fixes networknt#509 NPE with oneOf and custom URI Fetcher or Factory (networknt#515)

Author: stevehu

src/main/java/com/networknt/schema/utils/JsonNodeUtil.java

@@ -84,9 +84,11 @@ public static boolean equalsToSchemaType(JsonNode node, JsonType schemaType, Jso
             }
 
             ValidatorState state = (ValidatorState) CollectorContext.getInstance().get(ValidatorState.VALIDATOR_STATE_KEY);
-            if(JsonType.NULL.equals(nodeType) ){
-                if(state.isComplexValidator() && JsonNodeUtil.isNodeNullable(parentSchema.getParentSchema().getSchemaNode(), config) || JsonNodeUtil.isNodeNullable(parentSchema.getSchemaNode()) ){
-                    return true;
+            if(JsonType.NULL.equals(nodeType)) {
+                if(state.isComplexValidator() && parentSchema != null) {
+                    if( parentSchema.getParentSchema() != null && JsonNodeUtil.isNodeNullable(parentSchema.getParentSchema().getSchemaNode(), config) || JsonNodeUtil.isNodeNullable(parentSchema.getSchemaNode()) ) {
+                        return true;
+                    }
                 }
             }
 

src/test/java/com/networknt/schema/CustomUriTest.java

@@ -0,0 +1,64 @@
+package com.networknt.schema;
+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);
+        }
+    }
+}