Tuxedo ATMI Programming for Web Services

BEA SALT allows you to import external Web Services into Tuxedo Domains. To import external Web services into Tuxedo application, a WSDL file must first be loaded and converted. The BEA SALT WSDL conversion utility, wsdlcvt, translates each wsdl:operation into a BEA SALT proxy service. The translated SALT proxy service can be invoked directly through standard Tuxedo ATMI functions.

BEA SALT proxy service calls are sent to the GWWS server. The request is translated from Tuxedo typed buffers into the SOAP message, and then sent to the corresponding external Web Service. The response from an external Web Service is translated into Tuxedo typed buffers and returned to the Tuxedo application. The GWWS acts as the proxy intermediary.

If an error occurs during the service call, the GWWS server sets the error status using tperrno, which can be retrieved by Tuxedo applications. This enables you to detect and handle the SALT proxy service call error status.

Converting WSDL Model Into Tuxedo Model

BEA SALT provides a WSDL conversion utility, wsdlcvt, that converts external WSDL files into Tuxedo specific definition files so that you can develop Tuxedo ATMI programs to access services defined in the WSDL file.

WSDL-to-Tuxedo Object Mapping

BEA SALT converts WSDL object models into Tuxedo models using the following rules:

Only SOAP over HTTP binding are supported, each binding is defined and saved as a WSBinding object in the WSDF file.
Each operation in the SOAP bindings is mapped as one Tuxedo style service, which is also called a SALT proxy service. The operation name is used as the Tuxedo service name and indexed in the Tuxedo Service Metadata Repository.
Other Web service external application protocol information is saved in the generated WSDF file (including SOAP protocol version, SOAP message encoding style, accessing endpoints, and so).
XML Schema definitions embedded in the WSDL file are copied and saved in separate .xsd files.
Each wsdl:operation object and its input/output message details are converted as a Tuxedo service definition conforms to Tuxedo Service Metadata Repository input syntax.

Table 4-1 lists detailed mapping relationships between the WSDL file and Tuxedo definition files.

Table 4-1 WSDL Model / Tuxedo Model Mapping Rules
WSDL Object	Tuxedo/SALT Definition File	Tuxedo/SALT Definition Object
/wsdl:binding	SALT Web Service Definition File (WSDF)	/WSBinding
/wsdl:portType		/WSBinding/Servicegroup
/wsdl:binding/soap:binding		/WSBinding/SOAP
/wsdl:portType/operation	Metadata Input File (MIF)	/WSBinding/service
/wsdl:types/xsd:schema	FML32 Field Defintion Table	Field name type

Invoking SALT Proxy Services

The following sections include information on how to invoke the converted SALT proxy service from a Tuxedo application:

BEA SALT Supported Communication Pattern

BEA SALT only supports the Tuxedo Request/Response communication patterns for outbound service calls. A Tuxedo application can request the SALT proxy service using the following communication Tuxedo ATMIs:

tpcall(1) / tpacall(1) / tpgetreply(1)

These basic ATMI functions can be called with a Tuxedo typed buffer as input parameter. The return of the call will also carry a Tuxedo typed buffer. All these buffers will conform to the converted outside Web service interface. tpacall/tpgetreply is not related to SOAP async communication.

tpforward(1)

Tuxedo server application can use this function to forward a Tuxedo request to a specified SALT proxy service. The response buffer is sent directly to client application's response queue as if it's a traditional native Tuxedo service.

TMQFORWARD enabled queue-based communication.

Tuxedo system server TMQFORWARD can accept queued requests and send them to BEA SALT proxy services that have the same name as the queue.

Conversational communication
Event-based communication

Tuxedo Outbound Call Programming: Main Steps

When the GWWS is booted and BEA SALT proxy services are advertised, you can create a Tuxedo application to call them. To develop a program to access SALT proxy services, do the following:

Check the Tuxedo Service Metadata Repository definition to see what the SALT proxy service interface is.
Locate the generated FML32 field table files. Modify the FML32 field table to eliminate conflicting field names and assign a valid base number for the index.

Note:

The wsdlcvt generated FML32 field table files are always used by GWWS. you must make sure the field name is unique at the system level. If two or more fields are associated with the same field name, change the field name. Do not forget to change Tuxedo Service Metadata Repository definition accordingly.

The base number of field index in the generated FML32 field table must be changed from the invalid default value to a correct number to ensure all field index in the table is unique at the entire system level.

Generate FML32 header files with mkfldhdr32(1).
Boot the GWWS with correct FML32 environment variable settings.
Write a skeleton C source file for the client to call the outbound service (refer to Tuxedo documentation and the Tuxedo Service Metadata Repository generated pseudo-code if necessary). You can use tpcall(1) or tpacall(1) for synchronous or asynchronous communication, depending on the requirement.
For FML32 buffers, you need to add each FML32 field (conforming to the corresponding BEA SALT proxy service input buffer details) defined in the Tuxedo Service Metadata Repository, including FML32 field sequence and occurrence. The client source may include the generated header file to facilitate referencing the field name.
Get input buffer ready, user can handle the returned buffer, which should be of the type defined in Metadata.
Compile the source to generate executable.
Test the executable.

Managing Error Code Returned from GWWS

If the GWWS server encounters an error accessing external Web services, tperrno is set accordingly so the Tuxedo application can diagnose the failure. Table 4-2 lists possible BEA SALT proxy service tperrno values.

Table 4-2 Error Code Returned From GWWS/Tuxedo Framework
TPERRNO	Possible Failure Reason
TPENOENT	Requested SALT proxy service is not advertised by GWWS
TPESVCERR	The HTTP response message returned from external Web service application is not valid The SOAP response message returned from external Web service application is not well-formed.
TPEPERM	Authentication failure.
TPEITYPE	Message conversion failure when converting Tuxedo request typed buffer into XML payload of the SOAP request message.
TPEOTYPE	Message conversion failure when converting XML payload of the SOAP response message into Tuxedo response typed buffer.
TPEOS	Request is rejected because of system resource limitation
TPETIME	Timeout occurred. This timeout can either be a BBL blocktime, or a SALT outbound call timeout.
TPSVCFAIL	External Web service returns SOAP fault message
TPESYSTEM	GWWS internal errors. Check ULOG for more information.

Handling Fault Messages in a Tuxedo application

All rules listed in used to map WSDL input/output message into Tuxedo Metadata inbuf/outbuf definition. WSDL file default message can also be mapped into Tuxedo Metadata errbuf, with some amendments to the rules:

There are two modes for mapping Metadata errbuf into SOAP Fault messages: Tux Mode and XSD Mode.

Tux Mode is used to convert Tuxedo original error buffers returned with TPFAIL. The error buffers are converted into XML payload in <detail> element of SOAP fault.
XSD Mode is used to represent SOAP fault and WSDL file fault messages defined with Tuxedo buffers. The mapping rule include:

Each service in XSD mode (servicemode=webservice) will always has an errbuf in Metadata, with type=FML32.

The errbuf is a FML32 buffer. It is complete description for SOAP:Fault message that is possible to appear in correspondence, which will be different for SOAP 1.1 and 1.2. So the errbuf definitionís content will be determined by the SOAP version and WSDL fault message both.

Parameter detail/Detail (1.1/1.2) will be a FML32 field that each field of it represents for the wsdl:part defined in one wsdl:fault message (when wsdl:fault is present). Each part is defined as a param(field) in this FML32 field. The mapping rules are the same as input/output buffer. The difference is that each paramís requiredcount is 0, which means the part may not appear in SOAP fault message.

Other elements appears in soap:fault message will always be defined as a filed in errbuf, with requiredcount equals to 1 or 0 depending on the element is a MUST or OPTIONAL.

Each partís definition in Metadata will guide converting a <detail> in soap fault message into a field in error buffer.

Programming Web Services