Hibernate通过在ManyToMany关联上将完全限定类名添加到属性名来失败

Question

我正在尝试使用ManyToMany关联将两个对象相互映射,但出于某种原因,当我使用mappedBy属性时,hibernate似乎对我正在映射的内容感到困惑.关于我的映射唯一奇怪的是,关联不是在其中一个条目中的主键字段上完成的(尽管该字段是唯一的).

表格是:

Sequence (
  id NUMBER,
  reference VARCHAR,
)

Project (
  id NUMBER
)

Sequence_Project (
  proj_id number references Project(id),
  reference varchar references Sequence(reference)
)

对象看起来像(注释在getter上,将它们放在字段上以缩小一点):

class Sequence {
   @Id
   private int id;

   private String reference;

   @ManyToMany(mappedBy="sequences")
   private List<Project> projects;
}

而拥有方:

class Project {
    @Id
    private int id;

    @ManyToMany
    @JoinTable(name="sequence_project",
               joinColumns=@JoinColumn(name="id"),
               inverseJoinColumns=@JoinColumn(name="reference", 
                                     referencedColumnName="reference"))
    private List<Sequence> sequences;
}

这与MappingException失败:

在实体[test.local.entities.Project]上找不到property-ref [_test_local_entities_Project_sequences]

它似乎奇怪地预先填充了完全限定的类名,除以下划线.我怎样才能避免这种情况发生？

编辑:我多玩了一下这个.更改mappedBy属性的名称会引发另一个异常,即:

org.hibernate.AnnotationException:mappedBy引用未知的目标实体属性:test.local.entities.Project.sequences

因此注释正在正确处理,但不知何故,属性引用未正确添加到Hibernate的内部配置中.

Answer 1

我已经完成了你的问题提出的相同场景。而且，正如预期的那样，我得到了同样的例外。正如补充任务一样，我完成了相同的场景，但通过使用非主键作为连接列（例如引用）进行一对多多对一。我现在明白了

secondaryTable JoinColumn 不能引用非主键

嗯，这会是一个错误吗？？？嗯，是的（你的解决方法工作正常（+1））。如果要使用非主键作为主键，则必须确保它是唯一的。也许这可以解释为什么Hibernate不允许使用非主键作为主键（不知情的用户可能会得到意想不到的行为）。

如果你想使用相同的映射，你可以将你的 @ManyToMany 关系拆分为 @OneToMany-ManyToOne通过使用封装，你不需要担心你加入的类

项目

@Entity
public class Project implements Serializable {

    @Id
    @GeneratedValue
    private Integer id;

    @OneToMany(mappedBy="project")
    private List<ProjectSequence> projectSequenceList = new ArrayList<ProjectSequence>();

    @Transient
    private List<Sequence> sequenceList = null;

    // getters and setters

    public void addSequence(Sequence sequence) {
        projectSequenceList.add(new ProjectSequence(new ProjectSequence.ProjectSequenceId(id, sequence.getReference())));
    }

    public List<Sequence> getSequenceList() {
        if(sequenceList != null)
            return sequenceList;

        sequenceList = new ArrayList<Sequence>();
        for (ProjectSequence projectSequence : projectSequenceList)
            sequenceList.add(projectSequence.getSequence());

        return sequenceList;
    }

}

顺序

@Entity
public class Sequence implements Serializable {

    @Id
    private Integer id;
    private String reference;

    @OneToMany(mappedBy="sequence")
    private List<ProjectSequence> projectSequenceList = new ArrayList<ProjectSequence>();

    @Transient
    private List<Project> projectList = null;

    // getters and setters

    public void addProject(Project project) {
        projectSequenceList.add(new ProjectSequence(new ProjectSequence.ProjectSequenceId(project.getId(), reference)));
    }

    public List<Project> getProjectList() {
        if(projectList != null)
            return projectList;

        projectList = new ArrayList<Project>();
        for (ProjectSequence projectSequence : projectSequenceList)
            projectList.add(projectSequence.getProject());

        return projectList;
    }

}

项目序列

@Entity
public class ProjectSequence {

    @EmbeddedId
    private ProjectSequenceId projectSequenceId;

    @ManyToOne
    @JoinColumn(name="ID", insertable=false, updatable=false)
    private Project project;

    @ManyToOne
    @JoinColumn(name="REFERENCE", referencedColumnName="REFERENCE", insertable=false, updatable=false)
    private Sequence sequence;

    public ProjectSequence() {}
    public ProjectSequence(ProjectSequenceId projectSequenceId) {
        this.projectSequenceId = projectSequenceId;
    }

    // getters and setters

    @Embeddable
    public static class ProjectSequenceId implements Serializable {

        @Column(name="ID", updatable=false)
        private Integer projectId;

        @Column(name="REFERENCE", updatable=false)
        private String reference;

        public ProjectSequenceId() {}
        public ProjectSequenceId(Integer projectId, String reference) {
            this.projectId = projectId;
            this.reference = reference;
        }

        @Override
        public boolean equals(Object o) {
            if (!(o instanceof ProjectSequenceId))
                return false;

            final ProjectSequenceId other = (ProjectSequenceId) o;
            return new EqualsBuilder().append(getProjectId(), other.getProjectId())
                                      .append(getReference(), other.getReference())
                                      .isEquals();
        }

        @Override
        public int hashCode() {
            return new HashCodeBuilder().append(getProjectId())
                                        .append(getReference())
                                        .hashCode();
        }

    }

}