Allow language generators to supply a custom ExampleGenerator via CodegenModelFactory

Description

DefaultCodegen hard codes instantiation of ExampleGenerator which currently generates examples which differ from Swagger UI (i.e. uses "aeiou" for strings instead of "string", etc.)

Swagger-codegen version

2.2.3

Swagger declaration file content or url

http://petstore.swagger.io/v2/swagger.json

Command line used for generation

java -jar swagger-codegen-cli.jar generate -l html -i http://petstore.swagger.io/v2/swagger.json -o /tmp/swagger-codegen

Steps to reproduce

Using http://petstore.swagger.io/v2/swagger.json
generated examples look like:

[ {
  "photoUrls" : [ "aeiou" ],
  "name" : "doggie",
  "id" : 9,
  "category" : {
    "name" : "aeiou",
    "id" : 5
  },
  "tags" : [ {
    "name" : "aeiou",
    "id" : 9
  } ],
  "status" : "available"
} ]

Related issues

Suggest a Fix

In CodegenModelType, add EXAMPLE(ExampleGenerator.class);
and either an abstract interface for it, or let that be a base class.

In DefaultCodegen and others, use CodegenModelFactory.newInstance(EXAMPLE)
rather than hard-code the constructor call.

I also suggest refactoring some of the code in ExampleGenerator so the values (as strings)
can be reused in XmlExampleGenerator

Start by reading CodegenModelFactory, CodegenModelType, DefaultCodegen, and ExampleGenerator to trace where the example generator is instantiated. Run the documented Java CLI generation command against the petstore specification and compare the generated examples with the expected values. Done means language generators can supply a custom ExampleGenerator without hard-coded construction, while preserving reuse with XmlExampleGenerator.