12、Hibernate的映射小案例

ORM映射与配置实践

最新推荐文章于 2025-09-12 18:08:49 发布

转载最新推荐文章于 2025-09-12 18:08:49 发布 · 57 阅读

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原文链接：http://www.cnblogs.com/zhangbaowei/p/4869099.html

文章标签：

#java

本文介绍了使用Hibernate框架进行对象关系映射（ORM）的具体实现方法，包括基于Annotation和XML的配置方式。通过Special、Classroom及Student三个实体类之间的关联关系展示了如何设置一对一、一对多及多对多的关系。

1、实体的关系图

1.1基于Annotation的配置

Special.java

package org.zttc.itat.model;

import java.util.Set;

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

import org.hibernate.annotations.LazyCollection;
import org.hibernate.annotations.LazyCollectionOption;

@Entity
@Table(name="t_special")
public class Special {
    private int id;
    private String name;
    private String type;
    private Set<Classroom> clas;
    
    @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;
    }
    public String getType() {
        return type;
    }
    public void setType(String type) {
        this.type = type;
    }
    
    @OneToMany(mappedBy="special")
    @LazyCollection(LazyCollectionOption.EXTRA)
    public Set<Classroom> getClas() {
        return clas;
    }
    public void setClas(Set<Classroom> clas) {
        this.clas = clas;
    }
    
    
}

Classroom.java

package org.zttc.itat.model;

import java.util.Set;

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.OneToMany;
import javax.persistence.Table;

import org.hibernate.annotations.BatchSize;
import org.hibernate.annotations.Fetch;
import org.hibernate.annotations.FetchMode;
import org.hibernate.annotations.LazyCollection;
import org.hibernate.annotations.LazyCollectionOption;

@Entity
@Table(name="t_classroom")
@BatchSize(size=20)
public class Classroom {
    private int id;
    private String name;
    private int grade;
    private Set<Student> stus;
    private Special special;
    
    @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;
    }
    public int getGrade() {
        return grade;
    }
    public void setGrade(int grade) {
        this.grade = grade;
    }
    
    @OneToMany(mappedBy="classroom")
    @LazyCollection(LazyCollectionOption.EXTRA)
    @Fetch(FetchMode.SUBSELECT)
    public Set<Student> getStus() {
        return stus;
    }
    public void setStus(Set<Student> stus) {
        this.stus = stus;
    }
    
    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="spe_id")
    public Special getSpecial() {
        return special;
    }
    public void setSpecial(Special special) {
        this.special = special;
    }
    
    
    
}

Student.java

package org.zttc.itat.model;

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.Table;
import javax.persistence.Version;

import org.hibernate.annotations.Cache;
import org.hibernate.annotations.CacheConcurrencyStrategy;

@Entity
@Table(name="t_stu")
//@Cache(usage=CacheConcurrencyStrategy.READ_ONLY)
public class Student {
    private int id;
    private String name;
    private String sex;
    private Classroom classroom;
    private int version;
    
    @Version
    public int getVersion() {
        return version;
    }
    public void setVersion(int version) {
        this.version = version;
    }
    @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;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    @ManyToOne(fetch=FetchType.LAZY)//LAZY就是XML中的select,EAGER就表示XML中的join
    @JoinColumn(name="cid")
    public Classroom getClassroom() {
        return classroom;
    }
    public void setClassroom(Classroom classroom) {
        this.classroom = classroom;
    }
    
    
}

1.2基于XML的配置

Special.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 package="org.zttc.itat.model">
    <class name="Special" table="t_special">
        <id name="id">
              <generator class="native"/>
        </id>
        <property name="name"/>
        <property name="type"/>
        <set name="clas" inverse="true" lazy="extra">
            <key column="spe_id"/>
            <one-to-many class="Classroom"/>
        </set>
    </class>
</hibernate-mapping>

Classroom.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 package="org.zttc.itat.model">
    <class name="Classroom" table="t_classroom">
        <id name="id">
              <generator class="native"/>
        </id>
        <property name="name"/>
        <property name="grade"/>
        <many-to-one name="special" column="spe_id" fetch="join"/>
        <set name="stus" inverse="true" lazy="extra" fetch="subselect">
            <key column="cid"/>
            <one-to-many class="Student"/>
        </set>
    </class>
</hibernate-mapping>

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 package="org.zttc.itat.model">
    <class name="Student" table="t_stu">
        <!-- <cache usage="read-only"/> -->
        <id name="id">
              <generator class="native"/>
        </id>
         <version name="version"/>
        <property name="name"/>
        <property name="sex"/>
        <many-to-one name="classroom" column="cid" fetch="join"/>
    </class>
</hibernate-mapping>