无法发布到WSO2 ESB上的REST API

Question

我在WSO2 Integrator 6.4上按以下顺序创建了以下REST API：

<?xml version="1.0" encoding="UTF-8"?>
<api context="/dsb" name="evCaptureJSONProperties" 
                   xmlns="http://ws.apache.org/ns/synapse">
<resource methods="POST" uri-template="/api/SendSMS">
<inSequence>
  <log description="Entry Confirmation" level="custom">
    <property name="message" value="Request Entered the 
      evCaptureJSONProperties REST API"/>
  </log>
  <payloadFactory media-type="json">
     <format><!-- A json message was here --></format>
     <args/>
  </payloadFactory>
  <respond/>
</inSequence>
<outSequence/>
<faultSequence/>
 </resource>
 </api>

然后我使用以下命令发布请求JSON：

Curl -v -X POST --data @evCaptureJSONProperties.json http://localhost:8280/dsb/api/SendSMS --header "Content-Type:application/json"

但是没有返回有效载荷，而是在日志和控制台中出现了错误：

[2018-12-03 10:23:02,432] [EI-Core] ERROR - RelayUtils Error while building 
Passthrough stream
java.lang.StringIndexOutOfBoundsException: String index out of range: -1
at java.lang.String.substring(Unknown Source)
at org.apache.synapse.commons.builders.XFormURLEncodedBuilder.
extractParametersFromRequest(XFormURLEncodedBuilder.java:223)
at 
org.apache.synapse.commons.builders.XFormURLEncodedBuilder.
processDocumentWrapper(XFormURLEncodedBuilder.java:128)
at org.apache.synapse.commons.builders.XFormURLEncodedBuilder.
processDocument(XFormURLEncodedBuilder.java:52)

我谦虚地请求帮助。预先非常感谢。