Overriding Bean Configuration with annotations - spring

Question

Use case: I have my container configured via classpath scanning #ComponentScan. For my test configuration I need the ability to mock specific beans.
Due to the order of loading, beans loaded via classpath scan are not overriding properly when using #Configuration. The following code samples demonstrate the problem. BaseExample.java shows how it is possible to override beans via configuration. ScanExample.java shows that overriding a bean that was loaded via #ComponentScan is skipped (see final note).
A demo project is available on bitbucket.
// BaseExample.java
package com.glassworks.mock;
import org.mockito.Mockito;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.google.common.base.Joiner;
public class BaseExample {
private static final Logger log = LoggerFactory.getLogger(BaseExample.class);
private static AnnotationConfigApplicationContext ctx;
public static void main(String args[]) {
ctx = new AnnotationConfigApplicationContext(Config.class, OverrideConfig.class);
String beans[] = ctx.getBeanDefinitionNames();
log.info("{} beans found: {}", beans.length, Joiner.on(",").join(beans));
for(String bean : beans) {
log.info("{}: {}", bean, ctx.getBean(bean));
}
}
#Configuration
public static class Config {
#Bean
public AccountDao accountDao() {
log.debug("Creating accountDao [Config]");
return new AccountDao();
}
}
#Configuration
public static class OverrideConfig {
#Bean
public Object accountDao() {
log.debug("Creating accountDao [OverrideConfig]");
return Mockito.mock(AccountDao.class);
}
}
}
Output:
21:05 INFO | com.glassworks.mock.BaseExample | accountDao: Mock for AccountDao, hashCode: 666537607
[// ScanExample.java
package com.glassworks.mock;
import org.mockito.Mockito;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import com.google.common.base.Joiner;
public class ScanExample {
private static final Logger log = LoggerFactory.getLogger(ScanExample.class);
private static AnnotationConfigApplicationContext ctx;
public static void main(String args[]) {
ctx = new AnnotationConfigApplicationContext(Config.class, OverrideConfig.class);
String beans[] = ctx.getBeanDefinitionNames();
log.info("{} beans found: {}", beans.length, Joiner.on(",").join(beans));
for(String bean : beans) {
log.info("{}: {}", bean, ctx.getBean(bean));
}
}
#Configuration
#ComponentScan("com.glassworks.services")
public static class Config {
}
#Configuration
public static class OverrideConfig {
#Bean
public AccountDao accountDao() {
log.debug("Creating accountDao [OverrideConfig]");
return Mockito.mock(AccountDao.class);
}
}
}
Output:
21:08 INFO | com.glassworks.mock.ScanExample | accountDao: com.glassworks.services.AccountDao#48805ebb
// AccountDao.java
package com.glassworks.services;
import org.springframework.stereotype.Repository;
#Repository
public class AccountDao {
}
Note
Its worth noting on that with logging set to debug, Spring indicates that it is skipping over the definition. This appears to be a bug.
21:09 DEBUG | o.s.c.a.ConfigurationClassBeanDefinitionReader | Skipping loading bean definition for [BeanMethod:name=accountDao,declaringClass=com.glassworks.mock.ScanExample$OverrideConfig]: a definition for bean 'accountDao' already exists. This is likely due to an override in XML.