用于一对多双向映射的Hibernate和H2“违反参考完整性约束”
所以我有两个简单的豆子-
FatKid和Hamburgers。现在，出于我不知道的原因，我不仅需要查找某人吃过的所有汉堡包，而且还要查找谁吃了哪个特定的汉堡包。进入代码！
FatKid.java
import java.util.List;import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;
@Table
@Entity
public class FatKid {
private int id;
private String name;
private List<Hamburger> hamburgers;
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "FATKID_ID")
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Column
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@OneToMany(cascade = CascadeType.ALL)
@JoinColumn(name="HAMBURGER_ID")
public List<Hamburger> getHamburgers() {
return hamburgers;
}
public void setHamburgers(List<Hamburger> hamburgers) {
this.hamburgers = hamburgers;
}
}
汉堡包
import javax.persistence.CascadeType;import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Table
@Entity
public class Hamburger {
private int id;
private String description;
private FatKid whoDoneAteMe;
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "HAMBURGER_ID")
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Column
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
@ManyToOne(cascade = CascadeType.ALL)
@JoinColumn(name="FATKID_ID")
public FatKid getWhoDoneAteMe() {
return whoDoneAteMe;
}
public void setWhoDoneAteMe(FatKid whoDoneAteMe) {
this.whoDoneAteMe = whoDoneAteMe;
}
}
hibernate.cfg.xml
<?xml version='1.0' encoding='utf-8'?><!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.driver_class">org.h2.Driver</property>
<property name="hibernate.connection.url">jdbc:h2:~/routesetting</property>
<property name="hibernate.dialect">org.hibernate.dialect.H2Dialect</property>
<!-- JDBC connection pool (use the built-in) -->
<property name="connection.pool_size">1</property>
<!-- Enable Hibernate's automatic session context management -->
<property name="current_session_context_class">thread</property>
<!-- Disable the second-level cache -->
<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
<!-- Echo all executed SQL to stdout -->
<property name="show_sql">true</property>
<!-- Drop and re-create the database schema on startup -->
<property name="hbm2ddl.auto">create-drop</property>
<mapping class="FatKid" />
<mapping class="Hamburger" />
</session-factory>
</hibernate-configuration>
依存关系
<dependency> <groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>3.6.7.Final</version>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<version>1.3.160</version>
</dependency>
<dependency>
<groupId>javassist</groupId>
<artifactId>javassist</artifactId>
<version>3.9.0.GA</version>
</dependency>
客户
import org.hibernate.Session;import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class OmNom {
private static final SessionFactory sessionFactory = buildSessionFactory();
public static void main(String[] args) {
Session session = sessionFactory.openSession();
session.beginTransaction();
FatKid fk = new FatKid();
fk.setName("Darrell");
session.save(fk);
session.getTransaction().commit();
session.beginTransaction();
Hamburger hamburger_1 = new Hamburger();
hamburger_1.setDescription("Juicy quarter pounder with cheese");
hamburger_1.setWhoDoneAteMe(fk);
session.save(hamburger_1);
session.getTransaction().commit();
session.beginTransaction();
Hamburger hamburger_2 = new Hamburger();
hamburger_2.setDescription("Ground buffalo burger topped with bacon and a sunny-side egg");
hamburger_2.setWhoDoneAteMe(fk);
session.save(hamburger_2);
session.getTransaction().commit();
sessionFactory.close();
}
private static SessionFactory buildSessionFactory() {
try {
// Create the SessionFactory from hibernate.cfg.xml
return new Configuration().configure().buildSessionFactory();
}
catch (Throwable ex) {
// Make sure you log the exception, as it might be swallowed
throw new ExceptionInInitializerError(ex);
}
}
}
因此，当我运行代码时，我最终得到输出（以及截断的堆栈跟踪）
Hibernate: insert into FatKid (FATKID_ID, name) values (null, ?)Hibernate: insert into Hamburger (HAMBURGER_ID, description, FATKID_ID) values (null, ?, ?)
Hibernate: insert into Hamburger (HAMBURGER_ID, description, FATKID_ID) values (null, ?, ?)
Exception in thread "main" org.hibernate.exception.ConstraintViolationException: could not insert: [Hamburger]
...
Caused by: org.h2.jdbc.JdbcSQLException: Referential integrity constraint violation: "FK43797FE95067143: PUBLIC.HAMBURGER FOREIGN KEY(HAMBURGER_ID) REFERENCES PUBLIC.FATKID(FATKID_ID)"; SQL statement:
insert into Hamburger (HAMBURGER_ID, description, FATKID_ID) values (null, ?, ?) [23506-160]
...
因此，第一个汉堡被保存，但第二个被炸掉。两者都应该能够使用FatKid的ID作为其外键，但似乎不起作用。任何见识将不胜感激。
谢谢，凯文
回答：
您的映射对我来说很奇怪。关系的两边都有一个@JoinColumn，每个都指向另一个表的主键。那似乎不是一对多的关系。
您的OneToMany应该告诉关系的所有者：
@OneToMany(cascade = CascadeType.ALL, mappedBy = "whoDoneAteMe")public List<Hamburger> getHamburgers() {
return hamburgers;
}
然后在另一边：
@ManyToOne(cascade = CascadeType.ALL)@JoinColumn(name = "fatkid_id")
public FatKid getWhoDoneAteMe() {
return whoDoneAteMe;
}
您也许也可以进一步优化代码。由于您的FatKid对象可以识别Hamburger对象，并且已经配置了级联，因此您可以执行以下操作：
session.beginTransaction(); FatKid fk = new FatKid();
fk.setName("Darrell");
Hamburger hamburger_1 = new Hamburger();
hamburger_1.setDescription("Juicy quarter pounder with cheese");
hamburger_1.setWhoDoneAteMe(fk);
fk.getHamburgers().add(hamburger1);
Hamburger hamburger_2 = new Hamburger();
hamburger_2.setDescription("Ground buffalo burger topped with bacon and a sunny-side egg");
hamburger_2.setWhoDoneAteMe(fk);
fk.getHamburgers().add(hamburger2);
session.save(fk);
session.getTransaction().commit();
sessionFactory.close();
上面的代码应仅通过一次提交操作并在单个事务中保存完整的对象图。
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