one needs 3 inputs
i.e.
See details below.
Now that we are done with the setup of the needed input files, we move on to the execution phase
3. Execution:
With the various inputs done we would use
Hibernate’s HBM2DDL tool to create
the database using 1 of the options available below to run the SchemaExport.
1.
Invoking SchemaExport from “Java Main class”
2.
Running from the command line
3.
Running the SchemaExport
from ant build scripts.
3.1. Invoking HBM2DDL SchemaExport from the Java main class
Create a class, e.g. SchemaCreator.Java, to serve as
the point of invocation of the schema creation or SQL DDL generation. This
class makes use of the persistence session created by the HibernateUtil java class. The HibernateUtil
class is a specialised class, made use of by the Hibernate ORM framework,
which can contain configurations other than the settings in the hibernate.cfg.xml that the framework creates a
persistence session from. The location of hibernate.cfg.xml is shown located at the root of your java package structure as shot below.
Fig. 5. Content of a HibernateUtil Java file.
The HibernateUtil class is detailed below.
Fig. 6. Content of a HibernateUtil Java file.
The
SessionFactory creation from a hibernate.cfg.xml file is performed by the statement below, as shown by the screenshot above.
SessionFactory sessionFactory = new
Configuration().configure().buildSessionFactory();
Note: To have the
session created from a hibernate.cfg.xml located in another location as
desired, use below code.
sessionFactory = new Configuration().configure("<CUSTOM_DIRECTORY>/hibernate.cfg.xml").buildSessionFactory();
You can also add extra configuration parameters by using the instance methods addResource(~) and addProperties(~) on the Configuration class.
Fig. 7. instance methods of the Configuration class.
3.1.1 Invoking the schema creation from the
main class SchemaCreator java class
Fig. 8. Content of SchemaCreator invocation class
Note: The above class principally uses two static objects - SessionFactory and Session.
sessionFactory =
HibernateUtil.getSessionFactory()//fetches
session details from configs in HibernateUtil class
session = sessionFactory.getCurrentSession(); //does
loading of application session from Hibernate to be used for searches, updates
and saves of entity objects in an application.
Proceed to compile the above class and execute the class
file to get the output below
Fig. 9. Output of execution of SchemaCreator
Perform a refresh of the data schema to see the new tables
created in your database (remember,
the connection parameters and more were stated in the hibernate.cfg.xml file).
Fig. 10. Database loaded with tables modeled from mapping files and entities
3.2. Running
SchemaExport from the command
line
The syntax is stated below
3.2.1 This a java class invocation from the command line
java -cp 'hibernate_classpath' org.hibernate.tool.hbm2ddl.SchemaExport options my_hbm_mapping_files
hibernate_classpath = the runtime
resources needed by hibernate i.e. dependent classes and jar files
my_hbm_mapping_files
= the location of all the
*hbm.xml files
options = this states the
various command line parameter the SchemaExport
tool i.e.
parameter
|
purpose
|
--quiet
|
do
not output the script to stdout
|
--drop
|
only
drop the tables
|
--create
|
only
create the tables
|
--text
|
do
not export to the database
|
--output=db_schema.sql
|
output
the ddl script to a file
|
--config=hibernate.cfg.xml
|
read
Hibernate configuration from an XML file
|
--properties=hibernate.properties
|
read
database properties from a file(alt to --config)
|
--format
|
format
the generated SQL nicely in the script
|
--delimiter=;
|
set
an end of line delimiter for the script
|
3.2.2 Execution:
java -cp "$HBN_HOME/*" org.hibernate.tool.hbm2ddl.SchemaExport
--config=$PROJECT_HOME/src/java/hibernate.cfg.xml
--create $PROJECT_HOME/src/java/org/softlogic/blog/model/*.hbm.xml
Fig.11. Command line execution of the Hibernate tool’s SchemaExport as seen on Linux.
3.3. Running the SchemaExport from Apache ANT build scripts
The Ant script, being the most powerful java code-administration tool, is
essentially an xml file that contains the activities to be carried on a java
project during build and deployment time . It is also sometimes used to "set up" the various dependencies a project have before the “first-run” of the project.
In our case,
on first-run we want our database
created.
Just embed the code below, which you can customise, in the build.xml file
(or Netbeans' build-impl.xml which would have
its contents loaded into the build.xml file at compile time).The
build script is located on the root of your project folder as captured below.
Fig.12. compilation build file as seen in the project folder.
Modify project build script by embedding another build target node for schemaexport as shown below
<target
name="schemaexport">
<taskdef name="schemaexport"
classname="org.hibernate.tool.hbm2ddl.SchemaExportTask"
classpathref="class.path"/>
<schemaexport config="hibernate.cfg.xml"
quiet="no"
text="no"
create="yes"
delimiter=";">
<fileset
dir="src">
<include
name="**/*.hbm.xml"/>
</fileset>
</schemaexport>
</target>
Content of build.xml file.
Fig.13. config snippet from ant build file.
Perform a compilation of the project to have the schemaexport performed.Refresh the database to confirm new table additions
4.0 Legend
JPA=Java Persistnce
Application Programmer Interface
ORM=Object Relational
Mapping
DDL=Data Definition
Language
5.0 References
6.0 Dont get yourself bothered to work hard in Life;work smart J
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