Delete with Cascade

Let’s perform Delete operation with and without cascade to understand it better

Delete with Cascade

Annotation configuration

Applicant.java

@OneToMany(mappedBy="applicant")

@Cascade(CascadeType.DELETE)

    private Set<Address> addresses;

XML configuration

applicant.hbm.xml

<set name="addresses" table="Address" 
                inverse="true" lazy="true" fetch="select" cascade="delete">
            <key>
                <column name="Applicant_Id" not-null="true" />
            </key>
            <one-to-many class="Address" />
        </set>

Example to Delete Applicant and Address objects

	Applicant applicant = session.get(Applicant.class, 1);

	session.delete(applicant);

Output Queries generated

delete 

    from

        Address 

    where
        Address_Id=?


Hibernate: 

    delete 

    from

        Address 

    where
        Address_Id=?


Hibernate: 

    delete 

    from

        Applicant 

    where
        Applicant_Id=?

We can see that delete queries for Address are also executed even though we have deleted only Applicant which means Cascade has happened from Applicant to Address.

Output in DB

Delete without Cascade

If we want to delete both Applicant and its reference Address , we need to delete them individually but first we need to delete Address and then we need to delete Applicant.

Annotation configuration

Applicant.java

@OneToMany(mappedBy="applicant")

    private Set<Address> addresses;

XML configuration

applicant.hbm.xml

<set name="addresses" table="Address" 
                inverse="true" lazy="true" fetch="select">
            <key>
                <column name="Applicant_Id" not-null="true" />
            </key>
            <one-to-many class="Address" />
        </set>

Example to delete Applicant and Address objects

	Applicant applicantDelete = session.get(Applicant.class, 1);

		for (Address address : applicantDelete.getAddresses()) {

			session.delete(address);
		}
		session.delete(applicantDelete);

Output Queries generated

delete 

    from

        Address 

    where
        Address_Id=?


Hibernate: 

    delete 

    from

        Address 

    where
        Address_Id=?


Hibernate: 

    delete 

    from

        Applicant 

    where
        Applicant_Id=? 

We can see that delete queries for Address are executed first as we explictely called delete on Address object using the above code and then deleted Applicant object.

Output in DB

Raj

Founder of javainsimpleway.com
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