persistence

问题 I've got a class that will undergo certain version changes over the course of time. The data from inside this class is serialized and deserialized as part of the startup of my application. The problem I have is if I update the class by adding more properties, and then start the application, the old data does not get loaded properly. What I'm looking to do is override the deserialization step, I don't mind manually reconstructing the object from xml, as I have a version number stored and can

问题 Let's consider the typical Order and OrderItem example. Assuming that OrderItem is part of the Order Aggregate, it an only be added via Order. So, to add a new OrderItem to an Order, we have to load the entire Aggregate via Repository, add a new item to the Order object and persist the entire Aggregate again. This seems to have a lot of overhead. What if our Order has 10 OrderItems ? This way, just to add a new OrderItem , not only do we have to read 10 OrderItems , but we should also re

问题 I have a class A that has a set of B 's. However, these two objects are linked by fields that are NOT the primary key. For B , I can use <key column> , but how do I specify that the join should be in A . secondary_column ? Not A . table_primary_key_id ? <class table="a"> <id column="table_primary_key_id"> </id> <property column="secondary_column" /> <set table="B" lazy="false" > <key column="B_not_primary" /> <one-to-many class="BClass" /> </set> </class> 回答1: Solved with <set name="someSet"

问题 I have been looking into JPA/Hibernate @Entity inheritance for a while now and can't seem to find anything that addresses what I am trying to achieve. Basically I want to be able to define an @Entity with all of the column and table mappings as required. Then I want to be able to extend the @Entity in a number of different locations with different sets of @Transient methods defined in the body of each "sub-Entity". This is a basic example of what I am trying to achieve but with no success

问题 I am having some issue integrating mongodb with Symfony (version 2.5.0-DEV) using the doctrine mongodb cookbook on http://symfony.com/doc/current/bundles/DoctrineMongoDBBundle/index.html. Everything is okay up to the 'Persisting Objects to MongoDB' stage. When I add the line " $dm->persist($script); ", nothing happens to my remote database and I get the error message: ClassNotFoundException: Attempted to load class "Mongo" from the global namespace in /var/www/Symfony/vendor/doctrine/mongodb

问题 How do I disable lazy loading in Hibernate? I am using persistence annotations, not an hbm xml file. I am fetching a single object by ID and want all properties loaded. The session is closed before I use the object. Thanks! 回答1: You need to annotate the properties that you want non-lazy loaded with FetchType.EAGER @ManyToOne(fetch = FetchType.EAGER) You see, it isn't the object that you are loading that is lazy loaded. Rather, that object's associations are lazy, and you need to tell them not

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 5 years ago . I am trying to see some usage samples of JPA orm.xml. If some one direct me to a link, 回答1: The schema is here, http://java.sun.com/xml/ns/persistence/orm_2_0.xsd There are lots of samples of each mapping type here, http://en.wikibooks.org/wiki/Java_Persistence Lots of examples here, http://wiki.eclipse.org

问题 Using Spring Core 3.0.5, Hibernate 3.6.0. The title of this question is the message of a java.lang.IllegalStateException raised on starting a Tomcat webserver (6.0.29) with an application I am maintaining. applicationContext.xml says: <bean id="emf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean" scope="singleton"> <property name="jpaVendorAdapter"> <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" /> </property> </bean> persistence.xml is

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 6 years ago . So I have a list of defined classes that gets exported on the exit of the program.. and it looks like this: <__main__.Block object at 0x02416B70>, <__main__.Block object at 0x02416FF0>, <__main__.Block object at 0x0241C070>, <__main__.Block object at 0x0241C0D0>, <__main__.Block object at

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 6 years ago . So I have a list of defined classes that gets exported on the exit of the program.. and it looks like this: <__main__.Block object at 0x02416B70>, <__main__.Block object at 0x02416FF0>, <__main__.Block object at 0x0241C070>, <__main__.Block object at 0x0241C0D0>, <__main__.Block object at