I have a table called Person which I have already mapped in hibernate I has already some data which I do not want to loose. I need to add new column called address, Any idea how to do that in hibernate ?
Thanks in Advance..
If you current tables are generated by Hibernate , you can simply add the address property in the java entity class for the address column . Then set the hibernate.hbm2ddl.auto property to update and hibernate will automatically create this column when the SessionFactory is built next time . Hibernate will not change any data store in your database when hibernate.hbm2ddl.auto is update.
Or , you can manually issue the SQL to alter the table structure and then add the address property in the java entity class for the address column.
Likely you are not forced to use Hibernate to create/update database schema. I assume you have something like this in your configuration:
<property name="hibernate.hbm2ddl.auto" value="create-drop" />
Just change value to "validate", perform changes to the mappings and execute ALTER TABLE statements separately.
Other option is to use "update" to let Hibernate figure out how to update your table structure. I suggest to keep it in your hands and just execute DDL SQL manually.
You should also read this other SO question/answer: Hibernate: hbm2ddl.auto=update in production? before you set hibernate.hbm2ddl.auto to update.
Related
In my application i am using below property
spring.jpa.properties.hibernate.hbm2ddl.auto= validate
so does it validates schema like if manually i added one new column in my oracle table and not added this column in java entity .
so in this case will it give error on project startup ?
No, it's perfectly alright to have columns in a table that aren't mapped. An error would be a missing column or table that's mapped to an entity. Your database doesn't need to be identical to your mappings.
hi I have an entity with this annotation
#Entity
#Table(name = "REPORT_WORK")
But for some reason hibernate keep saying Missing Table: REPORT_REPORT_WORK
I know that is the problem because of when I change the name to "REPORT_WORKX"
It will say Missing Table: REPORT_REPORT_WORKX
Has any encountered this issue before?
Update: when I change the name to JJJJ
It will say Missing Table: REPORT_JJJJ
so for some reason there it is auto appending REPORT_
Configuration:
hibernate.hbm2ddl.auto=validate
I suspect that the problem is your Hibernate configurations. Specifically, if you don't have an appropriate setting for hibernate.hbm2ddl.auto, Hibernate won't automatically update the database schema when you change your model.
(And if you don't want the updates to happen automatically, then you need to figure out what schema changes are needed, code them as SQL DDL, and run them manually.)
Can you post your persistence.xml (or equivalent)?
It sounds like you are implementing org.hibernate.cfg.NamingStrategy, get rid of this configuration.
Some additional info:
JPA (Hibernate) and custom table prefixes
I am working on a project with MySQL,Hibernate,Java,GWT
I am making an entity class where i am making each and every field as per the fields in mysql
like there is a table UserInfo with fields ,id,name,password,and many other fields in MySQL
now when i am making an entity class in java/hibernate
I have to create each field i.e id,name,password and others with my hand
I was just wondering if there's a way with which my entity class automatically detects all fields which are in my Database table and make all the fields in java itself and link them with the database fields.
thanks
hibernate has a property called "hibernate.hbm2ddl.auto".
hibernate.hbm2ddl.auto
Automatically validates or exports schema DDL
to the database when the SessionFactory is created. With create-drop,
the database schema will be dropped when the SessionFactory is closed
explicitly.
e.g. validate | update | create | create-drop
you can set the proper value when you start creating your sessionfactory. then you will see the tables were created in your datastore, of course, the table creation was based on your entity classes.
if you want to generate java classes (entities) from your database table. you may want to check hibernate reverse engineering out:
http://docs.jboss.org/tools/3.3.0.M5/en/hibernatetools/html/reverseengineering.html
Try Hibernate Tools.
I have witten the POJO class, *.cfg.xml file, *.hbm.xml file and hibernate code to retrieve data.
But I didn't created any table. Is there any tag available in hibernate which will create table by using configuration files.
How to implement reverse engineering in hibernate ?
Thanks !
You can actually set a configuration property and instruct hibernate to create the database schema for you.
hibernate.hbm2ddl.auto = create-drop | update
See this link Asking hibernate to generate schema for you
Looks like jpa is something which makes me ask a lot of questions.
Having added this
<property name="toplink.ddl-generation" value="create-tables"/>
my JPA application always creates tables when running, which results in exceptions in case the tables already exist. I would like JPA to check if the tables already exist and if not create them, however I could not find a value for the property above which does this.
So if I just turn it off, is there a way to tell JPA manually at some point to create all the tables?
Update here's the exception I get
Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'tags' already exists
Error Code: 1050
Call: CREATE TABLE tags (ID BIGINT AUTO_INCREMENT NOT NULL, NAME VARCHAR(255), OCCURRENCE INTEGER, PRIMARY KEY (ID))
MySQLSyntaxErrorException?! Now that's wrong for sure
According to http://www.oracle.com/technology/products/ias/toplink/JPA/essentials/toplink-jpa-extensions.html#Java2DBSchemaGen toplink does not have an option to update exiting tables, I'm not sure if I would trust it to do the right thing anyway.
You could configure toplink to generate a sql script that you then would have to execute manually to create all tables. The filenames and location can be configured like this:
<property name="toplink.ddl-generation" value="create-tables"/>
<property name="toplink.ddl-generation.output-mode" value="sql-script"/>
<property name="toplink.create-ddl-jdbc-file-name" value="createDDL.sql"/>
<property name="toplink.drop-ddl-jdbc-file-name" value="dropDDL.sql"/>
<property name="toplink.application-location" value="/tmp"/>
I would like [my] JPA [provider] to check if the tables already exist and if not create them, however I could not find a value for the property above which does this.
Weird, according to the TopLink Essentials documentation about the toplink.ddl-generation extension, create-table should leave existing table unchanged:
TopLink JPA Extensions for Schema Generation
Specify what Data Descriptor Language
(DDL) generation action you want for
your JPA entities. To specify the DDL
generation target, see
toplink.ddl-generation.output-mode.
Valid values: oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider
none - do not generate DDL; no
schema is generated.
create-tables - create DDL for
non-existent tables; leave existing
tables unchanged (see also
toplink.create-ddl-jdbc-file-name).
drop-and-create-tables - create DDL for all tables; drop all existing
tables (see also
toplink.create-ddl-jdbc-file-name
and
toplink.drop-ddl-jdbc-file-name).
If you are using persistence outside
the EJB container and would like to
create the DDL files without creating
tables, additionally define a Java
system property INTERACT_WITH_DB and
set its value to false.
Liquibase (http://www.liquibase.org) is good at this. It takes some time to get fully used to it, but I think it's worth the effort.
The Liquibase-way is independent of which JPA persistence provider you use. Actually, it's even database agnostic.