Hibernate二级缓存不是在每种情况下都使用

Question

使用SpringBoot2、SpringDataJPA和Hibernate。我试图对一些从未更新过的实体使用Hibernate的二级缓存。

在我的例子中，实体DocumentType与其他实体相关，因此当查询一种文档类型时，Hibernate将进行4次sql查询。使用Hibernate二级缓存时，缓存用于某些实体，但仍有一个对数据库的sql查询。我想了解为什么在一种情况下不使用缓存。

这是我的实体的样子：

@Entity
@Table(name = "document_type")
@Cacheable
@org.hibernate.annotations.Cache(usage = CacheConcurrencyStrategy.READ_ONLY)
public class DocumentType {

    @Id
    private Long id;

    @Column
    private String subtypeCode;

    @OneToOne(cascade = {CascadeType.ALL})
    private Translation translation;

    @org.hibernate.annotations.Cache(usage = CacheConcurrencyStrategy.READ_ONLY)
    @ElementCollection(fetch = FetchType.EAGER)
    @CollectionTable(name = "business", joinColumns = @JoinColumn(name = "document_type_id"))
    @Enumerated(EnumType.STRING)
    @Column(name = "business")
    private Set<Business> businesses;

    @ManyToOne(cascade = {CascadeType.ALL})
    @JoinColumn(name = "equivalence_id")
    private Equivalence equivalence;

@Entity
@Table(name = "equivalence")
@Cacheable
@org.hibernate.annotations.Cache(usage = CacheConcurrencyStrategy.READ_ONLY)
public class Equivalence {

    @Id
    private Long id;

    @org.hibernate.annotations.Cache(usage = CacheConcurrencyStrategy.READ_ONLY)
    @OneToMany(mappedBy="equivalence", fetch = FetchType.EAGER)
    private List<DocumentType> documentTypeList;

当我第一次使用此方法获取文档类型时：

@Repository
public interface DocumentTypeRepository extends JpaRepository<DocumentType, Long> {

    DocumentType findBySubtypeCode(String subtypeCode);

我有以下会话指标：

    1704919 nanoseconds spent preparing 4 JDBC statements;
    33284024 nanoseconds spent executing 4 JDBC statements;
    0 nanoseconds spent executing 0 JDBC batches;
    2983589 nanoseconds spent performing 4 L2C puts;
    0 nanoseconds spent performing 0 L2C hits;
    1313315 nanoseconds spent performing 3 L2C misses;

第二次获取的相同文档类型提供：

    27855 nanoseconds spent preparing 1 JDBC statements;
    4348289 nanoseconds spent executing 1 JDBC statements;
    0 nanoseconds spent executing 0 JDBC batches;
    14421 nanoseconds spent performing 1 L2C puts;
    182655 nanoseconds spent performing 3 L2C hits;
    0 nanoseconds spent performing 0 L2C misses;

第二次我希望有0个JDBC语句，但事实并非如此。

Answer 1

二级缓存仅在实体通过其id检索时起作用，无论是使用EntityManager.find（...）还是在JPA需要获取相关实体时。默认情况下，查询结果永远不会缓存。

您需要的是Hibernate查询缓存和org.hibernate.cacheable查询提示。或者，您可以启用Spring缓存，并使用@Cacheable或@CachePlace注释。