I there any posibility to inject bean member into constructor of another bean member? Something like code below:
class Config {
#Resource("${root-service}")
IServiceRoot root;
#Resource("${child-service}")
IServiceChild child;
}
#Component("root1")
class ServiceRoot1 implements IServiceRoot {
}
#Component("root2")
class ServiceRoot2 implements IServiceRoot {
}
#Component("child1")
class ServiceChild1 implements IServiceChild {
public ServiceChild1(IServiceRoot r) {
root = r;
}
}
#Component("child2")
class ServiceChild2 implements IServiceChild {
public ServiceChild2(IServiceRoot r) {
root = r;
}
}
child-service and root-service props are set to "child1/child2" and "root1/root2" respectively. Now I want to be able to construct child member using root member.
#Resource(${child-service})
#ConstructorArg(member="root")
ServiceChild child;
So after constructing root by spring it will be used to construct child. How can I achieve behaviour like #ConstructorArg?
Related
I have a domain class that i want to inject into the facade of its module, this class have constructor arguments that are specified at runtime. The definition of this class is as shown below:
#Component("area")
#Scope("prototype")
public class GeographicalCircleArea {
private Location center;
private double radius;
private final IShopsProviderAdapter shopsProviderAdapter;
#Autowired
GeographicalCircleArea(double centerLatitude, double centerLongitude, double radiusInKm, IShopsProviderAdapter shopsProviderAdapter) {
this.center = makeCenter(centerLatitude, centerLongitude);
this.radius = radiusInKm;
this.shopsProviderAdapter = shopsProviderAdapter;
}
List<Shop> getShopsWithin() {
return shopsProviderAdapter.findShopsWithin(this);
}
public Location getCenter() {
return center;
}
public double getRadius() {
return radius;
}
private Location makeCenter(double latitude, double longitude) {
return new Location(latitude, longitude);
}
}
The facade where I want to inject the precedent bean is:
#Service
public class GeolocationInformationSystem {
#Autowired
private GeographicalCircleArea area;
public List<Shop> searchForNearbyShops(double centerLatitude, double centerLongitude, double radiusInKm) {
return area.getShopsWithin();
}
}
which gets the arguments to instantiate GeographicalCircleArea at runtime.
How to correctly apply the autowiring?
In the documentation they make it clear :
For each bean, its dependencies are expressed in the form of properties, constructor arguments, or arguments to the static-factory method if you are using that instead of a normal constructor. These dependencies are provided to the bean, when the bean is actually created.
That mean your application crash before running any code in runtime because of :
#Autowired
private GeographicalCircleArea area;
Simple reason you can't inject unknown values because they are unknown during container initialization process and bean creation step,
How to solve that: changing your implementation by changing the constructor
#Autowired
GeographicalCircleArea(IShopsProviderAdapter shopsProviderAdapter) {
this.shopsProviderAdapter = shopsProviderAdapter;
}
and change
List<Shop> getShopsWithin() {
return shopsProviderAdapter.findShopsWithin(this);
}
to take those arguments :
List<Shop> getShopsWithin(double centerLatitude, double centerLongitude,
double radiusInKm) {
this.center = makeCenter(centerLatitude, centerLongitude);
this.radius = radiusInKm;
return shopsProviderAdapter.findShopsWithin(this);
}
I want to implement an annotation which registers classes (not instances of classes) with a factory as soon as the application is started. I am using Spring Framework 4.2.7.
Consider a system with a dashboard and multiple widgets. The dashboard has a configuration file which contains a list of widgets to display for the current user. When displayed it reads the configuration and creates the widgets. The widgets will receive additional parameters from the configuration.
Here is a bit of code illustrating this:
public class TestDashboard implements Dashboard {
public void dashboardPreDisplay() {
List<String> widgets = getWidgetList(/* current user in session */);
for (String widgetId : widgets) {
// create instance of DashboardWidget with given ID
DashboardWidget x = widgetFactory.createWidget(widgetId);
}
}
public List<String> getWidgetList(String user) {
// load list of IDs of DashboardWidgets to be displayed for the user
}
#Autowired
private WidgetFactory widgetFactory;
}
#Service
public class WidgetFactory {
public DashboardWidget createWidget(String widgetId) {
// look up Class<> of DashboardWidget with given id in widgetClasses
// construct and initialize DashboardWidget
}
private HashMap<String, Class<?>> widgetClasses;
}
When implementing my widgets I don't want to deal with registering the widget with the factory class. Ideally I would just annotate the widget like that:
#DashboardWidget(id = "uniqueId")
public class DashboardWidgetA implements DashboardWidget {
// ...
}
When the application starts it should scan the classpath for #DashboardWidget annotations and register the classes with the factory, so that the widgets can be constructed by giving the createWidget-method the id of the widget.
At the moment I am a little bit confused. I think Spring has every tool on board to achieve this behavior. But I cannot think of a way how to do it.
Do you have some advice for me?
Nothing prevents you to create your custom annotation:
#Retention(RetentionPolicy.RUNTIME)
#Target(ElementType.TYPE)
public #interface DashboardWidget {}
Then you can annotate your Widget's classes and make them spring beans. You have to keep in mind if you want to have them as singletons (scope=singleton) , or separate instances per user (scope=prototype).
You have to implement:
public class WidgetInitializationListener implements ApplicationListener<ContextRefreshedEvent> {
#Override
public void onApplicationEvent(ContextRefreshedEvent event) {
ApplicationContext context = event.getApplicationContext();
String[] beanDefinitionNames = context.getBeanDefinitionNames();
for (String beanDefinitionName : beanDefinitionNames) {
String originalClassName = getOriginalClassName(beanDefinitionName, event);
if (originalClassName != null) {
Class<?> clazz = Class.forName(originalClassName);
if (hasWidgetAnnotation(clazz)) {
registerSomewhereYourWidget(context, beanDefinitionName, originalClassName);
}
}
}
}
private String getOriginalClassName(String name, ContextRefreshedEvent event) {
try {
ConfigurableListableBeanFactory factory =
(ConfigurableListableBeanFactory)event.getApplicationContext().getAutowireCapableBeanFactory();
BeanDefinition beanDefinition = factory.getBeanDefinition(name);
return beanDefinition.getBeanClassName();
} catch (NoSuchBeanDefinitionException e) {
LOG.debug("Can't get bean definition for : " + name);
return null;
}
}
So mostly here is nothing to do with spring except you just run through your beans to find annotated ones.
I have a number of classes, POJO style, that shares a single functionality, say readCSV method. So I want to use a single parent (or maybe abstract, not sure if it should be) class that these POJOs can extend. Here's a pseudo-code:
(abstract) class CSVUtil {
private String[] fileHeader = null;
protected void setFileHeader(fileHeader) {
this.fileHeader = fileHeader;
}
protected List<WhateverChildClass> readCSV(String fileName) {
// read CSV using Apache Commons CSV
// and return a List of child type
List<WhateverChildClass> list = null;
// some declarations
try {
list = new ArrayList<WhateverChildClass>();
csvParser = new CSVParser(fileReader, csvFormat);
List csvRecords = csvParser.getRecords();
for (...) {
CSVRecord record = (CSVRecord) csvRecords.get(i);
WhateverChildClass childClass = new WhateverChildClass();
// loop through fields of childClass using reflection and assign
for (// all fields of childClass) {
childClass.setWhateverField(record.get(fileHeader[i]));
}
list.add(childClass);
System.out.println(p);
ps.add(p);
}
}
...
return list;
}
}
on one of the child classes, say ChildA
class ChildA extends CSVUtil {
// fields, getters, setters
}
How do I code the CSVUtil such that I can determine in runtime the child class in readCSV defined in the parent class?
Is it possible to make this method static and still be inherited?
As an alternative, is there API in Apache Commons CSV that can generally read a CSV, determine its schema, and wrap it as a generic Object (I don't know if I make sense here), and return a list of whatever that Object is ?
You want that readCSV to be a static method ?
Then, i would say that ChildA class shouldn't inherit from CSVUtil, but implement an Interface ... something like that :
public final class CSVUtil {
private CSVUtil() {
}
public static <T extends ICSV> List<T> readCSV(String filename) {
...
}
class ChildA implements ICSV
Edit:
Perhaps a more concise way to ask this question is: Does Spring provide a way for me to resolve ambiguous candidates at injection time by providing my own listener/factory/decision logic?
In fact, arguably the #Environmental qualifier on the member field below is unnecessary: if an #Inject-ion is ambiguous... let me help? In fact, #ResolveWith(EnvironmentalResolver.class) would be alright too..
When Spring attempts to inject a dependency (using annotations) I understand that I need to #Qualifier an #Inject point if I am to have multiple components that implement that interface.
What I'd like to do is something like this:
class MyFoo implements Foo {
#Inject
#Environmental
private Bar bar;
}
#Environmental(Environment.Production)
class ProductionBar implements Bar {
}
#Environmental({Environment.Dev, Environment.Test})
class DevAndTestBar implements Bar {
}
I would expect that I need to create some kind of ambiguity resolver which would look something (vaguely) like this:
class EnvironmentalBeanAmbiguityResolver {
// set from configuration, read as a system environment variable, etc.
private Environment currentEnvironment;
public boolean canResolve(Object beanDefinition) {
// true if definition has the #Environmental annotation on it
}
public Object resolve(Collection<Object> beans) {
for (Object bean : beans) {
// return bean if bean #Environmental.values[] contains currentEnvironment
}
throw new RuntimeException(...);
}
}
One example of where this would be useful is we have a service that contacts end-users. Right now I just have a hacked together AOP aspect that before the method call to the "MailSender', checks for a "Production" environment flag and if it is not set, it sends the email to us instead of the users email. I'd like to instead of wrapping this in an AOP aspect specific to mail sending, instead be able to differentiate services based on the current environment. Sometime's it is just a matter of "production" or "not production" as I've demonstrated above, but a per-environment definition works too.
I think this can be reused for region too... e.g. #Regional and #Regional(Region.UnitedStates) and so on and so forth.
I'd imagine #Environmental would actually be a #Qualifier that way if you wanted to depend directly on something environmental you could (an #Environmental(Production) bean would likely depend directly on an #Environmental(Production) collaborator - so no ambiguity for lower level items --- same a #Regional(US) item would depend on other #Regional(US) items expiclitly and would bypass my yet-to-be-understood BeanAmbiguityResolver)
Thanks.
I think I solved this!
Consider the following:
public interface Ambiguity {
public boolean isSatisfiedBy(BeanDefinitionHolder holder);
}
#Target({ METHOD, CONSTRUCTOR, FIELD })
#Retention(RUNTIME)
public #interface Ambiguous {
Class<? extends Ambiguity> value();
}
#Target(TYPE)
#Retention(RUNTIME)
public #interface Environmental {
public static enum Environment {
Development, Testing, Production
};
Environment[] value() default {};
}
#Named
public class EnvironmentalAmbiguity implements Ambiguity {
/* This can be set via a property in applicationContext.xml, which Spring
can use place holder, environment variable, etc. */
Environment env = Environment.Development;
#Override
public boolean isSatisfiedBy(BeanDefinitionHolder holder) {
BeanDefinition bd = holder.getBeanDefinition();
RootBeanDefinition rbd = (RootBeanDefinition) bd;
Class<?> bc = rbd.getBeanClass();
Environmental env = bc.getAnnotation(Environmental.class);
return (env == null) ? false : hasCorrectValue(env);
}
private boolean hasCorrectValue(Environmental e) {
for (Environment env : e.value()) {
if (env.equals(this.env)) {
return true;
}
}
return false;
}
}
#Named
public class MySuperDuperBeanFactoryPostProcessor implements
BeanFactoryPostProcessor, AutowireCandidateResolver {
private DefaultListableBeanFactory beanFactory;
private AutowireCandidateResolver defaultResolver;
#Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory arg)
throws BeansException {
if (arg instanceof DefaultListableBeanFactory) {
beanFactory = (DefaultListableBeanFactory) arg;
defaultResolver = beanFactory.getAutowireCandidateResolver();
beanFactory.setAutowireCandidateResolver(this);
return;
}
throw new FatalBeanException(
"BeanFactory was not a DefaultListableBeanFactory");
}
#Override
public Object getSuggestedValue(DependencyDescriptor descriptor) {
return defaultResolver.getSuggestedValue(descriptor);
}
#Override
public boolean isAutowireCandidate(BeanDefinitionHolder holder,
DependencyDescriptor descriptor) {
Ambiguity ambiguity = getAmbiguity(descriptor);
if (ambiguity == null) {
return defaultResolver.isAutowireCandidate(holder, descriptor);
}
return ambiguity.isSatisfiedBy(holder);
}
private Ambiguity getAmbiguity(DependencyDescriptor descriptor) {
Ambiguous ambiguous = getAmbiguousAnnotation(descriptor);
if (ambiguous == null) {
return null;
}
Class<? extends Ambiguity> ambiguityClass = ambiguous.value();
return beanFactory.getBean(ambiguityClass);
}
private Ambiguous getAmbiguousAnnotation(DependencyDescriptor descriptor) {
Field field = descriptor.getField();
if (field == null) {
MethodParameter methodParameter = descriptor.getMethodParameter();
if (methodParameter == null) {
return null;
}
return methodParameter.getParameterAnnotation(Ambiguous.class);
}
return field.getAnnotation(Ambiguous.class);
}
}
Now if I have an interface MyInterface and two classes that implement it MyFooInterface and MyBarInterface like this:
public interface MyInterface {
public String getMessage();
}
#Named
#Environmental({ Environment.Testing, Environment.Production })
public class MyTestProdInterface implements MyInterface {
#Override
public String getMessage() {
return "I don't always test my code, but when I do, I do it in production!";
}
}
#Named
#Environmental(Environment.Development)
public class DevelopmentMyInterface implements MyInterface {
#Override
public String getMessage() {
return "Developers, developers, developers, developers!";
}
}
If I want to #Inject MyInterface I would get the same multiple bean definition error that one would expect. But I can add #Ambiguous(EnvironmentalAmbiguity.class) and then the EnvironmentalAmbiguity will tell which bean definition it is satisfied by.
Another approach would have been to use a List and go through them all seeing if they are satisfied by a given bean definition, this would mean that the dependnecy wouldn't need the #Ambiguous annotation. That might be more "IoC-ish" but I also thought it might perform poorly. I have not tested that.
I'm trying to use CDI events in my backend services, on JBoss AS6 - ideally with maximum code reuse.
I can see from the docs I can cut down on the qualifier annotation classes I have to create by using a qualifier with members e.g.
#Qualifier
#Retention(RUNTIME)
#Target({METHOD, FIELD, PARAMETER, TYPE})
public #interface Type {
TypeEnum value();
}
I can observe this with
public void onTypeAEvent(#Observes #Type(TypeEnum.TYPEA) String eventMsg) {...}
So far, so good. However, to further cut down on the number of classes needed, I want to have one EventFirer class, where the qualifier of the event thrown is dynamic. Not a problem with qualifiers without members:
public class DynamicEventFirer {
#Inject #Any private Event<String> event;
public void fireEvent(AnnotationLiteral<?> eventQualifier){
event.select(eventQualifier).fire("FIRED");
}
}
then called like
dynamicEventFirer.fireEvent(new AnnotationLiteral<Type>() {});
But what about when the qualifier should have members? Looking at the code for AnnotationLiteral, it's certainly setup for members, and the class element comment has the example:
new PayByQualifier() { public PaymentMethod value() { return CHEQUE; } }
This makes sense to me - you're overriding the value() method of the annotation interface. However, when I tried this myself:
dynamicEventFirer.fireEvent(new AnnotationLiteral<Type>() {
public TypeEnum value() {
return TypeEnum.TYPEA;
}
});
I receive the exception
java.lang.RuntimeException: class uk.co.jam.concept.events.MemberQualifierEventManager$1 does not implement the annotation type with members uk.co.jam.concept.events.Type
at javax.enterprise.util.AnnotationLiteral.getMembers(AnnotationLiteral.java:69)
at javax.enterprise.util.AnnotationLiteral.hashCode(AnnotationLiteral.java:281)
at java.util.HashMap.getEntry(HashMap.java:344)
at java.util.HashMap.containsKey(HashMap.java:335)
at java.util.HashSet.contains(HashSet.java:184)
at org.jboss.weld.util.Beans.mergeInQualifiers(Beans.java:939)
at org.jboss.weld.bean.builtin.FacadeInjectionPoint.<init>(FacadeInjectionPoint.java:29)
at org.jboss.weld.event.EventImpl.selectEvent(EventImpl.java:96)
at org.jboss.weld.event.EventImpl.select(EventImpl.java:80)
at uk.co.jam.concept.events.DynamicEventFirer.fireEvent(DynamicEventFirer.java:20)
Can anyone see what I'm doing wrong? MemberQualifierEventManager is an ApplicationScoped bean which calls on DynamicEventFirer to fire the event.
Thanks,
Ben
There's a slightly cleaner way to do it based on your post:
public class TypeQualifier extends AnnotationLiteral<Type> implements Type{
private TypeEnum type;
public TypeQualifier(TypeEnum t) {
this.type = t;
}
public TypeEnum value() {
return type;
}
}
then just fire like this:
dynamicEventFirer.fireEvent(new TypeQualifier(TypeEnum.TYPEA));
You need to declare an abstract TypeQualifier that extends AnnotationLiteral and implements Type
abstract class TypeQualifier extends AnnotationLiteral<Type> implements Type{}
and use it like this
dynamicEventFirer.fireEvent(new TypeQualifier() {
public TypeEnum value() {
return TypeEnum.TYPEA;
}
});
and later if you want to fire an event with TypeEnum.TYPEB
dynamicEventFirer.fireEvent(new TypeQualifier() {
public TypeEnum value() {
return TypeEnum.TYPEB;
}
});