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;
@Basic
private 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;
}
@Override
public 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 {
@PersistenceContext
private 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: EMP
Row:
Column Name: EMP_ID,
Column Type: BIGINT:
Column Value: 1
Column Name: NAME,
Column Type: VARCHAR:
Column Value: Tom
Column Name: PICTURE,
Column Type: BLOB:
Column Value: org.hsqldb.jdbc.JDBCBlobClient@5520ae93
Column Name: SURNAME,
Column Type: VARCHAR:
Column Value: Smith
Row:
Column Name: EMP_ID,
Column Type: BIGINT:
Column Value: 2
Column Name: NAME,
Column Type: VARCHAR:
Column Value: Jack
Column Name: PICTURE,
Column Type: BLOB:
Column Value: null
Column Name: SURNAME,
Column Type: VARCHAR:
Column Value: Kook