AccessType.PROPERTY和AccessType.FIELD的區別

 AccessType用來定義訪問Entity的方式：

1. AccessType.PROPERTY的例子：

@Entity(access=AccessType.PROPERTY)
@Table(name = "Person")
public class Person implements Serializable {

    private Long id;

    // auto-generated PK
    @Column(name="Id")
    @Id(generator="PersonIdGenerator")
    @SequenceGenerator(name="PersonIdGenerator", sequenceName="PersonIdGenerator")
    public Long getId() {
        return id;
    }

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

2. AccessType.FIELD的例子：
@Entity(access=AccessType.FIELD)
@Table(name = "Country")
public class Country implements Serializable {
   
@Id(generator="CountryIdGenerator")
    @SequenceGenerator(name="CountryIdGenerator", sequenceName="CountryIdGenerator")
    @Column(name="CountryId")
    public Long countryId;

    @Column(name="Name", length=128, nullable=false)
    public String name;

    ......
}

AccessType.PROPERTY: The EJB persistence implementation will load state into your class via JavaBean "setter" methods, and retrieve state from your class using JavaBean "getter" methods. This is the default.
     --> 通過getter和setter方法訪問Entity的變數，可以把變數定義為private；
     --> 需要在getter方法上定義欄位的屬性；

AccessType.FIELD: State is loaded and retrieved directly from your class' fields. You do not have to write JavaBean "getters" and "setters". 
    --> 直接存取Entity的變數，可以不定義getter和setter方法，但是需要將變數定義為public；
    --> 需要在變數上定義欄位的屬性；