关于@OnetoMany关系映射的排序问题,使用注解@OrderBy

@OneToMany(cascade = CascadeType.ALL,mappedBy = "product",fetch = FetchType.EAGER)
private List<Picture> pictures;

@Target({METHOD, FIELD})
@Retention(RUNTIME)
public @interface OrderBy { 
   /**
    * An <code>orderby_list</code>.  Specified as follows:
    *
    * <pre>
    *    orderby_list::= orderby_item [,orderby_item]*
    *    orderby_item::= [property_or_field_name] [ASC | DESC]
    * </pre>
    *
    * <p> If <code>ASC</code> or <code>DESC</code> is not specified,
    * <code>ASC</code> (ascending order) is assumed.
    *
    * <p> If the ordering element is not specified, ordering by
    * the primary key of the associated entity is assumed.
    */
    String value() default "";
}

@OneToMany(cascade = CascadeType.ALL,mappedBy = "product",fetch = FetchType.EAGER)
@OrderBy("ordernum ASC")
private List<Picture> pictures;

/**
 * 评论实体类，对应 TCOMMENT 表。
 * @author William
 */
@Entity
@Table(name = "TCOMMENT")
public class Comment {
 
 /**
  * 标识ID字段为主键，主键生成策略为：自动。
  */
 @Id @GeneratedValue
 private Long id;
 private String nickname;
 private String content;
 private Integer note;
 /**
  * 发表日期，对应 posted_date 字段，字段类型为TIMESTAMP。
  */
 @Column(name = "posted_date")
 @Temporal(TemporalType.TIMESTAMP)
 private Date postedDate;
 
 // Constructors, setters, getters
}

/**
 * 新闻实体类，对应 News表。
 * @author William
 */
@Entity
@NamedQuery(name = "findAllNews", query = "SELECT n FROM News n")
public class News {
 
 /**
  * 标识ID字段为主键，主键生成策略为：自动。
  */
 @Id @GeneratedValue
 private Long id;
 /**
  * content新闻内容，该字段必填。
  */
 @Column(nullable = false)
 private String content;
 /**
  * comments评论，与之进行一对多关联。<br/>
  * FetchType.EAGER 获取新闻时立即相关评论。<br/>
  * CascadeType.ALL 支持所有级联操作。<br/>
  * OrderBy 获取评论列表时，按照postedDate（发表日期）降序排列。
  */
 @OneToMany(fetch = FetchType.EAGER, cascade = {CascadeType.ALL})
 @JoinTable(name = "NEWS_COMMENT", joinColumns = @JoinColumn(name = "NEWS_ID"),
  inverseJoinColumns = @JoinColumn(name = "COMMENT_ID"))
 @OrderBy("postedDate DESC")
 private List<Comment> comments; 
 // Constructors, setters, getters
}

CREATE TABLE TCOMMENT (
 ID BIGINT,
 NICKNAME VARCHAR(50),
 CONTENT VARCHAR(500),
 NOTE INT,
 POSTED_DATE TIMESTAMP,
 PRIMARY KEY (ID)
);
 
CREATE TABLE NEWS (
 ID BIGINT,
 CONTENT VARCHAR(500),
 PRIMARY KEY (ID)
);
 
CREATE TABLE NEWS_COMMENT (
 NEWS_ID BIGINT,
 COMMENT_ID BIGINT,
 PRIMARY KEY (NEWS_ID, COMMENT_ID),
 FOREIGN KEY (NEWS_ID) REFERENCES NEWS(ID),
 FOREIGN KEY (COMMENT_ID) REFERENCES TCOMMENT(ID)
);