Hibernate filter Entity where oneToMany relation contains an object

问题

I want to use the hibernate filter but I don't know if what I want to do is possible

I have 2 entities :

Message and MessageUser.

A Message has a list of MessageUser.

I want to create a filter so I can do something like :

final Session filteredSession = sessionFactory.openSession();
final Filter filter = filteredSession.enableFilter("userRecipient");
filter.setParameter("userRecipient", myUser);
filter.validate();

final List<Message> userMessages = filteredSession.createQuery("from Message").list();

it returns me only the message where myUser is the recipient ?

is it possible to to and how?

Thanks a lot !

回答1:

If you are comfortable with Criteria you could create criteria like this

Session hbSession= sessionFactory.openSession();
Criteria criteria = hbSession.createCriteria(Message.class);
criteria.createCriteria("msgUserList","userListAlias");// msgUserList is variable name of users list in Message
criteria.add(Restrictions.eq("userListAlias.user",myUser));//user is variable for User type in msgUserList's class.
List<Message> userMessages = criteria.list();

Have a look at this for reference while creating criteria!

If you only want to use filter then I hope you have configured filter on your User List some thing like bellow

By *.hbm.xml

<hibernate-mapping package="com....">
    <class name="Message" table="message_table">
        ....
        <list name="msgUserList" inverse="true" cascade="all">
            <key column="user_id" />
            <one-to-many class="MessageUsers" />
            <filter name="userRecipient" condition="user_id =:userParam" />
        </list>
    </class>
    <filter-def name="userRecipient">
        <filter-param name="userParam" type="User" />//User is class
    </filter-def>
</hibernate-mapping>

Or By annotation

@Entity
@FilterDef(name="userRecipient", 
parameters=@ParamDef(name="userParam", type="PAKAGE.User" ))
@Table(name = "message_table", catalog = "your_db")
public class Message{

...
@OneToMany(fetch = FetchType.LAZY, mappedBy = "stock")
@Filter(name = "userRecipient",condition="user = :userParam")
public List<MessageUser> msgUserList;

after this you will be able get your filter working

Filter filter = session.enableFilter("userRecipient");
filter.setParameter("userParam", myUser);

Update

Purpose of Filter is different than the Criteria, from my understanding you can say that Filter is just like a Criteria that is already applied on your class or collection which has on and off switch. If your hibernate session has certain filter enabled with it's parameters set than that filter is on and all queries relating to the class or collection which has this filter specified will always return filtered result as per the condition. This means you don't have to explicitly define it every time and by using getEnabledFilter("filterName") you can just change that filter's parameters any time.

Example usage of filter can be if you have Movies table and Actor table with many-to-many relationship, like Leonardo Dicaprio can have many movies at the same times A titanic can have many actors, here when you get Actor obviously you would want only those movies which this Actor has performed in, so you can use filter here which is applied on collection of Movies that is mapped in Actor class. This way when you get Actor object say by simple criteria of name and nothing else and access it's Movie collection by . operator on Actor object it will return you only movies which that actor has performed. This also means no matter how you got Actor object from database when you access Movie collection of Actor it will provide you movies that this actor has performed in

Criteria on the other hand you can use when you require result from database with certain conditions which does not need to be replicated rather you don't want it to be replicated later in the hibernate session. Like Actor lets say Leonardo Dicaprio containing collection of Movies that got nominated him in Oscar. This collection will only be populated in Actor object when gone through certain criteria and will not be available on other Actor objects which have not being retrieved by this criteria.

I hope you understood basic concept of filter and criteria, and from my understanding of your problem it will be better if you use criteria!

来源：https://stackoverflow.com/questions/22007703/hibernate-filter-entity-where-onetomany-relation-contains-an-object

标签

java

hibernate

hibernate-filters