使用WSO2 Integration Studio将REST API暴露为SOAP API的参数兼容问题

方法1：使用Envelope Mediator提取SOAP Body内容 #

在PayloadFactory之前添加envelope mediator，直接提取SOAP Body中的内容作为新的消息负载，后续的XPath表达式就能正确匹配目标节点。

修改后的完整API配置：

<?xml version="1.0" encoding="UTF-8"?>
<api context="/test" name="test" xmlns="http://ws.apache.org/ns/synapse">
    <resource methods="POST">
        <inSequence>
            <!-- 提取SOAP Body内容，移除Envelope和Body标签 -->
            <envelope extractBody="true"/>
            
            <payloadFactory media-type="json">
                <format>{&#xd;
  "_poststudent": {&#xd;
    "name" : "$1",&#xd;
    "school": "$2",&#xd;
    "grade": $3&#xd;
  }&#xd;
}</format>
                <args>
                    <arg evaluator="xml" expression="//root/_poststudent/name"/>
                    <arg evaluator="xml" expression="//root/_poststudent/school"/>
                    <arg evaluator="xml" expression="//root/_poststudent/grade"/>
                </args>
            </payloadFactory>
            <call>
                <endpoint>
                    <http method="post" uri-template="http://ITMTNP219BS5:8290/services/RESTDataService/student">
                        <suspendOnFailure>
                            <initialDuration>-1</initialDuration>
                            <progressionFactor>-1</progressionFactor>
                            <maximumDuration>0</maximumDuration>
                        </suspendOnFailure>
                        <markForSuspension>
                            <retriesBeforeSuspension>0</retriesBeforeSuspension>
                        </markForSuspension>
                    </http>
                </endpoint>
            </call>
            <respond/>
        </inSequence>
        <outSequence/>
        <faultSequence/>
    </resource>
</api>

方法2：修改XPath表达式适配SOAP命名空间 #

如果不想修改消息结构，可直接调整PayloadFactory中的XPath表达式，引入SOAP命名空间并定位到Body内的节点：

修改后的PayloadFactory配置片段：

<payloadFactory media-type="json">
    <format>{&#xd;
  "_poststudent": {&#xd;
    "name" : "$1",&#xd;
    "school": "$2",&#xd;
    "grade": $3&#xd;
  }&#xd;
}</format>
    <args>
        <arg evaluator="xml" expression="//soap:Body/root/_poststudent/name" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"/>
        <arg evaluator="xml" expression="//soap:Body/root/_poststudent/school" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"/>
        <arg evaluator="xml" expression="//soap:Body/root/_poststudent/grade" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"/>
    </args>
</payloadFactory>

错误原因说明 #

出现INCOMPATIBLE_PARAMETERS_ERROR是因为原始请求包含SOAP Envelope和Body标签，且SOAP命名空间未被XPath表达式识别，导致//root/_poststudent/name这类表达式无法匹配到任何节点，PayloadFactory无法获取所需参数，从而抛出参数不兼容异常。

内容的提问来源于stack exchange，提问作者Oussama Nairi