My problem references to this issue here on github https://github.com/mapstruct/mapstruct/issues/1427
I got at least two versions of mappers with the same name. I want to use springs getBean/Autowired possibilities but this doesn't work out of the mapstructs box yet. :-)
I followed the second workaround mentioned in the upper link: extend Springs bean naming strategy. Did someone ever get this well ment proposal working?
If i follow the code parts from there the bean naming doesn't take place. For me its's clear why not: there aren't any components to scan and especially to find.
If i add a componenModel = "spring" to the mapper annotation i get a ConflictingBeanDefinitionException. Don't know why. Maybe there's a cat in the tail problem?
As stated from Filip here https://github.com/mapstruct/mapstruct/issues/1427 i followed his approach and with a few modifications it worked. I added a solution comment in the link.
The main changes are:
i added componentModel = "spring" to my mappers and used a filter to exclude all of my mapper classes (the interface all of my mappers are implementing: MapperInterface.class) within the Spring Boot application.
To my Spring Boot application class i added:
#ComponentScan(basePackages = { "com.application.spring_boot_class" }, excludeFilters = { #ComponentScan.Filter(value = { MapperInterface.class }, type = FilterType.ASSIGNABLE_TYPE) })
I had this issue before, and I resolved it using the Spring bean definition in a configuration class, a class annotated with #Configuration, with the Mapstruct mapper call like below:
#Bean
public IMyMapper offerWebMapper() {
return Mappers.getMapper(IMyMapper.class);
}
And then you can inject the mapper using #Autowired or getBean.
I encountered this issue when I'm trying to override the RibbonRoutingFilter bean defined in spring zuul. To emphasis, I'm doing an override, not just creating a bean of the same type. So end of the day, I want the "ribbonRoutingFilter" bean from zuul not registered at all.
So I have my own implementation. First thing I tried, I used the #component annotation and autowire the dependencies. Added a breakpoint in the constructor, and it ended up never being called. So I realize my definition must be loaded earlier than zuul's. So I created a configuration class with #Configuration annotation and #Order(Ordered.HIGHEST_PRECEDENCE), and use a #Bean annotation to instantiate my class there. Still, my method is always loaded earlier.
It turned out there's certain order Spring is following when loading configuration classes definitions and that is where overrides happen. Class org.springframework.context.annotation.ConfigurationClassParser has the detailed logic in method doProcessConfigurationClass(). I'll put my simplified summarization or the ordering rule here:
if you application class(where main() method is defined) has any classes defined in it, they are parsed and definition inside them are registered first
then it will registered Beans defined as #component and defined in #Configuration class
then it will add definitions introduced by #Import
then it will add definitions introduced by #ImportResource
then add definitions from #bean methods inside the application class
then from default methods on interfaces( I think it's java 8)
then try to do the same steps above for any parent classes you application class has extended.
This explained why my override was not working. It's because all I have been trying is in step 2. But zuul defined the bean by a #Import which is step 3.
So to solve my problem, I added a #Bean annotated method to my application class there and do the instanciation and the override just happend as expected.
The above summarization might not be accurate, it just give you an idea about what could have failed your override. You'd better debug the ConfigurationClassParser when you are trying your specific use case.
I am trying to understand how beans that we make using #Configuration tends to override the beans that are generated by SpringBoot by default. I have been working on a project where in many cases we create beans for things like ZuulConfigs and the assumption is, whatever we are making shall take precedence over the default generated bean. I have been trying to figure this out but can't. Basically,
Is Spring achieving this via some custom class loader
If not how is this precedence working. Can I give some precedence in similar manner to my beans
Can I generate similar hierarchy in my project,if so how
The help is highly appreciated
Spring AutoConfiguration is used to provide a basic configuration if certain classes are in the classpath or not.
If you want to configure the order in which beans are instantiated by spring you can use
#DependsOn("A")
public class B {
...
}
This would create bean "A", then "B". Hence you can order the configuration depending upon the beans need first to be done. Anyways Spring automatically detects the dependencies by analyzing the bean classes.
for more help check this question
Spring Boot AutoConfiguration Order
Alternative :
There is also "#AutoConfigureOrder" annotation(where you can prioritise the configuration), you can have a look in the code for deeper understanding.
Documentation of AutoConfiguration is here
First of all, class loading and bean creation are two different things. We don't need to create a bean to load a class, however, a class has to be loaded in order to create a bean.
Now, coming back to Spring's example, Spring looks into all the packages configured by #componentScan and creates beans of all the classes annotated with #Bean, #Configuration and/or #Component. Spring's container keeps track of all the beans created and hence, when it encounters user defined bean with same name and class type as default bean, it replaces the original definition with user defined one (e.g. we can create our custom #ObjectMapper to override Spring boot's own instance). You can also use #Primary annotation to make you bean take precedence if another definition with same class exists (documentation here).
Below are the answers for your questions:
Spring uses reflection to load the classes and create instances. Although you can load the classes with your custom class loader (more on that here), you don't need to worry about it for #Configuration.
Yes, you can use #Primary annotation to give your bean a precedence. You can also use #Order(here) to define the creation order for your beans.
With #Primary, #Order and #Qualifier annotation you can define your own hierarchy for bean creation.
Can I give some precedence in similar manner to my beans
Yes.
A) To define a specific order your Configuration classes will be handled (by the way, a Configuration class does not have to be annotated with #Configuration (so-called full definition), but it's enough to be annotated with #Component, #ComponentScan, #Import, #ImportResource or just have a method annotated with #Bean - so-called lite definition), you should
1) add your Configuration Candidates to your SpringApplication's primarySource, for example, in your main method like that
SpringApplication.run(
new Class[]{YourSpringBootApplication.class, Config1.class, Config2.class, ...},
args);
2) and annotate each of your Configuration Candidates with #Order annotation, any other ordering means like Ordered interface, #DependsOn etc will be ignored by ConfigurationClassPostProcessor, the order in the primarySource array will also be ignored.
Then ConfigurationClassPostProcessor will sort your Configuration Candidates and handle them according the #Order annotation value you specified.
B) The precedence can also be achieved by defining your own AutoConfiguration classes. Although both Configuration and AutoConfiguration are handled by the same ConfigurationClassPostProcessor, they are essentially distinctive machineries. To do so
1) define in your classpath /META-INF/spring.factories file and put in the EnableAutoConfiguration section of it your AutoConfiguration classes like that
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
your.package.AutoConfig1,your.package.AutoConfig2
2) and annotate your AutoConfiguration classes with #AutoConfigureOrder, #AutoConfigureAfter, or #AutoConfigureAfter annotations, any other ordering means again will be ignored.
Like #Strelok pointed out, AutoConfiguration classes, your own and provided e.g. by spring-boot-autoconfigure library alike, will be added to the end of the list of Configuration Candidates.
Remember, however, that the order the Configuration Candidates will be handled by ConfigurationClassPostProcessor does not necessarily coincide with the order the beans defined by the Configuration classes will be created. For example, you might define your Configuration class that overrides TomcatServletWebServerFactory to make your own customization of Tomcat web server like
#Configuration
public class EmbeddedTomcatConfig {
#Bean
public TomcatServletWebServerFactory containerFactory() {
...
return customizedTomcatWebServerFactory;
}
but this method will be called right at the moment when your Spring Boot application decides to create a Web server, regardless of how you defined the precedence for your EmbeddedTomcatConfig Configuration class.
Is Spring achieving this via some custom class loader
There is no need to. Although you could, as always with Spring, define your own ClassLoader for BeanFactory, standard ClassLoader is good enough if everything you need for Configuration in your application is available in the classpath. Please notice, that at first phase ConfigurationClassPostProcessor does not load (i.e. does not resolve) the Configuration candidates classes (otherwise, most of the classes in spring-boot-autoconfigure library will fail to load). Instead it analyzes their annotations with bytecode analyzer, ASM by default. For that purpose, it is just enough to get a binary form, a byte array, of a class to feed it to bytecode analyzer.
Just know this: Spring Boot (specifically) auto configuration classes are always configured last. After all user beans have been created. Spring Boot auto configuration classes almost always use the #ConditionalXXXX annotations to make sure that any beans of the same type/name and other conditions that are configured in your application will take precedence over the Spring Boot auto-configured beans.
If you want your #Component to take precedence over other #Component while scanning all the components by spring, use #Order(Ordered.LOWEST_PRECEDENCE) i.e. the max value to load your component over other.
#Primary is used to give your bean a default preference, we can override the default preference using #Qualifier
We use #Configuration classes with lots of #Bean annotated methods that essentially read like this:
#Bean
public TeamContactIndexer teamContactIndexer(GroupService groupService, ContactCrudService contactCrudService, ContactRetrieveService contactRetrieveService) {
return new TeamContactIndexer(groupService, contactCrudService, contactRetrieveService);
}
So this returns a new bean and injects other spring declared things via method arguments into the constructor by name.
The only way I know to reduce verbosity is to annotate the beans with #Component and constructor with #Autowired.
For many this is perfectly acceptable but I prefer to not litter my code with Spring annotations just to facilitate plumbing and keep a clean separation between completely spring free business logic and plumbing code in #Configuration annotated classes. I treat them as a more type safe, less verbose replacement for what we used to do in xml.
However, wouldn't it be nice if I could just go ...
#Bean
public TeamContactIndexer teamContactIndexer;
... and have spring figure out that it needs to autowire the constructor of that class (100% spring free) to produce the bean. This is not currently supported in Spring as far as I can see even though it should be quite easy to do as far as I can see. Am I missing something or is there really no way around me micromanaging constructor calls in my #Configuration classes (other than littering my code with annotations)? The vast majority of my #Bean methods should be easily replaced like this.
UPDATE
#bezmax has provided a workable approach here which is to use a component scan annotation.
#Configuration
#ComponentScan(
basePackages={"com.github.jsonj.tools"},
includeFilters = { #Filter(type = FilterType.ASSIGNABLE_TYPE, value = {JsonParser.class})})
public class JsonParserConfig {
}
I've used the above to provide a bean definition for a bean without annotations in a library that I use. This replaces the #Bean annotated factory method I had earlier. It's still somewhat verbose but at least you can put in a comma separated list of classes. The default for type is wrong for this usecase so you must specify it; likewise the package defintion is required even though it could be deduced from the class on the filter.
IMHO there is room for an obvious improvement in Spring, which is to provide an annotation that simply takes a comma separated list of classes. So, instead of scanning a package, simply list the bean classes you want initialized. There are probably still a few hairy issues with autowiring via the constructor.
This feature is implemented in Spring 4.3 (not yet released).
You can read more about that in the changelog (see 6.1)
Added:
As about registering your unannotated classes automatically, there seems to be a flexible way to achieve this using #ComponentScan annotation. This annotation allows you to specify a set of include filters, which, when matched on classes, are automatically registered as beans. I had not actually tried using more complex rules with this filter, and it seems that you have several options there (check out the documentation on #ComponentScan) but the easiest one would be something like this:
#Configuration
#ComponentScan(
value = "some.package.path",
includeFilters = {
#Filter(type = ASSIGNABLE_TYPE, value = {
MyClass1.class,
MyClass2.class,
MyClass3.class
})
})
public class WebConfig extends WebMvcConfigurerAdapter {
...
I am using Spring AOP with aspectj-autoproxy.
I use the #Around annotation to intercept certain classes and methods.
#Around(value = "#annotation(counter)")
This code should intercept methods annotated with #Counter annotation.
My question is, does this definition forces scan of all classes in the class path?
I am asking because I have a huge project that can suffer several minutes of loading time if all the class path will be scanned.
And if the answer is yes, how can I disable he scanning?
Limit the scan using:
execution(* com.my.package..*.*(..)) && #annotation(counter)
It will only scan the defined Spring beans, thus not the complete class path.. In addition the annotation #Counter should be specified as the Fully-Qualified Class Name and I don't think "counter" is the correct one..