Jackson exception during serialization

Question

I've faced the problem, which is a little bit close to this issue, but when I've done all the steps, i still have such an exception:

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[0]->com.myPackage.SomeEntity["mainEntity"]->com.myPackage.MainEntity["subentity1"]->com.myPackage.Subentity1_$$_javassist_8["handler"])

here is code with my entities:

@JsonAutoDetect public class MainEntity { private Subentity1 subentity1; private Subentity2 subentity2; @JsonProperty public Subentity1 getSubentity1() { return subentity1; } public void setSubentity1(Subentity1 subentity1) { this.subentity1 = subentity1; } @JsonProperty public Subentity2 getSubentity2() { return subentity2; } public void setSubentity2(Subentity2 subentity2) { this.subentity2 = subentity2; } } @Entity @Table(name = "subentity1") @JsonAutoDetect public class Subentity1 { @Id @Column(name = "subentity1_id") @GeneratedValue private Long id; @Column(name = "name", length = 100) private String name; @JsonIgnore @OneToMany(mappedBy = "subentity1") private List<Subentity2> subentities2; @JsonProperty public Long getId() { return id; } public void setId(Long id) { this.id = id; } @JsonProperty public String getName() { return name; } public void setName(String name) { this.name = name; } //here I didin't add @JsonProperty, cause it leads to cycling during serialization public List<Subentity2> getSubentity2s() { return subentity2s; } public void setSubentity2s(List<Subentity2> subentity2s) { this.subentity2s = subentity2s; } } @Entity @Table(name = "subentity2") @JsonAutoDetect public class Subentity2 { @Id @Column(name = "subentity2_id") @GeneratedValue private Long id; @Column(name = "name", length = 50) private String name; @ManyToOne @JoinColumn(name = "subentity1_id") private Subentity1 subentity1; @JsonProperty public Long getId() { return id; } public void setId(Long id) { this.id = id; } @JsonProperty public String getName() { return name; } public void setName(String name) { this.name = name; } @JsonProperty public Subentity1 getSubentity1() { return subentity1; } public void setSubentity1(Subentity1 subentity1) { this.subentity1 = subentity1; }

here is code of my method for transformation:

 private String toJSON(Object model) { ObjectMapper mapper = new ObjectMapper(); String result = ""; try { result = mapper.writeValueAsString(model); } catch (JsonGenerationException e) { LOG.error(e.getMessage(), e); } catch (JsonMappingException e) { LOG.error(e.getMessage(), e); } catch (IOException e) { LOG.error(e.getMessage(), e); } return result; }

I'll very grateful for any help, pieces of advice or code :)

UPD

alsp, I forgot to add piece of code from my controller:

String result = ""; List<SomeEntity> entities = someEntityService.getAll(); Hibernate.initialize(entities); for (SomeEntity someEntity : entities) { Hibernate.initialize(someEntity.mainEntity()); Hibernate.initialize(someEntity.mainEntity().subentity1()); Hibernate.initialize(someEntity.mainEntity().subentity2()); } result = this.toJSON(entities);

I can't ignore any fields, cause I need them

Are you using Jackson Hibernate module? (github.com/FasterXML/jackson-module-hibernate) — StaxMan
– StaxMan, Commented Nov 20, 2012 at 1:10
Ok. There was an earlier version of the module (that works with 1.9) as well (there's a branch, 1.9.0 version on Maven repo) for what that's worth. — StaxMan
– StaxMan, Commented Nov 21, 2012 at 5:55

hoaz · Accepted Answer · 2012-11-19 15:44:56Z

1

Basically some of your fields are wrapped into lazy hibernate proxies. Call Hibernate.initialize(model) before serializing your object, it will load your lazy collections and references.

But I would not mix database and view models, this is a bad practice. Create set of classes for your restful model and convert database entities to them before serialization.

answered Nov 19, 2012 at 15:44

hoaz

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5 Comments

hoaz Over a year ago

have you tried @JsonIgnoreProperties({"hibernateLazyInitializer", "handler"}) advice from your previous question?

John Smith Over a year ago

the actual problem is that I need all these fields

hoaz Over a year ago

why do you need proxy fields?

John Smith Over a year ago

i think it's rather useless question :) i need them, they are part of main entity and I need them for operation on the client-side

hoaz Over a year ago

handler is not part of your model, it is a field added by Javassist proxy, you don't need it and can ignore

John Smith · Accepted Answer · 2012-11-20 08:24:27Z

I created a Bean with plane fields(String, Boolean, Double, etc.), which are in my classes and made method for transformation

N. berouain · Accepted Answer · 2017-05-03 15:16:26Z

If you are using lazy loading add this

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

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