Hibernate学习笔记3.1（Hibernate关系映射）

主要指对象之间的关系

1.一对一关联

一对一单项外键关联

比如说一夫一妻

Wifi.java

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

@Entity

public class Wife {

    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;

    }

}

Huaband.java

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.OneToOne;

@Entity

public class Husband {

    private int id;

    private String name;

    private Wife wife;

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public String getName() {

        return name;

    }

    @OneToOne

    @JoinColumn(name="wifeId")

    public Wife getWife() {

        return wife;

    }

    public void setId(int id) {

        this.id = id;

    }

    public void setName(String name) {

        this.name = name;

    }

    public void setWife(Wife wife) {

        this.wife = wife;

    }

}

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>

<!DOCTYPE hibernate-configuration PUBLIC

        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"

        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>

        <property name="connection.url">jdbc:mysql://localhost/hibernate</property>

        <property name="connection.username">root</property>

        <property name="connection.password">bjsxt</property>

        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>

       <!--

        <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>

        <property name="connection.url">jdbc:oracle:thin:@localhost::SXT</property>

        <property name="connection.username">scott</property>

        <property name="connection.password">tiger</property>

          <property name="dialect">org.hibernate.dialect.OracleDialect</property>

       -->

        <!-- JDBC connection pool (use the built-in) -->

        <property name="connection.pool_size"></property>

        <!-- Enable Hibernate's automatic session context management -->

        <property name="current_session_context_class">thread</property>

        <!-- Disable the second-level cache  -->

        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->

        <property name="show_sql">true</property>

        <property name="format_sql">true</property>

        <!-- Drop and re-create the database schema on startup

        <property name="hbm2ddl.auto">update</property>

         -->

        <!--   -->

        <mapping resource="com/bjsxt/hibernate/Student.hbm.xml"/>

        <mapping resource="com/bjsxt/hibernate/StuIdCard.hbm.xml"/>

        <mapping class="com.bjsxt.hibernate.Husband"/>

        <mapping class="com.bjsxt.hibernate.Wife"/>

    </session-factory>

</hibernate-configuration>

test.java关键代码

@Test

    public void testSchemaExport() {

        new SchemaExport(new AnnotationConfiguration().configure()).create(false, true);

    }

实际建表关系

    @OneToOne

    @JoinColumn(name="wifeId")

    public Wife getWife() {

        return wife;

    }

    public void setId(int id) {

        this.id = id;

    }

上面可以指定生成的列名

2.单向关联

Student.java

package com.bjsxt.hibernate;

public class Student {

    private int id;

    private String name;

    private int age;

    private String sex;

    private boolean good;

    public boolean isGood() {

        return good;

    }

    public void setGood(boolean good) {

        this.good = good;

    }

    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 int getAge() {

        return age;

    }

    public void setAge(int age) {

        this.age = age;

    }

    public String getSex() {

        return sex;

    }

    public void setSex(String sex) {

        this.sex = sex;

    }

}

StuIdCard.java

package com.bjsxt.hibernate;

public class StuIdCard {

    private int id;

    private String num;

    private Student student;

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getNum() {

        return num;

    }

    public void setNum(String num) {

        this.num = num;

    }

    public Student getStudent() {

        return student;

    }

    public void setStudent(Student student) {

        this.student = student;

    }

}

StuIdCard.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.bjsxt.hibernate.StuIdCard">

        <id name="id">

            <generator class="native"></generator>

        </id>

        <property name="num"/>

        <many-to-one name="student" column="studentId" unique="true"></many-to-one>

    </class>

</hibernate-mapping>

从字面上看是多对一其实后面指定了unique 所以实际上是一对一

关系图

2.一对一双向外键关联

直接写@onetoone的话会导致产生两个外键

Husband.java

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.OneToOne;

@Entity

public class Husband {

    private int id;

    private String name;

    private Wife wife;

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public String getName() {

        return name;

    }

    @OneToOne

    @JoinColumn(name="wifeId")

    public Wife getWife() {

        return wife;

    }

    public void setId(int id) {

        this.id = id;

    }

    public void setName(String name) {

        this.name = name;

    }

    public void setWife(Wife wife) {

        this.wife = wife;

    }

}

Wife.java

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.OneToOne;

@Entity

public class Wife {

    private int id;

    private String name;

    private Husband husband;

    @OneToOne(mappedBy="wife")      //在对方那里设置

    public Husband getHusband() {

        return husband;

    }

    public void setHusband(Husband husband) {

        this.husband = husband;

    }

    @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;

    }

}

只要有双向关联，必须设@OneToOne(mappedBy="wife")

告诉hibernate对方那里是主导

2.XML设置

Student.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.bjsxt.hibernate.Student" dynamic-update="true">

        <id name="id">

            <generator class="native"></generator>

        </id>

        <property name="name"></property>

        <property name="age" />

        <property name="sex" />

        <property name="good" type="yes_no"></property>

        <one-to-one name="stuIdCard" property-ref="student"></one-to-one>

    </class>

</hibernate-mapping>

一对一单向双向的区别：在数据库没什么区别但是在Java程序中有区别单向和双向的区别能否靠对方找到自己

4.一对一单向主键关联

Husband.java

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.OneToOne;

import javax.persistence.PrimaryKeyJoinColumn;

@Entity

public class Husband {

    private int id;

    private String name;

    private Wife wife;

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public String getName() {

        return name;

    }

    @OneToOne

    @PrimaryKeyJoinColumn

    public Wife getWife() {

        return wife;

    }

    public void setId(int id) {

        this.id = id;

    }

    public void setName(String name) {

        this.name = name;

    }

    public void setWife(Wife wife) {

        this.wife = wife;

    }

}

wifi.java

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

@Entity

public class Wife {

    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;

    }

}

测试

    @Test

    public void testSchemaExport() {

        new SchemaExport(new AnnotationConfiguration().configure()).create(false, true);

    }

但实际上并没有产生关联这是一个bug

在xml里面配置正常

StuIdCard.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.bjsxt.hibernate.StuIdCard">

        <id name="id">

            <generator class="foreign">

                <param name="property">student</param>

            </generator>

        </id>

        <property name="num"/>

        <one-to-one name="student" constrained="true"></one-to-one>

    </class>

</hibernate-mapping>

constrained = “true” 就可以加一个外键约束

在实际开发中，一对一很少，一对一主键也很少

一对一双向主键关联不太重要一般不使用略

联合主键

Husband.java

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.JoinColumns;

import javax.persistence.OneToOne;

@Entity

public class Husband {

    private int id;

    private String name;

    private Wife wife;

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public String getName() {

        return name;

    }

    @OneToOne

    @JoinColumns(

        {

            @JoinColumn(name="wifeId", referencedColumnName="id"),

            @JoinColumn(name="wifeName", referencedColumnName="name")

        }

    )

    public Wife getWife() {

        return wife;

    }

    public void setId(int id) {

        this.id = id;

    }

    public void setName(String name) {

        this.name = name;

    }

    public void setWife(Wife wife) {

        this.wife = wife;

    }

}

Wife.java

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.Id;

import javax.persistence.IdClass;

@Entity

@IdClass(WifePK.class)

public class Wife {

    private int id;

    private String name;

    private int age;

    public int getAge() {

        return age;

    }

    public void setAge(int age) {

        this.age = age;

    }

    @Id

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    @Id

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

}

WifePK.java

package com.bjsxt.hibernate;

import java.io.Serializable;

public class WifePK implements Serializable {

    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;

    }

}

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>

<!DOCTYPE hibernate-configuration PUBLIC

        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"

        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>

        <property name="connection.url">jdbc:mysql://localhost/hibernate</property>

        <property name="connection.username">root</property>

        <property name="connection.password">bjsxt</property>

        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>

       <!--

        <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>

        <property name="connection.url">jdbc:oracle:thin:@localhost::SXT</property>

        <property name="connection.username">scott</property>

        <property name="connection.password">tiger</property>

          <property name="dialect">org.hibernate.dialect.OracleDialect</property>

       -->

        <!-- JDBC connection pool (use the built-in) -->

        <property name="connection.pool_size"></property>

        <!-- Enable Hibernate's automatic session context management -->

        <property name="current_session_context_class">thread</property>

        <!-- Disable the second-level cache  -->

        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->

        <property name="show_sql">true</property>

        <property name="format_sql">true</property>

        <!-- Drop and re-create the database schema on startup

        <property name="hbm2ddl.auto">update</property>

         -->

        <!--   -->

        <mapping class="com.bjsxt.hibernate.Husband"/>

        <mapping class="com.bjsxt.hibernate.Wife"/>

    </session-factory>

</hibernate-configuration>

Test

package com.bjsxt.hibernate;

import java.util.Date;

import org.hibernate.Query;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.AnnotationConfiguration;

import org.hibernate.tool.hbm2ddl.SchemaExport;

import org.junit.AfterClass;

import org.junit.BeforeClass;

import org.junit.Test;

public class HibernateORMappingTest {

    private static SessionFactory sessionFactory;

    //@BeforeClass

    public static void beforeClass() {

            sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();

    }

    //@AfterClass

    public static void afterClass() {

        sessionFactory.close();

    }

    @Test

    public void testSchemaExport() {

        new SchemaExport(new AnnotationConfiguration().configure()).create(false, true);

    }

    public static void main(String[] args) {

        beforeClass();

    }

}

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