Strictly speaking, a basic type is denoted with with the javax.persistence.Basic annotation. Generally speaking, the @Basic annotation can be ignored, as it is assumed by default. Both of the following examples are ultimately the same.

　　严格来说，一个基础的类型用javax.persistence.Basic注解来表示。通常来说，@Basic注解能够被忽略，因为他假设在默认的情况下，就像下面的例子最后都是一样的。

　　example 3. @Basic declared explicitly

@Entity(name = "Product")
public class Product {

    @Id
    @Basic
    private Integer id;

    @Basic
    private String sku;

    @Basic
    private String name;

    @Basic
    private String description;
}

@Entity(name = "Product")
public class Product {

    @Id
    private Integer id;

    private String sku;

    private String name;

    private String description;
}

The @Basic annotation defines 2 attributes.

optional - boolean (defaults to true)

Defines whether this attribute allows nulls. JPA defines this as "a hint", which essentially means that it effect is specifically required. As long as the type is not primitive, Hibernate takes this to mean that the underlying column should be NULLABLE.

fetch - FetchType (defaults to EAGER)

Defines whether this attribute should be fetched eagerly or lazily. JPA says that EAGER is a requirement to the provider (Hibernate) that the value should be fetched when the owner is fetched, while LAZY is merely a hint that the value be fetched when the attribute is accessed. Hibernate ignores this setting for basic types unless you are using bytecode enhancement. See the BytecodeEnhancement for additional information on fetching and on bytecode enhancement.

 

 

　　JPA defines rules for implicitly determining the name of tables and columns. For a detailed discussion of implicit naming see Naming.

For basic type attributes, the implicit naming rule is that the column name is the same as the attribute name. If that implicit naming rule does not meet your requirements, you can explicitly tell Hibernate (and other providers) the column name to use.

　　JPA定义规则隐式地确定表名和列名。

　　基础类型属性，隐式命名规则中列名与属性名一样。如果隐式命名规则不能满足你的需要，你能够显示的告诉HIbernate(并且提供其他)列名给它使用。

Example 5. Explicit column naming(显示列名命名 例5)

@Entity(name = "Product")
public class Product {

    @Id
    private Integer id;

    private String sku;

    private String name;

    @Column( name = "NOTES" )
    private String description;
}