- @Entity
當Class被標識為@Entity，代表這個Class可以被persist至DB，而該Class中的Field除特別以@Transient標記外皆預定會被儲存。 - @Id
每個Entity都需要ID做為識別的基準，產生ID的方式由@GeneratedValue來決定
@GeneratedValue
strategy => GenerationType:AUTO, TABLE, SEQUENCE, IDENTITY
GenerationType.AUTO 雖然方便，但建議僅供開發或Prototyping使用
GenerationType.TABLE 再利用@TableGenerator來指定記錄key的Table相關資料
GenerationType.SEQUENCE 部份DB支援Sequence, 利用DB的Sequence功能，也可以使用@SequenceGenerator來指定Sequence相關資料.
GenerationType.IDENTITY 部份DB支援identity column，這方式有個缺點，就是ID一定要在Insert之後才能確認。 - @Access
指出JPA存取Field的方式
AccessType.FIELD: 利用refection存取Field，無視getter跟setter，但是field的visibility不得定為public。例如：＠Id private int id;
AccessType.PROPERTY: 利用getter跟setter來存取field，但getter/setter的visibility一定要定為public或protected。例如：@public int getId() { return id; } - @Transient
表示該field不會被persist - @Table
提供Table name及所屬schema或catalog name - @Column
指定所存的Column Name - @Enumerated
記錄enum所用，ORDINAL用數字而STRING則以文字記錄該property.
EnumType.ORDINAL, EnumType.STRING - @Temporal
記錄時間用如java.util.Date、java.util.Calendar所用，如果是javax.sql.Date之類的就不用多費心了。
DATE, TIME, TIMESTAMP - @Basic
可以指定Fetch的方式，利用FetchType.LAZY可減少不必要的Query
FetchType.LAZY FetchType.EAGER - @Lob
CLOB char[] or BLOB byte[]
12 4月 2010
JPA2(1)--Basic Annotation
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