Chapter 6. Aspect Oriented Programming with Spring. Aspect-Oriented Programming (AOP) complements Object-Oriented Programming (OOP) by providing another way of thinking about program structure. In addition to classes, AOP gives you aspects. Aspects enable modularization of concerns such as transaction management that cut across multiple types and objects.
(Such concerns are often termed crosscutting concerns.) One of the key components of Spring is the AOP framework. While the Spring IoC container does not depend on AOP, meaning you don't need to use AOP if you don't want to, AOP complements Spring IoC to provide a very capable middleware solution. AOP is used in the Spring Framework: To provide declarative enterprise services, especially as a replacement for EJB declarative services. If you are interested only in generic declarative services or other pre-packaged declarative middleware services such as pooling, you don't need to work directly with Spring AOP, and can skip most of this chapter. Types of advice: 6.1.2. 6.2.1. 6.2.2. 6.2.3. Simple workaround for Hibernate lazy initialization problem | Antanas Veiverys blog.
Update: this workaround is not a solution, just delaying the problem. I’m currently looking for other possibilities, databinder project looks promising. I’ve been struggling with the infamous Lazy loading problem – LazyInitializationException and other related exceptions, such as “Could not initialize proxy – the owning Session was closed”. My current project uses Hibernate> ORM framework for persistence, simple Java in the business model layer and Wicket in the web layer. I chose to postpone learning the Spring framework because the task seemed simple enough to be solved without it, however I consider using it for the future projects. To my understanding, it is not the biggest problem that a Hibernate session is not open at the time when a lazy-loaded object is accessed. However, it is more important to keep in mind: even if there is an open session, any lazy object that was previously loaded in another session can not use it automatically.
Yet another solution WiaSession.java. Java - Best way to handle Hibernate Sessions in a layered Spring MVC Web application. What is n+1 problem and how to solve it. N+1 is one of the most famous question among java developers. It will give some performance issue if you where working on a large project. So it's better to resolve it using some below techniques. What is n+1 problem ? Ans: I am taking one example to let you understand that what n+1 problem is. Suppose you have number of students in a college and every students have some number of books. so one to many relation is between student and books. "select * from Students" "select * from Books where studentId=?
" Here you have 1 select statement for the student and if you have n number of students you have to fire n more query to select the books. Now the next question is how to solve it ? Using join fetching(it will join the parent and children and fetch all the information in a single statement) we can able to solve n+1 problem. "from Students s join fetch s.Books b" Wicket: A slightly better “Open Session in View” | Codepitbull's Blog. We recently participated at the The Plat_forms contest (more on that in a few days). Coding a full application in less than 30 hours is quite the task and there’s no room for wasting time.
Sadly, we wasted time. A lot. On the persistence layer. Wasted may be too hard of a word but we spent too much time building the actual business services needed to populate the view layer. You might wonder why it took so much time. Well, because each use case needs a different service method which provides an entity and all it’s relations initialized as deep as the view layer will use it.
Now you might give me a confused look and ask “Why the hell did you bother building those and didn’t use Open Session in View?” But sometimes you have to rethink opinions you held dear for a long time. Before I continue to dive into Open Session in View (OSiV) a little deeper, let’s take a look why I still prefer the verbose approach.
There’s a lot of things that can go wrong. Enter Open Session in View N+1 Select problem. Building a smart EntityModel. A lot of Wicket applications use an ORM framework to work with the database. Because ORMs provide a generic mechanism for loading entities we can create a generic Wicket model that can simplify binding between ORM and Wicket. In this article I will walk you through creating an EntityModel that will make using Wicket and ORM fun, read inside... In order to load an entity from the database we need two pieces of information: entity’s class and id. Since there is no standard way to get an id from an object we will create an interface that will standardize the process: 1 public interface Identifiable<T extends Serializable>2 {3 T getId();4 } The simplest entity model can then look like this: 1 public abstract class AbstractEntityModel<T extends Identifiable< ?
26: the method used to perform the actual loading of entity from the ORM This model can load any entity given an instance or a class and id, and will detach itself at the end of request. Handling Errors Then in our RequestCycle subclass: Hibernate: Understanding Lazy Fetching. HTML, CSS, and Javascript from the Ground Up - Google Code University - Google Code.