Does hibernate internally uses Serialization for persisting POJO classes? If yes, How does it use it in persisting data? If No, then how does it persist data to DB?
Hibernate persists data to the database using SQL. Java serialization is not used at all. (SQL) databases are language-agnostic. As such, they cannot depend on language-specific technology such as Java serialization.
Serialization is only relevant when you need to send a POJO over the wire to other servers running Java. For example, if you have some sort of cache of POJOs that spans multiple machines, you could use serialization to send copies of the POJO over the wire.
See https://stackoverflow.com/a/2726387/14731 for a related discussion.
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We are going to use Redis cache for faster performance. We require that we want to create single java domain class (for example Employee.java) which we can use for both Redis and Sybase ASE but the problem is Redis is NoSql database and Sybase ASE is a relational database.
If we store Employee object as key-value pair in Redis and then if we want to store it in the database (Sybase ASE) from extracting it from Redis cache then it will create a problem.
So, in short, we require a single java domain class. How can we achieve this?
Just serialize your Employee into a C-String value to put in Redis, for instance thanks to Kryo library. Then you just have to deserialize it from Redis to rebuild your Java instance and use it with Sybase (the other way works too).
Any process of java serialization into a C-String (bytearray) or classic string can be used, so you can look at Jackson (JSON serialization from and to Java), JSON-schema (that generates JSON serializable java classes), MessagePack (JSON serialization with compression), FlatBuffers... Even vanilla traditional Java serialization can be used.
I am new to Redis things.
I have some Object which is Externalizable.
But Spring Data Redis is not working with these Objects.
Does Spring Data Redis need Serializable strictly or there is some way to work with Externalizable as well?
Spring Data Redis supports different serialization strategies to represent your objects in binary form so it can be stored in Redis.
One of the serialization formats is using Java's serialization mechanism via ObjectOutputStream. There are no Spring Data specifics when using Java serialization.
What is the right way to persist data defined using protobuf3. I am using golang and Java, both place with support of ORMs. In java with Hibernate and golang with gorm. Both place i need to convert the Generated code to corresponding Entity model. I feel that is more pain full to maintain same object structure in order to be understandable by ORM. Is there any Database which i can use along with protobuf objects as is. Or i can define the relations between objects in the protobuf itself.
Any helps really appreciated.
There is a not-straightforward solution to this problem.
Protobuf 3 standardises JSON mapping for the messages. Once you serialise your message to JSON, you have multiple options for storing it in a database.
The following (and many more) databases can store JSON data:
MariaDB
PostgreSQL
MongoDB
Your ORM is dealing with objects, by definition. It should not know or care about serialization on the network. I'd suggest deserializing the protobuf message into objects that your ORM is used to and letting it persist them. There's no good reason to couple your persistence tier to the network protocol.
It might make sense to store the protobuf serialization directly if you get rid of JPA and go with a document based solution.
You have to decide how much value JPA is providing for you.
Although this question is quite old, things have happened since then and the FoundationDB Record Layer, released by Apple in 2018, stores Protocol Buffer natively.
In Go, I don't know about gorm, but it seems that with Ent (a competing ORM) Protobufs can be deserialized into exactly the same objects which are used for DB tables/relations. Ent's official tutorial for that.
The caveat is that you specify your Protobuf with Ent's Golang structures, not via the standard proto3 language.
We are now doing SOA migration and our old system's architecture is based on spring and hibernate. We use PO (persistence object) across all the layers.
When facing SOA migration, if we use DTO for remote procedure call, we have to create so many DTOs.
What are some suggestions on how to avoid this?
Develop a Canonical Model, probably the most important SOA pattern there is.
- Define a representation using an XML Schema for that model.
- Use jaxb to create the Java POJO representations.
Once you have these you 'could' map these to your existing Persistent Objects and then round-trip until they are equivalent.
Alternatively given you already use persistent object you could work bottom up with Jaxb, but in my experience that is more difficult/work intensive approach.
I'm about to start developing a dynamic web application with Java (i.e., Servlets and JSP).
Obviously I will need to keep a database with all sorts of information (Users, etc.). My question is - is there a good library for saving/storing/retrieving from a database for this kind of application?
I don't mean JDBC, which is used to send queries and parse results, but some sort of abstraction for saving and loading my object to/from the database.
Currently, I am trying to develop some sort of generic classes for handling of these cases in django style (i.e., classes have a save() method), but since these are generic, I suppose something ought to exist already.
It sounds like you are looking for an Object Relational Mapping (ORM) tool. ORMs map rows in a table to objects in your code. In fact, what you have been using in Django is an ORM.
Hibernate is one such ORM that will let you describe how your Java objects should be mapped.