Converting Java class structure to yml file

Question

I have a complex model class in Java that has attributes of different class. I wanted to get the schema of the class in yml format for better readability. I was able get the structure of the class to a JSON file but I feel that yml is less cluttered and easy to ready.

Example From

public class Phone {
    public String name;
    public String number;
}

To

Phone:
    fields:
      name:
        type: String
      number:
        type: String

Answer 1

The Jackson library offers the ability to generate a JSONSchema from a Java class. You should be able to serialize it into a YAML, although I haven't actually tested this part. Here how it might look like :

ObjectMapper m = new ObjectMapper();
SchemaFactoryWrapper visitor = new SchemaFactoryWrapper();
m.acceptJsonFormatVisitor(m.constructType(Phone.class), visitor);
JsonSchema jsonSchema = visitor.finalSchema();

ObjectMapper mapper = new ObjectMapper(new YAMLFactory());
mapper.writeValue(yamlFile, jsonSchema);

You may need this configuration if you use enums

mapper.configure(SerializationConfig.Feature.WRITE_ENUMS_USING_TO_STRING, true);

More details at the github page of the Yaml module and the JSON schema module

Answer 2

From RAM to File

If your use case is to just serialize your existing objects, without reading them first, you might try the approach from this answer using Jackson; it just writes to a file an example object.

// Create an ObjectMapper mapper for YAML
ObjectMapper mapper = new ObjectMapper(new YAMLFactory());

// Write object as YAML file
mapper.writeValue(new File("/path/to/yaml/file"), example);