I used to use hibernate native bootstrapping approaches, where I would like to add some customized things such as triggers, customized indexes etc.
Specifically, something like this:
Configuration configuration = new CustomConfiguration().configure()
.addAnnotatedClass(XXXXX.class)
...;
configuration.addAuxiliaryDatabaseObject(...); // add some customzied triggers and index here
// use this configure to create a hibernate native SessionFactory
Now our team is migrating to JPA standard APIs, so I'm wondering how should I do this with standard JPA's EntityManagerFactory?
The AuxiliaryDatabaseObject I used is a very hibernate-specific thing....so I guess the only way I do this is to get some hibernate delegate from EntityManagerFactory and do a hybrid bootstrapping....
Create a custom org.hibernate.boot.spi.MetadataContributor and register that as service through the Java service loader mechanism by adding a file META-INF/services/org.hibernate.boot.spi.MetadataContributor with the fully qualified name of your class as content.
This service will be picked up during boot automatically. In that class, you can add your auxiliary objects.
I'm using Spring Cacheable annotation and at the moment I'm struggling with a way of adding the cache name from property file.
I tried:
#Cacheable("${some.cache.name}")
and
#Cacheable("#{'${some.cache.name}'}")
There is a SPI to do that that is much more powerful than just using SpEL. You can implement CacheResolver and resolve cache instance(s) at runtime. You could use the annotated type or any name that is provided via the annotation.
You can specify the CacheResolver per annotation, at class-level using #CacheConfig or globally by implementing CacheConfigurer.
Check the documentation for more details
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
I am planning to take my some of my values from db like.
The value will be stored like key value pair in DB(same like properties file).
Could you please let me whether spring has any support for storing key value pair in db like spring property holder?
You can implement your own by extending org.springframework.context.support.AbstractMessageSource and injecting your DAO or using your Hibernate domain class(es) to resolve the messages and then registering it as your messageSource bean in your application context.
I'm trying to set an attribute in an annotation, using Spring #Value, but I get Type mismatch: cannot convert from Value to String. Here is what I tried:
#Table(name = "myTable", catalog = #Value("${database.myCatalog}") )
Is it possible? And if yes, how to do it?
I think you are a little bit confused with how Spring uses that annotation.
As far as I know, the only way that annotation can only be set at field or method/constructor parameters.
Also, for Spring to resolve it, the POJO must be a Spring managed bean. That means that it must be defined in the Spring (Web)ApplicationContext implementation to be resolved.
Your question seems like you are annotating a JPA Entity which is not a Spring bean but a Class to be used by the JPA implementation that you are using (e.g. Hibernate).