hibernate对象管理

1、多对一关联

xml配置

1）、一个组可以有多个用户，一个用户所以一个主。User表与Group表的关系是多对已

User表

package com.mr.cheng.associations;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Table(name="t_user")
public class User {
	private int id;
	private String name;
	private Group group;
	public Group getGroup() {
		return group;
	}
	public void setGroup(Group group) {
		this.group = group;
	}
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

　　Group表

package com.mr.cheng.associations;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.OrderBy;
import javax.persistence.Table;

@Entity
@Table(name="t_group")
public class Group {
	private int id;
	private String name;
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

　　User.hbm.<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
	<class name="com.bjsxt.hibernate.User" table="t_user">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"></property>

		<many-to-one name="group" column="groupId"></many-to-one>
    </class>
	
</hibernate-mapping>

　　Group.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
	<class name="com.mr.cheng.associations.Group" table="tt_group">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"></property>
    </class>
	
</hibernate-mapping>

　　2）、一对多配置

　　在Group对象中加一个Set类型的字段，代码如下

package com.mr.cheng.associations;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.OrderBy;
import javax.persistence.Table;

@Entity
@Table(name="t_group")
public class Group {
	private int id;
	private String name;
	private Set<User> userSet = new HashSet<User>();
	public Set<User> getUserSet() {
		return userSet;
	}
	public void setUserSet(Set<User> userSet) {
		this.userSet = userSet;
	}
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

Group.hbm.xml配置如下：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
	<class name="com.mr.cheng.associations.Group" table="tt_group">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"></property>
		<set name="userSet">
			<key column="groupId"></key>
			<one-to-many class="com.mr.cheng.associations.User"/>
		</set>
    </class>
	
</hibernate-mapping>

　　配置一对多时，在Group.hbm.xml文件中set属性名字对应Group的字段，key中的Column属性对应外键名字，即是通过groupId进行关联。 one-to-many 中的class对应关联的类。

　　User表

package com.mr.cheng.associations;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Table(name="t_user")
public class User {
	private int id;
	private String name;
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

　　User.hbm.xml配置如下：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
	<class name="com.mr.cheng.associations.User" table="tt_user">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"></property>
    </class>
	
</hibernate-mapping>

　　

 3）、多对一 与 已对多双向关联

User 对象代码如下：

package com.mr.cheng.associations;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Table(name="t_user")
public class User {
	private int id;
	private String name;
	private Group group;
	public Group getGroup() {
		return group;
	}
	public void setGroup(Group group) {
		this.group = group;
	}
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

　Group对象代码如下：　

package com.mr.cheng.associations;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.OrderBy;
import javax.persistence.Table;

@Entity
@Table(name="t_group")
public class Group {
	private int id;
	private String name;
	private Set<User> userSet = new HashSet<User>();
	public Set<User> getUserSet() {
		return userSet;
	}
	public void setUserSet(Set<User> userSet) {
		this.userSet = userSet;
	}
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

　　User.hbm.xml配日志如下：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
	<class name="com.mr.cheng.associations.User" table="tt_user">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"></property>
		<many-to-one name="group" column="groupId"></many-to-one>
    </class>
	
</hibernate-mapping>

　　Group.hbm.xml配置如下：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
	<class name="com.mr.cheng.associations.Group" table="tt_group">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"></property>
		<set name="userSet">
			<key column="groupId"></key>
			<one-to-many class="com.mr.cheng.associations.User"/>
		</set>
    </class>
	
</hibernate-mapping>

　　注意：group.hbm.xml中的一对多配置时 key 中column属性的值必须与User.hbm.xml中的 many-to-one属性中的name值一直。否则出现意想不到的结果。

4）、多对多双向关联

一个用户可以选择多个房间，一个房间可以住多个人，因此User表与Room表的关系就为多对多的关系。

User对象代码如下：

package com.mr.cheng.associations;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Table(name="t_user")
public class User {
	private int id;
	private String name;
	private Set<Room> roomSet = new HashSet<Room>();
	public Set<Room> getRoomSet() {
		return roomSet;
	}
	public void setRoomSet(Set<Room> roomSet) {
		this.roomSet = roomSet;
	}
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

　　Room对象的代码如下：

package com.mr.cheng.associations;

import java.util.HashSet;
import java.util.Set;

public class Room {
	private int id;
	private String name;
	private Set<User> userSet = new HashSet<User>();
	public Set<User> getUserSet() {
		return userSet;
	}
	public void setUserSet(Set<User> userSet) {
		this.userSet = userSet;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}	

　　User.hbm.xml的配置如下：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
	<class name="com.mr.cheng.associations.User" table="tt_user">
		<id name="id" column="userId">
			<generator class="native"></generator>
		</id>
		<property name="name"></property>
		<set name="roomSet" inverse="true" table="tt_user_room">
			<key column="userId"></key>
			<many-to-many class="com.mr.cheng.associations.Room" column="roomId"></many-to-many>
		</set>
    </class>
	
</hibernate-mapping>

　　Room.hbm.xml的配置如下：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
	<class name="com.mr.cheng.associations.Room" table="tt_room">
		<id name="id" column="roomId">
			<generator class="native"></generator>
		</id>
		<property name="name"></property>
		<set name="userSet" table="tt_user_room">
			<key column="roomId"></key>
			<many-to-many class="com.mr.cheng.associations.User" column="userId"></many-to-many>
		</set>
    </class>
	
</hibernate-mapping>