Hibernate4Module causes NullPointerException when @OneToMany map is encountered

[cowtowncoder]

(moved from https://jira.codehaus.org/browse/JACKSON-906 reported by Patrick Haas)

---

Serialization results in a NullPointerException when a Map field is annotated with @OneToMany and the Hibernate4Module is loaded.

Tested with jackson-datatype-hibernate4-2.2.2.jar

[cowtowncoder]

import static org.junit.Assert.*;
import java.util.LinkedHashMap;
import java.util.Map;
import javax.persistence.OneToMany;
import org.junit.Test;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.hibernate4.Hibernate4Module;

public class JacksonHibernateModuleTest {

private static final String EXPECTED_JSON = "{\"m\":{\"A\":\"A\"}}";

@Test
public void testMap() throws Exception {
    Y object = new Y();
    object.m.put("A", "A");

    assertEquals(EXPECTED_JSON, mapWithoutHibernateModule(object));
    assertEquals(EXPECTED_JSON, mapWithHibernateModule(object));
}

@Test
public void testMapWithOneToMany() throws Exception {
    X object = new X();
    object.m.put("A", "A");

    assertEquals(EXPECTED_JSON, mapWithoutHibernateModule(object));
    assertEquals(EXPECTED_JSON, mapWithHibernateModule(object));
}


private String mapWithHibernateModule(Object object) throws JsonProcessingException {
    return new ObjectMapper().registerModule(new Hibernate4Module()).writeValueAsString(object);
}

private String mapWithoutHibernateModule(Object object) throws JsonProcessingException {
    return new ObjectMapper().writeValueAsString(object);
}

private static final class X {
    @OneToMany
    public final Map<String, String> m = new LinkedHashMap<String, String>();
}

private static final class Y {
    public final Map<String, String> m = new LinkedHashMap<String, String>();
}
}

[cowtowncoder]

Fixed for 2.3.0 (and 2.2.4, if that ever gets released).