I am new in the hibernate world. My project task is to represent xml result from the SQL database. To do so, first step, I am trying to generate POJOs and mapping xml from my db by using hibernate tools auto generating feature. When, i am trying to generate a simple database (2/3 tables) its working fine.
But while i trying to convert my real database, which has 28 tables within different table relationships. Then i am facing the below problem. Not able to connect the database tables. Hibernate tools configuration showing this terrible message.(Foreign key name (fk_p_einheit) mapped to different tables! previous: org.hibernate.mapping.Table(public.einheit_quelle) current:org.hibernate.mapping.Table(public.spalten)
I checked google to get the solution but not get any proper solution related to eclipse IDE. Just got one BUG report from NetBeans site(https://netbeans.org/bugzilla/show_bug.cgi?id=205863).
My setup configuration is:eclipse-jee-luna-SR1-win32-x86_64, postgres (sql 9.1-901.jdbc4) and hibernate core (4.3.5.Final) with maven project and hibernate tools.
Any one please help me.
You need an object model that maps all of those 28 tables and relationships. Do you have one? If not, why are you using Hibernate?
You can ask Hibernate to generate an object model for you from the schema. Try it.
Why are you using all these unknown technologies (Hibernate, Eclipse, etc.) to do something simple?
If you're thinking in terms of tables and columns, and not objects, I'd say you'd be better off writing JDBC and straight SQL. ORM tools aren't for you.
Related
I am making a web app with Spring Boot. I am planning on using Spring Data JPA (Hibernate) connected to MySQL. One question I have is that I have already written out the SQL statements to create my database schema. I have my primary keys, foreign keys, relationships all set already. All the tutorials I've seen assume you don't have tables or anything in the database already. If I create entities, how can I ensure they match up to my already existing data model?
I don't mind recreating the entities by hand, since there's not that many classes and manually reverse-engineering won't take too much time. (I have seen a way to reverse engineering using Eclipse but I prefer to use IntelliJ, also I feel that manually writing the Entities may be easier than doing the reverse process.) But I want to make sure that the entity objects I create will match the tables I already have and won't cause trouble. I'm not sure what the best way to go about doing this is. Will Hibernate overwrite my existing schema when I run for the first time?
You can make hibernate to validate your mapping.
Set this property :
hibernate.hbm2ddl.auto=validate
I have 3 MySQL tables and i need to generate their corresponding entities in java (eclipse)
is there an easy way ?
im working on a spring boot application
While the majority of people will recommend jpa(spring data) this is codeFirst approach, for DB first approach I have a great framework recommendation:
If you have some time on your hand I will go and try Jooq
Jooq website
Jooq has a maven dependency for creating all necessary objects from your db:
Jooq auto code generation from db
codeGen configuration in maven
Jooq can connect to your db, and even connect to your liquibase schema upgrades so that the object are always on the same stage with the db
I don't have any connection to Jooq but Lukas Eder (#lukaseder) is an awsome guy, he always answer questions in stack Overflow, so you are in good hands, also if you are using reactor Jooq is fully compatible(also compatible with JavaRX)
Generally we generate tables from Hibernate JPA to Database, but however i want to generate reverse, i.e from Database to Entity (from table to pojo).
Can you please suggest solution for:
is it possible?
is it recommended(if you have near about 1000 table)?
or should I go manually by creating POJO.
(I am using Microsoft SqlServer as DB and Spring boot (STS) in back end)
Thanks in Advance!
I'm seeking for same functionality in Java that present in PHP's Doctrine ORM.
I can describe an entity and the doctrine:migrations:diff console command will make me a fine migration which will generate SQL for updating the database schema. then I can update current database schema with new fields/tables etc running doctrine:migrations:migrate
But what's the same way to do it in Java? I've tried to do it with Flyway, but had no luck because it can't just get the entity and generate diff: https://github.com/flyway/flyway/issues/648#issuecomment-64208848
So, I just tried to do it with liquibase, but don't understand how to do it.
I've tried to ask this question in #java room on irc.freenode.net, but the closest answer was "let hibernate create the schema and have liquibase extract it" (thank you, k5_)
but… how?
many sources say that I must use somewhat "hibernate.hbm2ddl.auto"… but how? what is it?
I'm surprised that there's no examples "for dummies" over internet for this important functionality
I think that it is a terrible way to write all migrations by hands and I just don't believe that there are no solutions exist
please, help me
thank you in advance!
UPD
In my particular case I'm using Hibernate, I have basic entities defined (with OneToMany, ManyToOne mappings)
I want to start on clean database and updating its schema with migrations.
So my goal is to generate this migrations automatically from entities descriptions compared to current database schema state.
UPD 2
The second closest answer is (thanks once again, k5_): "configure hibernate to create a schema when it doesnt exist (just add the configuration option you posted to the persistence.xml). Start the server it will create a schema in a database. Use the liquibase to extract the schema. Or use it to create a diff over two databases."
I need a tool for converting database tables to entity java files for hibernate.
There are 20 tables (mysql) and I don't want to copy table's column name to my Java file and so on.
Any suggestions ?
Thanks.
Hibernate Tools.
Keep in mind that entity classes / mappings that Database Reverse Engineering tool will generate may not be ideal (depending on complexity of your database) and you'll have to manually update them.
Take a look at this question as well.
Eclipse DALI, Netbeans jpa-plugin and Oracle JDevelopper.
If you have sql schema, you can use https://converter.aldoraweb.com to convert it