CODEWITHSUNDEEP
hibernate
dkr
dkr

Reputation: 5

Hibernate ManyToMany

Context: I have two tables Secret_Agent and Secret_Mission. Both have a @ManyToMany relationship with each other since many secret agents can be given to perform the same secret mission and the same secret agent can be given many secret missions.

Table SECRET_AGENT

Columns SecretAgentId, SecrentAgentName

Table SECRET_MISSION

Columns SecretMissionId, SecrentMissionName

JOIN Table

SECRET_AGENT_MISSION

Columns: SecretAgentId,SecretMissionId

Java Code:

class Secret_Agent {
.
.
.

@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "SECRET_AGENT_MISSION", joinColumns = { @JoinColumn(name = "SecretAgentId") }, inverseJoinColumns = { @JoinColumn(name = "SecretMissionId") }
private List <Secret_Mission> missions;
.
.
.
}

class Secret_Mission {
.
.
.

@ManyToMany(mappedBy = "missions")
private List <Secret_Agent> agents;
.
.
.
}

Problem: I am trying to fetch all secret agents who do not have a secret mission assigned through Hibernate Criteria in the below mentioned code:

Criteria criteria = session.createCriteria(Secret_Agent.class);

criteria.add(Restrictions.isNull("missions"));

However, it doesn't work. I am trying my luck with Projections and QBE meanwhile.

Another way is to use the Crieteria Association, but Association would work only with @OneToMany and @ManyToOne!

Please help me here.

Upvotes: 0

Views: 257

Answers (1)

Luca Basso Ricci
Luca Basso Ricci

Reputation: 18383

I'm assuming your mapping is correct: use Restrictions.isEmpty("missions") - Constrain a collection valued property to be empty (from javadoc)

PS: In Hibernate is best pratice to init collection in mapping as:

@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "SECRET_AGENT_MISSION", joinColumns = { @JoinColumn(name = "SecretAgentId") }, inverseJoinColumns = { @JoinColumn(name = "SecretMissionId") }
private List <Secret_Mission> missions = new ArrayList<Secret_Mission>();

and do the same for Secret_Agent.agents

Upvotes: 1

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