JPA中@javax.persistence.Lob注解有什么意义?

问题描述

我什么时候应该在 JPA 中使用 @javax.persistence.Lob 注释?这个注解可以注解哪些数据类型?

@javax.persistence.Lob 表示注解的字段应该在DataBase中表示为BLOB(二进制数据).p>

您可以使用此注解来注解任何 Serializable 数据类型.在 JPA 中，在持久化(检索)后，字段内容将使用标准 Java 序列化进行序列化(反序列化).

@Lob 的常见用途是在 Entity 中注释 HashMap 字段以存储一些未映射到 DB 列的对象属性.这样，所有未映射的值都可以以二进制表示形式存储在数据库中的一列中.当然，付出的代价是，由于它们以二进制格式存储，因此无法使用 JPQL/SQL 进行搜索.

When should I use @javax.persistence.Lob annotation in JPA? What datatypes can be annotated by this annotation?

@javax.persistence.Lob signifies that the annotated field should be represented as BLOB (binary data) in the DataBase.

You can annotate any Serializable data type with this annotation. In JPA, upon persisting (retrieval) the field content will be serialized (deserialized) using standard Java serialization.

Common use of @Lob is to annotate a HashMap field inside your Entity to store some of the object properties which are not mapped into DB columns. That way all the unmapped values can be stored in the DB in one column in their binarry representation. Of course the price that is paid is that, as they are stored in binary format, they are not searchable using the JPQL/SQL.

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