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package my.bean;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.SequenceGenerator;
@Entity
public class Student {
private int id;
private String sname;
private Set<Course> courses;
@Id
@SequenceGenerator(name="idGenerator", sequenceName="seq_student_id")
@GeneratedValue(generator="idGenerator")
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getSname() {
return sname;
}
public void setSname(String sname) {
this.sname = sname;
}
@ManyToMany(cascade={CascadeType.PERSIST, CascadeType.MERGE,
CascadeType.REFRESH})
@JoinTable(name="student_course",
joinColumns={@JoinColumn(name="student_id")},
inverseJoinColumns={@JoinColumn(name="course_id")})
public Set<Course> getCourses() {
return courses;
}
public void setCourses(Set<Course> courses) {
this.courses = courses;
}
}
package my.bean;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import javax.persistence.SequenceGenerator;
@Entity
public class Course {
private int id;
private String cname;
private Set<Student> students;
@Id
@SequenceGenerator(name="idGenerator", sequenceName="seq_course_id")
@GeneratedValue(generator="idGenerator")
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getCname() {
return cname;
}
public void setCname(String cname) {
this.cname = cname;
}
@ManyToMany(cascade={CascadeType.PERSIST, CascadeType.MERGE,
CascadeType.REFRESH}, mappedBy="courses")
public Set<Student> getStudents() {
return students;
}
public void setStudents(Set<Student> students) {
this.students = students;
}
}
package my.test;
import java.util.HashSet;
import java.util.Set;
import my.bean.Course;
import my.bean.Student;
import my.util.HibernateSessionFactory;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.tool.hbm2ddl.SchemaExport;
public class Test {
public static void main(String[] args) {
cascadeSave();
}
public static void cascadeSave() {
Student s1 = new Student();
s1.setSname("zhangsan");
s1.setCourses(new HashSet<Course>());
Course c1 = new Course();
c1.setCname("c++");
c1.setStudents(new HashSet<Student>());
Course c2 = new Course();
c2.setCname("java");
c2.setStudents(new HashSet<Student>());
Session session = null;
Transaction transaction = null;
try {
session = HibernateSessionFactory.getSession();
transaction = session.beginTransaction();
s1.getCourses().add(c1);
s1.getCourses().add(c2);
session.save(s1); //存储student对象时,无法自动存储级联的course对象,why?
transaction.commit();
} catch(HibernateException e) {
e.printStackTrace();
if(transaction != null) transaction.rollback();
} finally {
if(session != null) session.close();
}
}
}