How would I reuse definitions from objects?

[digital-h]

Hi,

imagine I have the following 2 classes in one package

package myPackage;

public class Foo {
   public String baz;
}

package myPackage;

public class Bar {
   public Foo foo;
}

and I run the maven-plugin defining the package

<configuration>
    <packageNames>
        <packageName>myPackage</packageName>
    </packageNames>
</configuration>

What currently happens, that two seperate schema are generated for Foo and Bar. But in Bar everything is generated for Foo as well instead of referencing to the Foo-Schema. Is it possible to configure this in a way?

Instead for Bar.schema as it is generated right now

{
  "$schema" : "http://json-schema.org/draft-07/schema#",
  "type" : "object",
  "properties" : {
    "foo" : {
      "type" : "object",
      "properties" : {
        "baz" : {
          "type" : "string"
        }
      },
      "additionalProperties" : false
    }
  },
  "additionalProperties" : false
}

it should become:

{
  "$schema" : "http://json-schema.org/draft-07/schema#",
  "type" : "object",
  "properties" : {
    "foo" : {
      "$ref": "Foo.schema.json",
    }
  },
  "additionalProperties" : false
}

Thanks for your help

[CarstenWickner]

Hi @digital-h,

Fortunately, I already answered a very similar question here: #246 (comment)
That includes a complete code example.

---

More generically speaking: What you ask for requires some custom configuration, as per this FAQ entry:
https://victools.github.io/jsonschema-generator/#how-to-reference-a-separate-schema-file

How to reference a separate schema/file?

By using withCustomDefinitionProvider() – one of the advanced configurations – you can fully control the contents of a type's sub-schema. Simply create a node that only contains your custom/external reference instead of the actual schema. It is recommended to mark the custom definition as "to be inlined", in order to avoid an extra entry in the "definitions"/"$defs".

configBuilder.forTypesInGeneral()
        .withCustomDefinitionProvider((javaType, context) -> {
            if (javaType.getErasedType() != MyExternalType.class) {
                // other types should be treated normally
                return null;
            }
            // define your custom reference value
            String refValue = "./" + javaType.getErasedType().getSimpleName();
            // produce the sub-schema that only contains your custom reference
            ObjectNode customNode = context.getGeneratorConfig().createObjectNode()
                    .put(context.getKeyword(SchemaKeyword.TAG_REF), refValue);
            return new CustomDefinition(customNode,
                    // avoid the creation of a reference to your custom reference schema
                    CustomDefinition.DefinitionType.INLINE,
                    // still allow for collected schema attributes to be added
                    CustomDefinition.AttributeInclusion.YES);
        });

If you want this kind of custom configuration to be applied by the Maven plugin, you'd have to wrap it into a Module and then reference it in your plugin configuration as mentioned here:
https://victools.github.io/jsonschema-generator/#further-configurations-through-modules

You can also group any kind of configuration into a Module of your own and include it via its full class name.
Make sure your custom module is on the classpath (considering the project itself as well as all compile and runtime dependencies) and has a default constructor.

<modules>
    <module>
        <className>com.myOrg.myApp.CustomModule</className>
    </module>
</modules>