hibernate一对多更新跳过uniqueConstraints检查

Question

我正在做一个项目，需要用关键字保存下载文件信息。典型的一对多场景，对吧？一个下载记录到许多下载关键字关系记录。

下面是Download.java的

@Entity
@Table(name = "downloads", catalog = "nbpx")
public class Download extends BaseEntity implements Serializable {
public Integer downloadId;
public String title;
public Set<DownloadKeyword> downloadKeywords = new HashSet<DownloadKeyword>(
0);
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "downloadId", unique = true, nullable = false)
public Integer getDownloadId() {
return downloadId;
}

public void setDownloadId(Integer downloadId) {
this.downloadId = downloadId;
}

public String getTitle() {
return title;
}

public void setTitle(String title) {
this.title = title;
}
@OneToMany(fetch = FetchType.EAGER, mappedBy = "download")
@Cascade({CascadeType.SAVE_UPDATE, CascadeType.DELETE})
public Set<DownloadKeyword> getDownloadKeywords() {
return downloadKeywords;
}
public void setDownloadKeywords(Set<DownloadKeyword> downloadKeywords) {
this.downloadKeywords = downloadKeywords;
}
}

由于我不希望表中有任何重复的下载关键字关系记录，所以我为类设置了一个JPA唯一的Constraints。但我没有使用复合键。这就是DownloadKeyword.java的样子：

@Entity
@Table(name = "downloadkeywords", catalog = "nbpx", uniqueConstraints =
@UniqueConstraint(columnNames = {"keywordId", "downloadId" }))
public class DownloadKeyword extends BaseEntity implements Serializable {
private static final long serialVersionUID = 1L;
public Integer downloadKeywordId;
public Download download;
public Integer keywordId;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "downloadKeywordId", unique = true, nullable = false)
public Integer getDownloadKeywordId() {
return downloadKeywordId;
}
public void setDownloadKeywordId(Integer downloadKeywordId) {
this.downloadKeywordId = downloadKeywordId;
}
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "downloadId", nullable = false, insertable=true)
public Download getDownload() {
return download;
}
public void setDownload(Download download) {
this.download = download;
}
public Integer getKeywordId() {
return keywordId;
}
public void setKeywordId(Integer keywordId) {
this.keywordId = keywordId;
}
}

当我保存下载实体时，我希望看到所有下载关键字关系实体都保存在下载实体保存会话中。并且我需要避免下载关键字关系表中的重复。但每次保存时，关系记录都会直接插入到DB中，而不会使用JPA注释检查重复。

所以我的问题是：当实体在一对多保存或更新会话中保存时，JPA注释的多列uniqueConstraints是否被忽略了？

Answer 1

uniqueConstraints仅用于表生成支持。请参阅文档。

由于您已经在Download类中使用了Set<DownloadKeyword>，因此可以在DownloadKeyword类别中实现hashCode和equals方法(包括主键downloadKeywordId以及keywordId属性)，以实现您想要的功能。

然而，我仍然更喜欢复合键方法。