I have 3 tables tbl_category, tbl_Advertisment and tbl_linkcategoryadvert (with numerous b / w category associations and ads)
My POJO as below
Advertisment.java
@Entity
@Table(name="tbl_advertisment")
public class Advertisment implements Serializable {
private long id;
private String title;
private String message;
private Set<Category> categories;
public Advertisment(String title, String message) {
this.title = title;
this.message = message;
this.categories=new HashSet<Category>();
}
protected Advertisment() {
}
@Id
@GeneratedValue
protected long getId() {
return id;
}
protected void setId(long id) {
this.id = id;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
@Column(nullable=false)
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
@ManyToMany(mappedBy="adverts")
public Set<Category> getCategories() {
return categories;
}
public void setCategories(Set<Category> categories) {
this.categories = categories;
}
}
Category.java
@Entity
@Table(name="tbl_category")
public class Category implements Serializable {
private long id;
private String title;
private Set<Advertisment> adverts=new HashSet<Advertisment>();
public Category(String title) {
this.title = title;
}
protected Category() {
}
@ManyToMany
@JoinTable(name="tbl_linkcategoryadvert")
public Set<Advertisment> getAdverts() {
return adverts;
}
public void setAdverts(Set<Advertisment> adverts) {
this.adverts = adverts;
}
public void addAdvert(Advertisment advert){
adverts.add(advert);
}
@Id
@GeneratedValue
protected long getId() {
return id;
}
protected void setId(long id) {
this.id = id;
}
@Column(unique=true,nullable=false)
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
}
PostAdvert.java - Main class
public class PostAdvertisment extends DAO{
public Advertisment post(String username,String catTitle,String title,String message)
throws DAOException {
try{
begin();
Query categoryQuery=getSession().createQuery("from Category where title=:categoryTitle");
categoryQuery.setString("categoryTitle", catTitle);
Category category=(Category)categoryQuery.uniqueResult();
Advertisment advert=new Advertisment(title,message,user);
getSession().save(advert);
category.addAdvert(advert);
getSession().save(category);
commit();
return advert;
} catch(HibernateException he){
he.printStackTrace();
throw new DAOException(he.getMessage());
}
}
public static void main(String[] args){
String catTitle="LCD";
String title="Bravia";
String message="High Contrast Television";
try{
PostAdvertisment post=new PostAdvertisment();
post.post(username, catTitle, title, message);
DAO.close();
} catch(DAOException daoEx){
System.out.println(daoEx.getMessage());
}
}
}
DAO.java
I do not provide DAO.java as it contains only the Hibernate template.
When I run the main class, I get the following exception:
SEVERE: Unknown column 'adverts0_.categories_id' in 'field list'
org.hibernate.exception.SQLGrammarException: could not initialize a collection: [hibernate.Category.adverts#3]
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:67)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.loader.Loader.loadCollection(Loader.java:2001)
at org.hibernate.loader.collection.CollectionLoader.initialize(CollectionLoader.java:36)
at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:565)
at org.hibernate.event.def.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:60)
at org.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:1716)
at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:344)
at org.hibernate.collection.PersistentSet.add(PersistentSet.java:189)
at hibernate.Category.addAdvert(Category.java:48)
at hibernate.client.PostAdvertisment.post(PostAdvertisment.java:35)
at hibernate.client.PostAdvertisment.main(PostAdvertisment.java:56)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'adverts0_.categories_id' in 'field list'
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
at com.mysql.jdbc.Util.getInstance(Util.java:384)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1054)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3566)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3498)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1959)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2113)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2568)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2113)
Please help me....
My tables look like this:
1. tbl_advert
id PK BIGINT
title VARCHAR(255)
2. tbl_category
id PK BIGINT
title VARCHAR(255)
3. tbl_linkcategoryadvert
advert_id FK references(advert.id)
category_id FK references(category.id)
Now my questions ...
- Am I accepting the wrong names for the fields in the table "link_categoryadvert"?
- How does hibernate look for column names and collation?
- What are the other possible attributes for @JoinTable Annotation?