How to change the implementing class when using annotations with Spring? - spring

Question

I'm used to Spring with xml configuration. With xml, I can have one main implementation and one test implementation for a class, so that the test implementation will be used for JUnit tests, how can I do this with annotations ? Cause it looks like the implementation is already chosen in the "#qualifier" annotation ?
Let's take an example :
<bean id="myService" class="example.Service" />
<bean id="myHibernateDao" class="example.HibernateDao" />
<bean id="myStubDao" class="example.StubDao" />
In xml config, I can have this in src/main/resources :
<bean id="myService" class="example.Service">
<ref="myHibernateDao" />
</bean>
And this in src/test/resources :
<bean id="myService" class="example.Service">
<ref="myStubDao" />
</bean>
How can I do this with annotations, if I have already declared #Qualifier("myHibernateDao") into my service class ?

Answer 1

As explained in the comment above and in spring blog, you can do this via #Profile annotation.
Please find a sample config from the example below,
DataConfig.java
interface DataConfig {
DataSource dataSource();
}
StandaloneDataConfig .java
#Configuration
#Profile("dev")
public class StandaloneDataConfig implements DataConfig {
#Bean
public DataSource dataSource() {
return new EmbeddedDatabaseBuilder().setType(EmbeddedDatabaseType.HSQL)
.addScript("classpath:com/bank/config/sql/schema.sql")
.addScript("classpath:com/bank/config/sql/test-data.sql")
.build();
}
}
JndiDataConfig.java
#Configuration
#Profile("production")
public class JndiDataConfig implements DataConfig {
#Bean
public DataSource dataSource() {
try {
Context ctx = new InitialContext();
return (DataSource) ctx.lookup("java:comp/env/jdbc/datasource");
} catch (NamingException ex) {
throw new RuntimeException(ex);
}
}
}
TransferServiceConfig.java
#Configuration
public class TransferServiceConfig {
#Autowired
DataConfig dataConfig;
#Bean
public TransferService transferService() {
return new DefaultTransferService(accountRepository(), feePolicy());
}
#Bean
public AccountRepository accountRepository() {
return new JdbcAccountRepository(dataConfig.dataSource());
}
#Bean
public FeePolicy feePolicy() {
return new ZeroFeePolicy();
}
}
Setting bean profile to an application context
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
ctx.getEnvironment().setDefaultProfiles("dev");
ctx.register(TransferServiceConfig.class, StandaloneDataConfig.class,
JndiDataConfig.class);
ctx.refresh();
Since the bean profile has been set to Dev, The TransferServiceConfigwill be injected with StandaloneDataConfig

Answer 2

You can basically do the same thing with #Configuration classes.
Production Setup
Let's assume you have many different DAO implementations that might or might not implement a common interface (it doesn't matter). Let's further assume that MyServiceDao is the concrete implementation that your Service class needs.
Write the following configuration classes:
#Configuration
public class MyServiceConfiguration {
#Bean
public Service myService(MyServiceDao dao) {
return new Service(dao);
}
}
-
#Configuration
public class MyProductionServiceDaoConfiguration {
#Bean
public MyServiceDao myServiceDao() {
return new MyServiceDao();
}
}
Methods in #Configuration classes that are annotated with #Bean are eligible for Spring's auto-wiring. In the MyServiceConfiguration above, Spring will use the type of the method parameter to find a matching bean. If you include MyProductionServiceDaoConfiguration when creating the Spring context, this will be the instance of MyServiceDao that myServiceDao() created.
Test Setup
In your tests, you want to replace MyServiceDao with a stub. The stub needs to extend MyServiceDao so that Spring can find the right bean based on types. Let's call the stub MyServiceDaoStub. Whether you create it using a library like Mockito (which can also create stubs, not just mocks) or actually write an extension of MyServiceDao is up to you.
Instead of including MyProductionServiceDaoConfiguration in your Spring configuration, use the following class:
#Configuration
public class MyTestServiceDaoConfiguration {
#Bean
public MyServiceDao myServiceDao() {
return new MyServiceDaoStub();
}
}
In your test use #ContextConfiguration to load the test setup:
#RunWith(SpringJUnit4ClassRunner.class)
#ContextConfiguration(classes = { MyServiceConfiguration.class, MyTestServiceDaoConfiguration.classs })
public class MyServiceTest {
// your tests
}
Using #Autowired
Spring will also process #Autowired annotations in objects returned from #Bean annotated methods. If your Service looks like this:
public class Service {
#Autowired
private MyServiceDao dao;
// more code
}
you can change the myService() method to:
#Bean
public Service myService() {
return new Service();
}