I was using #Conditional annotation and had to provide implementation of matches() of Condition interface. Since the Condition is a FunctionalInterface, how can I use Java 8 lambda to provide implementation in annotation rather than providing implementation.
#Conditional(value = MyCondition.class)
class MyCondition implements Condition {
#Override
public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
return ifMatches;
}
}
You can't.
Lambdas are instances of classes and #Conditional needs the class itself.
The lambda
Function<String, String> capitalize = text -> text.substring(0, 1).toUpperCase() + text.substring(1).toLowerCase();
Is functionally identical to
Function<String, String> capitalize = new Function<String, String>() {
public String apply(String text) {
return Function<String, String> capitalize = text -> text.substring(0, 1).toUpperCase() + text.substring(1).toLowerCase();
}
};
Both are instances of anonymous classes and not the anonymous class itself. There is no way to actually access anonymous classes (outside of reflection, but you can't use reflection in annotations).
Passing a a lambda where a class is expected would be like passing a String where a class is expected. I.e. something like this:
public #interface MyAnnotation {
Class<?> value();
}
#MyAnnotation("this is a string")
public class MyClass {
}
which you wouldn't expect to work.
Related
I have a use case where it would be extraordinarily nice to dynamically instantiate beans (using some kind of factory approach) based on annotation-arguments at the injection point. Specifically, I need to be able to specify a type-argument to the bean-creating factory.
A pretty relevant example would be a JSON deserializer that needs the type which it needs to deserialize to.
I envision either:
#Inject
#DeserializeQualifier(Car.class)
private Deserializer<Car> _carDeserializer;
#Inject
#DeserializeQualifier(Bus.class)
private Deserializer<Bus> _busDeserializer;
.. or simply, if it was possible to sniff the type from the generic type argument:
#Inject
private Deserializer<Car> _carDeserializer;
#Inject
private Deserializer<Bus> _busDeserializer;
The big point here is that I would not know beforehand which types was needed in the project, as this would be a generic tool that many projects would include. So you would annotate your #Configuration class with #EnableDeserializer and could then inject any type deserializer (The factory that makes these deserializers can handle any type, but to be able create one, it would need to know the desired type of the deserialized object - plain generics would not cut it, since Java ain't using reified generics).
So, I'd need to be able to inject into the spring context, or using any other Spring magic tricks, some kind of DeserializerFactory that takes the type argument.
Basically, I need to have Spring invoke the following method based based on either, as in the first example, the qualifier argument (or the entire DeserializeQualifier-instance for that matter), or as in the second example, the generic type argument:
DeserializerFactory {
<T> Deserializer<T> createDeserializer(Class<T> type) { ... }
}
You could create a BeanFactoryPostProcessor to set attributes annotated with a custom annotation. I've set up a small Spring Boot project to play around:
// Custom annotation
#Target(ElementType.FIELD)
#Retention(RetentionPolicy.RUNTIME)
public #interface InjectSomeClassHere {
Class value();
}
// Demo bean
#Component
public class SomeBean {
#InjectSomeClassHere(String.class)
private Class someValue;
public Class getInjectedClass() {
return someValue;
}
}
// The BeanFactoryPostProcessor
#Component
public class SomeBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
#Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
Arrays
.stream(beanFactory.getBeanDefinitionNames())
.filter(beanName -> hasAnnotatedField(beanFactory, beanName))
.forEach(beanName -> {
Object bean = beanFactory.getBean(beanName);
Stream.of(bean.getClass().getDeclaredFields()).forEach(field -> setFieldValue(bean, field));
});
}
private boolean hasAnnotatedField(ConfigurableListableBeanFactory beanFactory, String beanName) {
try {
String className = beanFactory.getBeanDefinition(beanName).getBeanClassName();
if (className == null) {
return false;
}
return Arrays.stream(Class.forName(className).getDeclaredFields())
.anyMatch(field -> field.isAnnotationPresent(InjectSomeClassHere.class));
} catch (ClassNotFoundException e) {
// Error handling here
return false;
}
}
private void setFieldValue(Object filteredBean, Field field) {
try {
// Note: field.isAccessible() is deprecated
if (!field.isAccessible()) {
field.setAccessible(true);
}
// Retrieve the value from the annotation and set the field
// In your case, you could call `createDeserializer(fieldValue);` and set the field using the return value.
// Note that you should change the type of `SomeBean#someValue` accordingly.
Class fieldValue = field.getAnnotation(InjectSomeClassHere.class).value();
field.set(filteredBean, fieldValue);
} catch (IllegalAccessException e) {
// Error handling here
e.printStackTrace();
}
}
}
// A small test to verify the outcome of the BeanFactoryPostProcessor
#RunWith(SpringRunner.class)
#SpringBootTest
public class SomeBeanTests {
#Autowired
private SomeBean someBean;
#Test
public void getInjectedClass_shouldHaveStringClassInjected() {
Assert.assertEquals(String.class, someBean.getInjectedClass());
}
}
Please note that this is a very naive implementation and requires further fine tuning. For instance, it scans all attributes in all spring components for the presence of an annotation.
Good luck with your project!
The use case is to implement a dirty field tracker. For this I have an interface:
public interface Dirtyable {
String ID = "dirty";
Set<String> getDirty();
static <T> T wrap(final T delegate) {
return DirtyableInterceptor.wrap(delegate, ReflectionUtils::getPropertyName);
}
static <T> T wrap(final T delegate, final Function<Method, String> resolver) {
return DirtyableInterceptor.wrap(delegate, resolver);
}
}
In the interceptor class the wrapping method is:
static <T> T wrap(final T delegate, final Function<Method, String> resolver) {
requireNonNull(delegate, "Delegate must be non-null");
requireNonNull(resolver, "Resolver must be non-null");
final Try<Class<T>> delegateClassTry = Try.of(() -> getClassForType(delegate.getClass()));
return delegateClassTry.flatMapTry(delegateClass ->
dirtyableFor(delegate, delegateClass, resolver))
.mapTry(Class::newInstance)
.getOrElseThrow(t -> new IllegalStateException(
"Could not wrap dirtyable for " + delegate.getClass(), t));
}
The method dirtyableFor defines a ByteBuddy which forwards to a specific instance at each call. However, instrumenting at every invocation is a bit expensive so it caches the instrumented subclass from the given instance's class. For this I use the resilience4j library (a.k.a. javaslang-circuitbreaker).
private static <T> Try<Class<? extends T>> dirtyableFor(final T delegate,
final Class<T> clazz,
final Function<Method, String> resolver) {
long start = System.currentTimeMillis();
Try<Class<? extends T>> r = Try.of(() -> ofCheckedSupplier(() ->
new ByteBuddy().subclass(clazz)
.defineField(Dirtyable.ID, Set.class, Visibility.PRIVATE)
.method(nameMatches("getDirty"))
.intercept(reference(new HashSet<>()))
.implement(Dirtyable.class)
.method(not(isDeclaredBy(Object.class))
.and(not(isAbstract()))
.and(isPublic()))
.intercept(withDefaultConfiguration()
.withBinders(Pipe.Binder.install(Function.class))
.to(new DirtyableInterceptor(delegate, resolver)))
.make().load(clazz.getClassLoader())
.getLoaded())
.withCache(getCache())
.decorate()
.apply(clazz));
System.out.println("Instrumentation time: " + (System.currentTimeMillis() - start));
return r;
}
private static <T> Cache<Class<? super T>, Class<T>> getCache() {
final CachingProvider provider = Caching.getCachingProvider();
final CacheManager manager = provider.getCacheManager();
final javax.cache.Cache<Class<? super T>, Class<T>> cache =
manager.getCache(Dirtyable.ID);
final Cache<Class<? super T>, Class<T>> dirtyCache = Cache.of(cache);
dirtyCache.getEventStream().map(Object::toString).subscribe(logger::debug);
return dirtyCache;
}
From the logs, the intrumentation time drops from 70-100ms for a cache miss to 0-2ms for a cache hit.
For completeness here is the interceptor method:
#RuntimeType
#SuppressWarnings("unused")
public Object intercept(final #Origin Method method, final #This Dirtyable dirtyable,
final #Pipe Function<Object, Object> pipe) throws Throwable {
if (ReflectionUtils.isSetter(method)) {
final String property = resolver.apply(method);
dirtyable.getDirty().add(property);
logger.debug("Intercepted setter [{}], resolved property " +
"[{}] flagged as dirty.", method, property);
}
return pipe.apply(this.delegate);
}
This solution works well, except that the DirtyableInterceptor is always the same for cache hits, so the delegate instance is also the same.
Is it possible to bind a forwarder to a supplier of an instance so that intercepted methods would forward to it? How could this be done?
You can create a stateless interceptor by making your intercept method static. To access the object's state, define two fields on your subclass which you access using the #FieldValue annotations in your now static interceptor. Instead of using the FixedValue::reference instrumentation, you would also need to use the FieldAccessor implementation to read the value. You also need to define the fields using the defineField builder method.
You can set these fields either by:
Adding setter methods in your Dirtyable interface and intercepting them using the FieldAccessor implementation.
Defining an explicit constructor to which you supply the values. This also allows you to define the fields to be final. To implement the constructor, you first need to invoke a super constructor and then call the FieldAccessor several times to set the fields.
Doing so, you have created a fully stateless class that you can reuse but one that you need to initialze. Byte Buddy already offers a built-in TypeCache for easy reuse.
I am using Spring version 4.3.3 and Jackson version 2.8.3. I am trying to filter out specific fields from an entity bean based on some custom logic that is determined at runtime. The #JsonFilter seems ideal for this type of functionality. The problem is that when I put it at the field or method level, my custom filter never gets invoked. If I put it at the class level, it gets invoked just fine. I don't want to use it at the class level though since then I would need to separately maintain the list of hardcoded field names that I want to apply the logic to. As of Jackson 2.3, the ability to put this annotation at the field level is supposed to exist.
Here is the most basic custom filter without any custom logic yet:
public class MyFilter extends SimpleBeanPropertyFilter {
#Override
protected boolean include(BeanPropertyWriter beanPropertyWriter) {
return true;
}
#Override
protected boolean include(PropertyWriter propertyWriter) {
return true;
}
}
Then I have the Jackson ObjectMapper configuration:
public class MyObjectMapper extends ObjectMapper {
public MyObjectMapper () {
SimpleFilterProvider filterProvider = new SimpleFilterProvider();
filterProvider.addFilter("myFilter", new MyFilter());
setFilterProvider(filterProvider);
}
}
Then finally I have my entity bean:
#Entity
public class Project implements Serializable {
private Long id;
private Long version;
#JsonFilter("myFilter") private String name;
#JsonFilter("myFilter") private String description;
// getters and setters
}
If I move the #JsonFilter annotation to the class level where #Entity is, the filter at least gets invoked, but when it is at the field level like in the example here, it never gets invoked.
I have the same need but after examining the unit tests I discovered that this is not the use-case covered by annotating a field.
Annotating a field invokes a filter on the value of the field not the instance containing the field. For example, imagine you have to classes, A and B, where A contains a field of type B.
class A {
#JsonFilter("myFilter") B foo;
}
Jackson applies "myFilter" to the fields in B not in A. Since your example contains fields of type String, which has no fields, Jackson never invokes your filter.
I have a need to exclude certain fields based on the caller's permissions. For example, an employee's profile may contain his taxpayer id, which is considered sensitive information and should only be serialized if the caller is a member of the Payrole department. Since I'm using Spring Security, I wish to integrate Jackson with the current security context.
public class EmployeeProfile {
private String givenName;
private String surname;
private String emailAddress;
#VisibleWhen("hasRole('PayroleSpecialist')")
private String taxpayerId;
}
The most obvious way to do this is to Jackson's filter mechanism but it has a few limitations:
Jackson does not support nested filters so adding an access filter prohibits using filters for any other purpose.
One cannot add Jackson annotations to existing, third-party classes.
Jackson filters are not designed to be generic. The intent is to write a custom filter for each class you wish to apply filtering. For example, I you need to filter classes A and B, then you have to write an AFilter and a BFilter.
For my use-case, the solution is to use a custom annotation introspector in conjunction with a chaining filter.
public class VisibilityAnnotationIntrospector extends JacksonAnnotationIntrospector {
private static final long serialVersionUID = 1L;
#Override
public Object findFilterId(Annotated a) {
Object result = super.findFilterId(a);
if (null != result) return result;
// By always returning a value, we cause Jackson to query the filter provider.
// A more sophisticated solution will introspect the annotated class and only
// return a value if the class contains annotated properties.
return a instanceof AnnotatedClass ? VisibilityFilterProvider.FILTER_ID : null;
}
}
This is basically a copy SimpleBeanProvider that replaces calls to include with calls to isVisible. I'll probably update this to use a Java 8 BiPredicate to make the solution more general but works for now.
This class also takes another filter as an argument and will delegate to it the final decision on whether to serialize the field if the field is visible.
public class AuthorizationFilter extends SimpleBeanPropertyFilter {
private final PropertyFilter antecedent;
public AuthorizationFilter() {
this(null);
}
public AuthorizationFilter(final PropertyFilter filter) {
this.antecedent = null != filter ? filter : serializeAll();
}
#Deprecated
#Override
public void serializeAsField(Object bean, JsonGenerator jgen, SerializerProvider provider, BeanPropertyWriter writer) throws Exception {
if (isVisible(bean, writer)) {
this.antecedent.serializeAsField(bean, jgen, provider, writer);
} else if (!jgen.canOmitFields()) { // since 2.3
writer.serializeAsOmittedField(bean, jgen, provider);
}
}
#Override
public void serializeAsField(Object pojo, JsonGenerator jgen, SerializerProvider provider, PropertyWriter writer) throws Exception {
if (isVisible(pojo, writer)) {
this.antecedent.serializeAsField(pojo, jgen, provider, writer);
} else if (!jgen.canOmitFields()) { // since 2.3
writer.serializeAsOmittedField(pojo, jgen, provider);
}
}
#Override
public void serializeAsElement(Object elementValue, JsonGenerator jgen, SerializerProvider provider, PropertyWriter writer) throws Exception {
if (isVisible(elementValue, writer)) {
this.antecedent.serializeAsElement(elementValue, jgen, provider, writer);
}
}
private static boolean isVisible(Object pojo, PropertyWriter writer) {
// Code to determine if the field should be serialized.
}
}
I then add a custom filter provider to each instance of ObjectMapper.
#SuppressWarnings("deprecation")
public class VisibilityFilterProvider extends SimpleFilterProvider {
private static final long serialVersionUID = 1L;
static final String FILTER_ID = "dummy-filter-id";
#Override
public BeanPropertyFilter findFilter(Object filterId) {
return super.findFilter(filterId);
}
#Override
public PropertyFilter findPropertyFilter(Object filterId, Object valueToFilter) {
if (FILTER_ID.equals(filterId)) {
// This implies that the class did not have an explict filter annotation.
return new AuthorizationFilter(null);
}
// The class has an explicit filter annotation so delegate to it.
final PropertyFilter antecedent = super.findPropertyFilter(filterId, valueToFilter);
return new VisibilityPropertyFilter(antecedent);
}
}
Finally, I have a Jackson module that automatically registers the custom annotaion introspector so I don't have to add it to each ObjectMapper instance manually.
public class FieldVisibilityModule extends SimpleModule {
private static final long serialVersionUID = 1L;
public FieldVisibilityModule() {
super(PackageVersion.VERSION);
}
#Override
public void setupModule(Module.SetupContext context) {
super.setupModule(context);
// Append after other introspectors (instead of before) since
// explicit annotations should have precedence
context.appendAnnotationIntrospector(new VisibilityAnnotationIntrospector());
}
}
There are more improvements that can be made and I still have more unit tests to write (e.g., handling arrays and collections) but this is the basic strategy I used.
You can try this approach for the same purpose:
#Entity
#Inheritance(
strategy = InheritanceType.SINGLE_TABLE
)
#DiscriminatorColumn(
discriminatorType = DiscriminatorType.STRING,
length = 2
)
#Table(
name = "project"
)
#JsonTypeInfo(
use = Id.CLASS,
include = As.PROPERTY,
property = "#class"
)
#JsonSubTypes({
#Type(
value = BasicProject.class,
name = "basicProject"
),
#Type(
value = AdvanceProject.class,
name = "advanceProject"
)})
public abstract class Project {
private Long id;
private Long version;
}
#Entity
#DiscriminatorValue("AD")
public class AdvanceProject extends Project {
private String name;
private String description;
}
#Entity
#DiscriminatorValue("BS")
public class BasicProject extends Project {
private String name;
}
I don't think you will make it work. I was trying and these are results of my investigation, maybe it will be helpful.
First of all, as #Faron noticed, the #JsonFilterannotation is applied for the class being annotated not a field.
Secondly, I see things this way. Let's imagine, somewhere in Jackson internals you are able to get the actual field. You can figure out if there is the annotation using Java Reflection API. You can even get the filter name. Then you get to the filter and pass the field value there. But it happens at runtime, how will you get the corresponding JsonSerializer of the field type if you decide to serialize the field? It is impossible because of type erasure.
The only alternative I see is to forget about dynamic logic. Then you can do the following things:
1) extend JacksonAnnotationIntrospector (almost the same as implement AnnotationIntrospector but no useless default code) overriding hasIgnoreMarker method. Take a look at this answer
2) criminal starts here. Kinda weird way taking into account your initial goal but still: extend BeanSerializerModifier and filter out fields there. An example can be found here. This way you can define serializer that actually doesn't serialize anything (again, I understand how strange it is but maybe one will find it helpful)
3) similar to the approach above: define useless serializer based on BeanDescription implementing ContextualSerializer's createContextual method. The example of this magic is here
Thanks to this really good blog, I was able to use #JsonView to filter out specific fields from an entity bean based on some custom logic that is determined at runtime.
Since the #JsonFilter does not apply for the fields within a class, I found this to be a cleaner workaround.
Here is the sample code:
#Data
#AllArgsConstructor
public class TestEntity {
private String a;
#JsonView(CustomViews.SecureAccess.class)
private Date b;
#JsonView(CustomViews.SecureAccess.class)
private Integer c;
private List<String> d;
}
public class CustomViews {
public static interface GeneralAccess {}
public static interface SecureAccess {}
public static class GeneralAccessClass implements GeneralAccess {}
public static class SecureAccessClass implements SecureAccess, GeneralAccess {}
public static Class getWriterView(final boolean hasSecureAccess) {
return hasSecureAccess
? SecureAccessClass.class
: GeneralAccessClass.class;
}
}
#Test
public void test() throws JsonProcessingException {
final boolean hasSecureAccess = false; // Custom logic resolved to a boolean value at runtime.
final TestEntity testEntity = new TestEntity("1", new Date(), 2, ImmutableList.of("3", "4", "5"));
final ObjectMapper objectMapper = new ObjectMapper().enable(MapperFeature.DEFAULT_VIEW_INCLUSION);
final String serializedValue = objectMapper
.writerWithView(CustomViews.getWriterView(hasSecureAccess))
.writeValueAsString(testEntity);
Assert.assertTrue(serializedValue.contains("a"));
Assert.assertFalse(serializedValue.contains("b"));
Assert.assertFalse(serializedValue.contains("c"));
Assert.assertTrue(serializedValue.contains("d"));
}
I am fairly new to Neo4J; I am developing a project for learning purposes on which I am facing an issue that I am not managing to solve. My model might be somewhat relational DB influenced, but design issues aside, I believe however that what I am attempting should technically be done.
I have a NodeEntity Foo with an nested object Bar, converted to- and from String via ConversionService. In effect, Bar contains only one single String field, making the mapping trivial.
#NodeEntity
public class Foo {
#GraphId
private Long id;
#Indexed
private Bar bar;
...
}
public class Bar {
private String value;
...
}
When returning from a fairly simple Cypher query defined as follows on my repository:
#RepositoryRestResource(...)
public interface FooRepository
extends PagingAndSortingRepository<Foo, Long> {
...
#Query ("MATCH (foo) RETURN foo.bar")
Iterable<Bar> listBars ();
...
}
Conversion is configured as follows:
#Configuration
#ComponentScan(value = "de.h7r.playground.sd.neo4j",
excludeFilters = #ComponentScan.Filter({ Configuration.class }))
public class PKanbanConfiguration {
#Bean
public ConversionServiceFactoryBean conversionService ()
throws Exception {
final ConversionServiceFactoryBean csfb = new ConversionServiceFactoryBean ();
csfb.setConverters (getConverters ());
return csfb;
}
private Set<Converter> getConverters () {
return Sets.newHashSet (new BarConverter.ToString (), new BarConverter.FromString ());
}
}
Where the code for BarConverter is as follows.
public class BarConverter {
public static class FromString <S extends String, P extends Bar>
implements Converter<S, P> {
#Override
public P convert (final S source) {
// sets value into new instance of Bar and returns
}
}
public static class ToString <P extends Bar, S extends String>
implements Converter<P, S> {
#Override
public S convert (final P source) {
// gets value from Bar and returns
}
}
}
I am getting the following exception.
org.springframework.data.mapping.model.MappingException: Unknown persistent entity test.domain.Bar
at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:178)
...
Bar is indeed not a persitent entity nor should in my understanding be one. I grasp that this might have something to do with the defined return type of listBars; on the other hand, the repository if of Foos, so I had expected it to work. I would very much not like to fetch the whole set of nodes and then filter only the nested objects; the same way I would not like to have Bar replaced by String on Foo, since their type might have semantic relevance.
I am a bit lost as to how to returning all the property values for the existing nodes, specially since this query works as expected from neo4j-shell, so I see this as a pure Spring mapping issue.
I can add any further information that might prove helpful upon request.
Any help is very much appreciated.
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.