`java.lang.NullPointerException` in `ObjectArraySerializer.acceptJsonFormatVisitor()` for array value with `@JsonValue`

[vdemay]

I'm using jackson 2.9.1

I'm trying to get JSON schema as following :

import org.junit.Test;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonRootName;
import com.fasterxml.jackson.annotation.JsonValue;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.module.jsonSchema.JsonSchema;
import com.fasterxml.jackson.module.jsonSchema.factories.SchemaFactoryWrapper;

public class SchemaGenerationTest {

    public static class Item {
        public String test;
    }

    @JsonRootName("root")
    public static class RootName {
        public Item[] items;

        @JsonCreator
        public RootName(Item[] queries) {
            this.items = items;
        }

        @JsonValue
        public Item[] getItems() {
            return items;
        }
    }

    /**
     * This throws an NPE :
     *
     * java.lang.NullPointerException
     *   at com.fasterxml.jackson.databind.ser.std.ObjectArraySerializer.acceptJsonFormatVisitor(ObjectArraySerializer.java:316)
     *   at com.fasterxml.jackson.databind.ser.std.JsonValueSerializer.acceptJsonFormatVisitor(JsonValueSerializer.java:265)
     *   at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.acceptJsonFormatVisitor(DefaultSerializerProvider.java:566)
     *   at com.fasterxml.jackson.databind.ObjectMapper.acceptJsonFormatVisitor(ObjectMapper.java:3862)
     */
    @Test
    public void testSchema() throws Exception {
        ObjectMapper mapper = new ObjectMapper();
        JavaType type = mapper.constructType(RootName.class);

        SchemaFactoryWrapper visitor = new SchemaFactoryWrapper();
        mapper.acceptJsonFormatVisitor(type, visitor);
        JsonSchema jsonSchema = visitor.finalSchema();
        try {
            System.out.println(mapper
                    .writerWithDefaultPrettyPrinter().writeValueAsString(jsonSchema));
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
    }
}

But when I'm running the test I get this exception:

java.lang.NullPointerException
	at com.fasterxml.jackson.databind.ser.std.ObjectArraySerializer.acceptJsonFormatVisitor(ObjectArraySerializer.java:316)
	at com.fasterxml.jackson.databind.ser.std.JsonValueSerializer.acceptJsonFormatVisitor(JsonValueSerializer.java:265)
	at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.acceptJsonFormatVisitor(DefaultSerializerProvider.java:566)
	at com.fasterxml.jackson.databind.ObjectMapper.acceptJsonFormatVisitor(ObjectMapper.java:3862)

I'm suspecting JsonValueSerializer#acceptJsonFormatVisitor.
It returns ser.acceptJsonFormatVisitor(visitor, null); leading to the NPE in ObjectArraySerializer

[cowtowncoder]

Thank you for reporting this. I'll see where the issue lies: some of null checks are required, others shouldn't be...