You need to fetch it while inside a transaction (thus, inside the service method), and not while outside a transaction (thus, inside e.g. JSF managed bean init/action method), that would thus throw a LazyInitializationException. So, your attempt hardware.getConnectivities().size(); has to take place inside a transaction. Create if necessary a new service method for the purpose … Read more
For singletons there is an elegant solution by delegating the task to the JVM code for static initialization. public class Something { private Something() { } private static class LazyHolder { public static final Something INSTANCE = new Something(); } public static Something getInstance() { return LazyHolder.INSTANCE; } } see http://en.wikipedia.org/wiki/Initialization_on_demand_holder_idiom and this blog post … Read more
For some reason, a lazy property needs an explicit type annotation if its initial value refers to self. This is mentioned on the swift-evolution mailing list, however I cannot explain why that is necessary. With lazy var first: FirstClass = FirstClass(second: self) // ^^^^^^^^^^^^ your code compiles and runs as expected. Here is another example … Read more
As correctly pointed out by vadian you should create an init in such scenarios: class MyOwn { let myUser: User var life: Int init() { self.myUser = User(name: “John”, age: 100) self.life = myUser.age } } You can’t provide a default value for a stored property that depends on another instance property.
Within your actual lambda, you can simply update the fooField with a new lambda, such as: class A<T>{ private Supplier<T> fooField = () -> { T val = expensiveInit(); fooField = () -> val; return val; }; public T getFoo(){ return fooField.get(); } } Again this solution is not thread-safe as is the .Net Lazy<T>, … Read more
Basically, you’re asking for synchronized creation of a singleton, without using any synchronization (previously-constructed variables). In general, no, this is not possible. You need something available for synchronization. As for your other question, yes, static variables which can be statically initialized (i.e. no runtime code necessary) are guaranteed to be initialized before other code is … Read more
You should provide exactly the model the view expects. If the JPA entity happens to match exactly the needed model, then just use it right away. If the JPA entity happens to have too few or too much properties, then use a DTO (subclass) and/or a constructor expression with a more specific JPQL query, if … Read more
Hibernate 4.1.6 finally solves this issue: https://hibernate.atlassian.net/browse/HHH-7457 You need to set the hibernate-property hibernate.enable_lazy_load_no_trans=true Here’s how to do it in Spring: <bean id=”entityManagerFactory” class=”org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean”> <property name=”dataSource” ref=”myDataSource”/> <property name=”packagesToScan” value=”com.mycompany.somepackage”/> <property name=”jpaVendorAdapter” ref=”hibernateVendorAdapter”/> <property name=”jpaDialect” ref=”jpaDialect”/> <property name=”jpaProperties”> <props> <prop key=”hibernate.enable_lazy_load_no_trans”>true</prop> </props> </property> </bean> Voila; Now you don’t have to worry about LazyInitializationException while navigating … Read more
The problem with this approach is that you can have the N+1 effect. Imagine that you have the following entity: public class Person{ @OneToMany // default to lazy private List<Order> orderList; } If you have a report that returns 10K of persons, and if in this report you execute the code person.getOrderList() the JPA/Hibernate will … Read more