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Web Services EntryPoint
=======================
This section of the document describes the use of the Web Service EntryPoint
(WS EntryPoint) support in the Apache Tuscany SCA C++ runtime.
The WS EntryPoint code is based on Apache Axis2C version 0.92
(http://ws.apache.org/axis2/c) and allows SCA components to be invoked via Web
Service calls.
WS EntryPoint currently supports Document/literal Wrapped style Web Services
only. There are also restrictions about the parameter and return types of the
operations in SCA components that can be exposed as Web Services, see below
for more details.
Defining and deploying an SCA Module with a WS EntryPoint
=========================================================
In this section we will use the Calculator sample as a worked example.
The Calculator code and files can be found at sca/samples/Calculator.
Pre-requisites:
o A working component within a module and subsystem, with SCAGEN generated
Proxy and Wrapper classes and a DLL or SO library compiled from these and
the component class files. The sca.module, *.componentType, *.fragment and
sca.subsystem files must also be available and working
1. Create the WSDL that defines the interface of your SCA component. See the
table "XML Schema Type to C++ Type Mapping" and "Notes on creating WSDL" below
for mapping the parameters and return types of the component operations to XML
schema types in the WSDL. This file needs to be accessible from the component,
so place it in the same directory as the component or in a subdirectory.
See the sca/samples/Calculator/CalculatorModule/Calculator.wsdl file as an
example.
2. Add an EntryPoint definition to the sca.module file, setting the
interface.wsdl interface attribute to the WSDL file defined above, the
reference element to the name of the component to be invoked and the binding.ws
port attribute to the namespace, service and port name specified in the
WSDL, in the form: "<namespace>#wsdl.endpoint(<service-name>/<port-name>)".
Also give the EntryPoint a name and set the multiplicity.
E.g. for the Calculator component, based on the Calculator.wsdl file:
<!-- Expose as a web service -->
<entryPoint name="WSCalculatorEntrypoint" multiplicity="1..1">
<interface.wsdl interface="Calculator.wsdl" />
<binding.ws port="tuscany/c/Calculator#wsdl.endpoint(CalculatorService/CalculatorServicePort)"/>
<reference>CalculatorServiceComponent</reference>
</entryPoint>
3. Create a file named Tuscany-model.config in the same directory as your
component. This file defines which WSDL and XML Schema files to include in the
Tuscany runtime environment for this module. Set the contents of the file
using the example below and use the path and name of the WSDL file created
above.
E.g. for the Calculator component
<?xml version="1.0" encoding="utf-8" ?>
<tuscany-model xmlns="http://org.apache.tuscany/xmlns/cpp/1.0">
<wsdl>
<file name="Calculator.wsdl"/>
</wsdl>
</tuscany-model>
These changes are all that are required in the Tuscany runtime environment to
expose a component as a Web Service; the following steps detail how to add the
Web Service to the list of Axis2C services.
4. Create a new directory within the Axis2C services directory. The name of
this directory defines the URL of your service. For example, if you create a
directory named "CalcWebService", the URL of the service will be
http://localhost:9090/axis2/services/CalcWebService
5. Create a file named services.xml within the new directory. This file defines
the library to use that contains the service code and the operations that the
service exposes. For the Tuscany WS EntryPoint, you also need to add some
Tuscany specific parameters to identify the Tuscany System Root directory and
the EntryPoint that will be invoked.
The TuscanySystemRoot parameter requires the full path to your system root
directory - this is the directory that contains the "modules" and "subsystem"
directories; which in turn contain your modules and subsystems.
The TuscanyEntryPoint parameter is of the form
"<subsystem-name>/<service-name>/<entrypoint-name>", with the subsystem and
service names defined in your sca.subsystem file and the EntryPoint name
defined in the EntryPoint definition you added to your sca.module file above.
Set the ServiceClass parameter to "tuscany_sca_ws_service" as this library
(tuscany_sca_ws_service.dll on Windows and libtuscany_sca_ws_service.so on
Linux) contains the service code that will invoke your component.
Finally, add all of the operations that your component defines that you want
to expose as Web Service operations.
E.g. for the Calculator WS EntryPoint,
axis2c/services/CalcWebService/services.xml contains:
<service name="CalcWebService">
<parameter name="ServiceClass" locked="xsd:false">tuscany_sca_ws_service</parameter>
<parameter name="TuscanySystemRoot" locked="xsd:false">C:/tuscany/cpp/sca/samples/runtime</parameter>
<parameter name="TuscanyEntryPoint" locked="xsd:false">CalculatorSubsystem/CalculatorService/WSCalculatorEntrypoint</parameter>
<operation name="add"/>
<operation name="sub"/>
<operation name="mul"/>
<operation name="div"/>
</service>
6. Copy the tuscany_sca_ws_service.dll file (or the
libtuscany_sca_ws_service.so file, if on Linux) to the new service directory
you created above. This library contains the code that Axis2C requires to call
a service implementation and links to the tuscany_sca.dll library (or
libtuscany_sca.so on Linux) which manages the invocation of your component.
7. Ensure the TUSCANY_SCACPP, TUSCANY_SDOCPP, AXIS2C_HOME and PATH environment
variables are correctly set
E.g. on Windows run the following commands with the correct directories:
set TUSCANY_SCACPP=C:/path_to_tuscany/sca/deploy
set TUSCANY_SDOCPP=C:/path_to_tuscany/sdo/deploy
set AXIS2C_HOME=C:/path_to_axis2c0.92
set PATH=%PATH%;C:/path_to_tuscany/sca/deploy/bin;C:/path_to_tuscany/sdo/deploy/bin;C:/path_to_axis2c0.92/lib
8. Optionally, enable logging in Tuscany by setting the TUSCANY_SCACPP_LOGGING
environment variable with the level you wish to log at (0 for minimal
logging, up to 9 for more detailed logging) and the TUSCANY_SCACPP_LOG
environment variable to define the file to log to (if this is not set, logging
will go to the console)
E.g. on Windows run the following commands:
set TUSCANY_SCACPP_LOGGING=5
set TUSCANY_SCACPP_LOG=C:/tuscany/mylogfile.txt
Additionally, Axis2C automatically writes logging files to the Axis2C logs
directory (e.g. C:/path_to_axis2c0.92/logs). In particular the Axis2.log file
may contain useful information about your service.
9. Start the Simple Axis server, or your Apache HTTP server if you have
deployed Axis2C to Apache.
E.g. on Windows run the following commands:
cd C:/path_to_axis2c0.92/bin
./axis2_http_server.exe
Your component should now be exposed as an Axis2C Web Service, via the WS
EntryPoint you created. See the Axis2C documentation for writing clients to
invoke the Web Service, or you can use any other Web Service client platform
(e.g. Axis2 for Java: http://ws.apache.org/axis2), or you can invoke your
component from another Tuscany runtime by using Tuscany's WS External Service
support.
XML Schema Type to C++ Type Mapping
===================================
To help define the WSDL that describes the interface of your component, the
table below lists how incoming XML data in Web Service messages is mapped to
C++ types used in the parameters and return types of your component operations.
This lists the only C++ types that can currently be used on the operations of a
component exposed as a Web Service. For other types, use an SDO DataObject to
wrap the data, and define that wrapping as a complexType in the WSDL. See the
SDO specifications (available from the Tuscany website) for the C++ types that
SDO supports.
XML Schema Type | C++ Type
-------------------------------------------------------------
|
string | char*
|
int | long
|
integer | long
|
short | short
|
float | float
|
double | long double
|
boolean | bool
|
hexBinary | char*
|
base64Binary | char*
|
byte | char
|
complexType | SDO DataObjectPtr
|
any | SDO DataObjectPtr with OpenDataObjectType
Notes on creating WSDL
======================
o Currently only Document/literal Wrapped style Web Services are supported by
WS EntryPoint, support for RPC style Web Services is planned for future
releases.
See the article at http://www.ibm.com/developerworks/webservices/library/ws-whichwsdl/
for an explanation of Document/literal Wrapped style WSDL and Web Services
o Operation parameter and return messages that are defined in the WSDL must be
XML Schema elements containing a complexType - there is currently no
support for simpleTypes or single-level elements. Also, Document/literal
Wrapped services require that the operation name is used as the name of the
incoming element that wraps the operation parameters.
For example, a component operation defined in C++ as:
long myOperation(char* arg1, short arg2, DataObjectPtr arg3);
will need to be described in WSDL with messages like:
<wsdl:message name="myOperationRequestMsg">
<wsdl:part element="tns:myOperation" name="myOperationRequestPart"/>
</wsdl:message>
<wsdl:message name="myOperationResponseMsg">
<wsdl:part element="tns:myOperationResponse" name="myOperationResponsePart"/>
</wsdl:message>
and will need an XML schema to define the types like:
<xsd:element name="myOperation">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="arg1" type="xsd:string" minOccurs="1"/>
<xsd:element name="arg2" type="xsd:short" minOccurs="1"/>
<xsd:element name="arg3" minOccurs="1">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="dataObjectFloatData" type="xsd:float"/>
<xsd:element name="dataObjectStringData" type="xsd:string"/>
<xsd:element name="dataObjectIntData" type="xsd:int"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="myOperationResponse">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="result" type="xsd:int" minOccurs="1"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
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