Configuring a JPA Entity Primary Key

Example 7-1 Primary Key Using @Id

@Id(generate=TABLE, generator="ADDRESS_TABLE_GENERATOR")
@TableGenerator(
    name="ADDRESS_TABLE_GENERATOR", 
    tableName="EMPLOYEE_GENERATOR_TABLE", 
    pkColumnValue="ADDRESS_SEQ"
)
@Column(name="ADDRESS_ID")
public Integer getId() {
    return id;
}

Example 7-2 Embeddable Composite Primary Key Class

@Embeddable
public class EmployeePK implements Serializable {
    private String name;
    private long id;

    public EmployeePK() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public int hashCode() {
        return (int) name.hashCode() + id;
    }

    public boolean equals(Object obj) {
        if (obj == this) return true;
        if (!(obj instanceof EmployeePK)) return false;
        if (obj == null) return false;
        EmployeePK pk = (EmployeePK) obj;
        return pk.id == id && pk.name.equals(name);
    }
}

Example 7-3 JPA Entity With an Embedded Composite Primary Key Class

@Entity
public class Employee implements Serializable {
    EmployeePK primaryKey;
 
    public Employee() {
    }
 
    @EmbeddedId
    public EmployeePK getPrimaryKey() {
        return primaryKey;
    }
 
    public void setPrimaryKey(EmployeePK pk) {
        primaryKey = pk;
    }
 
    ...
}

Example 7-4 Non-Embedded Composite Primary Key Class

public class EmployeePK implements Serializable {
    private String empName;
    private Date birthDay;

    public EmployeePK() {
    }

    public String getName() {
        return empName;
    }

    public void setName(String name) {
        empName = name;
    }

    public long getDateOfBirth() {
        return birthDay;
    }

    public void setDateOfBirth(Date date) {
        birthDay = date;
    }

    public int hashCode() {
        return (int) empName.hashCode();
    }

    public boolean equals(Object obj) {
        if (obj == this) return true;
        if (!(obj instanceof EmployeePK)) return false;
        if (obj == null) return false;
        EmployeePK pk = (EmployeePK) obj;
        return pk.birthDay == birthDay && pk.empName.equals(empName);
    }
}

Example 7-5 JPA Entity With a Mapped Composite Primary Key Class

@IdClass(EmployeePK.class)
@Entity
public class Employee {
    @Id String empName;
    @Id Date birthDay;
...
}

Example 7-6 GeneratedValue Strategy Table: @TableGenerator

@Entity
@Table(name="EJB_ADDRESS")
public class Address implements Serializable {
...
    @TableGenerator(
        name="ADDRESS_TABLE_GENERATOR", 
        tableName="ADDRESS_GENERATOR_TABLE", 
        pkColumnValue="ADDRESS_SEQ"
    )
    @Id @GeneratedValue(strategy="TABLE", generator="ADDRESS_TABLE_GENERATOR")
    @Column(name="ADDRESS_ID")
    public Integer getId() {
        return id;
    }
...
}

Example 7-7 GeneratedValue Strategy Sequence: @SequenceGenerator

@Entity
@Table(name="EJB_ADDRESS")
public class Address implements Serializable {
...
    @SequenceGenerator(
        name="ADDRESS_SEQUENCE_GENERATOR",
        sequenceName="ADDRESS_SEQ"
    )
    @Id @GeneratedValue(strategy="SEQUENCE", generator="ADDRESS_SEQUENCE_GENERATOR")
    @Column(name="ADDRESS_ID")
    public Integer getId() {
        return id;
    }
...
}

Example 7-8 @GeneratedValue Strategy Identity

@Entity
@Table(name="EJB_ADDRESS")
public class Address implements Serializable {
...
    @Id @GeneratedValue(strategy="IDENTITY")
    public Integer getId() {
        return id;
    }
...
}