spring休眠延迟加载与休眠 [英] spring rest lazy loading with hibernate

问题描述

我试图用hibernate开发spring rest api。
在谷歌搜索后，我还没有找到解决方案来延迟加载。
我有两个实体，如下所示：

University.java

 <$ c 
 @Table（schema =core，name =university）
 public class大学扩展BaseEntity {
 
 private String uniName; 
 private String uniTelephon; 
 
 
 @LazyCollection（LazyCollectionOption.FALSE）
 @OneToMany（fetch = FetchType.LAZY，mappedBy =university，cascade = CascadeType.ALL）
 @JsonManagedReference 
私人列表<学生>学生们; 
 
 // setter和getter 
} 
  

Student.java

  @Entity 
 @Table（schema =core，name =student）
 public class Student {
 
 @Id 
 @GeneratedValue 
私人长ID; 
 
 private String firstName; 
 
私人字符串姓氏; 
 
私有字符串部分; 
 
 @ManyToOne（fetch = FetchType.LAZY）
 @JoinColumn（name =UNIVERSITY_ID，nullable = false）
 @JsonBackReference 
私立大学; 
 // setter and getter 
} 
  

任何我的休息结束点

  @GetMapping（/ list）
 public ResponseEntity list（）抛出异常{
 //我需要只返回大学但它返回它热烈地与他们的学生
返回新的ResponseEntity（this.universityService.findAll（），HttpStatus.OK）; 
} 
  

在调用其余api后，它会让所有学生返回大学。

有没有办法告诉杰克逊不要序列化未提取的对象或集合？

有人可以帮助我证明解决方案？

解决方案

尝试添加以下依赖项（取决于您的hibernate版本）：

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

然后（假设您有基于Java的配置）在WebMvcConfigurerAdapter类中添加以下内容：

  @Override 
 public void configureMessageConverters（List< HttpMessageConverter<>>转换器）{
转换器。添加（jackson2HttpMessageConverter（））; 
} 
 
 @Bean 
 public MappingJackson2HttpMessageConverter jackson2HttpMessageConverter（）{
 MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter（）; 
 converter.setObjectMapper（this.jacksonBuilder（）。build（））; 
 
返回转换器; 
} 
 
 public Jackson2ObjectMapperBuilder jacksonBuilder（）{
 Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder（）; 
 
 Hibernate5Module hibernateModule = new Hibernate5Module（）; 
 
 hibernateModule.configure（Feature.FORCE_LAZY_LOADING，false）; 
 
 builder.modules（hibernateModule）; 
 
 // Spring MVC默认的Objectmapper配置
 builder.featuresToDisable（DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES）; 
 builder.featuresToDisable（MapperFeature.DEFAULT_VIEW_INCLUSION）; 
 
回报建造者; 
} 
  

它应该强制Jackson的objectMapper不读取延迟加载的值。

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?

解决方案

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.

这篇关于spring休眠延迟加载与休眠的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！