9_hibernate基础配置_注解

以下讲解部分注解的作用，其中需要在xml中修改的注解，在下图中展示：

1、当表明和类名不一致时，增加注解@table(name="sqlTableName")（from：javax.persistence）   

package com.mym.hibernate.model;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.Table;@Entity@Table(name="_Teacher")public class Teacher {    private int id;    private String name;    private String title;    @Id    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 getTitle() {        return title;    }    public void setTitle(String title) {        this.title = title;    }}

执行测试文件，控制台显示：

create table _Teacher (        id integer not null,        name varchar(255),        title varchar(255),        primary key (id)    )10:44:39,818  INFO SchemaExport:268 - schema export completeHibernate:    insert    into        _Teacher        (name, title, id)    values        (?, ?, ?)

2、字段名和属性相同

     所有没有定义注解的属性等价于在其上面添加了

                                                                      @Basic注解

3、字段名与属性名不同

     在getter方法上加注解：     

               @Cloumn(name ="sqlCloumnName")

package com.mym.hibernate.model;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.Table;@Entity@Table(name="_Teacher")public class Teacher {    private int id;    private String name;    private String title;    @Id    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    @Column(name="_name")    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getTitle() {        return title;    }    public void setTitle(String title) {        this.title = title;    }}

控制台显示：

drop table if exists _Teacher14:59:48,873 DEBUG SchemaExport:377 -    create table _Teacher (        id integer not null,        _name varchar(255),        title varchar(255),        primary key (id)    )14:59:48,950  INFO SchemaExport:268 - schema export completeHibernate:    insert    into        _Teacher        (_name, title, id)    values        (?, ?, ?)

4、若实体类中的某个属性不想在数据库中生成，则可以用注解@Transient，即透明的

package com.mym.hibernate.model;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.Table;import javax.persistence.Transient;@Entity@Table(name="_Teacher")public class Teacher {    private int id;    private String name;    private String title;    private String yourWifeName;    @Transient    public String getYourWifeName() {        return yourWifeName;    }    public void setYourWifeName(String yourWifeName) {        this.yourWifeName = yourWifeName;    }    @Id    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    @Column(name="_name")    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getTitle() {        return title;    }    public void setTitle(String title) {        this.title = title;    }}

控制台显示（并没有显示建立加过@Transient注解的字段）：

create table _Teacher (        id integer not null,        _name varchar(255),        title varchar(255),        primary key (id)    )15:10:04,473  INFO SchemaExport:268 - schema export completeHibernate:    insert    into        _Teacher        (_name, title, id)    values        (?, ?, ?)

在xml中如果不想要某个字段，直接不写即可

5、映射日期与时间类型，指定时间精度

     a、Annotation：@Temporal

如果在实体类中直接建立了Date（java.util.Date）类型的数据，注解为@Basic时，数据库中会自动生成datetime类型的数据2017-05-19 15:24:08，即包括日期，也包括时间，

package com.mym.hibernate.model;import java.util.Date;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.Table;import javax.persistence.Temporal;import javax.persistence.Transient;@Entity@Table(name="_Teacher")public class Teacher {    private int id;    private String name;    private String title;    private String yourWifeName;    private Date birthDate;    public Date getBirthDate() {        return birthDate;    }    public void setBirthDate(Date birthDate) {        this.birthDate = birthDate;    }    @Transient    public String getYourWifeName() {        return yourWifeName;    }    public void setYourWifeName(String yourWifeName) {        this.yourWifeName = yourWifeName;    }    @Id    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    @Column(name="_name")    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getTitle() {        return title;    }    public void setTitle(String title) {        this.title = title;    }}

数据库中显示：

可以通过@Temporal(TemporalType.DATE)设置只显示日期；

或者@Temporal(TemporalType.TIME)设置只显示时间

package com.mym.hibernate.model;import java.util.Date;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.Table;import javax.persistence.Temporal;import javax.persistence.TemporalType;import javax.persistence.Transient;@Entity@Table(name="_Teacher")public class Teacher {    private int id;    private String name;    private String title;    private String yourWifeName;    private Date birthDate;    @Temporal(TemporalType.DATE)    public Date getBirthDate() {        return birthDate;    }    public void setBirthDate(Date birthDate) {        this.birthDate = birthDate;    }    @Transient    public String getYourWifeName() {        return yourWifeName;    }    public void setYourWifeName(String yourWifeName) {        this.yourWifeName = yourWifeName;    }    @Id    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    @Column(name="_name")    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getTitle() {        return title;    }    public void setTitle(String title) {        this.title = title;    }}

6、映射枚举类型

     Annotation：@Enumerated

     xml：麻烦

新建一个Enume类型的类，命名为ZhiCheng

package com.mym.hibernate.model;public enum ZhiCheng {     A,B,C}

给Teacher建立ZhiCheng属性，并且使用@Enumerated(EnumType.STRING)和@Enumerated(EnumType.ORDINAL)分别对getter方法修饰：

package com.mym.hibernate.model;import java.util.Date;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.EnumType;import javax.persistence.Enumerated;import javax.persistence.Id;import javax.persistence.Table;import javax.persistence.Temporal;import javax.persistence.TemporalType;import javax.persistence.Transient;@Entity@Table(name="_Teacher")public class Teacher {    private int id;    private String name;    private String title;    private String yourWifeName;    private Date birthDate;    private ZhiCheng zhiCheng;    @Enumerated(EnumType.STRING)    public ZhiCheng getZhiCheng() {        return zhiCheng;    }    public void setZhiCheng(ZhiCheng zhiCheng) {        this.zhiCheng = zhiCheng;    }    @Temporal(TemporalType.DATE)    public Date getBirthDate() {        return birthDate;    }    public void setBirthDate(Date birthDate) {        this.birthDate = birthDate;    }    @Transient    public String getYourWifeName() {        return yourWifeName;    }    public void setYourWifeName(String yourWifeName) {        this.yourWifeName = yourWifeName;    }    @Id    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    @Column(name="_name")    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getTitle() {        return title;    }    public void setTitle(String title) {        this.title = title;    }}

测试文件中：

package com.mym.hibernate.model;import java.util.Date;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.cfg.AnnotationConfiguration;import org.hibernate.cfg.Configuration;import org.junit.AfterClass;import org.junit.BeforeClass;import org.junit.Test;public class TeacherTest {    private static SessionFactory sf = null;    @BeforeClass    public static void beforeClass(){        sf = new AnnotationConfiguration().configure().buildSessionFactory();    }    @Test    public void testTeacherSave(){        Teacher t = new Teacher();        t.setId(6);        t.setName("t1");        t.setTitle("tt2");        t.setBirthDate(new Date());        t.setZhiCheng(ZhiCheng.A);        Session session = sf.openSession();        session.beginTransaction();        session.save(t);        session.getTransaction().commit();        session.close();    }    @AfterClass    public static void afterClass(){        sf.close();    }}

情况一：

当使用@Enumerated(EnumType.STRING)修饰时，是以varchar（字符串）的类型将枚举（Enume）类型的值存入数据库

当使用@Enumerated(EnumType.ORDINAL)修饰时，是以integer（int）的类型将枚举（Enum）类中值的数组下标的值存入数据库中

7、字段映射的位置

     放到field（成员变量）上和get方法上效果一样

     建议放在get方法上

     因为field 定义的是private类型的，既然要定义为私有，就是不想再被进行更改。而如果将注解放到field上，就相当于hibernate通过映射，访问了field，不符合我们的想法，所以不建议放到field即成员变量上