How to call a webserivce in a bpmn file

Flowable Engine
1

Hi,can anyone help me out?
I need to call a webserivice ,but I have no idea how to define the webserivice task in the bpmn file.

Here is my wsld file :

<definitions targetNamespace="xxx" xmlns="http://schemas.xmlsoap.org/wsdl/" xmlns:http="http://schemas.xmlsoap.org/wsdl/http/" xmlns:mime="http://schemas.xmlsoap.org/wsdl/mime/" xmlns:s="http://www.w3.org/2001/XMLSchema" xmlns:s0="xxx" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/">

    <!-- Types -->

    <types>

    <s:schema elementFormDefault="qualified" targetNamespace="xxx">

    <s:complexType name="InputParams">

    <s:sequence id="InputSequence">

    <s:element maxOccurs="1" minOccurs="0" name="input1" type="s:string"/>

    </s:sequence>

    </s:complexType>

    <s:element name="XacuteRequest">

    <s:complexType>

    <s:sequence>

    <s:element maxOccurs="1" minOccurs="0" name="LoginName" type="s:string"/>

    <s:element maxOccurs="1" minOccurs="0" name="LoginPassword" type="s:string"/>

    <s:element maxOccurs="1" minOccurs="0" name="InputParams" type="s0:InputParams"/>

    </s:sequence>

    </s:complexType>

    </s:element>

    <s:complexType name="Rowset">

    <s:sequence>

    <s:element maxOccurs="unbounded" minOccurs="0" name="Row" type="s0:Row"/>

    </s:sequence>

    <s:attribute name="Message" type="s:string"/>

    </s:complexType>

    <s:complexType name="Row">

    <s:sequence id="RowSequence"></s:sequence>

    </s:complexType>

    <s:element name="XacuteResponse">

    <s:complexType>

    <s:sequence>

    <s:element maxOccurs="1" minOccurs="0" name="Rowset" type="s0:Rowset"/>

    </s:sequence>

    </s:complexType>

    </s:element>

    </s:schema>

    </types>

    <!-- Messages -->

    <message name="XacuteSoapIn">

    <part element="s0:XacuteRequest" name="parameters"/>

    </message>

    <message name="XacuteSoapOut">

    <part element="s0:XacuteResponse" name="parameters"/>

    </message>

    <!-- Ports -->

    <portType name="XacuteWSSoap">

    <operation name="Xacute">

    <input message="s0:XacuteSoapIn"/>

    <output message="s0:XacuteSoapOut"/>

    </operation>

    </portType>

    <!-- Bindings -->

    <binding name="XacuteWSSoap" type="s0:XacuteWSSoap">

    <soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>

    <operation name="Xacute">

    <soap:operation soapAction="xxx" style="document"/>

    <input>

    <soap:body use="literal"/>

    </input>

    <output>

    <soap:body use="literal"/>

    </output>

    </operation>

    </binding>

    <!-- Service mapping -->

    <service name="XacuteWS">

    <port binding="s0:XacuteWSSoap" name="XacuteWSSoap">

    <soap:address location="xxxx"/>

    </port>

    </service>

    </definitions>

What I want is call the method ‘Xacute’ with parameters .

I know how to import the wsdl file using the import tag ,but I’ve no idea how to associate the message with the item definitions.

Here is some piece of code :

<serviceTask id="webService"  invocation" implementation="##WebService" operationRef="tns:Xacute">
            <ioSpecification>
                <dataInput itemSubjectRef="tns:XacuteRequest" id="dataInputOfWebService" />
                <inputSet>
                    <dataInputRefs>dataInputOfWebService</dataInputRefs>
                </inputSet>
                <outputSet />
            </ioSpecification>
            <dataInputAssociation>
                <sourceRef>input</sourceRef>
                <targetRef>dataInputOfWebService</targetRef>
                <assignment>
                    <from>${input.username}</from>
                    <to>${dataInputOfWebService.loginName}</to>
                </assignment>
                <assignment>
                    <from>${input.password}</from>
                    <to>${dataInputOfWebService.loginPassword}</to>
                </assignment>
                <assignment>
                    <from>${input.inputParams}</from>
                    <to>${dataInputOfWebService.inputParams}</to>
                </assignment>
            </dataInputAssociation>
</serviceTask>

<interface name="Log Interface" implementationRef="log:XacuteWSSoap"> <!-- NEEDED FOR THE PORT -->
        <!-- Operation: implementationRef = QName of WSDL Operation -->
        <operation id="Xacute" name="WebService Operation" implementationRef="log:Xacute"> <!-- NEEDED FOR THE OPERATION NAME -->
            <inMessageRef>tns:XacuteSoapIn</inMessageRef>
        </operation>
 </interface>

    <message id="XacuteSoapIn" itemRef="tns:XacuteRequest" name="XacuteSoapIn"/>

    <itemDefinition id="XacuteRequest" structureRef="log:XacuteRequest" /><!-- QName of input element --> <!-- NEEDED FOR THE ARGUMENTS -->

when I run the process ,I got some type error exception:
Part {xxx}parameters should be of type xxx.XacuteRequest, not java.lang.String.

but when I change the structureRef of the itemDefinition to log:XacuteSoapIn,I got npe as there is no such structure in the imported structureMap.

I am so confused ,and any help will be appreciated.
Thank you.