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Hibernate注解：一对多外键关联
情形：两个表，cms_mode是主表，cms_model_field是子表，cms_model_field的model_id字段关联到cms_model的主键。
## Source for table cms_model#DROP TABLE IF EXISTS `cms_model`;CREATE TABLE `cms_model` ( `model_id` int(11) NOT NULL, `name` varchar(50) NOT NULL DEFAULT ‘‘, `title` varchar(100) NOT NULL DEFAULT ‘‘ COMMENT ‘名称‘,) ENGINE=MyISAM DEFAULT CHARSET=utf8 ROW_FORMAT=COMPACT COMMENT=‘CMS模型表‘;## Source for table cms_model_field#DROP TABLE IF EXISTS `cms_model_field`;CREATE TABLE `cms_model_field` ( `field_id` int(11) NOT NULL AUTO_INCREMENT, `model_id` int(11) NOT NULL DEFAULT ‘0‘ COMMENT ‘模型ID‘, `name` varchar(50) DEFAULT NULL COMMENT ‘名称‘, `title` varchar(250) NOT NULL DEFAULT ‘‘ COMMENT ‘标题‘, `priority` int(11) NOT NULL DEFAULT ‘0‘ COMMENT ‘权重‘, `data_type` char(1) NOT NULL DEFAULT ‘1‘ COMMENT ‘数据类型(S-字符,N-数值,D-日期,T-备注)‘, `is_reserved` tinyint(1) NOT NULL DEFAULT ‘0‘ COMMENT ‘是否保留‘, PRIMARY KEY (`field_id`)) ENGINE=MyISAM AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 COMMENT=‘CMS模型字段表‘;;
CmsModel.java：
@Entity@Table(name = "cms_model")@SuppressWarnings("serial")public class CmsModel implements Serializable{ @Id @GeneratedValue @Column(name = "model_id") private Integer id; @Column(name = "name") private String name; @Column(name = "title") private String title; @OneToMany(mappedBy = "model", fetch = FetchType.LAZY) private List<CmsModelField> fieldList;}
CmsModelField.java：
@Entity@Table(name = "cms_model_field")@SuppressWarnings("serial")public class CmsModelField implements Serializable{ @Id @GeneratedValue @Column(name = "field_id") private Integer id; @Column(name = "name") private String name; @Column(name = "title") private String title; @Column(name = "data_type") private String dataType; @Column(name = "priority") private Integer priority; @Column(name = "is_reserved") private Boolean reserved; @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "model_id") private CmsModel model;}
@OneToMany Default: FetchType.LAZY默认是延迟抓取，不需要左联接。如果是FetchType.EAGER即时抓取，就会是左联接查询。
@ManyToOne Default: FetchType.EAGER默认是即时抓取，做连接。如果fetch=FetchType.LAZY不是左联接，在需要One的时候直接select。
Hibernate注解：一对多外键关联
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