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rasonyang:
要早点更换,我也不至于 现在 用 freeswitch。 c ...
asterisk 终于要替换SIP协议栈了 -
redhacker:
你好,博主!你安装后破解了吗?
IBM RSA (IBM rational software architect ) V8 学习之一 安装 -
canghaifuyun1987:
lz 我来关注下你呗,写的好
Spring Aop例子(实现接口) -
zhaoshijie:
请问 这种方式可以拦截到目标方法:ClassPathXmlAp ...
Spring3.0中的AOP注解配置 -
jiji87432:
谢谢分享,有很大帮助。
post和get的区别
Hibernate注释大全
Hibernate注释大全收藏
声明实体Bean
<wbr></wbr>
@Entity
public class Flight implements Serializable {
<wbr>Long id;</wbr>
<wbr>@Id</wbr>
<wbr>public Long getId() { return id; }</wbr>
<wbr>public void setId(Long id) { this.id = id; }</wbr>
}
<wbr></wbr>
@Entity 注解将一个类声明为实体 Bean, @Id 注解声明了该实体Bean的标识属性。
<wbr></wbr>
Hibernate 可以对类的属性或者方法进行注解。属性对应field类别,方法的 getXxx()对应property类别。
<wbr></wbr>
定义表
<wbr></wbr>
通过 @Table 为实体Bean指定对应数据库表,目录和schema的名字。
<wbr></wbr>
@Entity
@Table(name="tbl_sky")
public class Sky implements Serializable {
<wbr></wbr>
...
<wbr></wbr>
@Table 注解包含一个schema和一个catelog 属性,使用@UniqueConstraints 可以定义表的唯一约束。
<wbr></wbr>
@Table(name="tbl_sky",
<wbr>uniqueConstraints = {@UniqueConstraint(columnNames={"month", "day"})}</wbr>
)
<wbr></wbr>
上述代码在 <wbr> "month"</wbr> 和 "day" 两个 field 上加上 unique constrainst.
<wbr></wbr>
@Version 注解用于支持乐观锁版本控制。
<wbr></wbr>
@Entity
public class Flight implements Serializable {
<wbr><wbr>...</wbr></wbr>
<wbr><wbr>@Version</wbr></wbr>
<wbr><wbr>@Column(name="OPTLOCK")</wbr></wbr>
<wbr><wbr>public Integer getVersion() { ... }</wbr></wbr>
}
<wbr></wbr>
version属性映射到 "OPTLOCK" 列,entity manager 使用这个字段来检测冲突。 一般可以用 数字 或者 timestamp 类型来支持 version.
<wbr></wbr>
实体Bean中所有非static 非 transient 属性都可以被持久化,除非用@Transient注解。
<wbr></wbr>
默认情况下,所有属性都用 @Basic 注解。
<wbr></wbr>
public transient int counter; //transient property
<wbr></wbr>
private String firstname; //persistent property
@Transient
String getLengthInMeter() { ... } //transient property
String getName() {... } // persistent property
@Basic
int getLength() { ... } // persistent property
@Basic(fetch = FetchType.LAZY)
String getDetailedComment() { ... } // persistent property
@Temporal(TemporalType.TIME)
java.util.Date getDepartureTime() { ... } // persistent property
@Enumerated(EnumType.STRING)
Starred getNote() { ... } //enum persisted as String in database
<wbr></wbr>
上述代码中 counter, lengthInMeter 属性将忽略不被持久化,而 firstname, name, length 被定义为可持久化和可获取的。
<wbr></wbr>
@TemporalType.(DATE,TIME,TIMESTAMP) 分别Map java.sql.(Date, Time, Timestamp).
<wbr></wbr>
@Lob 注解属性将被持久化为 Blog 或 Clob 类型。具体的java.sql.Clob, Character[], char[] 和 java.lang.String 将被持久化为 Clob 类型. java.sql.Blob, Byte[], byte[] 和 serializable type 将被持久化为 Blob 类型。
<wbr></wbr>
@Lob
public String getFullText() {
<wbr><wbr>return fullText; <wbr>// clob type</wbr></wbr></wbr>
}
<wbr></wbr>
<wbr></wbr>
@Lob
public byte[] getFullCode() {
<wbr>return fullCode; <wbr>// blog type</wbr></wbr>
}
<wbr></wbr>
@Column 注解将属性映射到列。
<wbr></wbr>
@Entity
public class Flight implements Serializable {
<wbr><wbr>...</wbr></wbr>
<wbr><wbr>@Column(updatable = false, name = "flight_name", nullable = false, length=50)</wbr></wbr>
<wbr><wbr>public String getName() { ... }</wbr></wbr>
<wbr></wbr>
定义 name 属性映射到 flight_name column, not null, can't update, length equal 50
<wbr></wbr>
@Column(
<wbr><wbr>name="columnName"; (1)</wbr></wbr> 列名
<wbr><wbr>boolean unique() default false; (2) <wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr>是否在该列上设置唯一约束
<wbr><wbr>boolean nullable() default true; (3) <wbr><wbr></wbr></wbr></wbr></wbr>列可空?
<wbr><wbr>boolean insertable() default true; (4)</wbr></wbr> 该列是否作为生成 insert语句的一个列
<wbr><wbr>boolean updatable() default true; (5) <wbr></wbr></wbr></wbr>该列是否作为生成 update语句的一个列
<wbr><wbr>String columnDefinition() default ""; (6) <wbr></wbr></wbr></wbr>默认值
<wbr><wbr>String table() default ""; (7) <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>定义对应的表(deault 是主表)
<wbr><wbr>int length() default 255; (8) <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>列长度
<wbr><wbr>int precision() default 0; // decimal precision (9) <wbr>decimal</wbr></wbr></wbr>精度
<wbr><wbr>int scale() default 0; // decimal scale <wbr><wbr><wbr><wbr><wbr><wbr><wbr>(10) <wbr>decimal</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>长度
<wbr></wbr>
嵌入式对象(又称组件)也就是别的对象定义的属性
<wbr></wbr>
组件类必须在类一级定义 @Embeddable 注解。在特定的实体关联属性上使用 @Embeddable 和 @AttributeOverride 注解可以覆盖该属性对应的嵌入式对象的列映射。
<wbr></wbr>
@Entity
public class Person implements Serializable {
<wbr><wbr>// Persistent component using defaults</wbr></wbr>
<wbr><wbr>Address homeAddress;</wbr></wbr>
<wbr><wbr>@Embedded</wbr></wbr>
<wbr><wbr>@AttributeOverrides( {</wbr></wbr>
<wbr><wbr><wbr><wbr><wbr>@AttributeOverride(name="iso2", column = @Column(name="bornIso2") ),</wbr></wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr><wbr>@AttributeOverride(name="name", column = @Column(name="bornCountryName") )</wbr></wbr></wbr></wbr></wbr>
<wbr><wbr>} )</wbr></wbr>
<wbr><wbr>Country bornIn;</wbr></wbr>
<wbr><wbr>...</wbr></wbr>
}
<wbr></wbr>
@Embeddable
public class Address implements Serializable {
<wbr><wbr>String city;</wbr></wbr>
<wbr><wbr>Country nationality; //no overriding here</wbr></wbr>
}
<wbr></wbr>
@Embeddable
public class Country implements Serializable {
<wbr><wbr>private String iso2;</wbr></wbr>
<wbr><wbr>@Column(name="countryName") private String name;</wbr></wbr>
<wbr><wbr>public String getIso2() { return iso2; }</wbr></wbr>
<wbr><wbr>public void setIso2(String iso2) { this.iso2 = iso2; }</wbr></wbr>
<wbr><wbr>public String getName() { return name; }</wbr></wbr>
<wbr><wbr>public void setName(String name) { this.name = name; }</wbr></wbr>
<wbr><wbr>...</wbr></wbr>
}
<wbr></wbr>
Person 类定义了 Address 和 <wbr>Country</wbr> 对象,具体两个类实现见上。
<wbr></wbr>
无注解属性默认值:
<wbr></wbr>
? 属性为简单类型,则映射为 @Basic
<wbr></wbr>
? 属性对应的类型定义了 @Embeddable 注解,则映射为 @Embedded
<wbr></wbr>
? 属性对应的类型实现了Serializable,则属性被映射为@Basic并在一个列中保存该对象的serialized版本。
<wbr></wbr>
? 属性的类型为 java.sql.Clob or java.sql.Blob, 则映射到 @Lob 对应的类型。
<wbr></wbr>
映射主键属性
<wbr></wbr>
@Id 注解可将实体Bean中某个属性定义为主键,使用@GenerateValue注解可以定义该标识符的生成策略。
<wbr></wbr>
? AUTO - <wbr></wbr>可以是 identity column, sequence 或者 table 类型,取决于不同底层的数据库
? TABLE - 使用table保存id值
? IDENTITY - identity column
? SEQUENCE - seque
<wbr></wbr>
nce
<wbr></wbr>
@Id @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="SEQ_STORE")
public Integer getId() { ... }
<wbr></wbr>
@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
public Long getId() { ... }
<wbr></wbr>
AUTO 生成器,适用与可移值的应用,多个@Id可以共享同一个 identifier生成器,只要把generator属性设成相同的值就可以。通过@SequenceGenerator 和 @TableGenerator 可以配置不同的 identifier 生成器。
<wbr></wbr>
<table-generator name="EMP_GEN"
<wbr><wbr><wbr><wbr>table="GENERATOR_TABLE"</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>pk-column-name="key"</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>value-column-name="hi"</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>pk-column-value="EMP"</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>allocation-size="20"/></wbr></wbr></wbr></wbr>
//and the annotation equivalent
@javax.persistence.TableGenerator(
<wbr><wbr><wbr><wbr>name="EMP_GEN",</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>table="GENERATOR_TABLE",</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>pkColumnName = "key",</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>valueColumnName = "hi"</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>pkColumnValue="EMP",</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>allocationSize=20</wbr></wbr></wbr></wbr>
)
<sequence-generator name="SEQ_GEN"
<wbr><wbr><wbr><wbr>sequence-name="my_sequence"</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>allocation-size="20"/></wbr></wbr></wbr></wbr>
//and the annotation equivalent
@javax.persistence.SequenceGenerator(
<wbr><wbr><wbr><wbr>name="SEQ_GEN",</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>sequenceName="my_sequence",</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>allocationSize=20</wbr></wbr></wbr></wbr>
)
<wbr></wbr>
The next example shows the definition of a sequence generator in a class scope:
<wbr></wbr>
@Entity
@javax.persistence.SequenceGenerator(
<wbr><wbr><wbr>name="SEQ_STORE",</wbr></wbr></wbr>
<wbr><wbr><wbr>sequenceName="my_sequence"</wbr></wbr></wbr>
)
public class Store implements Serializable {
<wbr><wbr>private Long id;</wbr></wbr>
<wbr><wbr>@Id @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="SEQ_STORE")</wbr></wbr>
<wbr><wbr>public Long getId() { return id; }</wbr></wbr>
}
<wbr></wbr>
Store类使用名为my_sequence的sequence,并且SEQ_STORE生成器对于其他类是不可见的。
<wbr></wbr>
通过下面语法,你可以定义组合键。
<wbr></wbr>
? 将组件类注解为 @Embeddable, 并将组件的属性注解为 @Id
? 将组件的属性注解为 @EmbeddedId
? 将类注解为 @IdClass,并将该实体中所有主键的属性都注解为 @Id
<wbr></wbr>
@Entity
@IdClass(FootballerPk.class)
public class Footballer {
<wbr>//part of the id key</wbr>
<wbr>@Id public String getFirstname() {</wbr>
<wbr><wbr><wbr>return firstname;</wbr></wbr></wbr>
<wbr>}</wbr>
<wbr>public void setFirstname(String firstname) {</wbr>
<wbr><wbr><wbr><wbr>this.firstname = firstname;</wbr></wbr></wbr></wbr>
<wbr>}</wbr>
<wbr>//part of the id key</wbr>
<wbr>@Id public String getLastname() {</wbr>
<wbr><wbr><wbr>return lastname;</wbr></wbr></wbr>
<wbr>}</wbr>
<wbr>public void setLastname(String lastname) {</wbr>
<wbr><wbr><wbr>this.lastname = lastname;</wbr></wbr></wbr>
<wbr>}</wbr>
<wbr>public String getClub() {</wbr>
<wbr><wbr><wbr>return club;</wbr></wbr></wbr>
<wbr>}</wbr>
<wbr>public void setClub(String club) {</wbr>
<wbr><wbr>this.club = club;</wbr></wbr>
<wbr>}</wbr>
<wbr>//appropriate equals() and hashCode() implementation</wbr>
}
<wbr></wbr>
@Embeddable
public class FootballerPk implements Serializable {
<wbr>//same name and type as in Footballer</wbr>
<wbr>public String getFirstname() {</wbr>
<wbr><wbr><wbr>return firstname;</wbr></wbr></wbr>
<wbr>}</wbr>
<wbr>public void setFirstname(String firstname) {</wbr>
<wbr><wbr><wbr>this.firstname = firstname;</wbr></wbr></wbr>
<wbr>}</wbr>
<wbr>//same name and type as in Footballer</wbr>
<wbr>public String getLastname() {</wbr>
<wbr><wbr><wbr>return lastname;</wbr></wbr></wbr>
<wbr>}</wbr>
<wbr>public void setLastname(String lastname) {</wbr>
<wbr><wbr>this.lastname = lastname;</wbr></wbr>
<wbr>}</wbr>
<wbr>//appropriate equals() and hashCode() implementation</wbr>
}
<wbr></wbr>
@Entity
@AssociationOverride( name="id.channel", joinColumns = @JoinColumn(name="chan_id") )
public class TvMagazin {
<wbr><wbr>@EmbeddedId public TvMagazinPk id;</wbr></wbr>
<wbr><wbr>@Temporal(TemporalType.TIME) Date time;</wbr></wbr>
}
<wbr></wbr>
<wbr></wbr>
@Embeddable
public class TvMagazinPk implements Serializable {
<wbr><wbr>@ManyToOne</wbr></wbr>
<wbr><wbr>public Channel channel;</wbr></wbr>
<wbr><wbr>public String name;</wbr></wbr>
<wbr><wbr>@ManyToOne</wbr></wbr>
<wbr><wbr>public Presenter presenter;</wbr></wbr>
}
<wbr></wbr>
映射继承关系
<wbr></wbr>
EJB支持3种类型的继承。
<wbr></wbr>
? Table per Class Strategy: the <union-class> element in Hibernate 每个类一张表
? Single Table per Class Hierarchy Strategy: the <subclass> element in Hibernate 每个类层次结构一张表
? Joined Subclass Strategy: the <joined-subclass> element in Hibernate 连接的子类策略
<wbr></wbr>
@Inheritance 注解来定义所选的之类策略。
<wbr></wbr>
每个类一张表
<wbr></wbr>
@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class Flight implements Serializable {
<wbr></wbr>
有缺点,如多态查询或关联。Hibernate 使用 SQL Union 查询来实现这种策略。 这种策略支持双向的一对多关联,但不支持 IDENTIFY 生成器策略,因为ID必须在多个表间共享。一旦使用就不能使用AUTO和IDENTIFY生成器。
<wbr></wbr>
每个类层次结构一张表
<wbr></wbr>
@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(
<wbr><wbr><wbr>name="planetype",</wbr></wbr></wbr>
<wbr><wbr><wbr>discriminatorType=DiscriminatorType.STRING</wbr></wbr></wbr>
)
@DiscriminatorValue("Plane")
public class Plane { ... }
<wbr></wbr>
@Entity
@DiscriminatorValue("A320")
public class A320 extends Plane { ... }
<wbr></wbr>
整个层次结构中的所有父类和子类属性都映射到同一个表中,他们的实例通过一个辨别符列(discriminator)来区分。
<wbr></wbr>
Plane 是父类。@DiscriminatorColumn 注解定义了辨别符列。对于继承层次结构中的每个类, @DiscriminatorValue 注解指定了用来辨别该类的值。 辨别符列名字默认为 DTYPE,其默认值为实体名。其类型为DiscriminatorType.STRING。
<wbr></wbr>
连接的子类
<wbr></wbr>
@Entity
@Inheritance(strategy=InheritanceType.JOINED)
public class Boat implements Serializable { ... }
<wbr></wbr>
<wbr></wbr>
@Entity
public class Ferry extends Boat { ... }
<wbr></wbr>
@Entity
@PrimaryKeyJoinColumn(name="BOAT_ID")
public class AmericaCupClass extends Boat { ... }
<wbr></wbr>
以上所有实体使用 JOINED 策略 Ferry和Boat class使用同名的主键关联(eg: Boat.id = Ferry.id), AmericaCupClass 和 Boat 关联的条件为 Boat.id = AmericaCupClass.BOAT_ID.
<wbr></wbr>
从父类继承的属性
<wbr></wbr>
@MappedSuperclass
public class BaseEntity {
<wbr>@Basic</wbr>
<wbr>@Temporal(TemporalType.TIMESTAMP)</wbr>
<wbr>public Date getLastUpdate() { ... }</wbr>
<wbr>public String getLastUpdater() { ... }</wbr>
<wbr>...</wbr>
}
<wbr></wbr>
<wbr></wbr>
@Entity class Order extends BaseEntity {
<wbr>@Id public Integer getId() { ... }</wbr>
<wbr>...</wbr>
}
<wbr></wbr>
继承父类的一些属性,但不用父类作为映射实体,这时候需要 @MappedSuperclass 注解。 上述实体映射到数据库中的时候对应 Order 实体Bean, 其具有 id, lastUpdate, lastUpdater 三个属性。如果没有@MappedSuperclass 注解,则父类中属性忽略,这是 Order 实体 Bean 只有 id 一个属性。
<wbr></wbr>
映射实体Bean的关联关系
<wbr></wbr>
一对一
<wbr></wbr>
使用 @On<wbr>eToOne</wbr> 注解可以建立实体Bean之间的一对一关系。一对一关系有3种情况。
<wbr></wbr>
? 关联的实体都共享同样的主键。
<wbr></wbr>
@Entity
public class Body {
<wbr>@Id</wbr>
<wbr>public Long getId() { return id; }</wbr>
<wbr>@On<wbr>eToOne(cascade = CascadeType.ALL)</wbr></wbr>
<wbr>@PrimaryKeyJoinColumn</wbr>
<wbr>public Heart getHeart() {</wbr>
<wbr><wbr><wbr><wbr>return heart;</wbr></wbr></wbr></wbr>
<wbr>}</wbr>
<wbr>...</wbr>
}
<wbr></wbr>
@Entity
public class Heart {
<wbr>@Id</wbr>
<wbr>public Long getId() { ...}</wbr>
}
<wbr></wbr>
通过@PrimaryKeyJoinColumn 注解定义了一对一的关联关系。
<wbr></wbr>
<wbr></wbr>
多对一
<wbr></wbr>
使用 @ManyToOne 注解定义多对一关系。
<wbr></wbr>
@Entity()
public class Flight implements Serializable {
<wbr>@ManyToOne( cascade = {CascadeType.PERSIST, CascadeType.MERGE} )</wbr>
<wbr>@JoinColumn(name="COMP_ID")</wbr>
<wbr>public Company getCompany() {</wbr>
<wbr><wbr><wbr>return company;</wbr></wbr></wbr>
<wbr>}</wbr>
<wbr>...</wbr>
}
<wbr></wbr>
其中@JoinColumn 注解是可选的,关键字段默认值和一对一关联的情况相似。列名为:主题的关联属性名 + 下划线 + 被关联端的主键列名。本例中为company_id,因为关联的属性是company, Company的主键为 id.
<wbr></wbr>
@ManyToOne 注解有个targetEntity属性,该参数定义了目标实体名。通常不需要定义,大部分情况为默认值。但下面这种情况则需要 targetEntity 定义(使用接口作为返回值,而不是常用的实体)。
<wbr></wbr>
@Entity()
public class Flight implements Serializable {
<wbr><wbr>@ManyToOne(cascade= <wbr><wbr>{CascadeType.PERSIST,CascadeType.MERGE},targetEntity= CompanyImpl.class)</wbr></wbr></wbr></wbr>
<wbr><wbr>@JoinColumn(name="COMP_ID")</wbr></wbr>
<wbr><wbr>public Company getCompany() {</wbr></wbr>
<wbr><wbr><wbr><wbr>return company;</wbr></wbr></wbr></wbr>
<wbr><wbr>}</wbr></wbr>
<wbr><wbr>...</wbr></wbr>
}
<wbr></wbr>
<wbr></wbr>
public interface Company {
<wbr><wbr>...</wbr></wbr>
<wbr></wbr>
多对一也可以通过关联表的方式来映射,通过 @JoinTable 注解可定义关联表。该关联表包含指回实体的外键(通过@JoinTable.joinColumns)以及指向目标实体表的外键(通过@JoinTable.inverseJoinColumns).
<wbr></wbr>
@Entity()
public class Flight implements Serializable {
<wbr></wbr>
<wbr><wbr>@ManyToOne( cascade = {CascadeType.PERSIST, CascadeType.MERGE} )</wbr></wbr>
<wbr><wbr>@JoinTable(name="Flight_Company",</wbr></wbr>
<wbr><wbr><wbr><wbr><wbr><wbr>joinColumns = @JoinColumn(name="FLIGHT_ID"),</wbr></wbr></wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr><wbr><wbr>inverseJoinColumns = @JoinColumn(name="COMP_ID")</wbr></wbr></wbr></wbr></wbr></wbr>
<wbr><wbr>)</wbr></wbr>
<wbr><wbr>public Company getCompany() {</wbr></wbr>
<wbr><wbr><wbr><wbr><wbr><wbr>return company;</wbr></wbr></wbr></wbr></wbr></wbr>
<wbr><wbr>}</wbr></wbr>
<wbr><wbr>...</wbr></wbr>
}
<wbr></wbr>
集合类型
<wbr></wbr>
<wbr></wbr>
<wbr></wbr>
<wbr></wbr>一对多
<wbr></wbr>
@On<wbr>eToMany</wbr> 注解可定义一对多关联。一对多关联可以是双向的。
<wbr></wbr>
双向
<wbr></wbr>
规范中多对一端几乎总是双向关联中的主体(owner)端,而一对多的关联注解为 @On<wbr>eToMany(mappedBy=)</wbr>
<wbr></wbr>
@Entity
public class Troop {
<wbr>@On<wbr>eToMany(mappedBy="troop")</wbr></wbr>
<wbr>public Set<Soldier> getSoldiers() {</wbr>
<wbr>...</wbr>
}
<wbr></wbr>
<wbr></wbr>
@Entity
public class Soldier {
<wbr>@ManyToOne</wbr>
<wbr>@JoinColumn(name="troop_fk")</wbr>
<wbr>public Troop getTroop() {</wbr>
<wbr>...</wbr>
<wbr>}</wbr>
<wbr></wbr>
Troop 通过troop属性和Soldier建立了一对多的双向关联。在 mappedBy 端不必也不能定义任何物理映射。
<wbr></wbr>
单向
<wbr></wbr>
@Entity
public class Customer implements Serializable {
<wbr><wbr>@On<wbr>eToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER)</wbr></wbr></wbr>
<wbr><wbr>@JoinColumn(name="CUST_ID")</wbr></wbr>
<wbr><wbr>public Set<Ticket> getTickets() {</wbr></wbr>
<wbr><wbr><wbr><wbr><wbr>...</wbr></wbr></wbr></wbr></wbr>
<wbr><wbr>}</wbr></wbr>
<wbr></wbr>
@Entity
public class Ticket implements Serializable {
<wbr><wbr>... //no bidir</wbr></wbr>
}
<wbr></wbr>
一般通过连接表来实现这种关联,可以通过@JoinColumn注解来描述这种单向关联关系。上例 Customer 通过 CUST_ID 列和 Ticket 建立了单向关联关系。
<wbr></wbr>
通过关联表来处理单向关联
<wbr></wbr>
@Entity
public class Trainer {
<wbr>@On<wbr>eToMany</wbr></wbr>
<wbr>@JoinTable(</wbr>
<wbr><wbr><wbr><wbr>name="TrainedMonkeys",</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>joinColumns = @JoinColumn( name="trainer_id"),</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>inverseJoinColumns = @JoinColumn( name="monkey_id")</wbr></wbr></wbr></wbr>
<wbr>)</wbr>
<wbr>public Set<Monkey> getTrainedMonkeys() {</wbr>
<wbr><wbr><wbr><wbr>...</wbr></wbr></wbr></wbr>
<wbr>}</wbr>
<wbr></wbr>
<wbr></wbr>
@Entity
public class Monkey {
<wbr>... //no bidir</wbr>
}
<wbr></wbr>
通过关联表来处理单向一对多关系是首选,这种关联通过 @JoinTable 注解来进行描述。上例子中 Trainer 通过TrainedMonkeys表和Monkey建立了单向关联关系。其中外键trainer_id关联到Trainer(joinColumns)而外键monkey_id关联到Monkey(inverseJoinColumns).
<wbr></wbr>
默认处理机制
<wbr></wbr>
通过连接表来建立单向一对多关联不需要描述任何物理映射,表名由一下3个部分组成,主表(owner table)表名 + 下划线 + 从表(the other side table)表名。指向主表的外键名:主表表名+下划线+主表主键列名 指向从表的外键定义为唯一约束,用来表示一对多的关联关系。
<wbr></wbr>
@Entity
public class Trainer {
<wbr>@On<wbr>eToMany</wbr></wbr>
<wbr>public Set<Tiger> getTrainedTigers() {</wbr>
<wbr>...</wbr>
}
<wbr></wbr>
<wbr></wbr>
@Entity
public class Tiger {
<wbr>... //no bidir</wbr>
}
<wbr></wbr>
上述例子中 Trainer 和 Tiger 通过 Trainer_Tiger 连接表建立单向关联关系。其中外键 trainer_id 关联到 Trainer表,而外键 trainedTigers_id 关联到 Tiger 表。
<wbr></wbr>
多对多
<wbr></wbr>
通过 @ManyToMany 注解定义多对多关系,同时通过 @JoinTable 注解描述关联表和关联条件。其中一端定义为 owner, 另一段定义为 inverse(对关联表进行更新操作,这段被忽略)。
<wbr></wbr>
@Entity
public class Employer implements Serializable {
<wbr>@ManyToMany(</wbr>
<wbr><wbr><wbr>targetEntity=org.hibernate.test.metadata.manytomany.Employee.class,</wbr></wbr></wbr>
<wbr><wbr><wbr>cascade={CascadeType.PERSIST, CascadeType.MERGE}</wbr></wbr></wbr>
<wbr>)</wbr>
<wbr>@JoinTable(</wbr>
<wbr><wbr><wbr>name="EMPLOYER_EMPLOYEE",</wbr></wbr></wbr>
<wbr><wbr><wbr>joinColumns=@JoinColumn(name="EMPER_ID"),</wbr></wbr></wbr>
<wbr><wbr><wbr>inverseJoinColumns=@JoinColumn(name="EMPEE_ID")</wbr></wbr></wbr>
<wbr>)</wbr>
<wbr>public Collection getEmployees() {</wbr>
<wbr><wbr><wbr>return employees;</wbr></wbr></wbr>
<wbr>}</wbr>
<wbr>...</wbr>
}
<wbr></wbr>
@Entity
public class Employee implements Serializable {
<wbr>@ManyToMany(</wbr>
<wbr><wbr><wbr>cascade = {CascadeType.PERSIST, CascadeType.MERGE},</wbr></wbr></wbr>
<wbr><wbr><wbr>mappedBy = "employees",</wbr></wbr></wbr>
<wbr><wbr><wbr>targetEntity = Employer.class</wbr></wbr></wbr>
<wbr>)</wbr>
<wbr>public Collection getEmployers() {</wbr>
<wbr><wbr><wbr>return employers;</wbr></wbr></wbr>
<wbr>}</wbr>
}
<wbr></wbr>
默认值:
<wbr></wbr>
关联表名:主表表名 + 下划线 + 从表表名;关联表到主表的外键:主表表名 + 下划线 + 主表中主键列名;关联表到从表的外键名:主表中用于关联的属性名 + 下划线 + 从表的主键列名。
<wbr></wbr>
用 cascading 实现传播持久化(Transitive persistence)
<wbr></wbr>
cascade 属性接受值为 CascadeType 数组,其类型如下:
<wbr></wbr>
? CascadeType.PERSIST: cascades the persist (create) operation to associated entities persist() is called or if the entity is managed 如果一个实体是受管状态,或者当 persist() 函数被调用时,触发级联创建(create)操作。
<wbr></wbr>
<wbr></wbr>
? CascadeType.MERGE: cascades the merge operation to associated entities if merge() is called or if the entity is managed 如果一个实体是受管状态,或者当 merge() 函数被调用时,触发级联合并(merge)操作。
<wbr></wbr>
<wbr></wbr>
? CascadeType.REMOVE: cascades the remove operation to associated entities if delete() is called 当 delete() 函数被调用时,触发级联删除(remove)操作。
<wbr></wbr>
<wbr></wbr>
? CascadeType.REFRESH: cascades the refresh operation to associated entities if refresh() is called <wbr></wbr>当 refresh() 函数被调用时,出发级联更新(refresh)操作。
<wbr></wbr>
<wbr></wbr>
? CascadeType.ALL: all of the above <wbr></wbr>以上全部
<wbr></wbr>
映射二级列表
<wbr></wbr>
使用类一级的 @SecondaryTable 和 @SecondaryTables 注解可以实现单个实体到多个表的映射。使用 @Column 或者 @JoinColumn 注解中的 table 参数可以指定某个列所属的特定表。
<wbr></wbr>
@Entity
@Table(name="MainCat")
@SecondaryTables({
<wbr><wbr><wbr>@SecondaryTable(name="Cat1", pkJoinColumns={</wbr></wbr></wbr>
<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>@PrimaryKeyJoinColumn(name="cat_id", referencedColumnName="id")}),</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
<wbr><wbr><wbr>@SecondaryTable(name="Cat2", uniqueConstraints={</wbr></wbr></wbr>
<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>@UniqueConstraint(columnNames={"storyPart2"})})</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
<wbr>})</wbr>
public class Cat implements Serializable {
<wbr>private Integer id;</wbr>
<wbr>private String name;</wbr>
<wbr></wbr>
<wbr>private String storyPart1;</wbr>
<wbr>private String storyPart2;</wbr>
<wbr>@Id @GeneratedValue</wbr>
<wbr>public Integer getId() {</wbr>
<wbr><wbr><wbr>return id;</wbr></wbr></wbr>
<wbr>}</wbr>
<wbr>public String getName() {</wbr>
<wbr><wbr><wbr>return name;</wbr></wbr></wbr>
<wbr>}</wbr>
<wbr>@Column(table="Cat1")</wbr>
<wbr>public String getStoryPart1() {</wbr>
<wbr><wbr><wbr>return storyPart1;</wbr></wbr></wbr>
<wbr>}</wbr>
<wbr>@Column(table="Cat2")</wbr>
<wbr>public String getStoryPart2() {</wbr>
<wbr><wbr><wbr>return storyPart2;</wbr></wbr></wbr>
<wbr>}</wbr>
<wbr></wbr>
上述例子中, name 保存在 MainCat 表中,storyPart1保存在 Cat1 表中,storyPart2 保存在 Cat2 表中。 Cat1 表通过外键 cat_id 和 MainCat 表关联, Cat2 表通过 id 列和 MainCat 表关联。对storyPart2 列还定义了唯一约束。
<wbr></wbr>
映射查询
<wbr></wbr>
使用注解可以映射 EJBQL/HQL 查询,@NamedQuery 和 @NamedQueries 是可以使用在类级别或者JPA的XML文件中的注解。
<wbr></wbr>
<entity-mappings>
<wbr><named-query name="plane.getAll"></wbr>
<wbr><query>select p from Plane p</query></wbr>
<wbr></named-query></wbr>
<wbr>...</wbr>
</entity-mappings>
...
@Entity
@NamedQuery(name="night.moreRecentThan", query="select n from Night n where n.date >= :date")
public class Night {
<wbr>...</wbr>
}
public class MyDao {
<wbr>doStuff() {</wbr>
<wbr><wbr>Query q = s.getNamedQuery("night.moreRecentThan");</wbr></wbr>
<wbr><wbr>q.setDate( "date", aMonthAgo );</wbr></wbr>
<wbr><wbr>List results = q.list();</wbr></wbr>
<wbr><wbr>...</wbr></wbr>
<wbr>}</wbr>
<wbr>...</wbr>
}
<wbr></wbr>
可以通过定义 QueryHint 数组的 hints 属性为查询提供一些 hint 信息。下图是一些 Hibernate hints:
<wbr></wbr>
<wbr></wbr>
<wbr></wbr>
映射本地化查询
<wbr></wbr>
通过@SqlResultSetMapping 注解来描述 SQL 的 resultset 结构。如果定义多个结果集映射,则用 @SqlResultSetMappings。
<wbr></wbr>
@NamedNativeQuery(name="night&area", query="select night.id nid, night.night_duration, "
<wbr><wbr><wbr><wbr>+ " night.night_date, area.id aid, night.area_id, area.name "</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>+ "from Night night, Area area where night.area_id = area.id", resultSetMapping="joinMapping")</wbr></wbr></wbr></wbr>
<wbr></wbr>
@SqlResultSetMapping( name="joinMapping", entities={
<wbr>@EntityResult(entityClass=org.hibernate.test.annotations.query.Night.class, fields = {</wbr>
<wbr><wbr>@FieldResult(name="id", column="nid"),</wbr></wbr>
<wbr><wbr>@FieldResult(name="duration", column="night_duration"),</wbr></wbr>
<wbr><wbr>@FieldResult(name="date", column="night_date"),</wbr></wbr>
<wbr><wbr>@FieldResult(name="area", column="area_id"),</wbr></wbr>
<wbr><wbr>discriminatorColumn="disc"</wbr></wbr>
<wbr>}),</wbr>
<wbr></wbr>
<wbr>@EntityResult(entityClass=org.hibernate.test.annotations.query.Area.class, fields = {</wbr>
<wbr><wbr>@FieldResult(name="id", column="aid"),</wbr></wbr>
<wbr><wbr>@FieldResult(name="name", column="name")</wbr></wbr>
<wbr>})</wbr>
<wbr>}</wbr>
)
<wbr></wbr>
上面的例子,名为“night&area”的查询和 "joinMapping"结果集映射对应,该映射返回两个实体,分别为 Night 和 Area, 其中每个属性都和一个列关联,列名通过查询获取。
<wbr></wbr>
@Entity
@SqlResultSetMapping(name="implicit",
<wbr>entities=@EntityResult(</wbr>
<wbr><wbr><wbr>entityClass=org.hibernate.test.annotations.@NamedNativeQuery(</wbr></wbr></wbr>
<wbr><wbr><wbr><wbr><wbr>name="implicitSample", query="select * from SpaceShip",</wbr></wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr><wbr>resultSetMapping="implicit")</wbr></wbr></wbr></wbr></wbr>
public class SpaceShip {
<wbr>private String name;</wbr>
<wbr>private String model;</wbr>
<wbr>private double speed;</wbr>
<wbr>@Id</wbr>
<wbr>public String getName() {</wbr>
<wbr>return name;</wbr>
<wbr>}</wbr>
<wbr>public void setName(String name) {</wbr>
<wbr>this.name = name;</wbr>
<wbr>}</wbr>
<wbr>@Column(name="model_txt")</wbr>
<wbr>public String getModel() {</wbr>
<wbr>return model;</wbr>
<wbr>}</wbr>
<wbr>public void setModel(String model) {</wbr>
<wbr>this.model = model;</wbr>
<wbr>}</wbr>
<wbr>public double getSpeed() {</wbr>
<wbr>return speed;</wbr>
<wbr>}</wbr>
<wbr>public void setSpeed(double speed) {</wbr>
<wbr>this.speed = speed;</wbr>
<wbr>}</wbr>
}
<wbr></wbr>
上例中 model1 属性绑定到 model_txt 列,如果和相关实体关联设计到组合主键,那么应该使用 @FieldResult 注解来定义每个外键列。@FieldResult的名字组成:定义这种关系的属性名字 + "." + 主键名或主键列或主键属性。
<wbr></wbr>
@Entity
@SqlResultSetMapping(name="compositekey",
<wbr>entities=@EntityResult(entityClass=org.hibernate.test.annotations.query.SpaceShip.class,</wbr>
<wbr>fields = {</wbr>
<wbr><wbr>@FieldResult(name="name", column = "name"),</wbr></wbr>
<wbr><wbr>@FieldResult(name="model", column = "model"),</wbr></wbr>
<wbr><wbr>@FieldResult(name="speed", column = "speed"),</wbr></wbr>
<wbr><wbr>@FieldResult(name="captain.firstname", column = "firstn"),</wbr></wbr>
<wbr><wbr>@FieldResult(name="captain.lastname", column = "lastn"),</wbr></wbr>
<wbr><wbr>@FieldResult(name="dimensions.length", column = "length"),</wbr></wbr>
<wbr><wbr>@FieldResult(name="dimensions.width", column = "width")</wbr></wbr>
<wbr>}),</wbr>
<wbr>columns = { @ColumnResult(name = "surface"),</wbr>
<wbr></wbr>
@ColumnResult(name = "volume") } )
<wbr>@NamedNativeQuery(name="compositekey",</wbr>
<wbr>query="select name, model, speed, lname as lastn, fname as firstn, length, width, length * width as resultSetMapping="compositekey")</wbr>
})
<wbr></wbr>
如果查询返回的是单个实体,或者打算用系统默认的映射,这种情况下可以不使用 resultSetMapping,而使用resultClass属性,例如:
<wbr></wbr>
@NamedNativeQuery(name="implicitSample", query="select * from SpaceShip",
<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>resultClass=SpaceShip.class)</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
public class SpaceShip {
<wbr></wbr>
Hibernate 独有的注解扩展
<wbr></wbr>
Hibernate 提供了与其自身特性想吻合的注解,org.hibernate.annotations package包含了这些注解。
<wbr></wbr>
实体
<wbr></wbr>
org.hibernate.annotations.Entity 定义了 <wbr>Hibernate</wbr> 实体需要的信息。
<wbr></wbr>
? mutable: whether this entity is mutable or not <wbr></wbr>此实体是否可变
<wbr></wbr>
<wbr></wbr>
? dynamicInsert: allow dynamic SQL for inserts <wbr><wbr></wbr></wbr>用动态SQL新增
<wbr></wbr>
<wbr></wbr>
? dynamicUpdate: allow dynamic SQL for updates <wbr><wbr></wbr></wbr>用动态SQL更新
<wbr></wbr>
<wbr></wbr>
? selectBeforeUpdate: Specifies that Hibernate should never perform an SQL UPDATE unless it is certain that an object is actually modified.指明Hibernate从不运行SQL Update,除非能确定对象已经被修改
<wbr></wbr>
<wbr></wbr>
? polymorphism: whether the entity polymorphism is of PolymorphismType.IMPLICIT (default) or PolymorphismType.EXPLICIT 指出实体多态是 PolymorphismType.IMPLICIT(默认)还是PolymorphismType.EXPLICIT
<wbr></wbr>
<wbr></wbr>
? optimisticLock: optimistic locking strategy (OptimisticLockType.VERSION, OptimisticLockType.NONE, OptimisticLockType.DIRTY or OptimisticLockType.ALL) 乐观锁策略
<wbr></wbr>
标识符
<wbr></wbr>
@org.hibernate.annotations.GenericGenerator和@org.hibernate.annotations.GenericGenerators允许你定义hibernate特有的标识符。
<wbr></wbr>
@Id @GeneratedValue(generator="system-uuid")
@GenericGenerator(name="system-uuid", strategy = "uuid")
public String getId() {
@Id @GeneratedValue(generator="hibseq")
@GenericGenerator(name="hibseq", strategy = "seqhilo",
<wbr><wbr>parameters = {</wbr></wbr>
<wbr><wbr><wbr><wbr>@Parameter(name="max_lo", value = "5"),</wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr>@Parameter(name="sequence", value="heybabyhey")</wbr></wbr></wbr></wbr>
<wbr><wbr>}</wbr></wbr>
)
public Integer getId() {
<wbr></wbr>
新例子
<wbr></wbr>
@GenericGenerators(
<wbr>{</wbr>
<wbr>@GenericGenerator(</wbr>
<wbr><wbr>name="hibseq",</wbr></wbr>
<wbr><wbr>strategy = "seqhilo",</wbr></wbr>
<wbr><wbr>parameters = {</wbr></wbr>
<wbr><wbr><wbr>@Parameter(name="max_lo", value = "5"),</wbr></wbr></wbr>
<wbr><wbr><wbr>@Parameter(name="sequence", value="heybabyhey")</wbr></wbr></wbr>
<wbr><wbr>}</wbr></wbr>
<wbr>),</wbr>
<wbr>@GenericGenerator(...)</wbr>
<wbr>}</wbr>
)
<wbr></wbr>
自然ID
<wbr></wbr>
用 @NaturalId 注解标识
<wbr></wbr>
公式
<wbr></wbr>
让数据库而不是JVM进行计算。
<wbr></wbr>
@Formula("obj_length * obj_height * obj_width")
public long getObjectVolume()
<wbr></wbr>
索引
<wbr></wbr>
通过在列属性(property)上使用@Index注解,可以指定特定列的索引,columnNames属性(attribute)将随之被忽略。
<wbr></wbr>
@Column(secondaryTable="Cat1")
@Index(name="story1index")
public String getStoryPart1() {
<wbr>return storyPart1;</wbr>
}
<wbr></wbr>
辨别符
<wbr></wbr>
@Entity
@DiscriminatorFormula("case when forest_type is null then 0 else forest_type end")
public class Forest { ... }
<wbr></wbr>
过滤 查询 ...
<wbr></wbr>
<wbr></wbr>
<wbr></wbr>
<wbr></wbr>
<wbr></wbr>
? 其中一个实体通过外键关联到另一个实体的主键。注:一对一,则外键必须为唯一约束。
<wbr></wbr>
@Entity
public class Customer implements Serializable {
<wbr><wbr>@On<wbr>eToOne(cascade = CascadeType.ALL)</wbr></wbr></wbr>
<wbr><wbr>@JoinColumn(name="passport_fk")</wbr></wbr>
<wbr><wbr>public Passport getPassport() {</wbr></wbr>
<wbr><wbr>...</wbr></wbr>
}
<wbr></wbr>
<wbr></wbr>
@Entity
public class Passport implements Serializable {
<wbr><wbr>@On<wbr>eToOne(mappedBy = "passport")</wbr></wbr></wbr>
<wbr><wbr>public Customer getOwner() {</wbr></wbr>
<wbr><wbr>...</wbr></wbr>
}
<wbr></wbr>
通过@JoinColumn注解定义一对一的关联关系。如果没有@JoinColumn注解,则系统自动处理,在主表中将创建连接列,列名为:主题的关联属性名 + 下划线 + 被关联端的主键列名。上例为 passport_id, 因为Customer 中关联属性为 passport, Passport 的主键为 id.
<wbr></wbr>
<wbr></wbr>
? 通过关联表来保存两个实体之间的关联关系。注:一对一,则关联表每个外键都必须是唯一约束。
<wbr></wbr>
@Entity
public class Customer implements Serializable {
<wbr><wbr>@On<wbr>eToOne(cascade = CascadeType.ALL)</wbr></wbr></wbr>
<wbr><wbr>@JoinTable(name = "CustomerPassports",</wbr></wbr>
<wbr><wbr><wbr><wbr><wbr><wbr><wbr>joinColumns = @JoinColumn(name="customer_fk"),</wbr></wbr></wbr></wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr><wbr><wbr><wbr>inverseJoinColumns = @JoinColumn(name="passport_fk")</wbr></wbr></wbr></wbr></wbr></wbr></wbr>
<wbr><wbr>)</wbr></wbr>
<wbr><wbr>public Passport getPassport() {</wbr></wbr>
<wbr><wbr>...</wbr></wbr>
}
<wbr></wbr>
<wbr></wbr>
@Entity public class Passport implements Serializable {
<wbr><wbr>@On<wbr>eToOne(mappedBy = "passport")</wbr></wbr></wbr>
<wbr><wbr>public Customer getOwner() {</wbr></wbr>
<wbr><wbr>...</wbr></wbr>
}
<wbr></wbr>
Customer 通过 CustomerPassports 关联表和 Passport 关联。该关联表通过 passport_fk 外键指向 Passport 表,该信心定义为 inverseJoinColumns 的属性值。 通过 customer_fk 外键指向 Customer 表,该信息定义为 joinColumns 属性值。
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