jpa级联删除(CascadeType.REMOVE)-白红宇

jpa级联删除(CascadeType.REMOVE)

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发布时间：2019-06-27

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Garage.java

Java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;

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;

}

(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

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

@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

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

@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

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=?