关系映射级别注解

妖狐艹你老母 2022-07-12 00:28 126阅读 0赞

# 实体之间的映射关系 #

1、一对一：一个公民对应一个身份证号码。

2、一对多（多对一）：一个公民有多个银行账号。

3、多对多：一个学生可以有多个老师，一个老师有多个学生。

# 1、一对一单向外键 #

@OneToOne(cascade=CascadeType.All)

@JoinColumn(name="pid",unique=true)

例子：

student类

package com.txr.oto.fk;
    
    import java.util.Date;
    
    import javax.persistence.CascadeType;
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    import javax.persistence.JoinColumn;
    import javax.persistence.OneToOne;
    
    
    //学生实体类
    @Entity
    public class Student {
    	
    	private int sid;
    
    	private IdCard card;
    	private String gender;
    	private Date birthday;
    	private String major;
    	
    	@OneToOne(cascade=CascadeType.ALL)
    	@JoinColumn(name="pid",unique=true)
    	public IdCard getCard() {
    		return card;
    	}
    	public void setCard(IdCard card) {
    		this.card = card;
    	}
    	@Id
    	@GeneratedValue
    	public int getSid() {
    		return sid;
    	}
    	public void setSid(int sid) {
    		this.sid = sid;
    	}
    	public String getGender() {
    		return gender;
    	}
    	public void setGender(String gender) {
    		this.gender = gender;
    	}
    	public Date getBirthday() {
    		return birthday;
    	}
    	public void setBirthday(Date birthday) {
    		this.birthday = birthday;
    	}
    	public String getMajor() {
    		return major;
    	}
    	public void setMajor(String major) {
    		this.major = major;
    	}
    	
    	public Student() {
    	}
    	public Student(IdCard card, String gender, Date birthday, String major) {
    		this.card = card;
    		this.gender = gender;
    		this.birthday = birthday;
    		this.major = major;
    	}
    	
    	
    	
    
    }

IdCard类

package com.txr.oto.fk;
    
    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    
    import org.hibernate.annotations.GenericGenerator;
    
    
    //身份证类
    @Entity
    public class IdCard {
    
    	
    	private String pid;//身份证号码
    	private String sname;//学生的姓名
    	@Id
    	@GeneratedValue(generator="pid")
    	@GenericGenerator(name="pid",strategy="assigned")
    	@Column(length=18)
    	public String getPid() {
    		return pid;
    	}
    	public void setPid(String pid) {
    		this.pid = pid;
    	}
    	public String getSname() {
    		return sname;
    	}
    	public void setSname(String sname) {
    		this.sname = sname;
    	}
    	public IdCard(String pid, String sname) {
    		super();
    		this.pid = pid;
    		this.sname = sname;
    	}
    	public IdCard() {
    	}
    	
    	
    	
    	
    }

**运行结果：**

![Center][]

**注意：**注解要么全部写在字段上，要不全部写在getXX()方法上，千万不能混合使用否则会报如下错误

org.hibernate.MappingException: Could not determine type for: com.txr.oto.fk.IdCard, at table: Student, for columns: \[org.hibernate.mapping.Column(card)\]  
at org.hibernate.mapping.SimpleValue.getType(SimpleValue.java:314)  
at org.hibernate.mapping.SimpleValue.isValid(SimpleValue.java:292)  
at org.hibernate.mapping.Property.isValid(Property.java:239)  
at org.hibernate.mapping.PersistentClass.validate(PersistentClass.java:483)  
at org.hibernate.mapping.RootClass.validate(RootClass.java:270)  
at org.hibernate.cfg.Configuration.validate(Configuration.java:1329)  
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1791)  
at oto\_fk.TestStudent.testOneTOneAnnocation(TestStudent.java:18)  
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)  
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)  
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)  
at java.lang.reflect.Method.invoke(Method.java:498)  
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)  
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)  
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)  
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)  
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)  
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)  
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)  
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)  
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)  
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)  
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)  
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)  
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)  
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)  
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)  
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)  
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)  
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)  
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

# 2、一对一双向外键关联 #

主控方的配置同一对一单向外键关联

@OneToOne(mappedBy="card")//被控方

双向关联，必须设置mappedBy属性。因为双向关联只能交给一方去控制，不可能在双方都设置外键保存关联关系，否则双方都无法保存。

将IdCard中添加Student的关联关系

package com.txr.oto.bfk;
    
    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    import javax.persistence.OneToOne;
    
    import org.hibernate.annotations.GenericGenerator;
    
    
    //身份证类
    @Entity
    public class IdCard {
    
    	@Id
    	@GeneratedValue(generator="pid")
    	@GenericGenerator(name="pid",strategy="assigned")
    	@Column(length=18)
    	private String pid;//身份证号码
    	private String sname;//学生的姓名
    	
    	@OneToOne(mappedBy="card")
    	private Student stu;
    	
    	public Student getStu() {
    		return stu;
    	}
    	public void setStu(Student stu) {
    		this.stu = stu;
    	}
    	public String getPid() {
    		return pid;
    	}
    	public void setPid(String pid) {
    		this.pid = pid;
    	}
    	public String getSname() {
    		return sname;
    	}
    	public void setSname(String sname) {
    		this.sname = sname;
    	}
    	public IdCard(String pid, String sname) {
    		super();
    		this.pid = pid;
    		this.sname = sname;
    	}
    	public IdCard() {
    	}
    	
    	
    	
    	
    }

运行结果：

![Center 1][]

# 3、一对一单向外键联合主键 #

**创建主键类**

**  主键类必须实现serializable接口，重写hashCode()和equals()方法。**

主键类

@Embeddable

实体类

@EmbeddedId

具体的详细部分请参见上一章的属性级别注解

# 4、多对一单向外键关联 #

多方持有一方的引用，比如：多个学生对应一个班级（多对一）

@ManyToOne(cascade=\{CascadeType.ALL\}, fetch=FetchType.EAGER )

@JoinColumn(name="cid",referencedColumnName="CID")

Student类

package com.txr.mto_fk;
    
    import java.util.Date;
    
    import javax.persistence.CascadeType;
    import javax.persistence.Entity;
    import javax.persistence.FetchType;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    import javax.persistence.JoinColumn;
    import javax.persistence.ManyToOne;
    import javax.persistence.OneToOne;
    
    
    //学生实体类
    @Entity
    public class Student {
    	
    	@Id
    	private int sid;
    	private String gender;
    	private Date birthday;
    	private String major;
    	@ManyToOne(cascade={CascadeType.ALL},fetch=FetchType.EAGER)
    	@JoinColumn(name="cid",referencedColumnName="CID")
    	private ClassRoom classRoom;
    	
    	
    	public ClassRoom getClassRoom() {
    		return classRoom;
    	}
    	public void setClassRoom(ClassRoom classRoom) {
    		this.classRoom = classRoom;
    	}
    	public Student() {
    	}
    	public int getSid() {
    		return sid;
    	}
    	public void setSid(int sid) {
    		this.sid = sid;
    	}
    	public String getGender() {
    		return gender;
    	}
    	public void setGender(String gender) {
    		this.gender = gender;
    	}
    	public Date getBirthday() {
    		return birthday;
    	}
    	public void setBirthday(Date birthday) {
    		this.birthday = birthday;
    	}
    	public String getMajor() {
    		return major;
    	}
    	public void setMajor(String major) {
    		this.major = major;
    	}
    	public Student(int sid, String gender, Date birthday, String major) {
    		super();
    		this.sid = sid;
    		this.gender = gender;
    		this.birthday = birthday;
    		this.major = major;
    	}
    	
    	
    
    }

ClassRoom类

package com.txr.mto_fk;
    
    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    
    import org.hibernate.annotations.GenericGenerator;
    
    //班级
    @Entity
    public class ClassRoom {
    	@Id
    	@GeneratedValue(generator="cid")
    	@GenericGenerator(name="cid",strategy="assigned")
    	@Column(length=4)
    	private String cid;
    	private String cname;
    	public String getCid() {
    		return cid;
    	}
    	public void setCid(String cid) {
    		this.cid = cid;
    	}
    	public String getCname() {
    		return cname;
    	}
    	public void setCname(String cname) {
    		this.cname = cname;
    	}
    	public ClassRoom(String cid, String cname) {
    		this.cid = cid;
    		this.cname = cname;
    	}
    	public ClassRoom() {
    	}
    	
    	
    	
    	
    }

测试：

package mto_fk;
    
    import org.hibernate.Session;
    import org.hibernate.SessionFactory;
    import org.hibernate.cfg.Configuration;
    import org.hibernate.service.ServiceRegistry;
    import org.hibernate.service.ServiceRegistryBuilder;
    import org.hibernate.tool.hbm2ddl.SchemaExport;
    import org.junit.Test;
    
    public class TestStudent {
    	@Test
    	public void testSchemaExport()
    	{
    		Configuration config=new Configuration().configure();
    		ServiceRegistry serviceRegistry=new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
    		SessionFactory sessionFactory=config.buildSessionFactory(serviceRegistry);
    		Session session=sessionFactory.openSession();
    		SchemaExport export =new SchemaExport(config);
    		export.create(true,true);
    	}
    }

测试结果：

![Center 2][]

# 5、一对多单向外键关联 #

一方持有多方的集合，一个班级有多个学生（一对多）

@OneToMany(cascade=\{CascadeType.ALL\},fetch=FetchType.LAZY)

@JoinColumn(name="cid")

总结：多对一时候，多方设置EAGER，一方设置LAZY

student类

package com.txr.mto_bfk;
    
    import java.util.Date;
    
    import javax.persistence.CascadeType;
    import javax.persistence.Entity;
    import javax.persistence.FetchType;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    import javax.persistence.JoinColumn;
    import javax.persistence.ManyToOne;
    import javax.persistence.OneToOne;
    
    
    //学生实体类
    @Entity
    public class Student {
    	
    	@Id
    	@GeneratedValue
    	private int sid;
    	private String name;
    	private String gender;
    	private Date birthday;
    	private String major;
    	
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public Student() {
    	}
    	public int getSid() {
    		return sid;
    	}
    	public void setSid(int sid) {
    		this.sid = sid;
    	}
    	public String getGender() {
    		return gender;
    	}
    	public void setGender(String gender) {
    		this.gender = gender;
    	}
    	public Date getBirthday() {
    		return birthday;
    	}
    	public void setBirthday(Date birthday) {
    		this.birthday = birthday;
    	}
    	public String getMajor() {
    		return major;
    	}
    	public void setMajor(String major) {
    		this.major = major;
    	}
    	public Student(int sid, String name,String gender, Date birthday, String major) {
    
    		this.sid = sid;
    		this.name=name;
    		this.gender = gender;
    		this.birthday = birthday;
    		this.major = major;
    	}
    	public Student(String name,String gender, Date birthday, String major) {
    
    		this.name=name;
    		this.gender = gender;
    		this.birthday = birthday;
    		this.major = major;
    	}
    	
    	
    
    }

班级类

package com.txr.mto_bfk;
    
    import java.util.List;
    
    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    
    import org.hibernate.annotations.GenericGenerator;
    
    //班级
    @Entity
    public class ClassRoom {
    	@Id
    	@GeneratedValue(generator="cid")
    	@GenericGenerator(name="cid",strategy="assigned")
    	@Column(length=4)
    	private String cid;
    	private String cname;
    	public String getCid() {
    		return cid;
    	}
    	public void setCid(String cid) {
    		this.cid = cid;
    	}
    	public String getCname() {
    		return cname;
    	}
    	public void setCname(String cname) {
    		this.cname = cname;
    	}
    	public ClassRoom(String cid, String cname) {
    		this.cid = cid;
    		this.cname = cname;
    	}
    	public ClassRoom() {
    	}
    	
    	
    	
    	
    }

测试类：

@Test
    	public void addStudentAndClass()
    	{
    		Configuration config=new Configuration().configure();
    		ServiceRegistry serviceRegistry=new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
    		SessionFactory sessionFactory=config.buildSessionFactory(serviceRegistry);
    		Session session=sessionFactory.openSession();
    		ClassRoom classRoom=new ClassRoom("1603", "软件三班");
    		Student student=new Student("txr","女", new Date(), "软件工程");
    		Student student1=new Student("xqh","女", new Date(), "软件工程");
    		student.setClassRoom(classRoom);
    		student1.setClassRoom(classRoom);
    		session.save(classRoom);
    		session.save(student1);
    		session.save(student);
    		Transaction transaction=session.beginTransaction();
    		transaction.commit();
    	}

运行结果

![Center 3][]

# 6、一对多双向外键关联 #

在双方添加注解

# 7、多对多单向外键关联 #

学生和教师构成多对多的关联关系。

其中一个多方持有另一个多方的集合对象(学生持有教师的集合)

创建中间表

//学生类

@ManyToMany

@JoinTable(

name="teachers\_students",//中间表表名

joinColumns=\{@JoinColumn(name="tid")\},//这俩个指定相应控制类字段

inverseJoinColumns=\{@JoinColumn(name="tid")\}

)

Student类

package com.txr.mtm_fk;
    
    import java.util.Date;
    import java.util.HashSet;
    import java.util.Set;
    
    import javax.persistence.CascadeType;
    import javax.persistence.Entity;
    import javax.persistence.FetchType;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    import javax.persistence.JoinColumn;
    import javax.persistence.JoinTable;
    import javax.persistence.ManyToMany;
    import javax.persistence.ManyToOne;
    import javax.persistence.OneToOne;
    
    
    //学生实体类
    @Entity
    public class Student {
    	
    	@Id
    	@GeneratedValue
    	private int sid;
    	private String name;
    	private String gender;
    	private Date birthday;
    	private String major;
    	
    	@ManyToMany
    	@JoinTable(
    			name="teachers_students",
    			joinColumns={@JoinColumn(name="sid")},
    			inverseJoinColumns={@JoinColumn(name="tid")}
    			)
    	
    	private Set<Teacher> teachers=new HashSet<Teacher>();
    	
    	
    	public Set<Teacher> getTeachers() {
    		return teachers;
    	}
    	public void setTeachers(Set<Teacher> teachers) {
    		this.teachers = teachers;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public Student() {
    	}
    	public int getSid() {
    		return sid;
    	}
    	public void setSid(int sid) {
    		this.sid = sid;
    	}
    	public String getGender() {
    		return gender;
    	}
    	public void setGender(String gender) {
    		this.gender = gender;
    	}
    	public Date getBirthday() {
    		return birthday;
    	}
    	public void setBirthday(Date birthday) {
    		this.birthday = birthday;
    	}
    	public String getMajor() {
    		return major;
    	}
    	public void setMajor(String major) {
    		this.major = major;
    	}
    	public Student(int sid, String name,String gender, Date birthday, String major) {
    
    		this.sid = sid;
    		this.name=name;
    		this.gender = gender;
    		this.birthday = birthday;
    		this.major = major;
    	}
    	public Student(String name,String gender, Date birthday, String major) {
    
    		this.name=name;
    		this.gender = gender;
    		this.birthday = birthday;
    		this.major = major;
    	}
    	
    	
    
    }

Teacher类

package com.txr.mtm_fk;
    
    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    
    import org.hibernate.annotations.GenericGenerator;
    
    //教师
    @Entity
    public class Teacher {
    	@Id
    	@GeneratedValue(generator="tid")
    	@GenericGenerator(name="tid",strategy="assigned")
    	@Column(length=4)
    	private String tid;
    	private String tname;
    	public String getTid() {
    		return tid;
    	}
    	public void setTid(String tid) {
    		this.tid = tid;
    	}
    	public String getTname() {
    		return tname;
    	}
    	public void setTname(String tname) {
    		this.tname = tname;
    	}
    	public Teacher() {
    		
    	}
    	public Teacher(String tid, String tname) {
    		super();
    		this.tid = tid;
    		this.tname = tname;
    	}
    	
    }

测试：

@Test
    	public void testStudent()
    	{
    
    		Configuration config=new Configuration().configure();
    		ServiceRegistry serviceRegistry=new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
    		SessionFactory sessionFactory=config.buildSessionFactory(serviceRegistry);
    		Session session=sessionFactory.openSession();
    		SchemaExport export=new SchemaExport(config);
    		export.create(true,true);
    	}

运行结果

![Center 4][]![Center 5][]  
添加数据：

@Test
    	public void addTS()
    	{
    		Configuration config=new Configuration().configure();
    		ServiceRegistry serviceRegistry=new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
    		SessionFactory sessionFactory=config.buildSessionFactory(serviceRegistry);
    		Session session=sessionFactory.openSession();
    		Transaction transaction=session.beginTransaction();
    		Teacher t=new Teacher("001", "txr");
    		Teacher t1=new Teacher("002", "xqh");
    		Student s1=new Student("lyh", "男", new Date(), "软件工程");
    		Student s2=new Student("pha", "男", new Date(), "软件工程");
    		s1.getTeachers().add(t);
    		s1.getTeachers().add(t1);
    		s2.getTeachers().add(t);
    		s2.getTeachers().add(t1);
    		session.save(t1);
    		session.save(t);
    		session.save(s1);
    		session.save(s2);
    		transaction.commit();
    		session.close();
    	}

运行结果：  
![Center 6][]

# 8、多对多双向外键关联 #

双方持有对方的集合对象，其中一方设置

//教师类

@ManyToMany(mappedBy="teachers")

另一方

//学生类

@ManyToMany

@JoinTable(

name="teachers\_students",

joinColumns=\{@JoinColumn(name="tid")\}

)

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