Strange Jackson exception being thrown when serializing Hibernate object

Jackson is throwing a weird exception that I don't know how to fix. I'm using Spring, Hibernate and Jackson.

I have already considered that lazy-loading is causing the problem, but I have taken measures to tell Jackson to NOT process various properties as follows:

@JsonIgnoreProperties({ "sentMessages", "receivedMessages", "educationFacility" })
public class Director extends UserAccount implements EducationFacilityUser {
   ....
}

I have done the same thing for all the other UserAccount subclasses as well.

Here's the exception being thrown:

org.codehaus.jackson.map.JsonMappingException: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: java.util.ArrayList[46]->jobprep.domain.educationfacility.Director_$$_javassist_2["handler"])
    at org.codehaus.jackson.map.ser.StdSerializerProvider$1.serialize(StdSerializerProvider.java:62)
    at org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:268)
    at org.codehaus.jackson.map.ser.BeanSerializer.serializeFields(BeanSerializer.java:146)
    at org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:118)
    at org.codehaus.jackson.map.ser.ContainerSerializers$IndexedListSerializer.serializeContents(ContainerSerializers.java:236)
    at org.codehaus.jackson.map.ser.ContainerSerializers$IndexedListSerializer.serializeContents(ContainerSerializers.java:189)
    at org.codehaus.jackson.map.ser.ContainerSerializers$AsArraySerializer.serialize(ContainerSerializers.java:111)
    at org.codehaus.jackson.map.ser.StdSerializerProvider._serializeValue(StdSerializerProvider.java:296)
    at org.codehaus.jackson.map.ser.StdSerializerProvider.serializeValue(StdSerializerProvider.java:224)
    at org.codehaus.jackson.map.ObjectMapper.writeValue(ObjectMapper.java:925)
    at org.springframework.http.converter.json.MappingJacksonHttpMessageConverter.writeInternal(MappingJacksonHttpMessageConverter.java:153)

Suggestions on how I can get more info to see what's causing this? Anyone know how to fix it?

EDIT: I discovered that getHander() and other get*() methods exist on the proxy object. GRR!! Is there any way I can tell Jackson to not process anything on the proxy, or am I sol? This is really weird because the method that spits out the JSON only crashes under certain circumstances, not all the time. Nonetheless, it's due to the get*() methods on the proxy object.

Aside: Proxies are evil. They disrupt Jackson, equals() and many other parts of regular Java programming. I am tempted to ditch Hibernate altogether :/

I had a similar problem with lazy loading via the hibernate proxy object. Got around it by annotating the class having lazyloaded private properties with:

@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})

I assume you can add the properties on your proxy object that breaks the JSON serialization to that annotation.

Avoid Jackson serialization on non fetched lazy objects

It's not ideal, but you could disable Jackson's auto-discovery of JSON properties, using @JsonAutoDetect at the class level. This would prevent it from trying to handle the Javassist stuff (and failing).

This means that you then have to annotate each getter manually (with @JsonProperty), but that's not necessarily a bad thing, since it keeps things explicit.

i got the same error, but with no relation to Hibernate. I got scared here from all frightening suggestions, which i guess relevant in case of Hibernate and lazy loading... However, in my case i got the error since in an inner class i had no getters/setters, so the BeanSerializer could not serialize the data...

Adding getters & setters resolved the problem.

For what it's worth, there is Jackson Hibernate module project that just started, and which should solve this problem and hopefully others as well. Project is related to Jackson project, although not part of core source. This is mostly to allow simpler release process; it will require Jackson 1.7 as that's when Module API is being introduced.

I had the same problem. See if you are using hibernatesession.load(). If so, try converting to hibernatesession.get(). This solved my problem.