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 database columns. That way, all the unmapped values can be stored in the database in one column in their binary 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.