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How do I prevent Spring Boot AOP from removing type annotations?

I am pretty new to Spring Boot and its flavor of AOP, but not new to programming in other languages and AOP frameworks. This one challenge I am not sure how to solve.
I have a simple metadata decorator:
#Target(ElementType.TYPE)
#Retention(RetentionPolicy.RUNTIME)
public #interface GreetingsMeta {
public float version() default 0;
public String name() default "";
}
It works just fine with dependency injection:
public GreetingController(List<IGreetingService> greetings) throws Exception {
this.greetings = new HashMap<>();
greetings.forEach(m -> {
Class<?> clazz = m.getClass();
if (clazz.isAnnotationPresent(GreetingsMeta.class)) {
GreetingsMeta[] s = clazz.getAnnotationsByType(GreetingsMeta.class);
this.greetings.put(s[0].name(), m);
}
});
}
Until I applied a standard logging aspect:
#Aspect
#Component
public class LoggingAspect {
#Around("execution(* com.firm..*(..)))")
public Object profileAllMethods(ProceedingJoinPoint joinPoint) throws Throwable {
MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
String methodName = methodSignature.getName();
final StopWatch stopWatch = new StopWatch();
stopWatch.start();
Object result = joinPoint.proceed();
stopWatch.stop();
LogManager.getLogger(methodSignature.getDeclaringType())
.info(methodName + " " + (stopWatch.getTotalTimeSeconds() * 1000) + " µs");
return result;
}
}
Then the list of annotationsData becomes empty, even the #Component annotation is gone.
Sample meta-decorated class:
#Component
#GreetingsMeta(name = "Default", version = 1.0f)
public class DefaultGreetingsService implements IGreetingService {
#Override
public String message(String content) {
return "Hello, " + content;
}
}
How should I troubleshoot?

How do I prevent Spring Boot AOP from removing type annotations?
Spring Boot does not remove anything, but for Spring AOP is uses dynamic proxies generated during runtime, i.e. subclasses or interface implementations with event hooks (joinpoints) for aspect advice code wired in via pointcuts. By default, annotations are not inherited, so this is just a JVM feature.
There is one exception for subclasses inheriting annotations from parent classes: You can add the meta annotation #Inherited to your own annotation class GreetingsMeta. The effect will be that if you annotate any class with it, all subclasses (also dynamic proxies created by Spring AOP) will inherit the annotation and your original code should run as expected.
So in this case there is no need to use AnnotationUtils as suggested by JC Carrillo. His approach works too, of course. It is just more complicated because AnnotationUtils uses a lot of reflection magic and lots of helper classes internally in order to compute results. Thus, I would only use AnnotationUtils in cases where you don't directly annotate a class but e.g. methods or interfaces because #Inherited has no effect on them as documented. Or if you rely on a hierarchy of Spring (or own) meta annotations (annotations on annotations) and you need to get information from them all merged into one, AnnotationUtils or MergedAnnotations are appropriate.

You may want to look into AnnotationUtils
Method method = methodSignature.getMethod();
GreetingsMeta greetingsMeta = AnnotationUtils.findAnnotation(method, GreetingsMeta.class);

Method invocation based on custom annotation in Spring?

I have a custom annotation:
#Target(ElementType.METHOD)
#Retention(RetentionPolicy.RUNTIME)
public #interface Controller {
EventType[] events() default EventType.MESSAGE;
}
And there are methods in class B using them like below:
#Controller(events = {EventType.MESSAGE, EventType.DIRECT_MESSAGE})
public void onMessage(Message msg) { }
#Controller(events = {EventType.STAR_ADDED})
public void onStarAdded(Message msg) { }
Now, I want to invoke the above methods based on the annotation events value from another class A. In other words, when class A receives an event of type STAR_ADDED, I want to invoke all methods in class B with annotation #Controller(events = {EventType.STAR_ADDED}).
I know how to do this in Java but does Spring provide any API to do this? If yes, a code snippet would be helpful too.

Solution 1:
You could also do something like this:
enum EventType {
MESSAGE {
#Override
public void handleMessage(Service service, Message message) {
service.onMessage(message);
}
},
STAR_ADDED {
#Override
public void handleMessage(Service service, Message message) {
service.onStarAdded(message);
}
public abstract void handleMessage(Service service, Message message);
}
}
In your other class, where you know what is the "active" event:
yourEvent.handleMessage(service, message);
Solution 2:
I don't know if spring has anything precisely for that, otherwise you could also use reflection. Here's an example using reflection (I much prefer the solution above => enum without reflection):
for(Method method: Service.class.getDeclaredMethods()){
Controller annotation = m.getAnnotation(Controller.class);
for(EventType event: annotation.events()){
if(event.equals(yourActiveEventType)){
method.invoke(service, message);
}
return ...
}
}
Hint (not a solution) 3:
I really don't think the following applies for your scenario, but I thought I'd mention it... Spring AOP lets you trigger some code when an annotated method is called (it's kind of the opposite of your scenario), check this answer, but it may be worth the read for you: aspectj-pointcut-for-all-methods-of-a-class-with-specific-annotation
#Around("execution(#Controller * com.exemple.YourService.*(..))")
public Object aroundServiceMethodAdvice(final ProceedingJoinPoint pjp)
throws Throwable {
// perform actions before
return pjp.proceed();
// perform actions after
}
Solution 4: (added after comments)
Using org.reflections
<dependency>
<groupId>org.reflections</groupId>
<artifactId>reflections</artifactId>
<version>0.9.10</version>
</dependency>
example:
Service service = ...;
Message message = ...;
Set<Method> methods =
ReflectionUtils.getMethods(Service.class, ReflectionUtils.withAnnotation(Controller.class),ReflectionUtils.withParametersAssignableTo(Message.class));
for(Method m: methods){
Controller controller = m.getAnnotation(Controller.class);
for(EventType eventType: controller.value()){
if(EventType.MESSAGE.equals(eventType)){
m.invoke(service, message);
}
}
}
This assumes that you already hold the reference to the Service object (where your methods are).
Since you are using Spring, if your 'Services' are spring managed, you may get the instance from spring's context, you'll have to try it out for yourself, as this is somewhat bound to your design:
#Autowired
private ApplicationContext appContext;
Reflections r = new Reflections(new MethodAnnotationsScanner(), "com.your.package");
Set<Method> methods = r.getMethodsAnnotatedWith(Controller.class);
for(Method m: methods){
Controller controller = m.getAnnotation(Controller.class);
for(EventType eventType: controller.value()){
if(EventType.MESSAGE.equals(eventType)){
String className = m.getDeclaringClass().getSimpleName();
className = className.replaceFirst(className.substring(0,1), className.substring(0,1).toLowerCase());
Object service = appContext.getBean(className);
m.invoke(service, message);
}
}
}
This works if your Class is spring managed and is added to the context using its default camelcase name.
You may simplify the logic, but I believe the principal elements are there.

Java Spring #Valid on a method call [duplicate]

Hej,
I want to use the #Validated(group=Foo.class) annotation to validate an argument before executing a method like following:
public void doFoo(Foo #Validated(groups=Foo.class) foo){}
When i put this method in the Controller of my Spring application, the #Validated is executed and throws an error when the Foo object is not valid. However if I put the same thing in a method in the Service layer of my application, the validation is not executed and the method just runs even when the Foo object isn't valid.
Can't you use the #Validated annotation in the service layer ? Or do I have to do configure something extra to make it work ?
Update:
I have added the following two beans to my service.xml:
<bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean"/>
<bean class="org.springframework.validation.beanvalidation.MethodValidationPostProcessor"/>
and replaced the #Validate with #Null like so:
public void doFoo(Foo #Null(groups=Foo.class) foo){}
I know it is a pretty silly annotation to do but I wanted to check that if I call the method now and passing null it would throw an violation exception which it does. So why does it execute the #Null annotation and not the #Validate annotation ? I know one is from javax.validation and the other is from Spring but I do not think that has anything to do with it ?

In the eyes of a Spring MVC stack, there is no such thing as a service layer. The reason it works for #Controller class handler methods is that Spring uses a special HandlerMethodArgumentResolver called ModelAttributeMethodProcessor which performs validation before resolving the argument to use in your handler method.
The service layer, as we call it, is just a plain bean with no additional behavior added to it from the MVC (DispatcherServlet) stack. As such you cannot expect any validation from Spring. You need to roll your own, probably with AOP.
With MethodValidationPostProcessor, take a look at the javadoc
Applicable methods have JSR-303 constraint annotations on their
parameters and/or on their return value (in the latter case specified
at the method level, typically as inline annotation).
Validation groups can be specified through Spring's Validated
annotation at the type level of the containing target class, applying
to all public service methods of that class. By default, JSR-303 will
validate against its default group only.
The #Validated annotation is only used to specify a validation group, it doesn't itself force any validation. You need to use one of the javax.validation annotations like #Null or #Valid. Remember that you can use as many annotations as you would like on a method parameter.

As a side note on Spring Validation for methods:
Since Spring uses interceptors in its approach, the validation itself is only performed when you're talking to a Bean's method:
When talking to an instance of this bean through the Spring or JSR-303 Validator interfaces, you'll be talking to the default Validator of the underlying ValidatorFactory. This is very convenient in that you don't have to perform yet another call on the factory, assuming that you will almost always use the default Validator anyway.
This is important because if you're trying to implement a validation in such a way for method calls within the class, it won't work. E.g.:
#Autowired
WannaValidate service;
//...
service.callMeOutside(new Form);
#Service
public class WannaValidate {
/* Spring Validation will work fine when executed from outside, as above */
#Validated
public void callMeOutside(#Valid Form form) {
AnotherForm anotherForm = new AnotherForm(form);
callMeInside(anotherForm);
}
/* Spring Validation won't work for AnotherForm if executed from inner method */
#Validated
public void callMeInside(#Valid AnotherForm form) {
// stuff
}
}
Hope someone finds this helpful. Tested with Spring 4.3, so things might be different for other versions.

#pgiecek You don't need to create a new Annotation. You can use:
#Validated
public class MyClass {
#Validated({Group1.class})
public myMethod1(#Valid Foo foo) { ... }
#Validated({Group2.class})
public myMethod2(#Valid Foo foo) { ... }
...
}

Be careful with rubensa's approach.
This only works when you declare #Valid as the only annotation. When you combine it with other annotations like #NotNull everything except the #Valid will be ignored.
The following will not work and the #NotNull will be ignored:
#Validated
public class MyClass {
#Validated(Group1.class)
public void myMethod1(#NotNull #Valid Foo foo) { ... }
#Validated(Group2.class)
public void myMethod2(#NotNull #Valid Foo foo) { ... }
}
In combination with other annotations you need to declare the javax.validation.groups.Default Group as well, like this:
#Validated
public class MyClass {
#Validated({ Default.class, Group1.class })
public void myMethod1(#NotNull #Valid Foo foo) { ... }
#Validated({ Default.class, Group2.class })
public void myMethod2(#NotNull #Valid Foo foo) { ... }
}

As stated above to specify validation groups is possible only through #Validated annotation at class level. However, it is not very convenient since sometimes you have a class containing several methods with the same entity as a parameter but each of which requiring different subset of properties to validate. It was also my case and below you can find several steps to take to solve it.
1) Implement custom annotation that enables to specify validation groups at method level in addition to groups specified through #Validated at class level.
#Target({ElementType.METHOD})
#Retention(RetentionPolicy.RUNTIME)
#Documented
public #interface ValidatedGroups {
Class<?>[] value() default {};
}
2) Extend MethodValidationInterceptor and override determineValidationGroups method as follows.
#Override
protected Class<?>[] determineValidationGroups(MethodInvocation invocation) {
final Class<?>[] classLevelGroups = super.determineValidationGroups(invocation);
final ValidatedGroups validatedGroups = AnnotationUtils.findAnnotation(
invocation.getMethod(), ValidatedGroups.class);
final Class<?>[] methodLevelGroups = validatedGroups != null ? validatedGroups.value() : new Class<?>[0];
if (methodLevelGroups.length == 0) {
return classLevelGroups;
}
final int newLength = classLevelGroups.length + methodLevelGroups.length;
final Class<?>[] mergedGroups = Arrays.copyOf(classLevelGroups, newLength);
System.arraycopy(methodLevelGroups, 0, mergedGroups, classLevelGroups.length, methodLevelGroups.length);
return mergedGroups;
}
3) Implement your own MethodValidationPostProcessor (just copy the Spring one) and in the method afterPropertiesSet use validation interceptor implemented in step 2.
#Override
public void afterPropertiesSet() throws Exception {
Pointcut pointcut = new AnnotationMatchingPointcut(Validated.class, true);
Advice advice = (this.validator != null ? new ValidatedGroupsAwareMethodValidationInterceptor(this.validator) :
new ValidatedGroupsAwareMethodValidationInterceptor());
this.advisor = new DefaultPointcutAdvisor(pointcut, advice);
}
4) Register your validation post processor instead of Spring one.
<bean class="my.package.ValidatedGroupsAwareMethodValidationPostProcessor"/>
That's it. Now you can use it as follows.
#Validated(groups = Group1.class)
public class MyClass {
#ValidatedGroups(Group2.class)
public myMethod1(Foo foo) { ... }
public myMethod2(Foo foo) { ... }
...
}

Validation of one attribute with Hibernate validator

Good evening, I'm trying to use Hibernate Validator, in the following scenario:
public class Car {
#NotNull
private String manufacturer;
#NotNull
#Size(min = 2, max = 14)
private String licensePlate;
#Min(2)
private int seatCount;
//setters and getters....
}
and I am trying to validate its attributes as follows:
public class CarMain {
public static Validator validator;
public static void main(String[] args) {
ValidatorFactory factory = Validation. buildDefaultValidatorFactory() ;
validator = factory. getValidator();
Car car = new Car(null,null,0);
Set<ConstraintViolation<Car>> st= validator.validate(car);
while(st.iterator.hasNext()){
ConstraintViolation<Car> cv = st.iterator.next();
System.out.println("Value: ("+cv.getInvalidValue()+") -->"+cv.getMessage());
System.out.println("Attribute: "+cv.getPropertyPath());
}
}
Here the whole entity is validated and the invalid values with the validation message and property path are displayed.
My question is:"Is it possible to validate only one attribute at a time with Hibernate Validator? Like I don't have to work with the whole object to validate it.

The Validator interface defines also a [Validator.validateProperty][1] method where you explicitly specify the property to validate. Mind you, you still need the object instance and you need to know the property you want to validate. This method is for example used by the integration of Bean Validation into JSF. Whether it makes sense to use it inm your case, will depend on your use case? Why don't you want to validate the whole object?
BTW, there is also Validator.validateValue which does not require an actual bean instance.

How to auto-generate docs for classes annotated spring jmx annotations

I have some code that uses these spring annotations:
org.springframework.jmx.export.annotation.ManagedAttribute;
org.springframework.jmx.export.annotation.ManagedOperation;
org.springframework.jmx.export.annotation.ManagedOperationParameter;
org.springframework.jmx.export.annotation.ManagedOperationParameters;
org.springframework.jmx.export.annotation.ManagedResource;
I want to generate some documentation (even just javadocs) using the comments in the annotations, for example consider the following method?
#ManagedOperation(description="Does foo to bar")
#ManagedOperationParameters({
#ManagedOperationParameter(name = "bar", description = "The bar you want to foo.")})
public long fooBar( Bar bar) throws Exception {
...
}
Is there some way I can automatically generate docs for this, or will I have to duplicate all the annotation strings in javadoc in addition to it?

First, create a custom AnnotationMbeanExporter with a public method that delegates to getRegisteredObjectNames(). Use this as your mbeanExporter.
For example:
#Component
// This is a copy of the AnnotationMBeanExporter with a public version of getRegisteredObjectNames()
public class AnnotationMBeanExporter extends MBeanExporter {
#Autowired
MBeanServer mbeanServer;
AnnotationJmxAttributeSource annotationSource = new AnnotationJmxAttributeSource();
AnnotationMBeanExporter() {
setServer(mbeanServer);
setNamingStrategy(new MetadataNamingStrategy(annotationSource));
setAssembler(new MetadataMBeanInfoAssembler(annotationSource));
setAutodetectMode(MBeanExporter.AUTODETECT_ALL);
}
public ObjectName[] getExportedObjectNames() {
return getRegisteredObjectNames();
}
}
Then for your report, iterate over the object names returned from getExportedObjectNames() and get the relevant metadata for each JMX bean.
For example:
for (ObjectName objectName: mbeanExporter.getExportedObjectNames()) {
MBeanInfo mbeanInfo = mbeanServer.getMBeanInfo(objectName);
MBeanOperationInfo[] operations = mbeanInfo.getOperations();
// etc.
}