I'm using ProGuard for my spring boot application code. After I upgraded to Spring Boot 2, I cannot start my application anymore.
Spring Boot 2 uses kotlin-reflect to create beans, which uses kotlin.Metadata annotation during reflection. This annotation has unobfuscated values and therefore kotlin-reflect is looking for methods with original names. and following exception is thrown:
kotlin.reflect.jvm.internal.KotlinReflectionInternalError: Could not compute caller for function: public constructor ProjectService(...
ProjectService is obfuscated to F, hence no such constructor.
When I keep class names, I have same problem elsewhere:
kotlin.reflect.jvm.internal.KotlinReflectionInternalError: Could not compute caller for function: public open fun addRole(...
Is there a way to fix the obfuscation of kotlin.Metadata annotation parameters? Annotation itself is not obfuscated and it still refers to original class names which are written as string values. I also tried to obfuscate the Metadata annotation to no avail.
Related
I am migrating an EJB project to Spring boot project. I have successfully replaced other annotations to the spring annotation, but havving problem with SessionContext object.
My legacy code is bellow
#Resource
SessionContext sessionContext;
.....
if (some condition) {
sessionContext.setRollbackOnly();
return false;
}
For this code i am getting the following error
A component required a bean of type 'javax.ejb.SessionContext' that could not be found.
Action:
Consider defining a bean of type 'javax.ejb.SessionContext' in your configuration.
I think you'll have to use a few different functionalities.
setRollbackOnly()
Most often I have seen Session Context used for Rollbacks. In Spring, you can replace this with:
TransactionAspectSupport.currentTransactionStatus().setRollbackOnly();
or annotate class with
#Transactional(rollbackFor = MyException.class)
so you can throw your exception from class to cause rollback.
getBusinessObject()
The second most commonly used feature is method to load a business object so that I can, for example, create a new transaction within a same bean. In this case you can use Self-inject:
#Lazy private final AccountService self;
and annote method with #Transactional. This, of course, solves any other cases where you need to use the power of a proxy object.
Other functionality is provided by other classes in Spring, but I think that these two are the most commonly used in the Java EE world and when migrating, one will look to replace them in Spring.
I have a Spring Boot 2 + Kotlin application opened with IntelliJ 2019.1.
In this application I annotate some Kotlin objects with #Component. Example:
#Component
object MyObject: MyInterface {
// code
}
I have many different implementation of MyInterface (all with Kotlin objects) and I want to inject all of them in a list in another bean. Example:
#Component
class MyComponent #Autowired constructor(private val objects: List<MyInterface>) {
// code
}
The code runs correctly (the beans are inject in the list objects) but IntelliJ shows an error saying:
Could not autowire. No beans of '? extends MyInterface' or 'List<? extends MyInterface>' types found.
If I change 'object' to 'class' at 'MyObject', the error disappears.
My questions are:
Is it a problem with IntelliJ?
Is it not recommended to annotate Kotlin objects with #Component?
For information, as a possible workaround while the ticket created by Николай in this answer is not treated, I'm ignoring the error/warning only where I need with #Suppress("SpringJavaInjectionPointsAutowiringInspection"). Example:
#Suppress("SpringJavaInjectionPointsAutowiringInspection")
#Autowired
private lateinit var kotlinObjectBeans: List<MyInterface>
I hope it can help others that don't want to disable this check elsewhere.
I would recommend not to use kotlin objects with #Component or any other bean annotation.
There are two aspects and heaving a mix of them leads to lots of problems:
It might be several ApplicationContext instances in your application.
Kotlin object is related to a specific ClassLoader
It is a little bit strange to use Kotlin objects as #Component-s, because if your class knows that it will be used inside Spring-container you'll get more flexibility if you delegate to Spring the decision should this class be a singleton or not and all the other lifecycle management.
But practically I don't see any reason why it could be "not recommended" if you know what you are doing, and aware of probably bugs if your object become stateful.
So I think IDEA should support your case, and I've filled up a ticket IDEA-211826
What's the recommended way to run a spring boot test where only the one subject under test is configured in the context.
If I annotate the test with
#RunWith(SpringRunner.class)
#SpringBootTest(properties = "spring.profiles.active=test")
#ContextConfiguration(classes = MyTestBean.class)
Then it seems to work - the test passes, the context starts quickly and seems to only contain the bean that I want. However, this seems like an incorrect use of the #ContextConfiguration(classes = MyTestBean.class) annotation. If I understand correctly the class that I reference is supposed to be a Configuration class, not a regular spring service bean or component for example.
Is that right? Or is this indeed a valid way to achieve this goal? I know there are more complex examples like org.springframework.boot.test.autoconfigure.json.JsonTest which use #TypeExcludeFilters(JsonExcludeFilter.class) to control the context - but this seems overkill for my use case. I just want a context with my one bean.
Clarification
I know that I can just construct the one bean I am testing as a POJO without a spring context test and remove the three annotations above. But in my precise use case I am actually reliant on some of the configuration applied to the context by settings in the application-test.properties file - which is why I've made this a Spring Boot test with a profile set. From my perspective this isn't a plain unit test of a single class in isolation of the spring context configuration - the test is reliant on certain configuration being applied (which is currently provided by the spring boot app properties). I can indeed just test the components as a POJO by creating a new instance outside of a spring context, I'm using constructor injection making the providing of necessary dependencies simple but the test does rely on things like the log level (the test actually makes assertions on certain logs being produced) which requires that the log level is set correctly (which is currently being done via logging.level.com.example=DEBUG in a properties file which sets up the spring context).
For starters, reading the documentation first (e.g., the JavaDoc linked below in this answer) is a recommend best practice since it already answers your question.
If I understand correctly the class that I reference is supposed to be
a Configuration class, not a regular spring service bean or
component for example.
Is that right?
No, that's not completely correct.
Classes provided to #ContextConfiguration are typically #Configuration classes, but that is not required.
Here is an excerpt from the JavaDoc for #ContextConfiguration:
Annotated Classes
The term annotated class can refer to any of the following.
A class annotated with #Configuration
A component (i.e., a class annotated with #Component, #Service, #Repository, etc.)
A JSR-330 compliant class that is annotated with javax.inject annotations
Any other class that contains #Bean-methods
Thus you can pass any "annotated class" to #ContextConfiguration.
Or is this indeed a valid way to achieve this goal?
It is in fact a valid way to achieve that goal; however, it is also a bit unusual to load an ApplicationContext that contains a single user bean.
Regards,
Sam (author of the Spring TestContext Framework)
It is definitely a reasonable and normal thing to only test a single class in a unit test.
There is no problem including just one single bean in your test context. Really, a #Configuration is (typically) just a collection of beans. You could hypothetically create a #Configuration class just with MyTestBean, but that would really be unnecessary, as you can accomplish doing the same thing listing your contextual beans with #ContextConfiguration#classes.
However, I do want to point out that for only testing a single bean in a true unit test, best practice ideally leans towards setting up the bean via the constructor and testing the class that way. This is a key reason why the Spring guys recommend using constructor vs. property injection. See the section entitled Constructor-based or setter-based DI of this article, Oliver Gierke's comment (i.e. head of Spring Data project), and google for more information. This is probably the reason you're getting a weird feeling about setting up the context for the one bean!
You can also use ApplicationContextRunner to create your context using a test configuration of your choice (even with one bean if you like, but as other people have already mentioned for one bean it's more reasonable to use the constructor the classical way without using any spring magic).
What I like this way of testing is the fact that test run very fast since you don't load all the context. This method is best used when the tested bean doesn't have any Autowired dependencies otherwise it's more convenient to use #SpringBootTest.
Below is an example that illustrates the way you can use it to achieve your goal:
class MyTest {
#Test
void test_configuration_should_contains_my_bean() {
new ApplicationContextRunner()
.withUserConfiguration(TestConfiguration.class)
.run(context -> {
assertThat(context.getBean(MyTestBean.class)).isNotNull();
});
}
#Configuraiton
public static class TestConfiguration {
#Bean
public MyTestBean myTestBean(){
new MyTestBean();
}
}
}
I'm experimenting with examples from this official Spring tutorials and there is a dependency on this code:
https://github.com/spring-guides/gs-async-method/tree/master/complete
If you look at the code on AppRunner.java class, I have 2 questions:
When server is starting, if I put a breakpoint in this class's constructor, seems like in the constructor, the GitHubLookupService is provided by spring, using the #Service bean that was configured. BUT, there was no #Autowired annotation on the constructor, so how in the world this constructor get called with the right dependency? It was supposed to be null.
Is it an automatic assumption of Spring Boot?
Does Spring see "private field + constructor argument, and it assumes it should look for an appropriate bean?
Is it Spring Framework or Spring boot?
Am I missing something?
As I remember, it was mendatory to provide default constructor to beans / service etc. How come this class (AppRunner) doesn't have a default constructor?
How does Spring knows that it should run the constructor with the argument?
Is it because it is the only constructor?
Starting with Spring 4.3, if a class, which is configured as a Spring bean, has only one constructor, the #Autowired annotation can be omitted and Spring will use that constructor and inject all necessary dependencies.
Regarding the default constructor: You either need the default constructor, a constructor with the #Autowired annotation when you have multiple constructors, or only one constructor in your class with or without the #Autowired annotation.
Read the #Autowired chapter from the official Spring documentation for more information.
Think of it this way... Suppose you have the following component:
#Component
public class FooService {
public FooService(Bar bar) { /*whatever*/ }
}
When Spring is scanning this class, it wants to know how it should go about constructing an instance. It's using reflection so it can get a list of all of the constructors at runtime.
In this case, it is completely unambiguous how Spring must construct this instance. There's only one constructor so there is no decision to be made, and no ambiguity at all.
If you add #Autowired here, you are not narrowing anything down, and you are not giving Spring any extra information to help make its decision - its decision is already made because there is only one candidate.
And so, as a convenience, the Spring team decided #Autowired should be optional. Since its not helping the Spring framework to make a decision, its presence is just noise.
If your component has multiple constructors then you can use #Autowired on one of them to tell Spring "use this one, not that one".
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.