Spring Boot JPA Lazy Fetch is not working

I have following two domain objects Suggestion and UserProfile

They are mapped with each other in one to many relationship. When I fetch all suggestions using Spring Data JPA, I get corresponding user object with each suggestion objects. This result is observed even when I have set fetch as FetchType.Lazy. Following is my code:

fetch

FetchType.Lazy

Suggestion.java

@Entity
@Table(name="suggestion")
@JsonIgnoreProperties({"suggestionLikes"})
public class Suggestion {

public Suggestion() {
// TODO Auto-generated constructor stub
}

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="suggestion_id")
private Integer suggestionId;

@Column(name="description")
private String description;

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name="suggestion_by")
private UserProfile user;

//getters and setters
}


UserProfile.java

@Entity
@Table(name = "user_master")
@JsonIgnoreProperties({"suggestions", "suggestionLikes"})
public class UserProfile implements Serializable {

/**
*
*/
private static final long serialVersionUID = 7400472171878370L;


public UserProfile() {

}


@Id
@NotNull
@Column(name = "username", length = 55)
private String userName;

@NotNull
@Column(name = "password")
private String password;

@OneToMany(mappedBy = "user", fetch = FetchType.LAZY)
private Set<Suggestion> suggestions;

//getters and setters
}


Following is the service which fetches the records:

@Override
@Transactional(propagation = Propagation.SUPPORTS, readOnly = true)
public List<Suggestion> getAllSuggestion() {
return suggestionRespository.findAll();;
}


SuggestionRepository:

@Repository
public interface SuggestionRespository extends JpaRepository<Suggestion,
Integer> {

public List<Suggestion> findAll();
}


Following is the Application class:

@EnableTransactionManagement
@SpringBootApplication
public class AngularSpringbootApplication {

public static void main(String args) {
SpringApplication.run(AngularSpringbootApplication.class, args);
}
}


application.properties:

spring.datasource.url=jdbc:mysql://localhost:3306/plan_trip
spring.datasource.username=root
spring.datasource.password=root

spring.jpa.properties.hibernate.dialect =
org.hibernate.dialect.MySQL5InnoDBDialect
spring.jpa.hibernate.ddl-auto = update
spring.jackson.serialization.fail-on-empty-beans=false


Response received when getAllSuggestions() is executed:

getAllSuggestions()

[
{
"suggestionId": 2,
"description": "Germanyi!",
"createdBy": "vinit2",
"createdDate": "2018-06-19T10:38:32.000+0000",
"modifiedBy": "vinit2",
"modifiedDate": "2018-06-19T10:38:32.000+0000",
"user": {
"userName": "vinit2",
"password":
"$2a$10$.hP0sQWpl6qqDKiNTkiu0OciQeHRFnkEbEWcDvnv1HY4QCi2tKo.2",
"firstName": "Vinit2",
"lastName": "Divekar2",
"emailAddress": "vinit@gmail.com",
"createdBy": null,
"modifedBy": null,
"createdDate": "2018-06-04",
"modifiedDate": "2018-06-04",
"isActive": "1",
"handler": {},
"hibernateLazyInitializer": {}
}
},
{
"suggestionId": 1,
"description": "Vasai!",
"createdBy": "vinit1",
"createdDate": "2018-06-19T10:37:38.000+0000",
"modifiedBy": "vinit1",
"modifiedDate": "2018-06-19T10:37:38.000+0000",
"user": {
"userName": "vinit1",
"password": "$2a$10$D0RMSTWu03Jw7wC1/zqFxOOjb0Do24o/4mq2PhDhRUyBrs8bdGvUG",
"firstName": "Vinit1",
"lastName": "Divekar1",
"emailAddress": "vinit@gmail.com",
"createdBy": null,
"modifedBy": null,
"createdDate": "2018-06-04",
"modifiedDate": "2018-06-04",
"isActive": "1",
"handler": {},
"hibernateLazyInitializer": {}
}
}


]

Expected response:

[{
"suggestionId": 2,
"description": "Germanyi!",
"createdBy": "vinit2",
"createdDate": "2018-06-19T10:38:32.000+0000",
"modifiedBy": "vinit2",
"modifiedDate": "2018-06-19T10:38:32.000+0000"
},
{
"suggestionId": 1,
"description": "Vasai!",
"createdBy": "vinit1",
"createdDate": "2018-06-19T10:37:38.000+0000",
"modifiedBy": "vinit1",
"modifiedDate": "2018-06-19T10:37:38.000+0000"
}
]


When I have declared FetchType as Lazy, I should not get User objects (in JSON) when I execute findAll()on Suggestion entity.

FetchType

Lazy

findAll()

What am I missing here?

suggestion.getUser().getUsername()

getUser()

getAllSuggestion()

2 Answers
2

when you declare fetch = FetchType.LAZY, it means hibernate create a proxy for this field in runtime. when getter of this field is called. the hibernate executes another select to fetch this object.
in case of your problem getter of "user" field is called by Jackson (if you use rest).
so if you don't want "user", try using a model mapper framework (dozer mapper is a good framework).

You can use @JsonManagedReference & @JsonBackReference to prevent proxy call by jakson. Following code may help you.

@JsonBackReference
@OneToMany(mappedBy = "user", fetch = FetchType.LAZY)
private Set<Suggestion> suggestions;

@JsonManagedReference
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "suggestion_by")
private UserProfile user;


Add the following dependency, change version according to your hibernate

<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-hibernate5</artifactId>
</dependency>


and finally add a new config

@Configuration
public class JacksonConfig {

@Bean
public Jackson2ObjectMapperBuilderCustomizer addCustomBigDecimalDeserialization() {
return new Jackson2ObjectMapperBuilderCustomizer() {
@Override
public void customize(Jackson2ObjectMapperBuilder jacksonObjectMapperBuilder) {
jacksonObjectMapperBuilder.featuresToDisable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
jacksonObjectMapperBuilder.modules(new Hibernate5Module());
}

};
}
}


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