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A Java developer (with lots of experience in sophisticated, high-performance environments) very recently commented that "composition is not used much anymore." I was surprised by this comment. Is this true?
On the one hand, other answers on this forum indicate that difference between composition and aggregation can be ambiguous (can the whole exist without the part; does the part exist throughout the life of the containing object?). But perhaps in all of these cases the question stands--how to add behavior to an existing class or class hierarchy.
The context of his comment was a discussion of possible alternatives to inheritance. If this developer is correct, what has replaced composition in working practice? Mix-ins through added interfaces?
Any perspectives are welcome!
If anything, it's probably used now more than ever thanks to dependency injection frameworks like Spring. The model that all of the Java developers I know use is to build classes that relate to one another in functionality more by interface and purpose and to use Spring to inject them according to a particular configuration (ex the ability to replace entire security frameworks just by changing a spring configuration file and adding a few new JAR files).
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Hi I'm setting up a new project and was struggeling with Java Annotations.
Are they related to Logic / API or Model
In Detail:
I have a started a multi maven module for example:
project-parent
project-model
project-persist
project-logic1
I separated model from every other module simple POJOs with JPA.
To use them with different frontends or REST etc.
Now I wanna use annotations from project-logic1 in the model.
Now i'm confused with the seperation.
Should I make an own API module (project-API) for this and similar annotation / interfaces
Should I simply add the annotation in the project-model
Should I add the dependency of project-logic1 into the project-model POM
I think the first one is correctly but I'm not sure.
From what I understand, you shouldn't use your model objects (with the JPA annotations) as DTO in your project.
You should have your model within the logic project, so DB related items are un the same place, and you create and API project with only POJO, not related to your DB, so you can use this API for REST services' answers and keep your implementation hidden.
If you have common code, I would suggest to wrap it into a dedicated module, so I would agree with your "API"-Approach (although the label "API" might be too much here).
Do not cross-reference your modules, dependencies must always go one way. And: Never repeat yourself, so c/p-ing your annotations is fundamentally wrong ;)
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I'm trying to make a small crud application using swing, with Authentication features and GUI.
Can you give me the right organization and naming of my packages ??
There's no hard and fast rule, but the rule of thumb is to start with your company's domain name in reverse:
com.mycompany
Then add on the project:
com.mycompany.project
This ensures you're unlikely to have clashes between your classes and those from the libraries you depend on.
Then personally I try break things down by their functional groups, for example
com.mycompany.project.domain // contains the business domain classes
com.mycompany.project.io // contains the classes that deal with network or file-system
com.mycompany.project.persistence // contains the classes that handle persistence of the business domain classes
com.mycompany.project.ui // contains the user interface related classes
Within those packages, I might have further group but that would be very specific to the project.
The important thing is to be consistent across your project.
Short answer: One package per module/feature, possibly with sub-packages. Put closely related things together in the same package. Avoid circular dependencies between packages.
Long answer: I agree with most of this article
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I tend to think that Groovy is a super-set of Java... But I would like to hear opinions of more seasoned developers.
Is there anything that you can do in Java, but not in Groovy?
Java EE specs are fairly complex and maybe some of them are not accessible via Groovy?
do { ... } while() comes to mind. You can emulate it using closures or whatever.
...
We are currently working on a Java EE 6 coded mostly in Groovy. No problems whatsoever. CDI, transactions, jsf's managed beans, all work flawlessly. Of course we are kinda restricted when it comes to metaprogramming, so we usually use it for tests, mocks and when there are only groovy objects talking.
You can do everything with Groovy you can do with Java. The only complication is when you want the two to interact.
You can also use all the popular frameworks like Spring. In fact, Spring even lets you configure your beans with a Groovy bean definition DSL.
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My question is fairly simple, I haven't found a direct answer to it.
Is redundant code between two or more packages to achieve package independence considered as a good or bad practice, for instance I have two packages one does a download-and-cache , the other is for readfromserver-and-cache. while cached data and mechanism are completely different but have some common classes/methods.
Shall I create a third package which holds commons, and break package in-dependency?
Or shall I continue with two packages and will result in redundant code?
Lastly, to go deep in design and dependency, I'd appreciate it if you suggest me good material to read.
*Please note : I write in java , common code is not that much
I think that you go for creating an interface for the Cache. If the cache is not the same for both packages then common code can be in a abstract class and the individual packages can implement the rest.
Of course if the code is identical, then strip it out to its own jar.
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I have the first meeting with my project manager and she assigned me a project which to be start soon. She explained to me few points related project e.g. technology, functionality, end user expectation etc.
MVC based web application
Not to use any framework
Server Side : use only Java, servlet, jsp
UI : Javascript, jQuery can also be used
integratation with existing project (at later stage)
There is one point i can not understand why she asked me to not to use any framework although i could not ask why. Does anybody clarify ? If i use any framework like spring then will it create any problem while integration with existing project.
I can recognize 2 sub questions in your question.
In what scenario the framework should not be used?
why she asked me to not to use any framework?
Answer 1
I can imagine situation when you don't need any framework. It is if you have to create extremely simple 1-2 screen application without any security, access rules and probably without DB based persistence. This means that IMHO framework-less application is good as a student exercise just to understand how things work.
Answer 2
She is ... not professional enough. I am sorry to say it but this is pretty obvious. To implement MVC without framework you have to perform a lot of dirty work. I believe that the key reason for this strange requirement is "integratation with existing project" that is probably created without any framework, so PM thinks that framework could bother you during this integration.
Moreover, product manager should never dictate R&D how to implement project. Project manager can politely ask to implement certain set of features.
I am sorry if my answer is helpful.