Thursday, December 22, 2011

Fix Jackson/JAXB JSON Serialization Problem with Spring Data Neo4j @NodeEntity Objects

Spring Data Neo4j @NodeEntity-annotated objects are proxy-enriched by Spring Data Neo4j aspects using AspectJ. There are times we want to expose these objects via JAX-RS REST API or JAX-WS / SOAP web services and then (by default) we will have problems.

The error stacktrace messages (here using JBoss AS 7.0.2) are along the lines of:

HTTP Status 500 - org.codehaus.jackson.map.JsonMappingException: No serializer found for class org.neo4j.graphdb.DynamicRelationshipType and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: com.satukancinta.domain.User["enjoyActivities"]->org.springframework.data.neo4j.fieldaccess.ManagedFieldAccessorSet[0]->com.satukancinta.domain.Activity["persistentState"]->org.neo4j.rest.graphdb.entity.RestNode["relationships"]->org.neo4j.rest.graphdb.entity.RestRelationship["type"])


type Status report

message org.codehaus.jackson.map.JsonMappingException: No serializer found for class org.neo4j.graphdb.DynamicRelationshipType and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: com.satukancinta.domain.User["enjoyActivities"]->org.springframework.data.neo4j.fieldaccess.ManagedFieldAccessorSet[0]->com.satukancinta.domain.Activity["persistentState"]->org.neo4j.rest.graphdb.entity.RestNode["relationships"]->org.neo4j.rest.graphdb.entity.RestRelationship["type"])

description The server encountered an internal error (org.codehaus.jackson.map.JsonMappingException: No serializer found for class org.neo4j.graphdb.DynamicRelationshipType and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: com.satukancinta.domain.User["enjoyActivities"]->org.springframework.data.neo4j.fieldaccess.ManagedFieldAccessorSet[0]->com.satukancinta.domain.Activity["persistentState"]->org.neo4j.rest.graphdb.entity.RestNode["relationships"]->org.neo4j.rest.graphdb.entity.RestRelationship["type"])) that prevented it from fulfilling this request.

To solve this problem, annotate your entity class with @JsonAutoDetect(JsonMethod.NONE) :

import org.codehaus.jackson.annotate.JsonAutoDetect;

import org.codehaus.jackson.annotate.JsonMethod;

import org.codehaus.jackson.annotate.JsonProperty;


@NodeEntity @JsonAutoDetect(JsonMethod.NONE)

public class User implements NodeBacked {

then manually annotate each property you want to serialize with @JsonProperty :

@JsonProperty

public String getName() {

return name;

}

Now the JAX-RS Application works as intended and everybody is happy. :-) There's also a StackOverflow thread that discusses this problem.

To learn more about Java Web Development using Java EE 6, I highly recommend The Java EE 6 Tutorial: Basic Concepts (4th Edition) (Java Series) by Eric Jendrock, Ian Evans, Devika Gollapudi and Kim Haase.