Persisting Set

Set provides an unordered data structure, and duplicate elements are not allowed. Some classes implemented by the Set interface are java.util.HashSet, java.util.LinkedHashSet, and so on. For this recipe, we will use the java.util.HashSet class, which implements the java.util.Set interface. The only difference between List and Set is that Set doesn't allow duplicate values. For example, in our previous example, we added the e-mail address with [e-mail] twice, and hibernate will allow us to do this. But in case of Set, you cannot add a duplicate value. Let's take a look at how to achieve this.

Getting ready

Now, we need the class to persist Set in hibernate. Use the next code snippet to create the Employee class.

Creating a class

Use the following code to create the classes:

Source file: Employee.java

@Entity
@Table(name = "employee")
public class Employee {

  @Id
  @GeneratedValue
  @Column(name = "id")
  private long id;

  @Column(name = "name")
  private...