Garage.java Java代码 收藏代码
package com.hibernate.jpa.bean1; import java.util.HashSet; import java.util.Set; import javax.persistence.CascadeType; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.OneToMany; @Entity public class Garage { /** * many to one 多对一 */ private Integer gid; private String garagenum; private Set<Auto> autos = new HashSet<Auto>(); @Id @GeneratedValue public Integer getGid() { return gid; } public void setGid(Integer gid) { this.gid = gid; } @Column(length=20) public String getGaragenum() { return garagenum; } public void setGaragenum(String garagenum) { this.garagenum = garagenum; } @OneToMany(cascade={CascadeType.PERSIST},mappedBy="garage") public Set<Auto> getAutos() { return autos; } public void setAutos(Set<Auto> autos) { this.autos = autos; } public void addGarageAuto(Auto auto) { auto.setGarage(this); this.autos.add(auto); } }Auto.java Java代码 收藏代码
package com.hibernate.jpa.bean1; import javax.persistence.CascadeType; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; @Entity public class Auto { /** * one to many 一对多关联 */ private Integer autoId; private String autotype; private String autonum; private Garage garage; @Id @GeneratedValue public Integer getAutoId() { return autoId; } public void setAutoId(Integer autoId) { this.autoId = autoId; } public String getAutotype() { return autotype; } public void setAutotype(String autotype) { this.autotype = autotype; } public String getAutonum() { return autonum; } public void setAutonum(String autonum) { this.autonum = autonum; } @ManyToOne() @JoinColumn(name="garageid") public Garage getGarage() { return garage; } public void setGarage(Garage garage) { this.garage = garage; } }持久化数据
mysql> select * from garage; +-----+-----------+ | gid | garagenum | +-----+-----------+ | 1 | room1 | | 2 | room2 | | 3 | room3 | +-----+-----------+ mysql> select * from auto; +--------+---------+----------+----------+ | autoId | autonum | autotype | garageid | +--------+---------+----------+----------+ | 1 | hk2222 | car | 1 | | 2 | bj0000 | car | 1 | | 3 | jn1d31 | bus | 3 | | 4 | sh3243 | car | 3 | +--------+---------+----------+----------+junit测试方法delete() Java代码 收藏代码
@Test public void delete() { EntityManagerFactory factory = Persistence.createEntityManagerFactory("jpa-hibernate"); EntityManager em = factory.createEntityManager(); em.getTransaction().begin(); Garage garage = em.find(Garage.class, 3); em.remove(garage); em.getTransaction().commit(); em.close(); factory.close(); }调用delete方法是myeclipse控制台出现异常
javax.persistence.RollbackException: Error while commiting the transaction Caused by: java.sql.BatchUpdateException: Cannot delete or update a parent row: a foreign key constraint fails (`itcast/auto`, CONSTRAINT `FK1F51CFA8A25FB2` FOREIGN KEY (`garageid`) REFERENCES `garage` (`gid`))发出的sql语句是： C#代码 收藏代码
Hibernate: select garage0_.gid as gid1_0_, garage0_.garagenum as garagenum1_0_ from Garage garage0_ where garage0_.gid=?（二）在Garage.java中添加CascadeType.REMOVE注解 Java代码 收藏代码
@OneToMany(cascade={CascadeType.PERSIST,CascadeType.REMOVE},mappedBy="garage") public Set<Auto> getAutos() { return autos; }此时再次调用junit单元测试的delete方法 测试显示成功，发出的sql语句为 Sql代码 收藏代码
Hibernate: select garage0_.gid as gid1_0_, garage0_.garagenum as garagenum1_0_ from Garage garage0_ where garage0_.gid=? Hibernate: select autos0_.garageid as garageid1_, autos0_.autoId as autoId1_, autos0_.autoId as autoId0_0_, autos0_.autonum as autonum0_0_, autos0_.autotype as autotype0_0_, autos0_.garageid as garageid0_0_ from Auto autos0_ where autos0_.garageid=? Hibernate: delete from Auto where autoId=? Hibernate: delete from Auto where autoId=? Hibernate: delete from Garage where gid=?此时表garage中的gid为3的字段被全部删除，同时也级联删除了与garage相关联表auto中garageid为3的字段 Sql代码 收藏代码
mysql> select * from garage; +-----+-----------+ | gid | garagenum | +-----+-----------+ | 1 | room1 | | 2 | room2 | +-----+-----------+Sql代码 收藏代码
mysql> select * from auto; +--------+---------+----------+----------+ | autoId | autonum | autotype | garageid | +--------+---------+----------+----------+ | 1 | hk2222 | car | 1 | | 2 | bj0000 | car | 1 | +--------+---------+----------+----------+怎么样，这下级联删除也明白了吧？
