Hibernate fail to create Foreign key - mysql

Question

I have three class with onetomany and manytoone annotated. Below
Category.java
#Entity
public class Category implements Serializable {
#Id
#GeneratedValue
int id;
String cat;
#OneToMany(cascade= CascadeType.ALL)
#JoinColumn(name="cat_id")
private Collection<Subject> subjects = new ArrayList<Subject>();
#OneToMany(cascade= CascadeType.ALL)
#JoinColumn(name="cat_id")
private Collection<Classes> classes = new ArrayList<Classes>();
#OneToMany(cascade= CascadeType.ALL)
#JoinColumn(name="cat_id")
private Collection<Exam> exam = new ArrayList<Exam>();
public Collection<Subject> getSubjects() {
return subjects;
}
public void setSubjects(Collection<Subject> subjects) {
this.subjects = subjects;
}
public Collection<Classes> getClasses() {
return classes;
}
public void setClasses(Collection<Classes> classes) {
this.classes = classes;
}
public Collection<Exam> getExam() {
return exam;
}
public void setExam(Collection<Exam> exam) {
this.exam = exam;
}
public Category() {
}
public Category(String cat) {
this.cat = cat;
}
//getters/setters}
Classes.java
#Entity
public class Classes implements Serializable {
#Id
#GeneratedValue
int id;
String name;
#Column(name="cat_id")
short cat_id;
short yr;
#ManyToOne
#JoinColumn(name="cat_id", updatable=false,insertable=false)
private Category cat;
public Category getCat() {
return cat;
}
public void setCat(Category cat) {
this.cat = cat;
}
public Classes() {
}
public Classes(String name, short cat_id, short yr) {
this.name = name;
this.cat_id = cat_id;
this.yr = yr;
}
//setters&getters
}
Exam.java
#Entity
public class Exam {
#Id
#GeneratedValue
int id;
String name;
short yr;
#Column(name="cat_id")
short cat_id;
short total;
#Temporal(TemporalType.TIMESTAMP)
Date date_time;
#ManyToOne
#JoinColumn(name="cat_id", updatable=false,insertable=false)
private Category cat;
public Category getCat() {
return cat;
}
public void setCat(Category cat) {
this.cat = cat;
}
public Exam() {
}
public Exam(String name, short yr, short cat_id, short total, Date date_time) {
this.name = name;
this.yr = yr;
this.cat_id = cat_id;
this.total = total;
this.date_time = date_time;
}
getter setter
}
spring xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:jee="http://www.springframework.org/schema/jee"
xmlns:lang="http://www.springframework.org/schema/lang"
xmlns:p="http://www.springframework.org/schema/p"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:util="http://www.springframework.org/schema/util"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee.xsd
http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd>
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd">
<mvc:annotation-driven />
<context:annotation-config />
<context:component-scan base-package="org.app.nebula." />
<bean id="jspViewResolver"
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="viewClass"
value="org.springframework.web.servlet.view.JstlView" />
<property name="prefix" value="/WEB-INF/pages/" />
<property name="suffix" value=".jsp" />
</bean>
<bean id="messageSource"
class="org.springframework.context.support.ReloadableResourceBundleMessageSource">
<property name="basename" value="classpath:resources/messages" />
<property name="defaultEncoding" value="UTF-8" />
</bean>
<bean id="propertyConfigurer"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"
p:location="/WEB-INF/jdbc.properties" />
<bean id="dataSource" class="org.springframework.jndi.JndiObjectFactoryBean">
<property name="jndiName" value="java:comp/env/jndiName"/>
</bean>
<bean id="sessionFactory"
class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="configLocation">
<value>classpath:resources/hibernate.cfg.xml</value>
</property>
<property name="packagesToScan" value="org.app.nebula.domain" />
<property name="configurationClass">
<value>org.hibernate.cfg.AnnotationConfiguration</value>
</property>
<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">${jdbc.dialect}</prop>
<prop key="hibernate.show_sql">true</prop>
<prop key="hibernate.hbm2ddl.auto">update</prop>
</props>
</property>
</bean>
<tx:annotation-driven />
<bean id="transactionManager"
class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory" ref="sessionFactory" />
</bean>
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver" />
</beans>
now when i run this project, the tables are created but it fails to alter and add a forign key and giving this error
[DEBUG] 33:01(SchemaUpdate.java:execute:203) alter table Classes add
index FK9619D00659EAC034 (cat_id), add constraint FK9619D00659EAC034
foreign key (cat_id) references Category (id)
[ERROR] 33:01(SchemaUpdate.java:execute:212) Unsuccessful: alter
table Classes add index FK9619D00659EAC034 (cat_id), add constraint
FK9619D00659EAC034 foreign key (cat_id) references Category (id)
[ERROR] 33:01(SchemaUpdate.java:execute:213) Can't create table
'nebula.#sql-83c_e3' (errno: 150)
[DEBUG] 33:01(SchemaUpdate.java:execute:203) alter table Exam add
index FK212C3F59EAC034 (cat_id), add constraint FK212C3F59EAC034
foreign key (cat_id) references Category (id)
[ERROR] 33:01(SchemaUpdate.java:execute:212) Unsuccessful: alter
table Exam add index FK212C3F59EAC034 (cat_id), add constraint
FK212C3F59EAC034 foreign key (cat_id) references Category (id)
[ERROR] 33:01(SchemaUpdate.java:execute:213) Can't create table
'nebula.#sql-83c_e3' (errno: 150)
Any help is appreciated.
Thanks & Regards

Answer 1

The Java type of the foreign key should be the same as the type you're referencing to.

Answer 2

You should always use Long values for generated numerical IDs.
Change your Category class as follows:
#Entity public class Category implements Serializable {
#Id
#GeneratedValue
Long id;
[...]
}
BTW: It uncommon to use the Java type short (if you do not have to access legacy C interfaces via JNI for instance).