JPA Lob列示例

JPA教程 - JPA Lob列示例

以下代碼顯示了如何使用@Lob注釋將字節(jié)數(shù)組保存到數(shù)據(jù)庫(kù)。

LOB在數(shù)據(jù)庫(kù)中有兩種類型：字符大對(duì)象（稱為CLOB）和二進(jìn)制大對(duì)象（或BLOB）。

CLOB列保存大字符序列，BLOB列可存儲(chǔ)大字節(jié)序列。

映射到BLOB列的Java類型是byte[] Byte[]和Serializable類型，而char[] Character[]和String對(duì)象映射到CLOB列。

例子

下面的代碼來(lái)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 + "]";
  }
}

下面的代碼來(lái)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();
  }
  
}

上面的代碼生成以下結(jié)果。

以下是數(shù)據(jù)庫(kù)轉(zhuǎn)儲(chǔ)。

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