[jboss-user] [Persistence, JBoss/CMP, Hibernate, Database] - Re: Does Hibernate 3.2 support generating Database schema fr

[andydale]

Yes Hibernate can create the DB schema from annotated classes, consider the following class
@Entity
  | @Table(name = "Student")
  | @SequenceGenerator(name = "Student_Sequence", initialValue = 1, allocationSize = 1, sequenceName = "student_seq")
  | 
  | public final class Student {
  |     //************** class variables *****************   
  |     /**
  |      * The ID of the entity.
  |      */
  |     private int mId;
  |     
  |     /**
  |      * Name of the student.
  |      */
  |     private String mName;
  |     
  |     
  |     /**
  |      * Course student is enrolled on
  |      */
  |     private Collection<Course> mCourses = new ArrayList<Course>();
  |     //************************************************
  |     
  |     //*********** getters and setters ****************
  |     
  |     /**
  |      * Return the courses the student is enrolled on.
  |      * @return mCourses courses
  |      */
  |     @ManyToMany(mappedBy = "students", fetch = FetchType.EAGER, cascade ={CascadeType.PERSIST, CascadeType.MERGE})
  |     public Collection<Course> getCourses() {      
  |         return mCourses;
  |     }
  |     
  |     /**
  |      * See the course the student is enrolled on
  |      * @param pCoursesEnrolledOn courses
  |      */
  |     public void setCourses(final Collection<Course> pCourses) {
  |         mCourses = pCourses;
  |     }
  | 
  |     /**
  |      * get the Id.
  |      * @return mId id
  |      */
  |     @Id
  |     @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "Student_Sequence")
  |     @Column(name = "student_id")
  |     public int getId() {
  |         return mId;
  |     }
  |         
  |     /**
  |      * Set the id.
  |      * @param pId id
  |      */
  |     public void setId(final int pId) {
  |         this.mId = pId;
  |     }
  |         
  |     /**
  |      * Return the name.
  |      * @return mName name
  |      */
  |     public String getName() {
  |         return mName;
  |     }
  |     
  |     /**
  |      * set the name.
  |      * @param pName name
  |      */
  |     public void setName(String pName) {
  |         this.mName = pName;
  |     }
  |     //************************************************
  | }
will create a table on deploy with the definition
CREATE TABLE student
  | (
  |   student_id int4 NOT NULL,
  |   name varchar(255),
  |   CONSTRAINT student_pkey PRIMARY KEY (student_id)
  | ) 

The above example is pretty simple, but you could just deploy a class annotated with @Entity.  On deploy JBoss/Hibernate would convert it into a DB table in the DB specified in a persistence.xml file (must be in META-INF of ejb.jar).

Experiment a bit, and possibly buy yourself the Enterprise JavaBeans 3.0 book (Bill Burke, Richard Monson-Haefel), as it gives you some decent examples of how EJB3 works.


Cheers,

Andy


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