Wiremock提取XML属性用于Webhook时出现null无效XML错误求助

处理API请求的XML报文时，需要提取属性并通过Webhook发送。已成功在API响应中提取该属性，但在serveEventListeners的Webhook配置中使用时，出现错误：attribute="[ERROR: null is not valid XML]"。

相关代码片段 #

XML请求 #

<ns2:ReqPay xmlns:ns2="http://npci.org/upi/schema/">
    <Head ver="2.0" ts="2021-01-17T11:18:11+05:30" orgId="929390493" msgId="randomMsgId"/>
    <Payer addr="shikhar@gios" name="Bobi Jacob" seqNum="1" type="PERSON" code="0000">
    </Payer>
</ns2:ReqPay>

Admin配置映射 #

{
    "request": {
        "method": "POST",
        "urlPattern": "/testing",
        "headers": {
            "Content-Type": {
                "equalTo": "application/xml"
            }
        }
    },
    "response": {
        "status": 200,
        "headers": {
            "Content-Type": "application/xml"
        },
        "transformers": [
            "response-template"
        ],
        "body": "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?><ns2:Ack xmlns:ns2=\"http://npci.org/upi/schema/\" api=\"npciApi\" reqMsgId=\"{{randomValue length=32 type='ALPHANUMERIC'}}\" addr=\"{{xPath request.body '/ReqPay/Payer/@addr'}}\" ts=\"{{now format='yyyy-MM-dd\'T\'HH:mm:ssXXX'}}\"/>"
    },
    "serveEventListeners": [
        {
            "name": "webhook",
            "parameters": {
                "method": "POST",
                "url": "https://nnccdd.requestcatcher.com/testing0100",
                "headers": {
                    "Content-Type": "application/xml"
                },
                "delay": {
                    "type": "fixed",
                    "milliseconds": 800
                },
                "body": "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<ns2:RespPay xmlns:ns2=\"http://npci.org/upi/schema/\" xmlns:ns3=\"http://npci.org/cm/schema/\">\n\t<Head msgId=\"xxx\" orgId=\"NPCI\" ts=\"{{now format='yyyy-MM-dd\'T\'HH:mm:ssXXX'}}\" ver=\"2.0\"/>\n\t<Ref addr=\"{{xPath request.body '/ReqPay/Payer/@addr'}}\" />\n\t</Resp>\n</ns2:RespPay>"
            }
        }
    ]
}

正常返回的API响应 #

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns2:Ack xmlns:ns2="http://npci.org/upi/schema/" api="npciApi" reqMsgId="e4gqglqg1xadizkpnvkr3ls1j5666pjk" addr="arunl@gip1" ts="2024-05-28T05:39:52Z"/>

出错的Webhook响应 #

<?xml version="1.0" encoding="UTF-8"?>
<ns2:RespPay xmlns:ns2="http://npci.org/upi/schema/" xmlns:ns3="http://npci.org/cm/schema/">
    <Head msgId="xxx" orgId="NPCI" ts="2024-05-28T05:39:52Z" ver="2.0"/>
    <Ref addr="[ERROR: null is not valid XML]" />
    </Resp>
</ns2:RespPay>

问题原因分析 #

1. XPath未处理XML命名空间：原始XML请求中的ReqPay和Payer元素属于http://npci.org/upi/schema/命名空间（前缀ns2），但Webhook中使用的XPath/ReqPay/Payer/@addr未指定命名空间，导致无法匹配目标元素，返回null。
2. XML语法错误：Webhook的body中存在多余的</Resp>闭合标签，无对应起始标签，会导致XML格式异常。

修复方案 #

1. 修改XPath以支持命名空间 #

有两种方式处理命名空间：

• 方式一：忽略命名空间匹配
  将Webhook body中的XPath替换为：

{{xPath request.body '/*[local-name()="ReqPay"]/*[local-name()="Payer"]/@addr'}}

• 方式二：显式指定命名空间映射
  若模板引擎支持传递命名空间参数，可使用：

{{xPath request.body '/ns2:ReqPay/ns2:Payer/@addr' namespaces='{"ns2":"http://npci.org/upi/schema/"}'}}

2. 修复XML语法错误 #

删除Webhook body中多余的</Resp>标签。

3. 完整修正后的Admin Mapping #

{
    "request": {
        "method": "POST",
        "urlPattern": "/testing",
        "headers": {
            "Content-Type": {
                "equalTo": "application/xml"
            }
        }
    },
    "response": {
        "status": 200,
        "headers": {
            "Content-Type": "application/xml"
        },
        "transformers": [
            "response-template"
        ],
        "body": "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?><ns2:Ack xmlns:ns2=\"http://npci.org/upi/schema/\" api=\"npciApi\" reqMsgId=\"{{randomValue length=32 type='ALPHANUMERIC'}}\" addr=\"{{xPath request.body '/ReqPay/Payer/@addr'}}\" ts=\"{{now format='yyyy-MM-dd\'T\'HH:mm:ssXXX'}}\"/>"
    },
    "serveEventListeners": [
        {
            "name": "webhook",
            "parameters": {
                "method": "POST",
                "url": "https://nnccdd.requestcatcher.com/testing0100",
                "headers": {
                    "Content-Type": "application/xml"
                },
                "delay": {
                    "type": "fixed",
                    "milliseconds": 800
                },
                "body": "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<ns2:RespPay xmlns:ns2=\"http://npci.org/upi/schema/\" xmlns:ns3=\"http://npci.org/cm/schema/\">\n\t<Head msgId=\"xxx\" orgId=\"NPCI\" ts=\"{{now format='yyyy-MM-dd\'T\'HH:mm:ssXXX'}}\" ver=\"2.0\"/>\n\t<Ref addr=\"{{xPath request.body '/*[local-name()=\"ReqPay\"]/*[local-name()=\"Payer\"]/@addr'}}\" />\n</ns2:RespPay>"
            }
        }
    ]
}

内容的提问来源于stack exchange，提问作者YoDO