ssh用注解生成数据表时,实体类之间的的关系应该怎么写

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多对一，一对多的关系：

@Entity@Table(name="employee")public class Employee implements java.io.Serializable{@Idprivate String sn;@ManyToOne@JoinColumn(name="identity")private Dept dept;public String getSn() {return sn;}public void setSn(String sn) {this.sn = sn;}@Column(name="name")private String name;@Column(name="password")private String password;@Column(name="status")private String status;public Dept getDept() {return dept;}public void setDept(Dept dept) {this.dept = dept;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}public String getStatus() {return status;}public void setStatus(String status) {this.status = status;}}

employee里的joinColumn里的值必须要和一方实体类的id名称对应,Table(name="数据库里要生成的表名"),cloumn:是数据库里要生成的列名，记住：多对一的类型要写一方实体类的类型

@Entity@Table(name="dept")public class Dept implements java.io.Serializable{@Id    @GeneratedValue(strategy=GenerationType.IDENTITY)private Integer identity;@Column(name="name")private String name;@OneToMany(mappedBy="dept",fetch=FetchType.LAZY,cascade=CascadeType.ALL)    private Set<Employee> emps=new HashSet(0);public Integer getIdentity() {return identity;}public void setIdentity(Integer identity) {this.identity = identity;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Set<Employee> getEmps() {return emps;}public void setEmps(Set<Employee> emps) {this.emps = emps;}}

mappedBy:写一方要生成的表名，fetch=FetchType.LAZY:是延迟加载的意思,cascadeType:ALL：就是对所有的增，删，改查都在这实现

一对一关系：

@Entity@Table(name="biz_leave")public class Leave implements java.io.Serializable{@Id    @GeneratedValue(strategy=GenerationType.IDENTITY)private Integer id;@JoinColumn(name="sn")     //一对一，一张请假条对应一名员工private Employee emp;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public Employee getEmp() {return emp;}public void setEmp(Employee emp) {this.emp = emp;}

@GeneratedValue():这里因为我用的是mysql数据库，所有这样写，其他数据库是不一样的写法,记住在写多对一，和一对一的时候，千万别出现两个实体类的id名称一样，除非这两个类不用被实现多对一和一对一的关系，否则它将分不清，你是要哪个表。

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