关于 java:ConverterNotFoundException 在 spring 集成中将字符串对象发送到 rest 服务

<int–http:outbound–gateway id="xtifygateway"
        request–channel="requestchannel" request–factory="requestFactory"
        url="${xtifyUrl}" http–method="POST">
</int–http:outbound–gateway>

<int:header–enricher input–channel="requestchannel">
    <int:header name="Content-Type" value="application/json"/>
</int:header–enricher>

public interface RequestGateway
{
    ResponseEntity< ? > pushNotification(String xtifyRequest);
}

  ObjectMapper objectMapper = new ObjectMapper();
  try {
      String xtifyJson = objectMapper.writeValueAsString(xtifyRequest);
  }

     <xsd:attribute name="expected-response-type" type="xsd:string">
        <xsd:annotation>
            <xsd:documentation>
                The expected type to which the response body should be converted.
                Default is ‘org.springframework.http.ResponseEntity’.
                This attribute cannot be provided if expected–response–type–expression has a value
            </xsd:documentation>
            <xsd:appinfo>
                <tool:annotation kind="direct">
                    <tool:expected–type type="java.lang.Class" />
                </tool:annotation>
            </xsd:appinfo>
        </xsd:annotation>
    </xsd:attribute>