns
status of the execution of the request, 0 if okay, !0 otherwise
See also
initialize()
build_data_request_plan()
execute_data_request_plan()
finish()
finish_with_error()
transmit_data()
log_status()
end_request()
exception_manager()

Definition at line 285 of file BESInterface.cc.

Member Data Documentation

◆ d_dhi_ptr

BESDataHandlerInterface* BESInterface::d_dhi_ptr
protected

Allocated by the child class.

Definition at line 121 of file BESInterface.h.

◆ d_transmitter

BESTransmitter* BESInterface::d_transmitter
protected

The Transmitter to use for the result.

Definition at line 122 of file BESInterface.h.


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