(14)基于annotation配置ManyToMany

ゝ一世哀愁。 2022-05-11 13:18 170阅读 0赞

**第一种方式（manytomany）：**

@Entity
    @Table(name="t_admin")
    public class Admin {
    	private int id;
    	private String name;
    	private Set<Role> roles;
    	public Admin() {
    		roles=new HashSet<>();
    	}
    	public void add(Role role) {
    		roles.add(role);
    	}
    	@Id
    	@GeneratedValue
    	public int getId() {
    		return id;
    	}
    	public void setId(int id) {
    		this.id = id;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	@ManyToMany(mappedBy="admins")
    	public Set<Role> getRoles() {
    		return roles;
    	}
    	public void setRoles(Set<Role> roles) {
    		this.roles = roles;
    	}
    	
    	
    }

**第二种方式：**

@Entity
    @Table(name="t_role")
    public class Role {
    private int id;
    private String name;
    private Set<Admin> admins;
    
    public Role() {
    	admins=new HashSet<>();
    }
    public void add(Admin admin) {
    	admins.add(admin);
    }
    @Id
    @GeneratedValue
    public int getId() {
    	return id;
    }
    public void setId(int id) {
    	this.id = id;
    }
    public String getName() {
    	return name;
    }
    public void setName(String name) {
    	this.name = name;
    }
    @ManyToMany
    @JoinTable(name="t_admin_role",joinColumns= {@JoinColumn(name="r_id")},inverseJoinColumns= {@JoinColumn(name="a_id")})
    public Set<Admin> getAdmins() {
    	return admins;
    }
    public void setAdmins(Set<Admin> admins) {
    	this.admins = admins;
    }
    
    
    }

**@JoinTable(name="t\_admin\_role",joinColumns= \{@JoinColumn(name="r\_id")\},inverseJoinColumns= \{@JoinColumn(name="a\_id")\})**

**jointable表示关联表，,joinColumns= \{@JoinColumn(name="r\_id")\}表示该属于该类的外键在关联表的名称，inverseJoinColumns= \{@JoinColumn(name="a\_id")\})表示另一个类的外键在关联表的名称**

**然后在另一个类也要加入@ManyToMany(mappedBy="admins")，表示由对立类的admins属性维护关系**

**第二种方式(两个manytoone)：**

@Entity
    public class TeacherCourse {
    private int id;
    private double ach;
    private Teacher teacher;
    private Course course;
    @Id
    @GeneratedValue
    public int getId() {
    	return id;
    }
    public void setId(int id) {
    	this.id = id;
    }
    public double getAch() {
    	return ach;
    }
    public void setAch(double ach) {
    	this.ach = ach;
    }
    @ManyToOne
    @JoinColumn(name="t_id")
    public Teacher getTeacher() {
    	return teacher;
    }
    public void setTeacher(Teacher teacher) {
    	this.teacher = teacher;
    }
    @ManyToOne
    @JoinColumn(name="c_id")
    public Course getCourse() {
    	return course;
    }
    public void setCourse(Course course) {
    	this.course = course;
    }
    
    }

@Entity
    public class Teacher {
    	private int id;
    	private String name;
    	private Set<TeacherCourse> tcs;
    	@Id
    	@GeneratedValue
    	public int getId() {
    		return id;
    	}
    	public void setId(int id) {
    		this.id = id;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	@OneToMany(mappedBy="teacher")
    	@LazyCollection(LazyCollectionOption.EXTRA)
    	public Set<TeacherCourse> getTcs() {
    		return tcs;
    	}
    	public void setTcs(Set<TeacherCourse> tcs) {
    		this.tcs = tcs;
    	}
    	
    }

@Entity
    public class Course {
    private int id;
    private String name;
    private Set<TeacherCourse> tcs;
    @Id
    @GeneratedValue
    public int getId() {
    	return id;
    }
    public void setId(int id) {
    	this.id = id;
    }
    public String getName() {
    	return name;
    }
    public void setName(String name) {
    	this.name = name;
    }
    @OneToMany(mappedBy="course")
    @LazyCollection(LazyCollectionOption.EXTRA)
    public Set<TeacherCourse> getTcs() {
    	return tcs;
    }
    public void setTcs(Set<TeacherCourse> tcs) {
    	this.tcs = tcs;
    }
    
    
    }