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.
Related
I have a Mysql DB, schema name "myschema". This schema has tables, where some of this tables are
audit tables. This is my dependency on my java project.
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-envers</artifactId>
<version>5.1.0.Final</version>
</dependency>
Now I had like to remore this audit tables on my currect DB and more them on a separate instance, with a branch new uri.
How can this be done? Any advise, thank you in advance
Please take a look at the Configuration Options:
org.hibernate.envers.default_schema
The default schema name that should be used for audit tables.
org.hibernate.envers.default_catalog
The default catalog name that should be used for audit tables.
The option that you should use depends on if your database.
There is also a bug that if you use the default revision entity mappings provided out of the box by Envers that those mappings won't be properly mapped when using these configuration options, only the tables that are related to the entity mappings.
In order to properly map the REVINFO table to the appropriate schema or catalog, a custom revision entity mapping will need to be used in cojunction with a the #Table annotation in order to explicitly specify the schema/catalog. Please see the section Revision Log that describes using a custom #RevisionEntity annotated entity mapping with Envers.
AFAIK Envers does not support using a separate database/DataSource. There seem to be a couple of ways to get the data to the other database: Oracle Database Link - MySQL Equivalent?
Alternatively I guess you could write a custom DataSource that delegates statements to different datasources depending on the statement.
Check if an auditing table is mentioned and if so send it to the audit database.
I am following https://www.javatpoint.com/crud-in-servlet
to create an CRUD application in servlets and mysql.
Each user inputs his information in a webpage and submit to the web server, which then invokes a servlet SaveServlet to save the information as a record in a database table. The database table however has an additional "id".
SaveServlet.java doesn't create an id for each record. So I was wondering how to create an id for each record?
Thanks.
If you are using jpa/hibernate then your entity must be having the #Id annotation on the record id field (you dont need to set it, it will be done automatically based on you Id generation mechanism defined in the entity class and database schema).
if you are using plain jdbc for persisting records then you need to check the database how primary key is defined. for oracle you can your sequence.nextvalue to set the primary key.
I have an issue testing a Hibernate application which queries multiple catalogs/schemas.
The production database is Sybase and in addition to entities mapped to the default catalog/schema there are two entities mapped as below. There are therefore three catalogs in total.
#Table(catalog = "corp_ref_db", schema = "dbo", name = "WORKFORCE_V2")
public class EmployeeRecord implements Serializable {
}
#Table(catalog = "reference", schema = "dbo", name="cntry")
public class Country implements Serializable {
}
This all works in the application without any issues. However when unit testing my usual strategy is to use HSQL with hibernate's ddl flag set to auto and have dbunit populate the tables.
This all works fine when the tables are all in the same schema.
However, since adding these additional tables, testing is broken as the DDL will not run as HSQL only supports one catalog.
create table corp_ref_db.dbo.WORKFORCE_V2
user lacks privilege or object not found: CORP_REF_DB
If there were only two catalogs then I think it would maybe be possible to get round this by changing the default catalog and schema in the HSQL database to that one explicitly defined:
Is there any other in-memory database for which this might work or is there any strategy for getting the tests to run in HSQL.
I had thought of providing an orm.xml file which specified the default catalog and schema (overiding any annotations and having all the defined tables created in the default catalog/schema) however these overrides do not seem to be observed when the DDL is executed i.e. I get the same error as above.
Essentially, then I would like to run my existing tests and either somehow have the tables created as they are defined in the mappings or somehow override the catalog/schema definitions at the entity level.
I cannot think of any way to achieve either outcome. Any ideas?
I believe H2 supports catalogs. I haven't used them in it myself, but there's a CATALOGS table in the Information Schema.
I managed to achieve something like this in H2 via IGNORE_CATALOGS property and version 1.4.200
However, the url example from their docs did not seem to work for me, so I added a statement in my schema.xml:
SET IGNORE_CATALOGS = true;
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
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.