Overriding Metadata Defaults

In this section we return to the Customer entity and override some of the default mapping options.

First we want to use the CLIENT table with columns CUSTOMER_ID, FIRST_NAME and LAST_NAME to store Customer entities. The primary key is CUSTOMER_ID. The table definition is:

The modified listing for Customer.java is shown below:

@Entity
@Table(name = "CLIENT")
public class Customer implements java.io.Serializable {
private int id;
private String firstName;
private String lastName;
public Customer() {};
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name = "CUSTOMER_ID")
public int getId() { return id; }
public void setId(int id) { this.id = id; }
@Column(name = "FIRST_NAME")
public String getFirstname() { return firstName; }
public void setFirstname(String firstName) {
this.firstName = firstName;
}
@Column(name = "LAST_NAME")
public String getLastname() { return lastName; }
public void setLastname(String lastName) {
this.lastName = lastName;
}
public String toString() {
return "[Customer Id =" + id + ",first name=" +
firstName + ",last name=" + lastName + "]";
}
}

Note we have used the @Table annotation to specify the table name as CLIENT. The default table name is the entity name, CUSTOMER in our example. The catalog element specifies the database catalog where the table is located. Many database systems, Derby included, do not support the concept of a catalog. So in our example we can leave this element out. The schema element specifies the database schema where the table is located. The default is persistence provider specific, in the case of the GlassFish APP is the default schema for the embedded Derby database. Again, in our example, we rely on the default.

We have explicitly specified an AUTO primary key generation strategy:

@Id
@GeneratedValue(strategy=GenerationType.AUTO)

Recall that GlassFish selects the TABLE strategy in this case.

Recall that by default column names are set to attribute names. To override this we use the @Column annotation. For example,

@Column(name = "CUSTOMER_ID")
public int getId() { return id; }

will map the id attribute to the CUSTOMER_ID column. In a similar fashion we map the firstName and lastName attributes to the FIRST_NAME and LAST_NAME columns respectively.