1 JPA 批注参考

示例 1-1 @MappedSuperclass

@MappedSuperclass
public class Employee {
@Id protected Integer id;
@Version protected Integer version;
@ManyToOne protected Address address;
...
}

示例 1-2 @AssociationOverride

@Entity@AssociationOverride(name="address", joinColumns=@JoinColumn(name="ADDR_ID"))public class PartTimeEmployee extends Employee {    @Column(name="WAGE")    protected Float hourlyWage;
...
}

示例 1-3 @AssociationOverrides

@Entity
@AssociationOverrides({
@AssociationOverride(name="address", joinColumn=@Column(name="ADDR_ID")),
@AssociationOverride(name="id", joinColumn=@Column(name="PTID"))
})
public class PartTimeEmployee extends Employee {
@Column(name="WAGE")
protected Float hourlyWage;
...
}

示例 1-4 @MappedSuperclass

@MappedSuperclass
public class Employee {
@Id protected Integer id;
@Version protected Integer version;
protected String address;
...
}

示例 1-5 @AttributeOverride

@Entity
@AttributeOverride(name="address", column=@Column(name="ADDR_STRING"))
public class PartTimeEmployee extends Employee {
@Column(name="WAGE")
protected Float hourlyWage;
...
}

示例 1-6 @AttributeOverrides

@Entity
@AttributeOverrides({
@AttributeOverride(name="address", column=@Column(name="ADDR_ID")),
@AttributeOverride(name="id", column=@Column(name="PTID"))
})
public class PartTimeEmployee extends Employee {
@Column(name="WAGE")
protected Float hourlyWage;
public PartTimeEmployee() {
...
}
public Float getHourlyWage() {
...
}
public void setHourlyWage(Float wage) {
...
}
}

示例 1-7 @Basic

@Entity
public class Employee implements Serializable {
...
@Basic(fetch=LAZY)
protected String getName() {
return name;
}
...
}

示例 1-8 @Column

@Entity
@SecondaryTable(name="EMP_HR")
public class Employee implements Serializable {
...
@Column(name="EMP_NUM", table="EMP_HR")
private Long empId;
private String empName;
...
}

示例 1-9 使用 @ColumnResult 的 Order 实体

@SqlResultSetMapping(
name="OrderResults",
entities={
@EntityResult(
entityClass=Order.class,
fields={
@FieldResult(name="id",       column="order_id"),
@FieldResult(name="quantity", column="order_quantity"),
@FieldResult(name="item",     column="order_item")
}
)
},
columns={
@ColumnResult(
name="item_name"
)
}
)
@Entity
public class Order {
@Id
protected int id;
protected long quantity;
protected Item item;
...
}

示例 1-10 Item 实体

@Entity
public class Item {
@Id
protected int id;
protected String name;
...
}

示例 1-11 结合使用 @SqlResultSetMapping 与 @ColumnResult 的原生查询

Query q = entityManager.createNativeQuery(
"SELECT o.id       AS order_id, " +
"o.quantity AS order_quantity, " +
"o.item     AS order_item, " +
"i.name     AS item_name, " +
"FROM Order o, Item i " +
"WHERE (order_quantity > 25) AND (order_item = i.id)",
"OrderResults"
);
List resultList = q.getResultList();
// List of Object arrays:{[Order, "Shoes"], [Order, "Socks"], ...}

示例 1-12 @DiscriminatorColumn 和 @DiscriminatorValue — 根类

@Entity
@Table(name="CUST")
@Inheritance(strategy=SINGLE_TABLE)
@DiscriminatorColumn(name="DISC", discriminatorType=STRING, length=20)
@DiscriminatorValue(value-"CUST")
public class Customer {
...
}

示例 1-13 @DiscriminatorValue — 子类

@Entity
@DiscriminatorValue(value="VIP")
public class ValuedCustomer extends Customer {
...
}

示例 1-14 @DiscriminatorColumn 和 @DiscriminatorValue — 根类

@Entity
@Table(name="CUST")
@Inheritance(strategy=SINGLE_TABLE)
@DiscriminatorColumn(name="DISC", discriminatorType=STRING, length=20)
@DiscriminatorValue(value-"CUST")
public class Customer {
...
}

示例 1-15 @DiscriminatorValue — 子类

@Entity
@DiscriminatorValue(value="VIP")
public class ValuedCustomer extends Customer {
...
}

示例 1-16 @Embeddable

@Embeddable
public class EmploymentPeriod {
java.util.Date startDate;
java.util.Date endDate;
...
}

示例 1-17 @Embedded

@Entity
public class Employee implements Serializable {
...
@Embedded
@AttributeOverrides({
@AttributeOverride(name="startDate", column=@Column("EMP_START")),
@AttributeOverride(name="endDate", column=@Column("EMP_END"))
)
public EmploymentPeriod getEmploymentPeriod() {
...
}
...
}

示例 1-18 可嵌入复合主键类

@Embeddable
public class EmployeePK implements Serializable
{
private String name;
private long id;
public EmployeePK()
{
}
public String getName()
{
return name;
}
public void setName(String name)
{
this.name = name;
}
public long getId()
{
return id;
}
public void setId(long id)
{
this.id = id;
}
public int hashCode()
{
return (int) name.hashCode() + id;
}
public boolean equals(Object obj)
{
if (obj == this) return true;
if (!(obj instanceof EmployeePK)) return false;
if (obj == null) return false;
EmployeePK pk = (EmployeePK) obj;
return pk.id == id && pk.name.equals(name);
}
}

示例 1-19 @EmbeddedId

@Entity
public class Employee implements Serializable
{
EmployeePK primaryKey;
public Employee()
{
}
@EmbeddedId
public EmployeePK getPrimaryKey()
{
return primaryKey;
}
public void setPrimaryKey(EmployeePK pk)
{
primaryKey = pk;
}
...
}

示例 1-20 @Entity

@Entity
public class Employee implements Serializable {
...
}

示例 1-21 @EntityListeners

@Entity
@EntityListeners(value={EmployeePersistListner.class, EmployeeRemoveListener.class})
public class Employee implements Serializable {
...
}

示例 1-22 EmployeePersistListener

public class EmployeePersistListener {
@PrePersist
employeePrePersist(Object employee) {
...
}
...
}

示例 1-23 EmployeeRemoveListener

public class EmployeeRemoveListener {
@PreRemove
@PostRemove
employeePreRemove(Object employee) {
...
}
...
}

示例 1-24 使用 @EntityResult 的 Order 实体

@SqlResultSetMapping(
name="OrderResults",
entities={
@EntityResult(
entityClass=Order.class,
fields={
@FieldResult(name="id",       column="order_id"),
@FieldResult(name="quantity", column="order_quantity"),
@FieldResult(name="item",     column="order_item")
}
),
@EntityResult(
entityClass=Item.class,
fields={
@FieldResult(name="id",       column="item_id"),
@FieldResult(name="name",     column="item_name"),
}
)
}
)
@Entity
public class Order {
@Id
protected int id;
protected long quantity;
protected Item item;
...
}

示例 1-25 Item 实体

@Entity
public class Item {
@Id
protected int id;
protected String name;
...
}

示例 1-26 结合使用 @SqlResultSetMapping 与 @EntityResult 的原生查询

Query q = entityManager.createNativeQuery(
"SELECT o.id       AS order_id, " +
"o.quantity AS order_quantity, " +
"o.item     AS order_item, " +
"i.id       AS item_id, " +
"i.name     AS item_name, " +
"FROM Order o, Item i " +
"WHERE (order_quantity > 25) AND (order_item = i.id)",
"OrderResults"
);
List resultList = q.getResultList();
// List of Object arrays:{[Order, Item], [Order, Item], ...}

示例 1-27 枚举常量

public enum EmployeeStatus {FULL_TIME, PART_TIME, CONTRACT}
public enum SalaryRate {JUNIOR, SENIOR, MANAGER, EXECUTIVE}

示例 1-28 @Enumerated

@Entity
public class Employee {
...
public EmployeeStatus getStatus() {
...
}
@Enumerated(STRING)
public SalaryRate getPayScale() {
...
}
...
}

示例 1-29 @ExcludeDefaultListeners

@Entity
@ExcludeDefaultListeners
public class Employee implements Serializable {
...
}

示例 1-30 超类级别的实体监听程序

@MappedSuperclass
@EntityListeners(value={EmployeeListener.class})
public class Employee {
...
}

示例 1-31 子类级别的 @ExcludeSuperclassListeners

@Entity
@ExcludeSuperclassListeners
@EntityListners(value={PartTimeEmployeeListener1.class, PartTimeEmployeeListener2.class})
public class PartTimeEmployee extends Employee {
...
}

示例 1-32 使用 @EntityResult 和 @FieldResult 的 Order 实体

@SqlResultSetMapping(
name="OrderResults",
entities={
@EntityResult(
entityClass=Order.class,
fields={
@FieldResult(name="id",       column="order_id"),
@FieldResult(name="quantity", column="order_quantity"),
@FieldResult(name="item",     column="order_item")
}
),
@EntityResult(
entityClass=Item.class,
fields={
@FieldResult(name="id",       column="item_id"),
@FieldResult(name="name",     column="item_name"),
}
)
}
)
@Entity
public class Order {
@Id
protected int id;
protected long quantity;
protected Item item;
...
}

示例 1-33 Item 实体

@Entity
public class Item {
@Id
protected int id;
protected String name;
...
}

示例 1-34 结合使用 @SqlResultSetMapping 与 @EntityResult 的原生查询

Query q = entityManager.createNativeQuery(
"SELECT o.id       AS order_id, " +
"o.quantity AS order_quantity, " +
"o.item     AS order_item, " +
"i.id       AS item_id, " +
"i.name     AS item_name, " +
"FROM Order o, Item i " +
"WHERE (order_quantity > 25) AND (order_item = i.id)",
"OrderResults"
);
List resultList = q.getResultList();
// List of Object arrays:{[Order, Item], [Order, Item], ...}