我正在一个项目中,我需要保存带有关键字的下载文件信息。
典型的一对多方案,对不对?一个下载记录到许多下载-关键字关系记录。
所以这是Download.java的样子
@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;
}
}
由于我不希望表中存在任何重复的下载关键字关系记录,因此我为该类设置了JPA唯一约束。但是我没有使用复合键。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;
}
}
保存下载实体时,我希望看到所有的下载关键字关系实体都保存在下载实体保存会话中。而且我需要避免在下载关键字关系表中重复。但是,每次保存时,关系记录都直接插入到DB中,而无需检查带有JPA批注的重复项。
所以这是我的问题: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?
最佳答案
uniqueConstraints仅用于表生成支持。
请参见documentation。
由于您已经在Download类中使用了Set<DownloadKeyword>
-您可以在DownloadKeyword类中实现hashCode和equals方法(包括主键downloadKeywordId和keywordId属性)以完成所需的操作。
但是,我仍然希望使用复合密钥方法。