$ref doesn't work when ref'ed message also has extends

[jmazzitelli]

I have one schema that extends another using $ref like this:

SimpleMessage.schema.json:

{
  "type": "object",
  "extends": {
    "$ref": "AuthMessage.schema.json"
  },
  "javaType": "org.abc.SimpleMessage",
  "additionalProperties": false,
  "properties": {
    "msg": {
      "type": "string"
    }
  },
  "required": ["msg"]
}

AuthMessage.schema.json:

{
  "type": "object",
  "extends": {
    "type": "object",
    "javaType": "org.abc.BasicMessage"
  },
  "javaType": "org.abc.AuthMessage",
  "additionalProperties": false,
  "properties": {
    "username": {
      "type": "string"
    },
    "password": {
      "type": "string"
    }
  }
}

As you see in the AuthMessage schema, I have my own org.abc.BasicMessage class that I want my AuthMessage to extend. I am expecting the generated java class declarations to look like this:

public class SimpleMessage extends AuthMessage { ... }
public class AuthMessage extends BasicMessage { ... }

However, what really happens is they both extend BasicMessage:

public class SimpleMessage extends BasicMessage { ... }
public class AuthMessage extends BasicMessage { ... }

It is quite possible I misunderstand how $ref is to work inside extends, but on its face, this looks like a bug. I have $ref referring to AuthMessage in my SimpleMessage schema, but SimpleMessage doesn't extend AuthMessage - it extends BasicMessage (which only AuthMessage should - SimpleMessage should extend AuthMessage). As it is generated now, SimpleMessage doesn't get any properties from AuthMessage (that is, SimpleMessage doesn't get setUsername() and setPassword() since it doesn't extend AuthMessage).

Hopefully, that made sense.

[joelittlejohn]

I don't seem to be able to replicate this at all, when I try the schemas you have provided, I get:

public class SimpleMessage
    extends AuthMessage

public class AuthMessage
    extends BasicMessage

Is it possible your project hasn't been cleaned and that the generated types are out-of-date and don't match your schema?

[joelittlejohn]

Is it possible that BasicMessage is marked final?

[jmazzitelli]

BasicMessage is abstract.

public abstract class BasicMessage { ... }

Let me try to put together a simple test project so you can replicate. I'll get back to you.

[jmazzitelli]

===UPDATE: SKIP TO THE NEXT COMMENT FOR A SMALLER REPLICATION PROJECT TO USE===
I will try to shrink this down to a minimal project [note: I did, see next comment], but clone this: https://github.com/jmazzitelli/hawkular-bus and build it (without testing to make it go faster): "mvn clean install -DskipTests" and then look at the generated source at "hawkular-bus/hawkular-bus-samples/hawkular-bus-sample-jsonschema/target/java-gen/org/hawkular/bus/sample/msg"

FWIW: here is what BasicMessage looks like:

https://github.com/jmazzitelli/hawkular-bus/blob/master/hawkular-bus-common/src/main/java/org/hawkular/bus/common/BasicMessage.java

[jmazzitelli]

Ok, much smaller replication project.

git clone [email protected]:jmazzitelli/test.git
cd test/jsonschema-issue408
mvn clean install

Look in "target/java-gen/org/abc" and see that AuthMessage.java and SimpleMessage.java both define classes that extend BasicMessage. Here are the schemas used:

https://github.com/jmazzitelli/test/tree/master/jsonschema-issue408/src/main/resources/schema

[jmazzitelli]

Here's another interesting thing - in my small project, comment out the dependency on the hawkular library (the one that pulls in BasicMessage) and run "mvn clean install" again. BasicMessage.java gets generated for you, but yet still both SimpleMessage and AuthMessage extend BasicMessage.

[jmazzitelli]

I think I see the problem, but don't know how to fix.

See org.jsonschema2pojo.rules.ObjectRule.getSuperType():

        if (node.has("extends")) {
            superType = ruleFactory.getSchemaRule().apply(nodeName + "Parent", node.get("extends"), jClassContainer, schema);
        }

This in turn calls org.jsonschema2pojo.rules.SchemaRule.apply():

        if (schemaNode.has("$ref")) {
            schema = ruleFactory.getSchemaStore().create(schema, schemaNode.get("$ref").asText());
            schemaNode = schema.getContent();

            if (schema.isGenerated()) {
                return schema.getJavaType(); // <---------- HERE!!!
            }

As I step through the code, I see this is parsing the SimpleMessage schema, and when it gets here the $ref is referring to AuthMessage.schema.json. SchemaRule will look it up, store AuthMessage schema in the "schema" variable at which point in time schema.getJavaType() returns "BasicMessage" and that is returned as the super type of SimpleMessage. Which is not right. It should be returning "AuthMessage" as the super type.

I am stepping through the source code from version 0.4.14

[joelittlejohn]

Thanks for the detailed report here, it really helped track down this subtle issue. It's dependent on the order in which schemas are read so was difficult to replicate.