Hibernate - getting started

In this blog, we'll explore how to run some hibernate from the source - hibernate.org. It has a nice tutorial, which is also short and sweet.

In order to get the tutorials up and running, download the code from here:

http://docs.jboss.org/hibernate/core/4.0/quickstart/en-US/html_single/#d0e127

and click on the files/hibernate-tutorials.zip link. Once the file is downloaded and unzipped, copy it into your STS workspace. (I'm assuming you have STS and maven installed - if not, you may need to research downloading maven/eclipse or just STS).

Once that's done, bring up a terminal window and navigate to hibernate-tutorials directory you just copied into the workspace. For each of the four tutorial projects (hbm, entitymanager, annotations and envers), navigate into the directory and type "mvn eclipse:eclipse". That creates an eclipse project file. That allows you import the four projects into STS. Use file, import, select "existing projects into workspace", and find one of the folders (e.g. hibernate-tutorial-hbm) and import it. Do this for all of the projects.

You can run them by right-clicking and select "junit test".

I won't rehash what's done in each of them. Here's the url for the very short, but very clear and easy to follow tutorial: http://docs.jboss.org/hibernate/core/4.0/quickstart/en-US/html/

The basics of are this:

Chapter 2 - Tutorial Using Native Hibernate APIs and hbm.xml Mappings

hibernate-tutorial-hbm:

- uses Hibernate mapping files (hbm.xml) to provide mapping information
- uses the native Hibernate APIs

The hibernate.cfg.xml file contains info like database driver, username, password, connection url, etc.
The Event.hbm.xml file contains the mapping of the field.


The next tutorial, chapter 3:

hibernate-tutorial-annotations

Tutorial Using Native Hibernate APIs and Annotation Mappings

Objectives

Use annotations to provide mapping information

Use the native Hibernate APIs

The event.hbm.xml file, which maps the class fields to the database fields, is gone. Annotations within the source code give the same information. The hibernate.hbm.xml file reflects the change with a declaration of the mapping class, "mapping class="org.hibernate.tutorial.annotations.Event".

Here's what event looks like with annotations:

import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

import org.hibernate.annotations.GenericGenerator;

@Entity
@Table( name = "EVENTS" )
public class Event {
private Long id;

private String title;
private Date date;

public Event() {
// this form used by Hibernate
}

public Event(String title, Date date) {
// for application use, to create new events
this.title = title;
this.date = date;
}

@Id
@GeneratedValue(generator="increment")
@GenericGenerator(name="increment", strategy = "increment")
public Long getId() {
return id;
}

private void setId(Long id) {
this.id = id;
}

@Temporal(TemporalType.TIMESTAMP)
@Column(name = "EVENT_DATE")
public Date getDate() {
return date;
}

public void setDate(Date date) {
this.date = date;
}

public String getTitle() {
return title;
}

public void setTitle(String title) {
this.title = title;
}
}

Chapter 4. Tutorial Using the Java Persistence API (JPA)

Objectives

Use annotations to provide mapping information.

Use JPA.

This chapter shows utilizes the Java persistence API instead of the native hibernate API. Here, the hibernate.hbm.xml is replaced by persistence.xml. persistence.xml, like the hibernate.hbm.xml file, shows the configuration information, such as jdbc driver, url, name password, plus a couple of hibernate-specific values which as a result begin with "hibernate-". The programmatic API is slightly different, using "persist" instead of "save.", but looks very similar

The final chapter adds some auditing capability via the @org.hibernate.envers.Audited annotation.