OneToMany 中间表关联

最新推荐文章于 2024-07-04 14:14:37 发布

原创最新推荐文章于 2024-07-04 14:14:37 发布 · 1k 阅读

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本文介绍了一种使用Java实现的学生与班级间一对多关系的ORM映射方法，通过实体类Class和Student展示了如何设置关联关系及进行数据库操作。

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Class

@Entity
public class Class {
	@Id
	@GeneratedValue
	@Column(name = "class_id")
	private int id;
	private String className;
	@OneToMany(mappedBy = "myclass", cascade = CascadeType.ALL)
	private Set<Student> students = new HashSet<Student>();

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getClassName() {
		return className;
	}

	public void setClassName(String className) {
		this.className = className;
	}

	public Set<Student> getStudents() {
		return students;
	}

	public void setStudents(Set<Student> students) {
		this.students = students;
	}
}

Student

@Entity
public class Student {
	@Id
	@GeneratedValue
	@Column(name = "student_id")
	private int id;
	private String studentName;
	@ManyToOne(cascade=CascadeType.ALL)
	@JoinTable(name = "student_class", joinColumns = @JoinColumn(name = "student_id"), inverseJoinColumns = @JoinColumn(name = "class_id"))
	private Class myclass;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getStudentName() {
		return studentName;
	}

	public void setStudentName(String studentName) {
		this.studentName = studentName;
	}

	public Class getMyclass() {
		return myclass;
	}

	public void setMyclass(Class myclass) {
		this.myclass = myclass;
	}
}

test

@Test
	public void testOneToManyJoinTable() {
		session.beginTransaction();
		OneToMany.joinTable.Class c = new OneToMany.joinTable.Class();
		c.setClassName("classNmae");

		OneToMany.joinTable.Student s1 = new OneToMany.joinTable.Student();
		OneToMany.joinTable.Student s2 = new OneToMany.joinTable.Student();
		OneToMany.joinTable.Student s3 = new OneToMany.joinTable.Student();

		s1.setStudentName("s1");
		s2.setStudentName("s1");
		s3.setStudentName("s1");

		c.getStudents().add(s3);
		c.getStudents().add(s2);
		c.getStudents().add(s1);
		s3.setMyclass(c);
		s2.setMyclass(c);
		s1.setMyclass(c);

		session.save(c);

		session.getTransaction().commit();
	}