org.hibernate.LazyInitializationException：无法延迟初始化角色集合：FQPropretyName，无法初始化代理 - 无会话

Posted 2023-02-26

【中文标题】org.hibernate.LazyInitializationException：无法延迟初始化角色集合：FQPropretyName，无法初始化代理 - 无会话

【英文标题】：org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: FQPropretyName, could not initialize proxy - no Session

【发布时间】：2018-02-25 20:16:26

【问题描述】：

我正在尝试使用 SpringBoot、SpringDataJpa 的多对一双向关联以及使用 SpringBootTest 的单元测试。但是，测试失败，堆栈跟踪如下所示。但是我无法找到原因。任何指针都会有所帮助

ManyToOne 双向关联的 Spring Boot JUnit 测试失败。

    @Test
    public void testFindByRegionIdEquals() 
        Region region = regionService.findByRegionIdEquals(1L);
        Region expectedRegion = new Region(1L, "Europe");
        assertThat(region).isNotNull().isEqualTo(expectedRegion);
        assertThat(region.getCountries()).isNotEmpty().doesNotContainNull().size().isEqualTo(8);
    

异常堆栈跟踪

    org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: zikzakjack.domain.Region.countries, could not initialize proxy - no Session
    at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:587)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:204)
    at org.hibernate.collection.internal.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:148)
    at org.hibernate.collection.internal.PersistentSet.isEmpty(PersistentSet.java:149)
    at org.assertj.core.util.IterableUtil.isNullOrEmpty(IterableUtil.java:35)
    at org.assertj.core.internal.Iterables.assertNotEmpty(Iterables.java:152)
    at org.assertj.core.api.AbstractIterableAssert.isNotEmpty(AbstractIterableAssert.java:145)
    at zikzakjack.service.RegionServiceTests.testFindByRegionIdEquals(RegionServiceTests.java:68)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

拥有实体 ManyToOne

@Data
@Entity
@Table(name = "COUNTRIES")
public class Country implements Serializable, Comparable<Country> 

    private static final long serialVersionUID = 1L;

    @Id
    @Column(name = "COUNTRY_ID")
    private String countryId;

    @Column(name = "COUNTRY_NAME")
    private String countryName;

    @ManyToOne
    @JoinColumn(name = "REGION_ID")
    private Region region;

    public Country() 

    

    public Country(String countryId, String countryName, Region region) 
        super();
        this.countryId = countryId;
        this.countryName = countryName;
        this.region = region;
    

*非拥有实体 OneToMany 与 mappedBy *

@Data
@Entity
@Table(name = "REGIONS")
public class Region implements Serializable, Comparable<Region> 

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "REGION_ID")
    private Long regionId;

    @Column(name = "REGION_NAME")
    private String regionName;

    @OneToMany(mappedBy = "region", fetch = FetchType.LAZY)
    private Set<Country> countries = new HashSet<Country>();

    public Region() 
    

    public Region(Long regionId, String regionName) 
        this.regionId = regionId;
        this.regionName = regionName;
    

    public Region(String regionName) 
        this.regionName = regionName;
    

    public void addCountry(Country country) 
        countries.add(country);
        country.setRegion(this);
    

【参考方案1】：

嗯，我从这篇帖子https://***.com/a/38690930/5266568找到了答案

在 application.properties 中添加下面的配置解决了这个问题：

spring.jpa.properties.hibernate.enable_lazy_load_no_trans=true

另一个对我有用的解决方案，但请注意，我仍然需要进一步了解它是如何真正解决问题的

@Transactional 确保该测试方法中的所有方法调用都发生在同一边界内。

    @Test
    @Transactional
    public void testFindByRegionIdEquals() 
        Region region = regionService.findByRegionIdEquals(1L);
        Region expectedRegion = new Region(1L, "Europe");
        assertThat(region).isNotNull().isEqualTo(expectedRegion);
        assertThat(region.getCountries()).isNotEmpty().doesNotContainNull().size().isEqualTo(8);
    

【讨论】：

enable_lazy_load_no_trans 是反模式导致 n+1 问题不要使用它。

是的@YouYou。见vladmihalcea.com/…

谢谢！我测试中的@Transactional 注释解决了我的问题（和你一样的问题）