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();
    }
}