Spring Boot How to load only specified #Repository components - spring

Question

I have a project containing many Dao annotated by #Repository each.
Also several spring boot projects, each having its spring context an can be run independently and they have a reference to the project containing the Daos.
The thing is, I don't want to load all Dao into the spring context in each project. Only some specified Dao are required for each spring boot project.
I used to specify Dao classes by defining them as beans in an XML configuration for each project.
Now we are moving to java and annotation based configuration.
Is there a way to tell the spring context only to load the #Repository that I specify?
I know I can make a #Configuration class and define #Bean methods but I still need them to be treated as #Repository and not a normal bean. Any idea if this is supported and how to implement this?

Answer 1

You can use #Conditional on each of those DAO classes.
Class will be loaded in context only when the condition mentioned using #Conditional annotation is fulfilled. You can have condition like:
#ConditionalOnProperty(
value="module.name",
havingValue = "module1",
matchIfMissing = false)
class DaoForModule1 {
This will load the DaoModule1 if and only if the property module.name has value module1. If you want to load this DaoModule1 when proerty is not set, you can change matchIfMissing to true.
You can also use #Profile annotation to limit the classes loaded based on profile
#Profile("module2")
class DaoForModule2 {
This would load DaoForModule2 only when you have module2 in the list of active profiles. But i would not prefer profile as the use case of profiles is different. We use profiles generally to specify variable resources based on environment.

Answer 2

#SpringBootApplication just combine #EnableAutoConfiguration , #SpringBootConfiguration and #ComponentScan.
The #ComponentScan is the guy that cause all #Repository beans under the scanned package to be registered automatically which is the thing that you don't want it to happen.
So you can use these annotations separately but excluding #ComponentScan. And use #Import to explicitly define the beans that you want to register.
The main application class will look like :
#SpringBootConfiguration
#EnableAutoConfiguration
#Import(value = {FooRepoistory.class, BarRepository.class,.......})
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}

Answer 3

From your question, I assume you want to reuse a Spring DAO project with multiple repositories and JPA Entity objects, maybe belonging to different datasources, in several other Spring projects. You prefer to load only a specific set of the JPA entities/repos. The first step is to organize the related entities and repositories into distinct packages and include this project in the path of the other projects.
This is one way to handle this, assuming you have separated the repositories and entities into different packages. Create your own Configuration bean that will instantiate a JPA EntityManagerFactory bean with the specific packages and datasource it needs. in this code below, EntityManagerFactory below will load the entities from MODEL_PACKAGE and the repositories from REPOSITORIES_PACKAGE.
#Configuration
#ComponentScan(basePackages = MODEL_PACKAGE)
#EnableJpaRepositories(basePackages = REPOSITORIES_PACKAGE,
entityManagerFactoryRef = "ENTITY_MANAGER_FACTORY")
#EnableTransactionManagement
public class PersistenceConfig {
public static final String MODEL_PACKAGE = "Your model package";
public static final String REPOSITORIES_PACKAGE = "Your repository package";
public static final String ENTITY_MANAGER_FACTORY = "entity_manager_factory";
public static final String TRANSACTION_MANAGER = "transaction_manager";
#Autowired //This is to get your property file entries (DB connection, etc).
private Environment environment;
#Bean(DATA_SOURCE)
public DataSource dataSource() {
//Create your datasource from environment properties. Example - org.apache.tomcat.jdbc.pool.DataSource
}
#Bean(ENTITY_MANAGER_FACTORY) #Autowired
public LocalContainerEntityManagerFactoryBean entityManagerFactory(
#Qualifier(DATA_SOURCE) DataSource dataSource) throws IllegalStateException {
LocalContainerEntityManagerFactoryBean entityManagerFactoryBean = new LocalContainerEntityManagerFactoryBean();
entityManagerFactoryBean.setDataSource(dataSource);
Properties jpaProperties = new Properties();
// set properties for your JPA, for example, hibernate.dialect, hibernate.format_sql, etc.
entityManagerFactoryBean.setJpaProperties(jpaProperties);
entityManagerFactoryBean.setJpaVendorAdapter(new HibernateJpaVendorAdapter());
entityManagerFactoryBean.setPackagesToScan(MODEL_PACKAGE);
}
#Bean(TRANSACTION_MANAGER) #Autowired
#Primary
#Qualifier(value = "transactionManager")
public JpaTransactionManager transactionManager(
#Qualifier(ENTITY_MANAGER_FACTORY) EntityManagerFactory entityManagerFactory) {
JpaTransactionManager transactionManager = new JpaTransactionManager();
transactionManager.setEntityManagerFactory(entityManagerFactory);
return transactionManager;