I have code which looks like the following:
MyContext context = new MyContext();
context.start();
MyEntity entity = context.getEntity();
I want to inject the MyEntity instance into various classes.
But I don't know how to setup my Spring configuration, where I first create an object, then call a method on it and then finally call another method which returns the entity I want to inject.
EDIT 2 - removed the Strings altogether
The most common type of dependencies injected using Spring don't depend on the user input for their construction. This includes data access objects, services etc.,
You are talking about injecting domain objects whose construction depends on the user input either directly or indirectly.
Spring provides #Configurable annotation to inject such domain objects that are created using new operator. You can search for "#Configurable Domain Driven Design" on the internet to get examples of how this can be implemented. I myself used it in one my applications and wrote a simple post here that might help you get started.
Edit:
To create a bean of type MyEntity as per the specification in your updated question, you would need to
define a bean of type MyContext
Create a MyEntityFactory class that would depend on the MyContext bean.
The factory method would take the MyContext bean as argument, calls context.start() on it and returns an instance of MyEntity.
You would define the MyEntity bean using this factory class.
The MyEntityFactory class would be as follows:
public class MyEntityFactory
{
public static MyEntity getMyEntity(MyContext context)
{
context.start();
return context.getEntity();
}
}
The spring bean configuration will be as follows:
<bean id="myContext" class="FQCN.Of.MyContext" />
<bean id="myEntity" class="FQCN.Of.MyEntityFactory" factory-method="getMyEntity">
<constructor-arg ref="myContext" />
</bean>
Since MyEntity is a singleton bean, the factory method will be called only once, btw.
More on creating beans using factory methods here.
Related
The SPRING doc says the following
Spring Framework 4.3, an #Autowired annotation on such a constructor
is no longer necessary if the target bean only defines one constructor
to begin with. However, if several constructors are available, at
least one must be annotated to teach the container which one to use.
As i understand if there are multiple constructors and we have not annotated any of them then i will get an error . I ran the following code
#Component // this is bean id
public class TennisCoach implements Coach {
private FortuneService fortuneservice;
public TennisCoach(FortuneService thefortuneservice) {
System.out.println(" inside 1 arg constructter");
fortuneservice = thefortuneservice;
}
public TennisCoach() {
System.out.println(" inside 0 arg constructter");
}
I call that using the below code
TennisCoach theCoach = myapp.getBean("tennisCoach", TennisCoach.class);
But i didn't get the error .I got the O/P as
inside 0 arg constructter
Why?
It looks like the text you've quoted from the Spring docs doesn't apply to a case where one of the constructors is a no-args (default) constructor. You can see this very easily if you try and add an bean reference parameter to it.
Spring attempts to determine the candidate constructors using AutowiredAnnotationBeanPostProcessor and in your scenario, will not find any single or autowired constructor, so it will record the no-args one and instantiate it in SimpleInstantiationStrategy.
I have a bean with final field.
public class Foo {
Service service;
final String bar;
public Foo(String bar){};
}
service is not final and has a setter. bar is final and can have many values. I cannot remove the final keyword. I try to create a spring factory that allows to create Foo's instances with injected service and dynamic bar value. factory.create(bar). Foo beans are instanciated at runtime because bar value is not known and unbounded
I have try:
#Configuration, but configuration does not allow parameters not managed by spring or dynamic parameter.
Lookup method needs a no-arg constructor.
Any idea ?
Thanks!
Take a look at ApplicationContext.getBean(String name, Object... args) method. You can pass arguments to bean creation with args parameter.
You can use constructor injection in the Application Context XML as one way to do this:
<bean name="foo" class="com.example.Foo">
<constructor-arg index="0">Bar</constructor-arg>
</bean>
EDIT: Missed that, check out this question: How to use #Autowired in spring
The second answer (not by me)
It looks like you might be able to use #Configurable annotation here.
I would like my other classes to interact with my domain's interfaces rather than implementation, and i would like to avoid hardcoding the implementation in the code, such as this example :
public void addToMyList(String s, int i) {
DomainModel model = new DefaultDomainModelImpl(); // it's hardcoding the implementation here
model.setName(s).setAge(i);
myList.add(model);
}
If i use spring container, with the prototype scope, i can use something like :
// <bean id="myDomainBean" scope="prototype" class="my.package.domain.MyDomainImpl" />
DomainModel myDomainModel = springContext.getBean("myDomainBean");
But i would like to avoid accessing springContext explicitly in my code.
I wonder what's the clean way to do this ?
Im currently thinking of creating a factory implementation for each domain implementation, and autowire the factory to create the beans, but that means different implementations of my domain will have different implementations of the factory also.
Please share your opinions, thank you !
Im currently thinking of creating a factory implementation for each domain implementation, and autowire the factory to create the beans, but that means different implementations of my domain will have different implementations of the factory also.
That is not 100% correct. You can have a factory that take the Interface (class) of the Domain objects that needs to be create. You can inject that factory in you class.
So you will get all the requriements you asked for:
no hard coded new
the domain object code has no dependence to spring
you only have one factory class and one factory method.
example
#Inject
MyStrangeSpringHiddingFactory myStrangeSpringHiddingFactory;
DomainModel myDomainModel = this.myStrangeSpringHiddingFactory.
createInstanceOf(DomainModel.class);
class MyStrangeSpringHiddingFactory implements MyStrangeSpringHiddingFactory {
#Inject
ApplicationContext springContext:
public <T> createInstanceOf(Class<T> clazz) {
return springContext.getBean(clazz);
}
}
This are only my thoughts, because I do not know your use case: Do you really need such in abstraction? Do you really have a domain model where a domain class have several subclasses that need a factory.
Let's say I have a client who has a list of orders and a wishlist. In my model, I have a ClientRepo, OrderRepo, and WishListRepo. In the controller, where should I be instantiating these repositories? Is it a good idea to make them class-level instances?
component ClientController
{
ClientRepo = new ClientRepo();
OrderRepo = new OrderRepo();
WishListRepo = new WishListRepo();
public void function HomePage(any event)
{
var clientId = event.getValue("id");
var client = ClientRepo.getClientById(clientId);
var orders = OrderRepo.getOrdersForClientId(clientId);
// put the variables into the event object for the view to access
}
}
Or would a better design be to instantiate them within the function?
public void function HomePage(any event)
{
var ClientRepo = new ClientRepo();
var orderRepo = new OrderRepo();
var wishListRepo = new WishListRepo();
// rest of the code is the same
}
The assumption here is that other functions in ClientController need access to the same repositories.
Also, what is the lifetime of the controller? Is it once-per-request, once-per-session, or once-per-application?
Disclosure: I'm a contributor to the Model-Glue project so I probably know what I'm talking about :-)
CFML doesn't have true class-level instances like Java. If you want singletons (a single instance shared across many parts of an application) you need to either put it in a shared scope (yuk!) or use a bean container. Fortunately Model-Glue has tight integration with ColdSpring (a popular bean container for CFML), and Model-Glue 3 makes it easier than ever to use ColdSpring beans in your controllers.
First, edit your ColdSpring.xml to include definitions for your singletons:
<bean id="ClientRepo" class="MyApp.model.client.ClientRepo"/>
<bean id="OrderRepo" class="MyApp.model.order.OrderRepo"/>
This is only a simple example of course. ColdSpring is a powerful dependency injection framework based on Java's Spring. Check out the ColdSpring Quickstart for some of the other things you can do with it.
Once the beans are defined in ColdSpring, you could have your controller explicitly ask for them via getModelGlue().getBean() calls. However a better way is to declare your controller's dependency on those beans and let Model-Glue inject them into your controller for you. The dependency can be declared either in ModelGlue.xml or in your controller CFC. Here's how to declare bean dependencies in your controller:
component ClientController beans="ClientRepo,OrderRepo"
{
public void function HomePage(any event)
{
var clientId = event.getValue("id");
var client = beans.ClientRepo.getClientById(clientId);
var orders = beans.OrderRepo.getOrdersForClientId(clientId);
// put the variables into the event object for the view to access
}
}
Any declared beans are injected into the "beans" scope of your controller by the framework so they're ready to use by any listener functions. Note however that bean injection occurs after initialization, so you cannot use them an init() function.
ColdSpring beans are singletons by default, so if the same ColdSpring bean is injected into multiple controllers they will all end up with the same instance of the bean. If you add singleton="false" to the bean definition then each controller will each end up with a different instance; I can't think of why you would want to do that though.
For more information on bean injection in Model-Glue, check out the Bean Injection HOWTO on the Model-Glue Wiki.
Model-Glue 3.1 instantiates all its controllers at framework initialization time as singletons, so each controller is created once-per-application. Future versions may delay the instantiating of controllers until they are first needed, so it's best to not make assumptions on when they are initialized. If you really need to have some code in a controller executed on application initialization time, I suggest you add an onApplicationStart listener to it.
My spring bean have a constructor with an unique mandatory argument, and I managed to initialize it with the xml configuration :
<bean name="interfaceParameters#ota" class="com.company.core.DefaultInterfaceParameters">
<constructor-arg>
<value>OTA</value>
</constructor-arg>
</bean>
Then I use this bean like this and it works well.
#Resource(name = "interfaceParameters#ota")
private InterfaceParameters interfaceParameters;
But I would like to specify the contructor arg value with the annocations, something like
#Resource(name = "interfaceParameters#ota")
#contructorArg("ota") // I know it doesn't exists!
private InterfaceParameters interfaceParameters;
Is this possible ?
Thanks in advance
First, you have to specify the constructor arg in your bean definition, and not in your injection points. Then, you can utilize spring's #Value annotation (spring 3.0)
#Component
public class DefaultInterfaceParameters {
#Inject
public DefaultInterfaceParameters(#Value("${some.property}") String value) {
// assign to a field.
}
}
This is also encouraged as Spring advises constructor injection over field injection.
As far as I see the problem, this might not suit you, since you appear to define multiple beans of the same class, named differently. For that you cannot use annotations, you have to define these in XML.
However I do not think it is such a good idea to have these different beans. You'd better use only the string values. But I cannot give more information, because I dont know your exact classes.
As Bozho said, instead of constructor arg you could set the property...#PostConstruct will only get called after all the properties are set...so, you will still have your string available ...