April 2003
Beginner to intermediate
380 pages
12h 25m
English
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Serialization
When an instance is serialized in Java, the graph of instances
reachable via non-transient fields is
written to an output stream. In this context, non-transient refers to fields that have not been
declared transient in Java. Java’s
transient fields and JDO’s managed
fields are independent concepts, so any combination of Java’s transient or non-transient fields with JDO’s persistent,
transactional, or transient fields is possible in your persistent
classes.
You can serialize and deserialize instances of your persistent classes. You do not need to do anything special for serialization to work. In fact, the JDO implementation automatically fetches the graph of instances, even if they have not yet been loaded into the JVM from the datastore.
However, you should be aware that the instances reachable from the
instance being serialized might include a large number of instances from
the datastore. If your persistent classes are highly interconnected, you
may unintentionally serialize a large percentage of your datastore. You
can use Java’s transient modifier to
prevent the serialization of referenced instances. Chapter 4 showed how to make Java
transient fields persistent in JDO by
setting the persistent-modifier
attribute to "persistent“. This lets
you serialize persistent instances in JDO without extracting and
serializing a large portion of the data from your datastore.
JDO enhancement allows you to serialize transient and persistent instances of persistent classes to a format ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.