I m reading a book about spring 5 certifications.
I have read the following sentence The Spring Framework IoC component is the nucleus of the framework. It uses dependency injection to assemble Spring-provided (also called infrastructure components) and development-provided components to rapidly wrap up an application.
I believe that development-provided components are my annotated java classes that will be injected using DI for example a #Controller or a #Repository.
However I m curious about the second part: Infrastructure Components. what are these. where they are being injected ? can I consider the AuthenticationManagerBuilder an Infrastructure Component or are they referencing to another thing?
Thanks
After the completion of this book chapter
I conclude that some provided spring components that bootstraps the spring application are like below:
org.springframework.context.annotation.internalConfigurationAnnotationProcessor
org.springframework.context.annotation.internalAutowiredAnnotationProcessor
org.springframework.context.annotation.internalCommonAnnotationProcessor
and more .
Related
I have a spring-boot project. Some of the classes I am using it in the 'spring' way, meaning that they are annotated by "#Service", "#Repository", "#Autowired". At the same time, I have lots of classes, which are only used in the normal Java way, meaning that there are no any Spring annotations, and they are created in the standard way of constructing an object in a constructor.
For example, one of the non-annotated classes is:
public class GenericTree<T>
{
private GenericTreeNode<T> root;
public GenericTree ()
{
root = null;
}
public GenericTreeNode<T> getRoot ()
{
return this.root;
}
public void setRoot (GenericTreeNode<T> root)
{
this.root = root;
}
...
}
Is it OK or normal to have a mixure of classes with or without Spring annotations? Probably, I could convert all non-annotated classes into annotated classes by using Spring's annotation markers. Does that really benefit or is it necessary?
BTW, my application's main logic and functions are not web-centric, although they are created as a Spring project. The reason I created in Spring is I want to provide a restful service for my interface so that I can easily test in browser in development, and others can use it with Restful service.
Yes it is ok.
Keep in mind that annotations are not Spring exclusive. Annotations were introduced in Java 5 and they are just meta data for your Java code. This meta data can be useful at:
Compile time
Build time
Runtime
You can even create your own custom annotations and annotate your code with them.
Spring framework comes with some annotations and each one of them has its purpose, but that doesn't mean you have to annotate all your classes with Spring annotations when you are using this framework.
When you annotate your classes as Spring Beans, they become part of the Spring Application Context, thus making them available to be injected with the #Autowired annotation (Spring framework is based on the dependency injection design pattern). But Spring annotations have other implications too, I cannot go into the detail of each one of them but for example, you have to consider that the default scope of annotations like #Bean, #Component, #Controller, #Repository, #Service is Singleton. So whenever you annotate a class with one of these annotations and you don't define a scope, what you get is a singleton class shared all over your application. Other scopes are:
singleton
prototype
request
session
application
websocket
Taking in consideration your GenericTree class, does it make sense to annotate an abstract data structure class as a Spring Bean? Probably not.
So yes, when you develop an application based on Spring framework the normal thing is to have a mixture of Spring annotated classes and regular POJO's.
I recommend you to read the Spring framework documentation, learn what dependency injection is and the purpose and implications of the most used Spring annotations.
I have a huge set of really old Portlets code I am being required to "refactor" due to a bug that was found in Prod. The refactor is requiring me to update to a new library, and as a result move from a custom DAO structure using "Query" classes to one that uses Springs JdbcTemplate and annotations to wire everything together.
BUT, there are a LOT of portlets. Is there a way to use Spring with Annotations for DI that does NOT require me to completely re-write the Portlet to use DispatcherPortlet and the #RequestMappings? I just want to mark all the Portlets, and the handful of Servlets as well, with #Component just to have Spring inject the classes I need. Where I am struggling is in how to bootstrap the ApplicationContext without using the Spring-provided dispatcher portlet/servlet to initiate the context. I would like to not have to use the ApplicationContext directly to pull the necessary beans out by hand, if possible. I do have contextConfigLocation and the ContextLoaderListener defined in my web.xml already.
Is there a Java EE 6 / 7 equivalent annotation for Spring's #Configuration?
If the answer is yes then are the equivalents for its surrounding annotations, such as #ComponentScan and #EnableWebMvc?
I did, of course, look for it in Java EE 6 / 7 (I admit I skipped a paragraph here and there), in javadocs (specifically among annotations), in Spring doc, tutorials, blogs, SO and Google.
JEE CDI has also an annotation of creating bean programmatically and exposing them, so it offers bean factories, called producers:
https://dzone.com/articles/cdi-and-the-produces-annotation-for-factory
CDI offers Producer methods (annotated with #Produces) which is the equivalent of #Bean in spring. You can than implement Producers classes that are beans which contain a bunch of producer methods. However, this is by far not as powerful as a spring configuration since as far as I am aware of, there is no possibity to e.g. "import" other configurations (producer classes).
This makes it especially difficult to test CDI applications.
You can either
heavily use mocks to test a single CDI bean to totally avoid injected objects
blow up your test class just to create the instance under test with all dependencies
use testing frameworks like CDI-Unit that creates the beans for you
With 1. Test Driven Development becomes almost impossible and tests have always to be adapted when implementation changes, even if the contract does not change.
With 2. you end up in a lot compiler errors in tests as soon as dependencies between your Beans change
With 3. you need to point your testing framework to the implementation of your beans. Since there exists no Configuration that knows about all beans, the test needs to know about it. Again, if things change your tests will break.
I admit... I don't like CDI ;-P
The javax.servlet.annotation package defines a number of annotations to be used to register Servlet, Filter, and Listener classes as well as do some other configuration, for example, security.
You can also use the ServletContainerInitializer class to configure your ServletContext through Java instead of through the XML deployment descriptor. Spring provides its own implementation of ServletContainerInitializer in which case all you have to do is create a class that implements WebApplicationInitializer and does servlet, filter, and listener registration and leave that class on the classpath.
Examples abound in the javadoc.
I have two maven projects say MvnSpring and MvnGuice.MvnSpring is working on spring and hibernate frame works.
And MvnGuice is working on google guice and mybatis. I need to combine both the features together.
Both are following singleton pattern. I need to get some class of MvnSpring in MvnGuice while coding. So that I created a jar of MvnSpring and put it in .m2 repository and give the dependacy details in MvnGuice. Now I can import classes of MvnSpring in MvnGuice classes.MvnSpring uses spring dependency injection and MvnGuice uses guice dependency injection for object creation. Now in MvnSpring flow is MSserviceImpl(implements MSservice) > MSdaoImpl(implements MSdao). Now I need to call MSService class from MvnGuice. Then at run time it shows error like MSService class is null. Then I made a guice dependency injection for MSService class in MvnGuice. Now the control reaches MSserviceImpl but now MSdao is null at here. Is it possible to start MvnSpring along with MvnGuice. I hope then I can solve the issue.
While Spring and Guice are targeted at the same problem, IoC, they take very different approaches to solve it. They differ both in functionality and in how they are configured, where Spring has bean definitions and Guice uses bindings.
Fortunately they do have common grounds in that they both support JSR-330, a standards specification that defines a set of annotations. This enables you to write your singletons and describe the injections that they need without depending on either Spring or Guice.
This way you can share your singletons between projects irregardless of the framework you use in a particular project. I would not recommend using both Guice and Spring in the same project, except if there's a clearly defined separation between them. For instance you might use Guice for a module that is used by Spring code via a defined API that hides the fact that it internally is based on Guice.
There was already mentioned JSR-330.
For some cases it can be not enough, e.g., you have code:
final String className = config.getProperty(«serviceImpl»);
// Class.forName(name) and check required interface for type safety
final Class<? extends Service> serviceClass = Reflection.classForName(className, Service.class);
final Service service = injector.getInstance(serviceClass);
In different DI environments you are supposed to support both com.guice.inject.Injector.getInstance() and org.springframework.context.ApplicationContext.getBean() implementations.
There is the draft solution sdif4j Simple Dependency Injection Facade.
The idea of this project is to encapsulate different DI frameworks logic with own abstraction to extend default JSR-330 possibilities. Note, there is no public releases yet, but you can find ideas how to solve your problem or make an internal release in a fork.
The general issue, is that your both MvnSpring and MvnGuice projects are supposed to be based on JSR-330 (instead of guice/spring annotations) and org.sdif4j:sdif4j-api (or your own abstraction; only if Injector functionality is required). It is recommended to make guice and spring dependencies optional (to compile but not export) to allow the library clients to choose the DI themselves.
In your MvnCompineGuiceAndSpring you just declare sdif4j-guice or sdif4j-spring dependency (it is similar to slf4j usage) and configure your DI environment. You can find different examples in testing subproject.
Some more notes:
Spring default scope is singleton, Guice - prototype (Spring terminology). So, if you want a prototype bean, you can use:
#org.springframework.context.annotation.Scope("prototype")
#javax.inject.Named
public class TestPrototype {
}
The Spring #Scope annotation should be ignored by guice even if spring does not present in your classpath.
Also you have to declare all your Singleton beans with #javax.inject.Named and #javax.inject.Singleton annotation to support both Spring and Guice, like this:
#javax.inject.Named
#javax.inject.Singleton
public class TestSingleton implements ITestSingleton {
public TestSingleton() {
}
}
As with #Scope annotation, you can use #ImplementedBy(#ProvidedBy) guice annotations on your code (when feasible; be careful with it, in general it is not a good practice), that should be also ignored in Spring DI (in both cases if Spring exists in classpath or not).
Hope, that's clear.
All the examples I've seen so far integrating spring/mvc with JSF uses DAO class, DAOImp, Service, ServiceImp and then JSF ManagedBean and as far as I know with EJB 3.1 all I need is EJB and JSF ManagedBean. I am not mentioning entities. So based on my understanding with Spring + JSF I need:
5 classes and with EJB + JSF I need only two classes. Please correct me if am wrong but if am right then what's the advantage of using spring with JSF.
Thanks.
You are wrong. -- You can skipp the DAO, DAOImpl and ServiceImpl if you want to implment all in the Service Class.
But even in EJB it is best practice to seperate the Service and the DAOs.
The usage of Interfaces is a kind of style. If you use interfaces, at least you can skip them to and create your services (and Dao) like EJB 3.1 interface free Beans (I don't know the correct name at the moment). At least there are the same pro and cons to use interfaces in Spring and EJB 3.1.
Summary: You can build Spring JSF2 Apps with 2 classes to, but it is best practice to seperate at least JSP (view), Service (EJB's) and DAOs.
comment by Spring or JSF: Ralph please give me an example, suppose I've an entity: Person with id, firstName and lastName what would be the code I need from spring aspect?
In traditonal Spring architecure you have the:
Person (Entity) Class -- the one with the #Entity
PersonDao - Interface that provides data base Load, Strore, Delete and Find Methods for the Person
PersonDaoImpl - implementation of the PersonDao Interface - (#Repository)
PersonService - Interface that provides business functionality arround the person, for example a create method that send an email after a person is created
PersonServiceImpl - Implementation of the PersonService Interface - it uses for example the PersonDao and other Sevices to provides its functionality (#Service)
PersonJSF-Managed Bean - handles the JSF stuff but has no business functionality, it uses the PersonService (or an other Service) to start business functionality
This is one of the most common architecural style (not only in Spring). But even for this there are some variants:
how DAO's can be invoked? All Dao Functions must be invoked via the according Service -- or direct
DAOs with or whithout Interfaces? (may you need the Interfaces for your Test Mock Framework?) -- (have a look at Hades, there is only the Interface, but in most cases no Impl)
Services with or whithout Interfaces? (
...
BTW: one other very intresting architural style, is the one hat Spring ROO uses: It has only the View (PersonController) and the Model (Person), and all DAO and Service Functionality is put in the Model class. -- That is a bit of real OO Design.