The translator sets the content type by default: https://github.com/teiid/teiid/blob/06b9828a3fd6dafa358ff93f0a4803e69a3bfdf4/connectors/odata/translator-odata/src/main/java/org/teiid/translator/odata/BaseQueryExecution.java#L227
This seems to be handled differently by CXF and spring webservice sources. A user is reporting that a simple request (without a payload) succeeds with CXF, but fails with spring.
the translator throw org.springframework.web.client.HttpClientErrorException$UnsupportedMediaType: 415 Unsupported Media Type by executing Query, for example "Select * from categories", by jdbc client such as SQuirrel.