Mapping domain objects using JPA

Take a look at the following steps to learn about mapping the domain objects:

1. Let's begin by mapping our Event.java file so all the domain objects will use JPA, as follows:

//src/main/java/com/packtpub/springsecurity/domain/Event.java

import javax.persistence.*;
@Entity
@Table(name = "events")
public class Event implements Serializable{
 @Id
 @GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
@NotEmpty(message = "Summary is required")
private String summary;
@NotEmpty(message = "Description is required")
private String description;
@NotNull(message = "When is required")
private Calendar when;
@NotNull(message = "Owner is required")
 @ManyToOne(fetch = FetchType.LAZY)
 @JoinColumn(name="owner", referencedColumnName="id")
private CalendarUser owner;
 @ManyToOne(fetch = FetchType.LAZY)
 @JoinColumn(name="attendee", referencedColumnName="id")
private CalendarUser attendee;

1. We need to create a Role.java file with the following contents:

//src/main/java/com/packtpub/springsecurity/domain/Role.java

import javax.persistence.*;
@Entity
@Table(name = "role")
public class Role implements Serializable {
 @Id
 @GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
private String name;
 @ManyToMany(fetch = FetchType.EAGER, mappedBy = "roles")
private Set<CalendarUser> users;

1. The Role object will be used to map authorities to our CalendarUser table. Let's map our CalendarUser.java file, now that we have a Role.java file:

//src/main/java/com/packtpub/springsecurity/domain/CalendarUser.java

import javax.persistence.*;
import java.io.Serializable;
import java.util.Set;
@Entity
@Table(name = "calendar_users")
public class CalendarUser implements Serializable {
   @Id
   @GeneratedValue(strategy = GenerationType.AUTO)
   private Integer id;
   private String firstName;
   private String lastName;
   private String email;
   private String password;
   @ManyToMany(fetch = FetchType.EAGER)
   @JoinTable(name = "user_role",
           joinColumns = @JoinColumn(name = "user_id"),
           inverseJoinColumns = @JoinColumn(name = "role_id"))
   private Set<Role> roles;

At this point, we have mapped our domain objects with the required JPA annotation, including @Entity and @Table to define the RDBMS location, as well as structural, reference, and association mapping annotations.

The application will not work at this point, but this can still be considered a marker point before we continue on to the next steps of conversion.

You should be starting with the source from chapter05.02-calendar.