MappingJackson2HttpMessageConverter and MappingJacksonHttpMessageConverter should use configured JSON prefix instead of hardcoded value.

Thanks for adding the ability to configure a custom JSON prefix in MappingJackson(2)HttpMessageConverter in SPR-10627: https://jira.springsource.org/browse/SPR-10627.

Unfortunately the custom value is not used when writing out the JSON, instead the hardcoded string "{} && " is used.

This line (see GitHub links below) should instead read:

jsonGenerator.writeRaw(jsonPrefix);

Links (to v3.2.4.RELEASE code):

MappingJackson2HttpMessageConverter: https://github.com/SpringSource/spring-framework/blob/v3.2.4.RELEASE/spring-web/src/main/java/org/springframework/http/converter/json/MappingJackson2HttpMessageConverter.java#L202

MappingJacksonHttpMessageConverter: https://github.com/SpringSource/spring-framework/blob/v3.2.4.RELEASE/spring-web/src/main/java/org/springframework/http/converter/json/MappingJacksonHttpMessageConverter.java#L199