we have decided to use spring for declaratively transcation management in our application.We are using hibernate (Independently not spring template approach) for the persistance layer but want to use spring's power to manage transcation demarcations.
I was going though Spring refrence material to get an idea about the Transcation management,since its using AOP for managing the things.I just get an basic ideas about the pointcuts and its expressions but not a complete or deep understanding of Spring's AOP.
My question is how much one need to know about the AOP in order to use spring's Transcation managment,since what i understood is the only thing matters in the transcations is the pointcut expression.
any help/suggestion will be much appriciated
You don't need to know that much beyond pointcuts. Spring makes it relatively easy for you. A deep understanding is not required. They use Spring AOP, not AspectJ, which is more powerful and complex.
Related
I am learning AOP and came to know that is useful for separation of concern, for example, logging, transaction management, security etc.
So far good to know AOP.
Now, I read about Spring transaction management in Spring framework we can have annotation #Transactional.
It is this point which is make me confused why should we use AOP in which we have to create Aspects rather than using the annotation which Spring provides.
For example:
#Transactional
public void dataAccessTrans() {
}
When Spring is already having transaction related functionality, then why should we use AOP to do transaction management?
If we use AOP, then don't we have to create Aspect and create advice which would act on the method; does't this make us to do manual work, rather than handling it by spring framework itself by its own annotations.
Can anyone help me understand this which I am not able to understand clearly.
Spring relies on AOP to implement declarative transactions.
The Spring Framework’s declarative transaction management is made
possible with Spring aspect-oriented programming (AOP), although, as
the transactional aspects code comes with the Spring Framework
distribution and may be used in a boilerplate fashion, AOP concepts do
not generally have to be understood to make effective use of this
code.
So as you use the #Transactional annotation :
#Transactional
public void dataAccessTrans() {
...
}
you use indirectly AOP.
So in the very most of cases, you never need to declare any custom aspects to handle the transaction management.
I want to understand what is the exact meaning of term "autowiring" and AOP in Spring Framework.
From the official Spring Framework Reference:
The Spring container can autowire relationships between collaborating
beans. You can allow Spring to resolve collaborators (other beans)
automatically for your bean by inspecting the contents of the
ApplicationContext.
Which basically means you can leave it up to the Spring Framework to initialize your beans and ensure they're there when you need them. For example, lets say I have a number of Things in my app. Now, if I want to get all the Things and have them placed in a List<Thing>, in Spring (assuming I've configured it properly), I can simply use this code:
#Autowired
private List<Thing> things;
With no additional effort on my part I have the list I needed.
The question concerning Aspect Oriented Programming (AOP) as it relates to Spring would be quite a bit to put in a post. The simple explanation can be seen in the official Spring Framework Reference:
Aspect-Oriented Programming (AOP) complements Object-Oriented
Programming (OOP) by providing another way of thinking about program
structure. The key unit of modularity in OOP is the class, whereas in
AOP the unit of modularity is the aspect. Aspects enable the
modularization of concerns such as transaction management that cut
across multiple types and objects. (Such concerns are often termed
crosscutting concerns in AOP literature.)
One of the key components of Spring is the AOP framework. While the
Spring IoC container does not depend on AOP, meaning you do not need
to use AOP if you don’t want to, AOP complements Spring IoC to provide
a very capable middleware solution.
That section is very detailed and worth a read if you're interested in AOP.
Autowiring is a mechanism of resolving dependencies in Spring IoC container, as per Spring Reference. So instead of directly specifying the dependency (in XML or in Java configuration), you can depend on container itself to provide you with candidate(s). Spring itself should abort if you find more than one matching dependency (unless you are looking for a collection of beans).
I am learning Spring and am new to it, I want to skip learning the AOP and continue with learning how to work with DAO .Can I have a good understanding of DAO without even knowing the AOP?
Yes, you can. Spring AOP is not required for learning DAO. AOP is a different concept. But according to requirements, you can integrate both of them.
EJB 3.0 comes with the concept of Interceptors, but then again they are applicable to EJBs only. My project requires developing Interceptors for POJO classes. One option for this is to use Spring AOP. I want to know if it's worth the overhead of including the libraries such as commons-logging, spring-aop, cglib that are required for Spring AOP.
Spring is much more than Spring AOP, and you can not use Spring AOP without Spring, and I am talking not only to the Spring libs, but to the Spring programming model too!
So if you think Spring is useful for your application (believe me, it is very useful to many application), then you can use it. - But it is a complete programming model, like EJB, not only a lib or a simple framework.
But I think every modern not trivial application should have a ICO container, so Spring is one of the choices you have.
Sure, it's worth, but be aware it won't be enough if you need to have interceptors for you POJOs : You will also need a "spring agent" to be passed as an argument to your jvm ("Load-Time Weaving"), or you won't be able to intercept your pojos methods, or you will have to use "Compile-Time Weaving".
In short : POJOs have to be created via Spring for them to be "interceptable".
CTW (or LTW) makes compilation (or startup) quite slower.
Is implementing the Abstract Factory pattern for a spring-based project with AOP should be any different than in a normal project?
It should be simpler, all things considered; technically, Spring acts like an Abstract Factory itself, and that pattern deeply informs most things that Spring "wants" you to do with it.
Without a more concrete example, I'd have to say "no". Spring AOP is pretty good at working around your code, whatever structure it's in.
Depends on your AOP. If you're using AspectJ with load time or compile time weaving, then you don't have an issue. If you're using the spring based AOP, then you have an issue because spring will only put aspects onto beans it creates. Meaning that if your factory makes the bean, it won't have any AOP instrumentation