spring rest lazy loading with hibernate

问题

I am trying to develop spring rest api with hibernate. after searching in google, I have not find solution to lazy loading. I have two entity like below:

University.java

@Entity()
@Table(schema = "core", name = "university")
public class University extends BaseEntity {

    private String uniName;
    private String uniTelephon;


    @LazyCollection(LazyCollectionOption.FALSE)
    @OneToMany(fetch = FetchType.LAZY, mappedBy = "university", cascade = CascadeType.ALL)
    @JsonManagedReference
    private List<Student> students;

//setter and getter
}

Student.java

@Entity
@Table(schema = "core",name = "student")
public class Student {

    @Id
    @GeneratedValue            
    private long id;        

    private String firstName;        

    private String lastName;        

    private String section;

    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name = "UNIVERSITY_ID",nullable = false)
    @JsonBackReference
    private University university;
    // setter and getter
}

any my rest end point

@GetMapping("/list")
public ResponseEntity list() throws Exception {
    // I need to return just Universities But it return it eagerly with their students
    return new ResponseEntity(this.universityService.findAll(), HttpStatus.OK);
}

after calling the rest api, it return university with all students.

There is a way to tell Jackson to not serialize the unfetched objects or collections?

Can somebody help me with a proved solution?

回答1:

Try adding the following dependancy (depending on your hibernate version):

<dependency>
    <groupId>com.fasterxml.jackson.datatype</groupId>
    <artifactId>jackson-datatype-hibernate5</artifactId>
    <version>${jackson.version}</version>
</dependency>

And then (assuming you have a Java based configuration) add the following in the WebMvcConfigurerAdapter class:

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    converters.add(jackson2HttpMessageConverter());
}

@Bean
public MappingJackson2HttpMessageConverter jackson2HttpMessageConverter() {
    MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
    converter.setObjectMapper(this.jacksonBuilder().build());

    return converter;
}

public Jackson2ObjectMapperBuilder jacksonBuilder() {
    Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();

    Hibernate5Module hibernateModule = new Hibernate5Module();

    hibernateModule.configure(Feature.FORCE_LAZY_LOADING, false);

    builder.modules(hibernateModule);

    // Spring MVC default Objectmapper configuration
    builder.featuresToDisable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
    builder.featuresToDisable(MapperFeature.DEFAULT_VIEW_INCLUSION);

    return builder;
}

It should force the Jackson's objectMapper to not fetch lazy-loaded values.

来源：https://stackoverflow.com/questions/46190099/spring-rest-lazy-loading-with-hibernate

标签

json

hibernate

lazy-loading

one-to-many

spring-rest