大对象不能在自动提交模式下使用 [英] Large Objects may not be used in auto-commit mode

问题描述

我有一个 Spring 应用程序，它在 PostgreSQL 数据库上使用 Hibernate.我正在尝试将文件存储在数据库表中.它似乎将行与文件一起存储(我只是在 EntityManager 上使用持久方法)，但是当从数据库加载对象时，我得到以下异常:

I have a Spring application which uses Hibernate on a PostgreSQL database. I'm trying to store files in a table of the database. It seems it stores the row with the file (I just use persist method on EntityManager), but when the object is loaded from the database I get the following exception:

org.postgresql.util.PSQLException: Large Objects may not be used in auto-commit mode.

为了加载数据，我使用了 MultipartFile 瞬态属性，并在其设置器中设置了我想要保留的信息(字节 []、文件名、大小).我坚持的实体看起来像这样(我省略了其余的 getter/setter):

To load the data I'm using a MultipartFile transient atribute and in its setter I'm setting the information I want to persist (byte[], fileName, size). The entity I'm persisting looks like this one (I've ommitted the rest of getters/setters):

@Entity
@Table(name="myobjects")
public class MyClass {

    @Id
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="sequence")
    @SequenceGenerator(name="sequence", sequenceName="myobjects_pk_seq", allocationSize=1)
    @Column(name="id")
    private Integer id;

    @Lob
    private String description;

    @Temporal(TemporalType.TIMESTAMP)
    private Date creationDate;

    @Transient
    private MultipartFile multipartFile;

    @Lob
    @Basic(fetch=FetchType.LAZY, optional=true)
    byte[] file;

    String fileName;

    String fileContentType;

    Integer fileSize;

    public void setMultipartFile(MultipartFile multipartFile) {
        this.multipartFile = multipartFile;
        try {
            this.file = this.multipartFile.getBytes();
            this.fileName = this.multipartFile.getOriginalFilename();
            this.fileContentType = this.multipartFile.getContentType();
            this.fileSize = ((Long) this.multipartFile.getSize()).intValue();
        } catch (IOException e) {
            logger.error(e.getStackTrace());
        }
    }
}

我可以看到，当它被持久化时，我在行中有数据，但是当我调用这个方法时它失败了:

I can see that when it is persisted I have the data in the row but when I call this method it fails:

public List<MyClass> findByDescription(String text) {
    Query query = getEntityManager().createQuery("from MyClass WHERE UPPER(description) like :query ORDER BY creationDate DESC");
    query.setParameter("query", "%" + text.toUpperCase() + "%");
    return query.getResultList();
}

此方法仅在结果包含带有文件的对象时失败.我试图在我的persistence.xml中设置

This method only fails when the result has objects with files. I've tried to set in my persistence.xml

<property name="hibernate.connection.autocommit" value="false" />

但它并没有解决问题.

总的来说，应用程序运行良好，它只在事务完成时提交数据，如果出现故障，它会执行回滚，所以我不明白为什么会发生这种情况.

In general the application works well it only commit the data when the transaction is finished and it performs a rollback if something fails, so I don't understand why is this happening.

有什么想法吗?

谢谢.

更新

查看 Shekhar 提供的链接，建议将调用包含在事务中，因此我在事务中设置了服务调用并且它可以工作(我添加了 @Transactional 注释).

Looking at the link given by Shekhar it is suggested to include the call in a transation, so I've set the service call inside a transaction an it works (I've added @Transactional annotation).

@Transactional
public List<myClass> find(String text) {
    return myClassDAO.findByDescription(text);
}

问题是我不想保留任何数据，所以我不明白为什么它应该包含在事务中.当我只从数据库加载了一些数据时，进行提交是否有意义?

the problem is that I don't want to persist any data so I don't understand why it should be include inside a transaction. Does it make any sense to make a commit when I've only loaded some data form the database?

谢谢.

推荐答案

一个大对象可以存储在多个记录中，这就是您必须使用事务的原因.所有记录都正确或根本没有.

A large object can be stored in several records, that's why you have to use a transaction. All records are correct or nothing at all.

https://www.postgresql.org/docs/current/static/大对象.html

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