java - 使用一对一关系时如何修复 "A different object with the same identifier value was already associated with the session"错误

Question

我正在尝试在两个实体之间创建一对一的关系:

• 项目实体

  @Entity
  @Table(name = "projects")
  public class Project {
  
      @Id
      @GeneratedValue(strategy = GenerationType.IDENTITY)
      private Long id;
  
      @OneToOne(mappedBy = "project", cascade = CascadeType.ALL, optional = false, fetch = FetchType.LAZY)
      private CrawlerConfiguration crawlerConfiguration;
  
      // Getters and setters ...
  
      public void setCrawlerConfiguration(CrawlerConfiguration crawlerConfiguration) {
          if (crawlerConfiguration == null) {
              if (this.crawlerConfiguration != null) {
                  this.crawlerConfiguration.setProject(null);
              }
          } else {
              crawlerConfiguration.setProject(this);
          }
  
          this.crawlerConfiguration = crawlerConfiguration;
      }
  

• CrawlerConfiguration 实体

  @Entity
  @Table(name = "crawler_configurations")
  public class CrawlerConfiguration {
  
      @Id
      private Long id;
  
      @OneToOne(fetch = FetchType.LAZY)
      @MapsId
      private Project project;
  
      // Getters and setters ...
  }
  

当用户创建新项目时，还应该为该项目创建配置。

@Transactional
public Project createProject(Project project) {
    project.setCrawlerConfiguration(new CrawlerConfiguration());
    return projectRepository.save(project);
}

不幸的是，它会导致以下异常:

javax.persistence.EntityExistsException: A different object with the same identifier value was already associated with the session : [com.github.peterbencze.serritorcloud.model.entity.CrawlerConfiguration#1]

创建实体的正确方法是什么？

Answer 1

试试这个

 @OneToOne(fetch = FetchType.LAZY)
 @PrimaryKeyJoinColumn
 private Project project;

在您的 CrawlerConfiguration 实体中