JPA教程 - JPA Lob列示例

以下代码显示了如何使用@Lob注释将字节数组保存到数据库。

LOB在数据库中有两种类型：字符大对象（称为CLOB）和二进制大对象（或BLOB）。

CLOB列保存大字符序列，BLOB列可存储大字节序列。

映射到BLOB列的Java类型是byte[] Byte[]和Serializable类型，而char[] Character[]和String对象映射到CLOB列。

例子

下面的代码来自Person.java。

package cn.w3cschool.common;import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Lob;
import javax.persistence.Table;@Entity
@Table(name="EMP")
public class Person {@Id@Column(name = "EMP_ID")private long id;@Basicprivate String name;private String surname;@Lob private byte[] picture;public Person() {}public Person(String name, String surname) {this.name = name;this.surname = surname;}public Long getId() {return id;}public void setId(Long id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getSurname() {return surname;}public void setSurname(String surname) {this.surname = surname;}public byte[] getPicture() {return picture;}public void setPicture(byte[] picture) {this.picture = picture;}@Overridepublic String toString() {return "Person [id=" + id + ", name=" + name + ", surname=" + surname + "]";}
}

下面的代码来自PersonDaoImpl.java。

package cn.w3cschool.common;import java.util.List;import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;import org.springframework.transaction.annotation.Transactional;@Transactional
public class PersonDaoImpl {@PersistenceContextprivate EntityManager em;public Long save(Person person) {em.persist(person);return person.getId();}public List<Person>getAll() {return em.createQuery("SELECT p FROM Person p", Person.class).getResultList();}}上面的代码生成以下结果。

以下是数据库转储。

Table Name: EMPRow:Column Name: EMP_ID,Column Type: BIGINT:Column Value: 1Column Name: NAME,Column Type: VARCHAR:Column Value: TomColumn Name: PICTURE,Column Type: BLOB:Column Value: org.hsqldb.jdbc.JDBCBlobClient@5520ae93Column Name: SURNAME,Column Type: VARCHAR:Column Value: SmithRow:Column Name: EMP_ID,Column Type: BIGINT:Column Value: 2Column Name: NAME,Column Type: VARCHAR:Column Value: JackColumn Name: PICTURE,Column Type: BLOB:Column Value: nullColumn Name: SURNAME,Column Type: VARCHAR:Column Value: Kook