OrderBy (Java EE 5 SDK)

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Java EE 5 SDK

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摘要: REQUIRED | OPTIONAL

详细信息: ELEMENT

javax.persistence Annotation Type OrderBy

@Target(value={METHOD,FIELD}) @Retention(value=RUNTIME) public @interface OrderBy

This annotation specifies the ordering of the elements of a collection valued association at the point when the association is retrieved.

The syntax of the value ordering element is an orderby_list, as follows:

    orderby_list::= orderby_item [,orderby_item]*
    orderby_item::= property_or_field_name [ASC | DESC]

If ASC or DESC is not specified, ASC (ascending order) is assumed.

If the ordering element is not specified, ordering by the primary key of the associated entity is assumed.

The property or field name must correspond to that of a persistent property or field of the associated class. The properties or fields used in the ordering must correspond to columns for which comparison operators are supported.

    Example:
    
    @Entity public class Course {
     ...
     @ManyToMany
     @OrderBy("lastname ASC")
     public List getStudents() {...};
     ...
    }
    
    @Entity public class Student {
      ...
      @ManyToMany(mappedBy="students")
      @OrderBy // PK is assumed
      public List getCourses() {...};
      ...
    }

从以下版本开始:: Java Persistence 1.0

Optional Element Summary
`String`	`value` An `orderby_list`, specified as follows: orderby_list::= orderby_item [,orderby_item]* orderby_item::= property_or_field_name [ASC \| DESC] If `ASC` or `DESC` is not specified, `ASC` (ascending order) is assumed.

value

public abstract String value

An orderby_list, specified as follows:

    orderby_list::= orderby_item [,orderby_item]*
    orderby_item::= property_or_field_name [ASC | DESC]