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使用annotation配置hibernate（2）：一对多关系配置

2024-07-11 08:28:05   221人阅读

数据表结构

 

 

单向一对多

Student.java

 1 @Entity 2 @Table(name = "student") 3 public class Student { 4     @Id 5     @Column(name = "id") 6     @GenericGenerator(name = "generator",strategy = "native") 7     @GeneratedValue(generator = "generator") 8     private int id; 9     10     @Column(name = "name")11     private String name;12     13     @ManyToOne(cascade=CascadeType.ALL,fetch=FetchType.EAGER)14     @JoinColumn(name="grade_id")15     private Grade grade;16 }

Grade.java

 1 @Entity 2 @Table(name="grade") 3 public class Grade { 4     @Id 5     @Column(name = "id") 6     @GenericGenerator(name = "generator", strategy = "native") 7     @GeneratedValue(generator = "generator") 8     private int id; 9     10     @Column(name = "name")11     private String name;12 }

 

单向多对一

Student.java

@Entity@Table(name = "student")public class Student {    @Id    @Column(name = "id")    @GenericGenerator(name = "generator",strategy = "native")    @GeneratedValue(generator = "generator")    private int id;        @Column(name = "name")    private String name;        @ManyToOne(cascade=CascadeType.ALL,fetch=FetchType.EAGER)    @JoinColumn(name="grade_id")    private Grade grade;}

  Grade.java

 1 @Entity 2 @Table(name="grade") 3 public class Grade { 4     @Id 5     @Column(name = "id") 6     @GenericGenerator(name = "generator", strategy = "native") 7     @GeneratedValue(generator = "generator") 8     private int id; 9     10     @Column(name = "name")11     private String name;12 }

 

双向关联

Student.java

 1 @Entity 2 @Table(name = "student") 3 public class Student { 4     @Id 5     @Column(name = "id") 6     @GenericGenerator(name = "generator",strategy = "native") 7     @GeneratedValue(generator = "generator") 8     private int id; 9     10     @Column(name = "name")11     private String name;12     13     @ManyToOne(cascade=CascadeType.ALL,fetch=FetchType.EAGER)14     @JoinColumn(name="grade_id")15     private Grade grade;16 }

 Grade.java

 1 @Entity 2 @Table(name="grade") 3 public class Grade { 4     @Id 5     @Column(name = "id") 6     @GenericGenerator(name = "generator", strategy = "native") 7     @GeneratedValue(generator = "generator") 8     private int id; 9     10     @Column(name = "name")11     private String name;12     13     @OneToMany(cascade=CascadeType.ALL,fetch=FetchType.EAGER,mappedBy="grade")14     private Set<Student> students = new HashSet<Student>(); 15 }

  

自身一对多

Category.java

 1 @Entity 2 @Table(name = "category") 3 public class Category { 4     @Id 5     @Column(name = "id") 6     @GenericGenerator(name = "generator",strategy = "native") 7     @GeneratedValue(generator = "generator") 8     private int id; 9     10     @OneToMany(cascade=CascadeType.ALL,fetch=FetchType.LAZY,mappedBy="category")11     private Set<Category> categorys = new HashSet<Category>();12     13     @ManyToOne(cascade=CascadeType.ALL,fetch=FetchType.EAGER)14     @JoinColumn(name="father_category")15     private Category category;16 17 }

 

关于mappedBy关键字的具体作用可以参考 http://xiaoruanjian.iteye.com/blog/1094253


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