hibernate3 Annotation的使用

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Hibernate Bean Access SQL ORM

注解映射必须满足两大条件：Hibernate3.2以上版本和JSEE 5。

@Entity 类注释，所有要持久化的类都要有

Java代码

@Entity
public class Org implements java.io.Serializable {
}

@Entitypublic class Org implements java.io.Serializable {}

@Id 主键

Java代码

@Id
@GeneratedValue
private String orgId;
private String orgName;

@Id @GeneratedValue private String orgId; private String orgName;

@Column(name="...") 该属性对应表中的字段是什么，没有name表示一样

@Table 对象与表映射

@UniqueConstraint 唯一约束

@Version 方法和字段级，乐观锁用法，返回数字和timestamp，数字为首选

@Transient 暂态属性，表示不需要处理

@Basic 最基本的注释。有两个属性：fetch是否延迟加载，optional是否允许null

@Enumerated 枚举类型

@Temporal 日期转换。默认转换Timestamp

@Lob 通常与@Basic同时使用，提高访问速度。

@Embeddable 类级，表可嵌入的

@Embedded 方法字段级，表被嵌入的对象和@Embeddable一起使用

@AttributeOverrides 属性重写

@AttributeOverride 属性重写的内容和@AttributeOverrides一起嵌套使用

@SecondaryTables 多个表格映射

@SecondaryTable 定义辅助表格映射和@SecondaryTables一起嵌套使用

@GeneratedValue 标识符生成策略，默认Auto

表与表关系映射

@OneToOne：一对一映射。它包含五个属性：

targetEntity:关联的目标类

Cascade:持久化时的级联操作，默认没有

fetch:获取对象的方式，默认EAGER

Optional:目标对象是否允许为null，默认允许

mappedBy:定义双向关联中的从属类。

单向：

@JoinColumn:定义外键(主表会多一字段，做外键)

@OneToMany：一对多映射；@ManyToOne：多对一映射

单向一对多：

@OneToMany(cascade=CascadeType.ALL)

@JoinColumn(name="book_oid")/**book：表；oid：book表的主键；无name会按此规则自动生成*/

单向多对一：

@ManyToOne(cascade=CascadeType.ALL)

@JoinColumn(name="author_oid")

关联表格一对多：

@OneToMany(cascade=CascadeType.ALL)

@JoinTable(joinColumn={@JoinColumn(name="BOOK_OBJECT_OID")},inverseJoinColumns={@JoinColumn(name="AUTHER_OBJECT_OID")})

双向一对多或多对一：

不需要多一张表，只是使用mappedBy:使用在One一方，值为One方类名表示Many的从属类。

Java代码

@Entity
public class Org implements java.io.Serializable {
// Fields
@Id
@GeneratedValue
private String orgId;
private String orgName;
@OneToMany(mappedBy = "org")
private List<Department> departments;
// Constructors
...
// Property accessors
...
}

@Entitypublic class Org implements java.io.Serializable { // Fields @Id @GeneratedValue private String orgId; private String orgName; @OneToMany(mappedBy = "org") private List<Department> departments; // Constructors... // Property accessors...}

Java代码

@Entity
public class Department implements java.io.Serializable {
// Fields
@Id
@GeneratedValue
private String id;
private String name;
@ManyToOne(fetch=FetchType.EAGER)
@JoinColumn(name="org_orgId")
private Org org;
@OneToMany(mappedBy = "department")
private List<Employee> employees;
// Constructors
public List<Employee> getEmployees() {
return employees;
}
public void setEmployees(List<Employee> employees) {
this.employees = employees;
}
public Org getOrg() {
return org;
}
public void setOrg(Org org) {
this.org = org;
}
/** default constructor */
.
.
.
}

@Entitypublic class Department implements java.io.Serializable { // Fields @Id @GeneratedValue private String id; private String name; @ManyToOne(fetch=FetchType.EAGER) @JoinColumn(name="org_orgId") private Org org; @OneToMany(mappedBy = "department") private List<Employee> employees; // Constructors public List<Employee> getEmployees() { return employees; } public void setEmployees(List<Employee> employees) { this.employees = employees; } public Org getOrg() { return org; } public void setOrg(Org org) { this.org = org; } /** default constructor */ . . . }

Java代码

@Entity
public class Employee implements java.io.Serializable {
// Fields
@Id
@GeneratedValue
private String employeeId;
private String employeeName;
private String passWord;
private Integer age;
private Integer sex;
@ManyToOne(fetch=FetchType.EAGER)
@JoinColumn(name="department_id")
private Department department;
public Department getDepartment() {
return department;
}
public void setDepartment(Department department) {
this.department = department;
}
/** default constructor */
...
// Property accessors
...
}

@Entitypublic class Employee implements java.io.Serializable { // Fields @Id @GeneratedValue private String employeeId; private String employeeName; private String passWord; private Integer age; private Integer sex; @ManyToOne(fetch=FetchType.EAGER) @JoinColumn(name="department_id") private Department department; public Department getDepartment() { return department; } public void setDepartment(Department department) { this.department = department; } /** default constructor */ ... // Property accessors ...}

双向多对多：@ManyToMany.单向多对多这里不在赘述（没有太多实际意义）

这个比较简单，看下代码就明白了：

Java代码

@Entity
public class Book implements java.io.Serializable {
@Id
private int id;
private String name;
private float money;
@ManyToMany(cascade = CascadeType.ALL)
private List<Author> authors;
public List<Author> getAuthors() {
return authors;
}
public void setAuthors(List<Author> authors) {
this.authors = authors;
}
...
}

@Entitypublic class Book implements java.io.Serializable { @Id private int id; private String name; private float money; @ManyToMany(cascade = CascadeType.ALL) private List<Author> authors; public List<Author> getAuthors() { return authors; } public void setAuthors(List<Author> authors) { this.authors = authors; } ...}

Java代码

@Entity
public class Author implements java.io.Serializable {
@Id
private int id;
private String name;
private int age;
@ManyToMany(mappedBy="authors")
private List<Book> books;
public List<Book> getBooks() {
return books;
}
public void setBooks(List<Book> books) {
this.books = books;
}
...
}

@Entitypublic class Author implements java.io.Serializable { @Id private int id; private String name; private int age; @ManyToMany(mappedBy="authors") private List<Book> books; public List<Book> getBooks() { return books; } public void setBooks(List<Book> books) { this.books = books; } ...}

需要注意的是：注释最好加在属性上，不要加在get方法上，那样做有时候就会出错。比如:@ManyToMany的时候就会报错！

注意import javax.xx.Entity ，而不是org.hibernate.xx.Entity。

Descn属性不存在于数据库中，用@Transient 注明

------------------------------------------

1,需要: Hibernate库文件,Hibernate Annotations库,ejb3-persstence.jar(Java 持久化API)

sessionFactory=new AnnotationConfiguration().buildSessionFactory();

------------------------------------------

2,<bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">

<list>

<value>com.onjava.modelplanes.domain.PlaneType</value>

</list>

</property>

</bean>

------------------------------------------

1,@Entity

@Table(name = "teacher_info")

@IdClass(UUIDHexGenerator.class)

public class UserMember implements java.io.Serializable

2,@entity通过getters/setters方法访问，或直接访问他的成员变量。

@Entity(access = AccessType.PROPERTY)

@Entity(access = AccessType.FIELD)

------------------------------------------

映射标识符

1,@Id

@GeneratedValue(strategy = GenerationType.AUTO)

private String id;

2,@Id(generate=GeneratorType.SEQUENCE, generator='SEQ_STORE')

3,@Id(generate=GeneratorType.IDENTITY)

------------------------------------------

映射属性

1,@Transient

2,@Column(name="PLANE_ID", length=80, nullable=true)

3,@Basic(fetch = FetchType.LAZY)

4,@Serialized 凡标识@Serialized的属性将被序列化

public Country getCountry() { ... }

5,@Lob标识了存储对象可能是个CLOB或者BLOB。

@Lob(type=LobType.CLOB)

public String getFullText(){return fullText;}

@Lob(type = LobType.BLOB)

public byte[] getFullCode() {return fullCode;}

@Version 定义乐观锁机制使用

------------------------------------------

关联关系:

一、一对一:

1,@OneToOne(mappedBy = "address")

public User getUser() {

return user;

}

1、两边都定义了@OneToOne，但都没有定义mappedBy,则user和address表都会生成到对方的外键，双方都是这个关系的拥有者。

2、两边都定义了@OneToOne，如果user定义了mappedBy，则在address表生成到user的外键，address是这个关系的拥有者；如果address定义

了mappedBy，则在user表生成到address的外键，user是这个关系的拥有者。

二、一对多,多对一:

2,@ManyToOne( cascade = {CascadeType.PERSIST, CascadeType.MERGE} )

3,@OneToMany(mappedBy="planeType",cascade=CascadeType.ALL, fetch=FetchType.EAGER)

@OrderBy("name")

public List<ModelPlane> getModelPlanes() {

return modelPlanes;

}

其中定义mappedBy的是@OneToMany,也就是说One这一方是关系的拥有者。Many一方的表中生成到关联类的外键。

三、@ManyToMany

private Set authors = new HashSet<Author>();

@ManyToMany

public Set<Author> getAuthors(){

return authors;

}

private Set books = new HashSet<Book>();

@ManyToMany(mappedBy="authors")

public Set<Book> getBooks(){

return books;

}

@ManyToMany会生成中间表，具体表名和字段可以通过@AssociationTable来定义，默认的就可以了，同样关系的非拥有者，需要定义mappedBy属性。

------------------------------------------

命名查询

你也可以通过注解,利用@NameQueries和@NameQuery注解,如下:

@NamedQueries(

{

@NamedQuery(name="planeType.findAll",query="select p from PlaneType p" ),

@NamedQuery(name="planeType.delete",query="delete from PlaneType where id=:id" )

}

)

------------------------------------------

内嵌对象（组件）

@Embedded({

@AttributeOverride(name='iso2', column = @Column(name='bornIso2') ),

@AttributeOverride(name='name', column = @Column(name='bornCountryName') )

})

Country bornIn;

...

}

@Embeddable(access = AccessType.FIELD)

public class Address implements Serializable {

String city;

Country nationality;

}

@Embeddable

public class Country implements Serializable {

private String iso2;

private String name;

public String getIso2() { return iso2; }

public void setIso2(String iso2) { this.iso2 = iso2; }

@Column(name='countryName')

public String getName() { return name; }

public void setName(String name) { this.name = name; }

...

}

------------------------------------------

自定义的主键生成策略

@javax.persistence.GeneratedIdTable(

name='GEN_TABLE',

table = @Table(name='GENERATOR_TABLE'),

pkColumnName = 'key',

valueColumnName = 'hi'

)

@javax.persistence.TableGenerator(

name='EMP_GEN',

tableName='GEN_TABLE',

pkColumnValue='EMP',

allocationSize=20

)

@javax.persistence.SequenceGenerator(

name='SEQ_GEN',

sequenceName='my_sequence'

)

package org.hibernate.test.metadata;

school和userMember是一对多关系

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import org.hibernate.annotations.Formula;
import org.hibernate.annotations.GenericGenerator;
@Entity
@Table(name = "school_info")
public class SchoolInfo implements java.io.Serializable {
@Id
@GeneratedValue(generator = "system-uuid")
@GenericGenerator(name = "system-uuid", strategy = "uuid")
private String id;//hibernate的uuid机制,生成32为字符串
@Column(name = "actcodeId", updatable = false, nullable = true, length = 36)
private String actcodeId;
@Formula("select COUNT(*) from school_info")
private int count;
@Temporal(TemporalType.TIMESTAMP)//不用set,hibernate会自动把当前时间写入
@Column(updatable = false, length = 20)
private Date createTime;
@Temporal(TemporalType.TIMESTAMP)
private Date updateTime;// 刚开始我默认insertable=false,但会读取出错提示如下:
// Value '0000-00-00' can not be represented as java.sql.Timestamp
// mappedBy="school"就相当于inverse=true,(mappedBy指定的是不需要维护关系的一端)
// 应该注意的是mappedBy值对应@ManyToOne标注的属性,我刚开始写成"schoolId",让我郁闷了好一会
@OneToMany(mappedBy = "school", cascade = CascadeType.ALL, fetch = FetchType.EAGER, targetEntity = UserMember.class)
// 用范性的话,就不用targetEntity了
private List users = new ArrayList();
}

@GeneratedValue(strategy=GenerationType.AUTO)我们常用的自增长机制,我这里采用的是hibernate的uuid生成机制.

需要注意的是import javax.xx.Entity ，而不是org.hibernate.xx.Entity。

郁闷的是我上面用到@Formula,生成的sql竟然是'select COUNT(*) from school_info as formula0_ from school_info schoolinfo0_,当然不能执行了,寻求正解中~!!!!!!!!!

UserMember.java(前面引入的包已经贴过了,下面就不贴了)

@Entity
@Table(name = "teacher_info")//实体类和数据库表名不一致时,才用这个
public class UserMember implements java.io.Serializable {
@Id
@GeneratedValue(generator = "system-uuid")
@GenericGenerator(name = "system-uuid", strategy = "uuid")
private String id;
@Column(updatable = false, nullable = false, length = 20)
private String logonName;
@Temporal(TemporalType.TIMESTAMP)
@Column(updatable = false, length = 20)
private Date createTime;
@Temporal(TemporalType.TIMESTAMP)
private Date updateTime;
@ManyToOne(cascade = { CascadeType.MERGE })
@JoinColumn(name = "schoolId")
private SchoolInfo school;
//注意该类就不用声明schoolId属性了,如果不用@JoinColumn指明关联的字段,hibernate默认会是school_id.

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2009-08-05 18:37
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