Hibernate学习之属性级别注解

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属性级别注解

添加方式

1. 写在属性字段上面

2. 写在属性getter方法上面

@Id：必须，定义了映射到数据库表的主键属性，一个实体可以有一个或多个属性被映射为主键（如果有多个属性定义为主键属性，则必须实现Serializable接口）

@EmbeddableId ：可选，使用嵌入式主键类实现复合主键（嵌入式主键类必须实现Serializable接口、必须有默认的无参构造器、必须覆盖equals和hashCode方法）

@GeneratedValue：可选，用于定义主键生成策略（@GeneratedValue(strategy=GenerationType.*, generator="")）

strategy：定义主键生成策略

- GenerationType.AUTO：根据底层数据库自动选择（默认）

- GenerationType.IDENTITY：根据数据库的Identity字段生成

- GenerationType.SEQUENCE：根据Sequence来决定主键的取值

- GenerationType.TABLE：使用指定表来决定主键取值，结合@TableGenerator使用

generator：引用@GenericGenerator指定的主键生成策略

@Column：可选，将属性映射到列，使用该注解来覆盖默认值

常用属性：

- name ：可选，表示数据库中该字段的名称，默认与属性名称一致

- nullable：可选，表示该字段是否允许为null，默认true

- unique：可选，表示该字段是否是唯一标识，默认false

- length：可选，表示该字段的长度，仅对String类型的字段有效，默认255（如果是主键则不能使用默认值）

- insertable：可选，表示在ORM框架执行插入操作时，该字段是否出现在insert语句中，默认true

- updateable：可选，表示在ORM框架执行更新操作时，该字段是否出现在update语句中，默认true

（对于一经创建就不能修改的字段，该属性非常有效。eg：出生日期、插入时间等）

@Embeddable ：可选，表示该属性的类是嵌入类（嵌入类也必须标注@Embeddable注解）

@Transient ：可选，表示该属性并非一个数据库表的字段的映射，ORM框架将忽略该属性

实例

1.项目结构

2.pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

  	<modelVersion>4.0.0</modelVersion>

	<groupId>org.hibernate</groupId>

	<artifactId>Hibernate-AttributeAnnotation</artifactId>

	<version>0.0.1-SNAPSHOT</version>

	<packaging>jar</packaging>

	<properties>

		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

		<hibernate.version>5.1.7.Final</hibernate.version>

	</properties>

	<dependencies>

		<!-- Junit -->

		<dependency>

			<groupId>junit</groupId>

			<artifactId>junit</artifactId>

			<version>4.12</version>

			<scope>test</scope>

		</dependency>

		<!-- Hibernate  -->

		<dependency>

		    <groupId>org.hibernate</groupId>

		    <artifactId>hibernate-core</artifactId>

		    <version>${hibernate.version}</version>

		</dependency>

		<!-- MySQL -->

		<dependency>

		    <groupId>mysql</groupId>

		    <artifactId>mysql-connector-java</artifactId>

		    <version>5.1.42</version>

		</dependency>

	</dependencies>

</project>

3.StudentPK.java

package org.hibernate.model;

import java.io.Serializable;

import javax.persistence.Column;

import javax.persistence.GeneratedValue;

import org.hibernate.annotations.GenericGenerator;

/**

 * 学生主键类

 *

 */

public class StudentPK implements Serializable {

	private static final long serialVersionUID = 1L;

	@GeneratedValue

	private long sid;// 学号

	@GeneratedValue(generator="custom")

	@GenericGenerator(name="custom", strategy="assigned")

	@Column(length = 18)

	private String id; // 身份证号

	public StudentPK() {

	}

	public StudentPK(long sid, String id) {

		this.sid = sid;

		this.id = id;

	}

	public long getSid() {

		return sid;

	}

	public void setSid(long sid) {

		this.sid = sid;

	}

	public String getId() {

		return id;

	}

	public void setId(String id) {

		this.id = id;

	}

	@Override

	public int hashCode() {

		return super.hashCode();

	}

	@Override

	public boolean equals(Object obj) {

		return super.equals(obj);

	}

}

4.Address.java

package org.hibernate.model;

import javax.persistence.Embeddable;

/**

 * 地址类

 *

 */

@Embeddable

public class Address {

	private String postCode;// 邮编

	private String address;// 地址

	private String telephone;// 电话

	public Address() {

	}

	public Address(String postCode, String address, String telephone) {

		this.postCode = postCode;

		this.address = address;

		this.telephone = telephone;

	}

	public String getPostCode() {

		return postCode;

	}

	public void setPostCode(String postCode) {

		this.postCode = postCode;

	}

	public String getAddress() {

		return address;

	}

	public void setAddress(String address) {

		this.address = address;

	}

	public String getTelephone() {

		return telephone;

	}

	public void setTelephone(String telephone) {

		this.telephone = telephone;

	}

}

5.Student.java

package org.hibernate.model;

import java.util.Date;

import javax.persistence.Embedded;

import javax.persistence.EmbeddedId;

import javax.persistence.Entity;

import javax.persistence.Table;

import javax.persistence.Transient;

@Entity

@Table(name="t_student")

public class Student {

	@EmbeddedId

	public StudentPK id;// 主键

	public String name;// 姓名

	public String sex;// 性别

	public Date birthday;// 出生日期

	@Embedded

	public Address address;// 地址

	@Transient

	public String gf;// 女朋友

	public Student(StudentPK id, String name, String sex, Date birthday, Address address, String gf) {

		this.id = id;

		this.name = name;

		this.sex = sex;

		this.birthday = birthday;

		this.address = address;

		this.gf = gf;

	}

	public StudentPK getId() {

		return id;

	}

	public void setId(StudentPK 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;

	}

	public Date getBirthday() {

		return birthday;

	}

	public void setBirthday(Date birthday) {

		this.birthday = birthday;

	}

	public Address getAddress() {

		return address;

	}

	public void setAddress(Address address) {

		this.address = address;

	}

	public String getGf() {

		return gf;

	}

	public void setGf(String gf) {

		this.gf = gf;

	}

}

6.hibernate.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE hibernate-configuration PUBLIC

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

	"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

	<!-- SessionFactory配置 -->

	<session-factory>

		<!-- 数据库配置 -->

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

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

		<property name="connection.url">

			jdbc:mysql:///hibernate?useSSL=true&amp;characterEncoding=UTF-8

		</property>

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

		<property name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>

		<!-- 使用常用配置 -->

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

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

		<!-- 引入映射类 -->

		<mapping class="org.hibernate.model.Student"/>

	</session-factory>

</hibernate-configuration>

7.TestAttributeAnnotation.java

package org.hibernate.test;

import java.util.Date;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.Transaction;

import org.hibernate.cfg.Configuration;

import org.hibernate.model.Address;

import org.hibernate.model.Student;

import org.hibernate.model.StudentPK;

import org.junit.After;

import org.junit.Before;

import org.junit.Test;

public class TestAttributeAnnotation {

	private SessionFactory sessionFactory;

	private Session session;

	private Transaction transaction;

	@Before

	public void before() {

		sessionFactory = new Configuration().configure().buildSessionFactory();// 创建SessionFactory对象

		session = sessionFactory.openSession();// 获取Session对象

		transaction = session.beginTransaction();// 开启事务

	}

	@After

	public void after() {

		transaction.commit();// 提交事务

		session.clear();// 关闭Session

		sessionFactory.close();// 关闭SessionFactory

	}

	@Test

	public void testAnnotation() {

		Address address = new Address("100000", "北京市", "15812345678");

		StudentPK pk = new StudentPK(1L, "123456780123456789");

		Student student = new Student(pk, "张三", "男", new Date(), address, "李四");

		session.save(student);

	}

}