Question

I have an application which has to handle a list of objects (retrieved from the database using JPA) which contain an image serialized.

The issue is that when I get around 50 instances of this object stored on the database, it becomes quite slow to load 50 pictures from the database (~5 seconds), which becomes annoying to the user.

Is there a way to set this column from the database to a lazy initialization? Or should I create a separate object to carry the image, and reference it using an ID?

Thanks for your help.

Answer 1

Yes there is a layz loading attriubte for properties.

 @Basic(fetch = FetchType.LAZY)
 private String myBigString;

From the JPA 2.0 Specification

11.1.6 Basic Annotation The Basic annotation is the simplest type of mapping to a database column. The Basic annotation can be applied to a
persistent property or instance variable of any of the following
types: Java primitive types, wrappers of the primitive types,
java.lang.String, java.math.BigInteger, java.math.BigDecimal,
java.util.Date, java.util.Calendar, java.sql.Date, java.sql.Time,
java.sql.Timestamp, byte[], Byte[], char[], Character[], enums, and
any other type that implements Serializable.

…

The FetchType enum defines strategies for fetching data from the
database: public enum FetchType { LAZY, EAGER };

…

The LAZY strategy is a hint to the persistence provider runtime that
data should be fetched lazily when it is first accessed. The
implementation is permitted to eagerly fetch data for which the LAZY
strategy hint has been specified. In particular, lazy fetching might
only be available for Basic mappings for which property-based access
is used.

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One other technique would to have a second mapping of the same table, but only with the attributes you need.