Hibernate4Step2_2

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hardwork

本着应用的目的快速学习Hibernate4框架

  • Hibernate映射

前面的话

本节主要介绍：

  1. 一对一关系映射主键和外键方式
  2. 多对多关系映射单向和双向方式

一对一关系映射主键方式

通过一个Demo来理解，用户和用户地址具有一对一关系，类图如下：

user_address.mgc

User.java

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package cn.codeforgod.model;

public class User
{
	private int id;
	private String name;
	private Address address;
	
	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;
	}
	public Address getAddress()
	{
		return address;
	}
	public void setAddress(Address address)
	{
		this.address = address;
	}
}

Address.java

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package cn.codeforgod.model;

public class Address
{
	private int id;
	private String address;
	private String zipcode;	// 邮政编码
	private User user;
	
	public int getId()
	{
		return id;
	}
	public void setId(int id)
	{
		this.id = id;
	}
	public String getAddress()
	{
		return address;
	}
	public void setAddress(String address)
	{
		this.address = address;
	}
	public String getZipcode()
	{
		return zipcode;
	}
	public void setZipcode(String zipcode)
	{
		this.zipcode = zipcode;
	}
	public User getUser()
	{
		return user;
	}
	public void setUser(User user)
	{
		this.user = user;
	}
}

User.hbm.xml

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

<hibernate-mapping package="cn.codeforgod.model">

	<class name="User" table="t_user">
		<id name="id" column="userId">
			<generator class="native"></generator>
		</id>

		<property name="name" column="userName" type="string"></property>

		<one-to-one name="address" class="cn.codeforgod.model.Address"
			cascade="all"></one-to-one>
	</class>

</hibernate-mapping>

Address.hbm.xml

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

<hibernate-mapping package="cn.codeforgod.model">

	<class name="Address" table="t_address">
		<!-- 既是t_address主键也是t_user的外键 -->
		<id name="id" column="addressId">
			<generator class="foreign">
				<param name="property">user</param>
			</generator>
		</id>

		<property name="address" column="address" type="string"></property>

		<property name="zipcode" column="zipcode" type="string"></property>
		
		<!-- constrained约束，共享t_user主键 -->
		<one-to-one name="user" class="cn.codeforgod.model.User"
			constrained="true"></one-to-one>
	</class>

</hibernate-mapping>

数据库中表的关系如下图：

user_address

一对一关系映射外键方式

类图如下：

user2_address2.mgc

User2.java

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package cn.codeforgod.model;

public class User2
{
	private int id;
	private String name;
	private Address2 address;
	
	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;
	}
	public Address2 getAddress()
	{
		return address;
	}
	public void setAddress(Address2 address)
	{
		this.address = address;
	}
}

Address2.java

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package cn.codeforgod.model;

public class Address2
{
	private int id;
	private String address;
	private String zipcode;	// 邮政编码
	private User2 user;
	
	public int getId()
	{
		return id;
	}
	public void setId(int id)
	{
		this.id = id;
	}
	public String getAddress()
	{
		return address;
	}
	public void setAddress(String address)
	{
		this.address = address;
	}
	public String getZipcode()
	{
		return zipcode;
	}
	public void setZipcode(String zipcode)
	{
		this.zipcode = zipcode;
	}
	public User2 getUser()
	{
		return user;
	}
	public void setUser(User2 user)
	{
		this.user = user;
	}
}

User2.hbm.xml

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

<hibernate-mapping package="cn.codeforgod.model">

	<class name="User2" table="t_user2">
		<id name="id" column="userId">
			<generator class="native"></generator>
		</id>

		<property name="name" column="userName" type="string"></property>

		<!-- 通过unique属性设置t_user2外键唯一，
			那么一条记录只能有唯一一条address与之对应，
			否则多条记录可以有相同address与之对应就是多对一了 
			-->
		<many-to-one name="address" column="address"
			class="cn.codeforgod.model.Address2" cascade="all" unique="true"></many-to-one>
	</class>

</hibernate-mapping>

Address2.hbm.xml

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

<hibernate-mapping package="cn.codeforgod.model">

	<class name="Address2" table="t_address2">
		<id name="id" column="addressId">
			<generator class="native"></generator>
		</id>

		<property name="address" column="address" type="string"></property>

		<property name="zipcode" column="zipcode" type="string"></property>
		
		<one-to-one name="user" class="cn.codeforgod.model.User2" property-ref="address"></one-to-one>
	</class>

</hibernate-mapping>

数据库中表的关系如下图：

user2_address2

多对多关系单向映射

类图如下：

student_course.mgc

Student.java

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package cn.codeforgod.model;

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

public class Student
{
	private int id;
	private String name;
	private Set<Course> courses = new HashSet<Course>();
	
	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;
	}
	public Set<Course> getCourses()
	{
		return courses;
	}
	public void setCourses(Set<Course> courses)
	{
		this.courses = courses;
	}
}

Course.java

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package cn.codeforgod.model;

public class Course
{
	private int id;
	private String name;
	
	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;
	}
}

Student.hbm.xml

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

<hibernate-mapping package="cn.codeforgod.model">

	<class name="Student" table="t_student">
		<id name="id" column="studentId">
			<generator class="native"></generator>
		</id>

		<property name="name" column="studentName"></property>

		<!-- 需要通过中间表t_student_course实现多对多 -->
		<set name="courses" table="t_student_course" cascade="save-update">
			<key column="studentId"></key>
			<many-to-many class="cn.codeforgod.model.Course" column="courseId"></many-to-many>
		</set>
	</class>

</hibernate-mapping>

Course.hbm.xml

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

<hibernate-mapping package="cn.codeforgod.model">

	<class name="Course" table="t_course">
		<id name="id" column="courseId">
			<generator class="native"></generator>
		</id>
		
		<property name="name" column="courseName"></property>
	</class>

</hibernate-mapping>

数据库中表的关系如下图：

manyToMany1

多对多关系双向映射

类图如下：

student2_course2.mgc

Student2.java

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package cn.codeforgod.model;

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

public class Student2
{
	private int id;
	private String name;
	private Set<Course2> courses = new HashSet<Course2>();
	
	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;
	}
	public Set<Course2> getCourses()
	{
		return courses;
	}
	public void setCourses(Set<Course2> courses)
	{
		this.courses = courses;
	}
}

Course2.java

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package cn.codeforgod.model;

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

public class Course2
{
	private int id;
	private String name;
	private Set<Student2> students = new HashSet<Student2>();
	
	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;
	}
	public Set<Student2> getStudents()
	{
		return students;
	}
	public void setStudents(Set<Student2> students)
	{
		this.students = students;
	}
}

Student2.hbm.xml

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

<hibernate-mapping package="cn.codeforgod.model">

	<class name="Student2" table="t_student2">
		<id name="id" column="studentId">
			<generator class="native"></generator>
		</id>
		
		<property name="name" column="studentName"></property>
		
		<set name="courses" table="t_student_course2" cascade="save-update">
			<key column="studentId"></key>
			<many-to-many class="cn.codeforgod.model.Course2" column="courseId"></many-to-many>
		</set>
	</class>

</hibernate-mapping>

Course2.hbm.xml

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

<hibernate-mapping package="cn.codeforgod.model">

	<class name="Course2" table="t_course2">
		<id name="id" column="courseId">
			<generator class="native"></generator>
		</id>
		
		<property name="name" column="courseName"></property>
		
		<set name="students" table="t_student_course2" inverse="true">
			<key column="courseId"></key>
			<many-to-many class="cn.codeforgod.model.Student2" column="studentId"></many-to-many>
		</set>
	</class>

</hibernate-mapping>

数据库中表的关系如下图：

manyToMany2

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