NPE with oneOf and custom URI Fetcher or Factory

[chrswk]

Hi

I tried to update my project from 1.0.52 to 1.0.66 and now get a NPE with schemas that use oneOf with a custom URI fetcher. Or at least I think it's related to the URI fetcher, since oneOf with $ref to a definition, etc. still work fine.

java.lang.NullPointerException: Cannot invoke "com.networknt.schema.JsonSchema.getSchemaNode()" because the return value of "com.networknt.schema.JsonSchema.getParentSchema()" is null
    at com.networknt.schema.utils.JsonNodeUtil.equalsToSchemaType(JsonNodeUtil.java:88)
    at com.networknt.schema.TypeValidator.validate(TypeValidator.java:120)
    at com.networknt.schema.JsonSchema.validate(JsonSchema.java:285)
    at com.networknt.schema.JsonSchemaRef.validate(JsonSchemaRef.java:38)
    at com.networknt.schema.RefValidator.validate(RefValidator.java:139)
    at com.networknt.schema.JsonSchema.validate(JsonSchema.java:285)
    at com.networknt.schema.OneOfValidator.validate(OneOfValidator.java:160)
    at com.networknt.schema.JsonSchema.validate(JsonSchema.java:285)
    at com.networknt.schema.PropertiesValidator.validate(PropertiesValidator.java:68)
    at com.networknt.schema.JsonSchema.validate(JsonSchema.java:285)
    at com.networknt.schema.BaseJsonValidator.validate(BaseJsonValidator.java:114)
    ...

The same code does not produce a NPE with release 1.0.57, so I guess it has something to do with the changes in 1.0.58. Here is a test case to reproduce the issue:

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.base.Charsets;
import com.google.common.io.CharSource;
import com.networknt.schema.JsonSchema;
import com.networknt.schema.JsonSchemaFactory;
import com.networknt.schema.SpecVersion;
import com.networknt.schema.ValidationMessage;
import com.networknt.schema.uri.URIFactory;
import com.networknt.schema.uri.URIFetcher;
import org.junit.jupiter.api.Test;

import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.util.Set;

import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.MatcherAssert.assertThat;

public class CustomUriTest {
    @Test
    public void customUri() throws Exception {
        /* Given */
        final JsonSchemaFactory factory = buildJsonSchemaFactory();
        final JsonSchema schema = factory.getSchema("""
            {
                "$schema": "https://json-schema.org/draft/2019-09/schema",
                "type": "object",
                "additionalProperties": false,
                "properties": {
                    "customAnyOf": {
                        "anyOf": [
                            {"type": "null"},
                            {"$ref": "custom:date"}
                        ]
                    },
                    "customOneOf": {
                        "oneOf": [
                            {"type": "null"},
                            {"$ref": "custom:date"}
                        ]
                    }
                }
            }""");
        final ObjectMapper mapper = new ObjectMapper();
        final JsonNode value = mapper.readTree("""
            {
                "customAnyOf": null,
                "customOneOf": null
            }""");

        /* When */
        final Set<ValidationMessage> errors = schema.validate(value);

        /* Then */
        assertThat(errors.isEmpty(), is(true));
    }

    private JsonSchemaFactory buildJsonSchemaFactory() {
        return JsonSchemaFactory.builder(JsonSchemaFactory.getInstance(SpecVersion.VersionFlag.V201909))
            .uriFetcher(new CustomUriFetcher(), "custom").uriFactory(new CustomUriFactory(), "custom").build();
    }

    private static class CustomUriFetcher implements URIFetcher {
        private static final String SCHEMA = """
            {"$schema": "https://json-schema.org/draft/2019-09/schema","$id":"custom:date","type":"string","format":"date"}""";

        @Override
        public InputStream fetch(final URI uri) throws IOException {
            return CharSource.wrap(SCHEMA).asByteSource(Charsets.UTF_8).openStream();
        }
    }

    private static class CustomUriFactory implements URIFactory {
        @Override
        public URI create(final String uri) {
            return URI.create(uri);
        }

        @Override
        public URI create(final URI baseURI, final String segment) {
            return baseURI.resolve(segment);
        }
    }
}

anyOf is just included here because I was interested to know if it's affected and the answer is no.

Thanks
Chris

[stevehu]

@chrswk Thanks a lot for your help. I am on it.

[stevehu]

@chrswk I am getting a hard time making your test case works in the project with some syntax error. I am wondering if you could submit a PR into the project with your test case above? Thanks.

[chrswk]

@stevehu Sorry, I'm used to text blocks now. 😆 Here's a version without them and I also removed Guava specific classes.

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.networknt.schema.JsonSchema;
import com.networknt.schema.JsonSchemaFactory;
import com.networknt.schema.SpecVersion;
import com.networknt.schema.ValidationMessage;
import com.networknt.schema.uri.URIFactory;
import com.networknt.schema.uri.URIFetcher;
import org.junit.jupiter.api.Test;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.nio.charset.StandardCharsets;
import java.util.Set;

import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.MatcherAssert.assertThat;

public class CustomUriTest {
    @Test
    public void customUri() throws Exception {
        /* Given */
        final JsonSchemaFactory factory = buildJsonSchemaFactory();
        final JsonSchema schema = factory.getSchema(
            "{\"$schema\": \"https://json-schema.org/draft/2019-09/schema\",\"type\": \"object\",\"additionalProperties\": false,\"properties\": {\"customAnyOf\": {\"anyOf\": [{\"type\": \"null\"},{\"$ref\": \"custom:date\"}]},\"customOneOf\": {\"oneOf\": [{\"type\": \"null\"},{\"$ref\": \"custom:date\"}]}}}");
        final ObjectMapper mapper = new ObjectMapper();
        final JsonNode value = mapper.readTree("{\"customAnyOf\": null,\"customOneOf\": null}");

        /* When */
        final Set<ValidationMessage> errors = schema.validate(value);

        /* Then */
        assertThat(errors.isEmpty(), is(true));
    }

    private JsonSchemaFactory buildJsonSchemaFactory() {
        return JsonSchemaFactory.builder(JsonSchemaFactory.getInstance(SpecVersion.VersionFlag.V201909))
            .uriFetcher(new CustomUriFetcher(), "custom").uriFactory(new CustomUriFactory(), "custom").build();
    }

    private static class CustomUriFetcher implements URIFetcher {
        private static final String SCHEMA = "{\"$schema\": \"https://json-schema.org/draft/2019-09/schema\",\"$id\":\"custom:date\",\"type\":\"string\",\"format\":\"date\"}";

        @Override
        public InputStream fetch(final URI uri) throws IOException {
            return new ByteArrayInputStream(SCHEMA.getBytes(StandardCharsets.UTF_8));
        }
    }

    private static class CustomUriFactory implements URIFactory {
        @Override
        public URI create(final String uri) {
            return URI.create(uri);
        }

        @Override
        public URI create(final URI baseURI, final String segment) {
            return baseURI.resolve(segment);
        }
    }
}