Cascade is a convenient feature to save the lines of code needed to manage the state of the other side manually.
The “Cascade” keyword is often appear on the collection mapping to manage the state of the collection automatically. In this tutorials, this one-to-many example will be used to demonstrate the cascade effect.
Cascade save / update example
In this example, if a ‘Stock’ is saved, all its referenced ‘stockDailyRecords’ should be saved into database as well.
1. No save-update cascade
In previous section, if you want to save the ‘Stock’ and its referenced ‘StockDailyRecord’ into database, you need to save both individually.
Stock stock = new Stock();
StockDailyRecord stockDailyRecords = new StockDailyRecord();
//set the stock and stockDailyRecords data
stockDailyRecords.setStock(stock);
stock.getStockDailyRecords().add(stockDailyRecords);
session.save(stock);
session.save(stockDailyRecords);
Output
Hibernate:
insert into mkyong.stock (STOCK_CODE, STOCK_NAME)
values (?, ?)
Hibernate:
insert into mkyong.stock_daily_record
(STOCK_ID, PRICE_OPEN, PRICE_CLOSE, PRICE_CHANGE, VOLUME, DATE)
values (?, ?, ?, ?, ?, ?)
2. With save-update cascade
The cascade=”save-update” is declared in ‘stockDailyRecords’ to enable the save-update cascade effect.
<!-- Stock.hbm.xml -->
<set name="stockDailyRecords" cascade="save-update" table="stock_daily_record"...>
<key>
<column name="STOCK_ID" not-null="true" />
</key>
<one-to-many class="com.mkyong.common.StockDailyRecord" />
</set>
Stock stock = new Stock();
StockDailyRecord stockDailyRecords = new StockDailyRecord();
//set the stock and stockDailyRecords data
stockDailyRecords.setStock(stock);
stock.getStockDailyRecords().add(stockDailyRecords);
session.save(stock);
Output
Hibernate:
insert into mkyong.stock (STOCK_CODE, STOCK_NAME)
values (?, ?)
Hibernate:
insert into mkyong.stock_daily_record
(STOCK_ID, PRICE_OPEN, PRICE_CLOSE, PRICE_CHANGE, VOLUME, DATE)
values (?, ?, ?, ?, ?, ?)
The code session.save(stockDailyRecords); is no longer required, when you save the ‘Stock’, it will “cascade” the save operation to it’s referenced ‘stockDailyRecords’ and save both into database automatically.
Cascade delete example
In this example, if a ‘Stock’ is deleted, all its referenced ‘stockDailyRecords’ should be deleted from database as well.
1. No delete cascade
You need to loop all the ‘stockDailyRecords’ and delete it one by one.
Query q = session.createQuery("from Stock where stockCode = :stockCode ");
q.setParameter("stockCode", "4715");
Stock stock = (Stock)q.list().get(0);
for (StockDailyRecord sdr : stock.getStockDailyRecords()){
session.delete(sdr);
}
session.delete(stock);
Output
Hibernate:
delete from mkyong.stock_daily_record
where DAILY_RECORD_ID=?
Hibernate:
delete from mkyong.stock
where STOCK_ID=?
2. With delete cascade
The cascade=”delete” is declared in ‘stockDailyRecords’ to enable the delete cascade effect. When you delete the ‘Stock’, all its reference ‘stockDailyRecords’ will be deleted automatically.
<!-- Stock.hbm.xml -->
<set name="stockDailyRecords" cascade="delete" table="stock_daily_record" ...>
<key>
<column name="STOCK_ID" not-null="true" />
</key>
<one-to-many class="com.mkyong.common.StockDailyRecord" />
</set>
Query q = session.createQuery("from Stock where stockCode = :stockCode ");
q.setParameter("stockCode", "4715");
Stock stock = (Stock)q.list().get(0);
session.delete(stock);
Output
Hibernate:
delete from mkyong.stock_daily_record
where DAILY_RECORD_ID=?
Hibernate:
delete from mkyong.stock
where STOCK_ID=?
Cascade delete-orphan example
In above cascade delete option, if you delete a Stock , all its referenced ‘stockDailyRecords’ will be deleted from database as well. How about if you just want to delete two referenced ‘stockDailyRecords’ records? This is called orphan delete, see example…
1. No delete-orphan cascade
You need to delete the ‘stockDailyRecords’ one by one.
StockDailyRecord sdr1 = (StockDailyRecord)session.get(StockDailyRecord.class,
new Integer(56));
StockDailyRecord sdr2 = (StockDailyRecord)session.get(StockDailyRecord.class,
new Integer(57));
session.delete(sdr1);
session.delete(sdr2);
Output
Hibernate:
delete from mkyong.stock_daily_record
where DAILY_RECORD_ID=?
Hibernate:
delete from mkyong.stock_daily_record
where DAILY_RECORD_ID=?
2. With delete-orphan cascade
The cascade=”delete-orphan” is declared in ‘stockDailyRecords’ to enable the delete orphan cascade effect. When you save or update the Stock, it will remove those ‘stockDailyRecords’ which already mark as removed.
<!-- Stock.hbm.xml -->
<set name="stockDailyRecords" cascade="delete-orphan" table="stock_daily_record" >
<key>
<column name="STOCK_ID" not-null="true" />
</key>
<one-to-many class="com.mkyong.common.StockDailyRecord" />
</set>
StockDailyRecord sdr1 = (StockDailyRecord)session.get(StockDailyRecord.class,
new Integer(56));
StockDailyRecord sdr2 = (StockDailyRecord)session.get(StockDailyRecord.class,
new Integer(57));
Stock stock = (Stock)session.get(Stock.class, new Integer(2));
stock.getStockDailyRecords().remove(sdr1);
stock.getStockDailyRecords().remove(sdr2);
session.saveOrUpdate(stock);
Output
Hibernate:
delete from mkyong.stock_daily_record
where DAILY_RECORD_ID=?
Hibernate:
delete from mkyong.stock_daily_record
where DAILY_RECORD_ID=?
In short, delete-orphan allow parent table to delete few records (delete orphan) in its child table.
How to enable cascade ?
The cascade is supported in both XML mapping file and annotation.
1. XML mapping file
In XML mapping file, declared the cascade keyword in your relationship variable.
<!-- Stock.hbm.xml -->
<set name="stockDailyRecords" cascade="save-update, delete"
table="stock_daily_record" ...>
<key>
<column name="STOCK_ID" not-null="true" />
</key>
<one-to-many class="com.mkyong.common.StockDailyRecord" />
</set>
2. Annotation
In annotation, declared the CascadeType.SAVE_UPDATE (save, update) and CascadeType.REMOVE (delete) in @Cascade annotation.
//Stock.java
@OneToMany(mappedBy = "stock")
@Cascade({CascadeType.SAVE_UPDATE, CascadeType.DELETE})
public Set<StockDailyRecord> getStockDailyRecords() {
return this.stockDailyRecords;
}
Further study – Cascade – JPA & Hibernate annotation common mistake.
inverse vs cascade
Both are totally different notions, see the differential here.
Conclusion
Cascade is a very convenient feature to manage the state of the other side automatically. However this feature come with a price, if you do not use it wisely (update or delete), it will generate many unnecessary cascade effects (cascade update) to slow down your performance, or delete (cascade delete) some data you didn’t expected.
Hi I have a doubt on Hibernate multilevel deletion
Excellent!!! and Simple Articulation..
Thanks, nice tips
Hi, here is shown a error:
Hibernate:
insert
into
QUESTAO
(QUESTAO)
values
(?)
Hibernate:
insert
into
ALTERNATIVA
(IDQUESTAO, ALTERNATIVA)
values
(?, ?)
Jul 06, 2015 3:59:05 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
WARN: SQL Error: 1048, SQLState: 23000
Jul 06, 2015 3:59:05 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
ERROR: Column ‘IDquestao’ cannot be null
Jul 06, 2015 3:59:05 PM org.apache.catalina.core.StandardWrapperValve invoke
Grave: Servlet.service() for servlet [dispatcher] in context with path [/Research] threw exception [Request processing failed; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement] with root cause
com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column ‘IDquestao’ cannot be null
@Entity
@Table(name = "QUESTAO")
public class Question {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "IDQUESTAO")
private long id;
@NotEmpty
@Column(name = "QUESTAO", nullable = false)
private String text;
@Column(name = "STATUS", nullable = false, insertable = false)
private int status;
@Valid
@OneToMany(mappedBy = "question")
@Cascade({CascadeType.PERSIST})
private List answers;
-------------------------------------------------------
@Entity
@Table(name = "ALTERNATIVA")
public class Answer {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "IDALTERNATIVA")
private Long id;
@NotEmpty
@Column(name = "ALTERNATIVA", nullable = false)
private String text;
@ManyToOne
@JoinColumn(name = "IDQUESTAO")
public Question question;
Can you help me?
Very nice article. Thanking you mkyong 🙂
I have de same configuration on hbm, but.. the result is :
Hibernate:
insert into TLMS005_CONTRATO
(CD_CLIENTE, CD_CUENTA, NB_PRODUCTO, CD_FOLIODIGIT, TM_RECEPCION, CD_ESTATUS, CD_CONTRATO) values (?, ?, ?, ?, ?, ?, ?)
Hibernate:
update TLMS004_RECUARCH set
TP_ARCHIVO=?,
NB_RUTAARCH=?,
TX_MSGERR=?,
TM_ACTUALIZACION=?,
ST_RECUPERACION=?
where
CD_CONTRATO=?
why get an update??? .. should be a two inserts… whats is wrong???
any body can help me!!!
sorry if I’m very late. Surely you have solved it but it can be used for other people
to be able to insert you need the id to be null
If you are looking for an object (or you bring it from the DTO, or you have EAGER configured) and it has changes, update is done.
With the id in null it has no where to update and executes the insert
Hi, What is the use of cascade=merge? can you explain me like above cascade= delete-orphan.
very nice thanks alot
I read topic about inverse=”false” and inverse=”true”.
when using cascade=”delete” (cascade=”all” ) and inverse=”false” in file xml.
example code :
Stock stock = new Stock();
stock = stockDao.getStock ById(7);
stock Dao.deleteStock (stock);
Error : could not execute statement
Because Hibernate will update StockId=null
I want explain more ! thank.
when using inverse=”false” everything is good.
Yes.. Even I had the same issue of when combining invere=true and cascade=”delete”, it doesnt work. Tried
session.delete(stock_daily_record) also.
I have a question, when you write about the “delete” you explained the cascade effect would delete all the objects related to that object (one to many), then you talked about the “delete-orphan”, which it is used to delete just related objects to a main one, now my question is how can I write the clause to get both effects at the same time? the clause would be “delete-delete-ophan” or “delete-orphan” will do it?
Hey there! I understand this is somewhat off-topic but I
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as yours require a large amount of work? I’m brand new to running a blog however I do write in my journal on a daily basis. I’d like to start a blog
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In a example similar to this
for stock.getStockDailyRecords().add(stockDailyRecords);
I am getting null pointer exception for stock.getStockDailyRecords().
How do I avoid this?
you try :
if (stock.getStockDailyRecords() == null) {
stock.setStockDailyRecords(new HashSet());
}
stock.getStockDailyRecords().add(stockDailyRecords);
Thanks – your delete-orphan stuff helped me a lot
THANK YOU SO MUCH!!!
I struggled for TWO DAYS with an error and this solved it for me!! 😀
Genius you are 😉
this it really help me a lot thank you
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hi. Mkyong. how you doing.. i have a One to many relationship.. and working very well. but when i try to update the many relationship is insert new rows instead of deleting the old records and updating the new records…
i have a table Users and other table usersbyline. suppose the relationship like this.
Users have one or many Usersbyline. my code is the next.
public static void main(String...Arg) throws Exception { Session Session = HibernateUtil.getSessionFactory().openSession(); System.out.println("--------Start-----------------------"); Long A = System.currentTimeMillis(); Integer idUser = 25; String Operation = "edit"; org.com.Models.Usuarios Users = (org.com.Models.Usuarios)Session.get(org.com.Models.Usuarios.class,idUser);//Ignore this. if(Users==null){System.out.println("User Not Found...");return;} Boolean isInsert = Operation.equalsIgnoreCase("add")?true:false;//CRUD operation UsuarioController Controller = new UsuarioController(); Controller.Dao.setClazz(Users); Controller.Dao.setSession(Session); Controller.Dao.setShouldIUseSessionFromChild(true); String idLinea[] = "1000009".split(","); java.util.Set<org.com.Models.UsuariosLinea>ULineas = new java.util.HashSet<org.com.Models.UsuariosLinea>(idLinea.length); for(String Item:idLinea)//adding the new lines to the user. i want to delete the previous. { org.com.Models.UsuariosLinea UsuariosLinea = new org.com.Models.UsuariosLinea(); UsuariosLinea.setLinea(new org.com.Models.Lineas(Item)); UsuariosLinea.setUsuario(Controller.Dao.Clazz); ULineas.add(UsuariosLinea); } Controller.Dao.Clazz.setUsuariosLineas(ULineas); System.out.println(Controller.Dao.Clazz.getUsuariosLineas().size()); Controller.Dao.saveOrUpdate(isInsert); Long B = System.currentTimeMillis(); String Action = (isInsert)?(System.currentTimeMillis()-A)+"ms..[En Executives[Inserting]]":((System.currentTimeMillis()-A)+"ms..[En Executives[Updating]]"); System.out.println(Action);//String the client. JavaMisc.cleanResource(Session); }suppose the user have related 2 Users line with idLine is 1000011 and 1000012; all i want to do is.. when the user is update delete the old records the user have and insert the new ones. in this case only 1000011. but i am getting the old records + the new ones 4 records related to the user. what i am doing wrong.
Users.java
@OneToMany(fetch = FetchType.EAGER, mappedBy = "Usuario") @Cascade(CascadeType.ALL) private Set<org.com.Models.UsuariosLinea> UsuariosLineas = new HashSet<org.com.Models.UsuariosLinea>();UsersByLine.java
@Id @GeneratedValue(strategy=GenerationType.IDENTITY) @Column(name="id",nullable=false,updatable=false,length=10,insertable=true) private Integer Id; @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "iduser",nullable=false,insertable=true,updatable=true) private org.com.Models.Usuarios Usuario; @ManyToOne(fetch = FetchType.EAGER) @JoinColumn(name = "idlinea",nullable=false,insertable=true,updatable=true) private org.com.Models.Lineas Linea; public Integer getId(){return Id;} public void setId(Integer Id){this.Id = Id;} public Lineas getLinea(){return Linea;} public void setLinea(Lineas Linea){this.Linea = Linea;} public Usuarios getUsuario(){return Usuario;} public void setUsuario(Usuarios Usuario){this.Usuario = Usuario;}any help is huge appreciate.
All these cascade operations works with only Bi-directional associations, right? or It can support unidirectional associations? What about inverse then…I think that should work with Bidirectional.
Thank you
Hi
your article is too good . very easy to undersatnd and get the basics right.
i have a requiremnt where my StockDetail extend my stock class and when i say
session.save(StockDetail ); which is my child class
a record should be inserted into parent table(Stock) and then insertion should happen in my child table(StockDetail)
Thanks indeed!It was simple and great!
It helped me a lot!
See ya in the future!
Thanks, it’s very easy to understand the cascade from your article!
Thanks for your excellent work. I am confused with your delete-orphan demo:
if Stock side is not ownership (inverse=”false”), remove StockDailyRecord from its list will only lead to set StockDailyRecord.STOCK_ID to be null but won’t remove StockDailyRecord from DB.
What’s more:
1) I am using Hibernate 3.2.6
2) if I set many-to-one(insert=”false” update=”false”) in StockDailyRecord side. delete-orphan works properly.
I liked your article on fetch strategies but this one, imo, could be improved for explaining delete-orphan. I found the following better: http://docs.jboss.org/hibernate/core/3.3/reference/en/html/example-parentchild.html
I’d emphasize that ‘delete-orphan’ handles the case when we want to delete the child object from the parent’s collection and have this reflected in the database without having to do an explicit session.delete() on the child objects. e.g.
1) Without delete-orphan:
stock.getStockDailyRecords().remove(sdr1);
stock.getStockDailyRecords().remove(sdr2);
sdr1.setStock(null);
sdr2.setStock(null);
session.saveOrUpdate(stock);
results in an update to the the StockDailyRecord table to set the Foreign Key to Stock for sdr1 and sdr2 to null (keeps those records in that table)
2) With delete-orphan:
The same code as above results in sdr1 and sdr2 being deleted.
why delete-orphan doesn’t work?
Session session = HibernateUtil.getSession();
Transaction tx = session.beginTransaction();
Book book = (Book)session.get(Book.class, 1);
tx.commit();
session.close();
Session session2 = HibernateUtil.getSession();
Transaction tx2 = session2.beginTransaction();
Publisher publisher = (Publisher)session2.get(Publisher.class, 1);
publisher.getBooks().remove(book);
session.saveOrUpdate(publisher);
tx2.commit();
session2.close();
Not work cause you close session 1 too soon
Excellent Work! best explanation of inverse i could find on the internet.
Your examples arequite simple and easy to understand..thanks and make I wish to have some more examples in spring mvc.
Please visit this collection of Spring MVC tutorials.
You simply doing great job man. With such simple example you making people knowledgeable about complex concpets of hibernate.
SIMPLY GREAT!!!
Thanks man! It’s help so much!
good article buddy. keep it up.. thx.