hibernate联合主键生成机制(annotation方式)

这里记录hibernate中组合主键的annotation方式。

hibernate-annotations说明文档中有说到组合主键使用annotation的方式实现,如下几种

下面是定义组合主键的几种语法:

1.  将组件类注解为@Embeddable,并将组件的属性注解为@Id

2.  将组件的属性注解为@EmbeddedId

3.  将类注解为@IdClass,并将该实体中所有属于主键的属性都注解为@Id

 

第一种方式实例:

1.主键类,如下

package com.seed.lee.model;

import javax.persistence.Column; 
import javax.persistence.Embeddable;

/** 
* 这个类作为Person类的(组合主键)主键类 

* @author Administrator 

*/ 
@Embeddable  //这里就是annotation文档中所说的,将组件类注解为@Embeddable

public class PeopleUionPKID implements java.io.Serializable {

    private String firstName;

    private String secondName;

    @Column(length=20) 
    public String getFirstName() { 
        return firstName; 
    }

    public void setFirstName(String firstName) { 
        this.firstName = firstName; 
    } 
    @Column(length=20) 
    public String getSecondName() { 
        return secondName; 
    }

    public void setSecondName(String secondName) { 
        this.secondName = secondName; 
    }

    @Override 
    public boolean equals(Object obj) { 
        if(obj instanceof PeopleUionPKID){ 
            PeopleUionPKID pk=(PeopleUionPKID)obj; 
            if(this.firstName.equals(pk.firstName)&&this.secondName.equals(pk.secondName)){ 
                return true; 
            } 
        } 
        return false; 
    }

    @Override 
    public int hashCode() { 
        return super.hashCode(); 
    }

}

 

 

2.与数据库表对应的类

package com.seed.lee.model;

import javax.persistence.Column; 
import javax.persistence.Entity; 
import javax.persistence.Id;

@Entity 
public class Peopel {

    PeopleUionPKID uionPKID = new PeopleUionPKID();

    private int age;

    private String sex;

    private String job;

    @Id   //这里就是文档中所述的,并将组件的属性注解为@Id 
    public PeopleUionPKID getUionPKID() { 
        return uionPKID; 
    }

    public void setUionPKID(PeopleUionPKID uionPKID) { 
        this.uionPKID = uionPKID; 
    }

    public int getAge() { 
        return age; 
    }

    public void setAge(int age) { 
        this.age = age; 
    }

    @Column(length=4) 
    public String getSex() { 
        return sex; 
    }

    public void setSex(String sex) { 
        this.sex = sex; 
    }

    @Column(length=20) 
    public String getJob() { 
        return job; 
    }

    public void setJob(String job) { 
        this.job = job; 
    }

}

 

说明:除了代码中标为粗体的与普通的单主键类不同之外,其他都大同小异.

 

 

第二种方式比较简单

1.主键类,这个类不需要做任何的注解

package com.seed.lee.model;

import javax.persistence.Column;

/** 
* 这个类作为Person类的(组合主键)主键类 

* @author Administrator 

*/

public class PeopleUionPKID implements java.io.Serializable {

    private String firstName;

    private String secondName;

    @Column(length=20) 
    public String getFirstName() { 
        return firstName; 
    }

    public void setFirstName(String firstName) { 
        this.firstName = firstName; 
    } 
    @Column(length=20) 
    public String getSecondName() { 
        return secondName; 
    }

    public void setSecondName(String secondName) { 
        this.secondName = secondName; 
    }

    @Override 
    public boolean equals(Object obj) { 
        if(obj instanceof PeopleUionPKID){ 
            PeopleUionPKID pk=(PeopleUionPKID)obj; 
            if(this.firstName.equals(pk.firstName)&&this.secondName.equals(pk.secondName)){ 
                return true; 
            } 
        } 
        return false; 
    }

    @Override 
    public int hashCode() { 
        return super.hashCode(); 
    }

}

 

 

2.数据表映射的类(只需要在主键类的引用中添加@EmbeddedId就可以)

package com.seed.lee.model;

import javax.persistence.Column; 
import javax.persistence.EmbeddedId; 
import javax.persistence.Entity; 
import javax.persistence.Id;

@Entity 
public class Peopel {

    PeopleUionPKID uionPKID = new PeopleUionPKID();

    private int age;

    private String sex;

    private String job;

    @EmbeddedId 
    public PeopleUionPKID getUionPKID() { 
        return uionPKID; 
    }

    public void setUionPKID(PeopleUionPKID uionPKID) { 
        this.uionPKID = uionPKID; 
    }

    public int getAge() { 
        return age; 
    }

    public void setAge(int age) { 
        this.age = age; 
    }

    @Column(length=4) 
    public String getSex() { 
        return sex; 
    }

    public void setSex(String sex) { 
        this.sex = sex; 
    }

    @Column(length=20) 
    public String getJob() { 
        return job; 
    }

    public void setJob(String job) { 
        this.job = job; 
    }

}

 

 

第三种方式,这种方式相对麻烦一点,据说这种是符合常人的编码规范的,所以有很多人用

1.  依然需要主键类,类中不需要注解任何的属性

package com.seed.lee.model;

import javax.persistence.Column;

/** 
* 这个类作为Person类的(组合主键)主键类 

* @author Administrator 

*/

public class PeopleUionPKID implements java.io.Serializable {

    private String firstName;

    private String secondName;

    @Column(length=20) 
    public String getFirstName() { 
        return firstName; 
    }

    public void setFirstName(String firstName) { 
        this.firstName = firstName; 
    } 
    @Column(length=20) 
    public String getSecondName() { 
        return secondName; 
    }

    public void setSecondName(String secondName) { 
        this.secondName = secondName; 
    }

    @Override 
    public boolean equals(Object obj) { 
        if(obj instanceof PeopleUionPKID){ 
            PeopleUionPKID pk=(PeopleUionPKID)obj; 
            if(this.firstName.equals(pk.firstName)&&this.secondName.equals(pk.secondName)){ 
                return true; 
            } 
        } 
        return false; 
    }

    @Override 
    public int hashCode() { 
        return super.hashCode(); 
    }

}

 

2.数据表对应的类(这个类中需要将表的组合主键也记录成属性,并在所有的主键字段的get方法上注解@id,最后就是在类名上方注解

@IdClass(value=PeopleUionPKID.class),PeopleUionPKID就是主键类的类短名 

package com.seed.lee.model;

import javax.persistence.Column; 
import javax.persistence.Entity; 
import javax.persistence.Id; 
import javax.persistence.IdClass;

@Entity 
@IdClass(value=PeopleUionPKID.class) 
public class Peopel {

//    PeopleUionPKID uionPKID = new PeopleUionPKID(); 
    private String firstName; 
    private String secondName;

    private int age;

    private String sex;

    private String job;

//    @EmbeddedId 
//    public PeopleUionPKID getUionPKID() { 
//        return uionPKID; 
//    } 
// 
//    public void setUionPKID(PeopleUionPKID uionPKID) { 
//        this.uionPKID = uionPKID; 
//    }

    public int getAge() { 
        return age; 
    }

    @Id 
    public String getFirstName() { 
        return firstName; 
    }

    public void setFirstName(String firstName) { 
        this.firstName = firstName; 
    }

    @Id 
    public String getSecondName() { 
        return secondName; 
    }

    public void setSecondName(String secondName) { 
        this.secondName = secondName; 
    }

    public void setAge(int age) { 
        this.age = age; 
    }

    @Column(length=4) 
    public String getSex() { 
        return sex; 
    }

    public void setSex(String sex) { 
        this.sex = sex; 
    }

    @Column(length=20) 
    public String getJob() { 
        return job; 
    }

    public void setJob(String job) { 
        this.job = job; 
    }

}

 

具体查看hibernate annotation的说明文档。

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