/** * 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) );