Request-Level Interceptor API

Each of these interfaces is a locality-constrained object. Any attempt to pass a reference outside its locality (that is, its process), or any attempt to externalize an object supporting this interface using the CORBA ORB object_to_string operation, results in the CORBA MARSHAL system exception (CORBA::MARSHAL) being raised.

The method signatures for operations on classes derived from the RequestLevelInterceptor interface include parameters for the following interfaces:

The Interceptors::Interceptor interface is defined as the base interface of all types of interceptors, including request-level interceptors. This interface contains the set of operations and attributes that are supported by all types of interceptors. The Interceptors::Interceptor interface is defined as an abstract interface; thus an instance of the interface cannot be instantiated.

The implementation of the operations _duplicate, _narrow, and _nil are inherited from the implementation of the CORBA::LocalBase interface provided by the CORBA ORB in the Oracle Tuxedo product.

#ifndef _INTERCEPTORS_H
#define _INTERCEPTORS_H

#include <string.h>
#include <CORBA.h>

class OBBEXPDLL Interceptors
  {
  public:
  class Interceptor;
  typedef Interceptor * Interceptor_ptr;

  enum InvokeReturnStatus
    {
    INVOKE_NO_EXCEPTION,// proceed normally
    REPLY_NO_EXCEPTION, // stop proceeding; start reply processing
    REPLY_EXCEPTION // stop proceeding; reply with exception
    };

  enum ResponseReturnStatus
    {
        RESPONSE_NO_EXCEPTION, // proceed normally
        RESPONSE_EXCEPTION
    };

  enum ShutdownReturnStatus
    {
    SHUTDOWN_NO_EXCEPTION,
    SHUTDOWN_EXCEPTION
    };

  enum ShutdownReason
    {
    ORB_SHUTDOWN,
    CONNECTION_ABORTED,
    RESOURCES_EXCEEDED
    };

  struct Version
    {
    CORBA::Octet major_version;
    CORBA::Octet minor_version;
    };
  typedef Version * Version_ptr;

  //+
  // Abstract base interface for all Interceptors
  //-
  class OBBEXPDLL Interceptor : public virtual CORBA::LocalBase
    {
    public:
      static Interceptor_ptr _duplicate(Interceptor_ptr obj);
      static Interceptor_ptr _narrow(Interceptor_ptr obj);
      static Interceptor_ptr _nil();
      virtual ShutdownReturnStatus
        shutdown( ShutdownReason reason,
                  CORBA::Exception_ptr & excep_val) = 0;
      virtual CORBA::String id() = 0;

    protected:
      Interceptor();
      virtual ~Interceptor();
    };
  };#endif /* _INTERCEPTORS_H */

The id accessor operation is used by the ORB to obtain the vendor assigned identity of the interceptor as a string value. This attribute is used primarily for debugging and tracing of operations on the interceptors called by the ORB.

A ShutdownReason value that indicates the reason why the interceptor is being shut down. The following ShutdownReason values can be passed to the operation:

A reference to an ExceptionValue in which the operation is to store any exception raised. This parameter is valid only if a value of SHUTDOWN_EXCEPTION is returned from the operation.

The shutdown operation is used by the ORB to notify an implementation of an interceptor that the interceptor is being shut down. The ORB destroys the instance of the interceptor once control is returned from the operation back to the ORB.

The RequestLevelInterceptor::RequestInterceptor interface is the base interface of all request-level interceptors. It inherits directly from the Interceptors::Interceptor interface. The RequestLevelInterceptor::RequestInterceptor interface:

The local keyword in OMG IDL indicates that the RequestInterceptor interface is not a normal CORBA object, so it cannot be used as such.

The implementation of the RequestInterceptor interface inherits from CORBA::LocalBase rather than from CORBA::Object. CORBA::LocalBase provides an implementation of the operations _duplicate, _narrow, and _nil, similar to those of CORBA::Object.

#ifndef _RequestLevelInterceptor_h
#define _RequestLevelInterceptor_h

#include <CORBA.h>
#include <IOP.h>
#include <GIOP.h>
#include <Interceptors.h>

class OBBEXPDLL RequestLevelInterceptor
  {
  public:
    class RequestInterceptor;
    typedef RequestInterceptor * RequestInterceptor_ptr;

    struct RequestContext
      {
      Interceptors::Version struct_version;
      CORBA::ULong request_id;
      CORBA::Octet response_flags;
      GIOP::TargetAddress target;
      CORBA::String_var interface_id;
      CORBA::String_var operation;
      RequestContext &operator=(const RequestContext &_obj);
      };

    typedef RequestContext * RequestContext_ptr;
    typedef GIOP::ReplyStatusType_1_2 ReplyStatus;

    struct ReplyContext
     {
      Interceptors::Version struct_version;
      CORBA::ULong request_id;
      ReplyStatus reply_status;
      };

    typedef ReplyContext * ReplyContext_ptr;

    class OBBEXPDLL RequestInterceptor :
            public virtual Interceptors::Interceptor
      {
      public:
        static RequestInterceptor_ptr
                 _duplicate(RequestInterceptor_ptr obj);
        static RequestInterceptor_ptr
                 _narrow(RequestInterceptor_ptr obj);
        inline static RequestInterceptor_ptr _nil() { return 0; }

        virtual void
          exception_occurred( const ReplyContext & reply_context,
                              CORBA::Exception_ptr excep_val) = 0;

      protected:
        RequestInterceptor(CORBA::LocalBase_ptr obj = 0) { }
        virtual ~RequestInterceptor(){ }

      private:
        RequestInterceptor( const RequestInterceptor&) { }
        void operator=(const RequestInterceptor&) { }
      }; // class RequestInterceptor
#endif /* _RequestLevelInterceptor_h */

struct RequestContext
{
Interceptors::Version struct_version;
CORBA::ULong request_id;
CORBA::Octet response_flags;
GIOP::TargetAddress target;
CORBA::String_var interface_id;
CORBA::String_var operation;
RequestContext &operator=(const RequestContext &_obj);
};

The lowest order bit of response_flags is set to 1 if a reply message is expected for this request. If the operation is not defined as oneway, and the request is not invoked via the DII with the INV_NO_RESPONSE flag set, response_flags will be set to \x03.

When this flag is set to \x01 for a oneway operation, receipt of a reply does not imply that the operation has necessarily completed.

The RequestContext data object contains the information that represents the context in which a request is to be processed. The context information contained in the RequestContext provides information necessary to coordinate between the processing of a given request and its corresponding reply.

The context information in the RequestContext structure cannot be modified by the interceptor implementation. The ORB maintains ownership of the RequestContext and is responsible for freeing any resources associated with the RequestContext when it has completed using it.

An indication of the version of the ReplyContext that provides an indication of the format and members. The version information is separated into the following two pieces:

The ReplyContext data object contains the information that represents the context in which a reply is to be processed. The context information contained in ReplyContext provides information necessary to coordinate between the processing of a given request and its corresponding reply.

The context information in ReplyContext cannot be modified by the interceptor implementation. The ORB maintains ownership of ReplyContext and is responsible for freeing any resources associated with ReplyContext when it has completed using it.

A reference to a ReplyContext that contains information about the context in which the reply is being performed.

The exception_occurred operation is called on a request-level interceptor implementation in one of three cases:

A client deletes a Request object that was used to initiate a deferred synchronous DII. The exception_occurred method is called instead of the client_response or target_response method of that interceptor. The ORB calls the exception_occurred method to allow the interceptor implementation to clean up any state that it might have been managing that is specific to a request.

This is the base interface of all request-level interceptors. It inherits directly from the RequestLevelInterceptor::RequestInterceptor interface. The interface contains the set of operations and attributes that are supported by all client-side request-level interceptors.

//File: RequestLevelInterceptor.idl

#ifndef _REQUEST_LEVEL_INTERCEPTOR_IDL
#define _REQUEST_LEVEL_INTERCEPTOR_IDL

#include <orb.idl>
#include <Giop.idl>
#include <Interceptors.idl>

#pragma prefix “beasys.com”

module RequestLevelInterceptor
  {
  local ClientRequestInterceptor : RequestInterceptor
    {
    InvokeReturnStatus
      client_invoke(
             in    RequestContext           request_context,
             in    ServiceContextList       service_context,
             in    CORBA::DataInputStream   request_arg_stream,
             in    CORBA::DataOutputStream  reply_arg_stream,
             out   ExceptionValue           excep_val
                   );

    ResponseReturnStatus
      client_response(
                    in    ReplyContext           reply_context,
                    in    ServiceContextList     service_context,
                    in    CORBA::DataInputStream arg_stream,
                    out   ExceptionValue         excep_val
                     );
    };
  };
#endif /* _REQUEST_LEVEL_INTERCEPTOR_IDL */

The implementation of the operations _duplicate, _narrow, and _nil are inherited indirectly from the implementation of the CORBA::LocalBase interface provided by the CORBA ORB in the Oracle Tuxedo product.

A pointer to a ServiceContextList containing service context information to be sent as part of the request to the target object.

A pointer to a DataInputStream that can be used by the interceptor implementation to retrieve the value of the parameter of the operation.

The DataInputStream contains all in and inout parameters, in the order in which they are specified in the operation’s IDL definition, from left to right. A nil DataInputStream indicates that no arguments exist.

A pointer to a CORBA::DataOutputStream that can be used to populate the parameters to be returned to the initiator of the invocation as a reply. The use of this parameter is only valid if a status of REPLY_NO_EXCEPTION is returned.

The client_invoke operation is called on an interceptor implementation that supports the RequestLevelInterceptor::ClientRequestInterceptor interceptor interface. The operation is called by the ORB anytime that an invocation is being sent to a target object, regardless of whether the target object is in a different address space or the same address space as the target object.

Indicates that the interceptor encountered an error that should result in the discontinued processing of the request toward the target. The parameter excep_val is used to report the exception to the ORB. The ORB calls interceptors on the way back to the client application with the exception_occurred operation rather than with the client_response operation. Note that the ORB is responsible for the memory management for the excep_val parameter.

Is called on an interceptor implementation that supports the RequestLevelInterceptor::ClientRequestInterceptor interface.

A reference to a ReplyContext that contains information about the context in which the reply is being performed.

A pointer to a ServiceContextList containing service context information received as a result of processing the request by the target object.

A pointer to a DataInputStream that can be used by the interceptor implementation to retrieve the value of the reply parameters of the operation.

The following table identifies what the client_response method returns in the DataInputStream object based on the status contained in the ReplyContext object:

Note: Exceptions contain a string followed by any exception members. The string contains the repository ID for the exception. The exception members are passed in the same manner as a struct. A system exception contains two unsigned long members, a minor code, and a completion status.

The client_response operation is called on an interceptor implementation that supports the RequestLevelInterceptor::ClientRequestInterceptor interface. The operation is called by the ORB anytime that a reply to an invocation is being received by the initiator of the request, regardless of whether the initiator is in a different address space or the same address space as the target object.

Indicates that the interceptor encountered an error. The parameter excep_val is used to report the exception to the ORB. Any interceptors not yet called on the way back to the client have their exception_occurred operation called by the ORB to notify them that processing the request has failed.

A reference to a RequestContext that contains information about the context in which the request is being performed.

A pointer to a ServiceContextList containing service context information received as part of the request to the target object.

A pointer to a DataInputStream that can be used by the interceptor implementation to retrieve the value of the parameter of the operation.

A pointer to a DataOutputStream that can be used to populate the parameters to be returned to the initiator of the invocation as a reply. The use of this parameter is only valid if a status of REPLY_NO_EXCEPTION is returned.

The target_invoke operation is called on an interceptor implementation that supports the RequestLevelInterceptor::TargetRequestInterceptor interface. The operation is called by the ORB anytime that an invocation is being received by a target object, regardless of whether the target object is in a different address space or the same address space as the target object.

Indicates that the interceptor encountered an error that should result in the discontinued processing of the request in order to deliver it to the target object. The parameter excep_val is used to report the exception to the ORB. The ORB calls interceptors on the way back to the client with the exception_occurred operation, rather than with the target_response operation. Note that the ORB is responsible for the memory management for the excep_val parameter.

A reference to a ReplyContext that contains information about the context in which the reply is being performed.

A pointer to a ServiceContextList containing service context information to be sent as a result of processing the request by the target object.

A pointer to a DataInputStream that can be used by the interceptor implementation to retrieve the value of the reply parameters of the operation.

The following table identifies what the target_response method returns in the DataInputStream object based on the status contained in the ReplyContext object:

The target_response operation is called on an interceptor implementation that supports the RequestLevelInterceptor::TargetRequestInterceptor interface. The operation is called by the target-side ORB anytime that a reply to an invocation is being sent to the initiator of the request, regardless of whether the initiator is in a different address space or the same address space as the target object.

Indicates that the interceptor encountered an error. The parameter excep_val is used to report the exception to the ORB. Any interceptors not yet called on the way back to the client have their exception_occurred operation called by the ORB in order to notify them that processing the request has failed. Note that the ORB is responsible for the memory management for the excep_val parameter.

A pointer in which to return a pointer to the instance of the RequestLevelInterceptor::ClientRequestInterceptor that was instantiated for use by the ORB.

A pointer in which to return a pointer to the instance of the RequestLevelInterceptor::TargetRequestInterceptor that was instantiated for use by the ORB.

A pointer to a location into which the interceptor implementation indicates whether the instantiation and initialization of the interceptor was successful. A value of CORBA::TRUE is used to indicate that instantiation and initialization of the interceptors was successful. A value of CORBA::FALSE is used to indicate that the instantiation and initialization of the interceptors was unsuccessful for some reason.

The AppRequestInterceptorInit function is a user-provided function that is used by the ORB to instantiate and initialize client-side and target-side interceptors.

The abstract valuetype keywords in IDL applied to DataInputStream indicates that it is not the same as an interface.

The implementation of CORBA::DataInputStream inherits from CORBA::ValueBase rather than from CORBA::Object. You cannot use, for example, _duplicate, _narrow, and _nil operations since they apply only to CORBA::Object. At this time, there is nothing of interest for users in the CORBA::ValueBase interface.

The operations to read a primitive element (<primitive>) from a DataInputStream all have the same format. Each operation returns a value from the stream.

Note:

String_var, TypeCode_var, or Object_var can be used for memory management. Otherwise, strings must be released using the string_free() operation on the CORBA object, and TypeCode or Object pointers must be released using the release() operation on the CORBA object.

AnySeq (Not implemented)
BooleanSeq
CharSeq
OctetSeq
ShortSeq
UshortSeq
LongSeq
UlongSeq
FloatSeq
DoubleSeq

The operations to read an array of primitive elements (<primitive>) from a DataInputStream all have the same format. Each operation returns an array of primitive values from the stream into a CORBA sequence of that same primitive type.

AnySeq (Not implemented)
BooleanSeq
CharSeq
OctetSeq
ShortSeq
UshortSeq
LongSeq
UlongSeq
FloatSeq
DoubleSeq

Status Value	Description
ORB_SHUTDOWN	Indicates that the ORB is being shut down.
RESOURCES_EXCEEDED	Indicates that resources of the process have been exhausted.
CONNECTION_ABORTED	This exception is not reported in Oracle Tuxedo 8.0.

Version Member	Description
major_version	Indicates the major version value. The value of this member is incremented anytime a change is made to the contents or layout of a RequestContext that is not backward compatible with previous versions.
minor_version	Indicates the minor version value. The value of this member is incremented anytime a change is made to the contents or layout of a RequestContext that is backward compatible with previous versions.

Version Member	Description
major_version	Indicates the major version value. The value of this member is incremented anytime a change is made to the contents or layout of a ReplyContext that is not backward compatible with previous versions.
minor_version	Indicates the minor version value. The value of this member is incremented anytime a change is made to the contents or layout of a ReplyContext that is backward compatible with previous versions.

Status Value	Description
NO_EXCEPTION	Indicates that the requested operation completed successfully and that the value of the arg_stream parameter contains the return values of the operation.
USER_EXCEPTION	Indicates that the requested operation failed because of an exception reported by the target object.
SYSTEM_EXCEPTION	Indicates that the request operation failed because of an exception reported either by the target object or by the infrastructure.
LOCATION_FORWARD	Indicates that the body contains an object reference (IOR). The client ORB is responsible for resending the original request to that (different) object. This resending is transparent to the client program making the request, but the resending is not transparent to the interceptor.
LOCATION_FORWARD_PERM	Indicates that the body contains an object reference. The usage is similar to LOCATION_FORWARD, but when used by a server, this value also provides an indication to the client that the client may replace the old IOR with the new IOR. Both the old IOR and the new IOR are valid, but the new IOR is preferred for future use. This resending is transparent to the client program making the request, but the resending is not transparent to the interceptor.
NEEDS_ADDRESSING_MODE	Indicates that the body contains a GIOP::AddressingDisposition. The client ORB is responsible for resending the original request using the requested addressing mode. This resending is transparent to the client program making the request, but the resending is not transparent to the interceptor.

Status Value	Description
LOCATION_FORWARD, LOCATION_FORWARD_PERM, or NEEDS_ADDRESSING_MODE	A nil DataInputStream is supplied.
NO_EXCEPTION	The DataInputStream contains first any operation return value, then any inout and out parameters in the order in which they appear in the operation's IDL definition, from left to right. A nil DataInputStream indicates that no arguments exist.
USER_EXCEPTION or SYSTEM_EXCEPTION	The DataInputStream contains the exception that was raised by the operation.