[Java] Getter/Setter naming convention not followed in generated models

Description

When generating a client library (resttemplate), the getters/setters for a field xField are getXField and setXField. As per naming conventions, this is wrong: https://stackoverflow.com/questions/2948083/naming-convention-for-getters-setters-in-java

We found this issue when testing our API - the responses contained "xfield" and "xField" as jackson serializer did not match the field to the getter generated.

Swagger-codegen version

Using swagger codegen 2.3.1.

Swagger declaration file content or url

		  "xField" : {
			"type" : "string"
		  },

Command line used for generation

Using swagger-codegen-maven-plugin. Maven -> Generate sources

Steps to reproduce

Run generate-sources on a specification containing a field name in some object of form "xField" (a single lower case character followed by upper-case). Generated java model contains getXField() when it should be named getxField().

Suggest a fix/enhancement

Enhance whatever code creates getters and setters for fields in the specification.

Reproduce the issue with the provided xField specification using the swagger-codegen-maven-plugin and Maven generate-sources. Trace the Java model generation templates or entry point that produces getters and setters, then verify the generated model uses getxField() and setxField() without creating mismatched Jackson properties.