Spring @Configuration and FactoryBean

Biju KunjummenAugust 16th, 2012Last Updated: October 22nd, 2012

0 122 2 minutes read

Consider a FactoryBean for defining a cache using a Spring configuration file:

<cache:annotation-driven />
<context:component-scan base-package='org.bk.samples.cachexml'></context:component-scan>
 
<bean id='cacheManager' class='org.springframework.cache.support.SimpleCacheManager'>
 <property name='caches'>
  <set>
   <ref bean='defaultCache'/>
  </set>
 </property>
</bean>
 
<bean name='defaultCache' class='org.springframework.cache.concurrent.ConcurrentMapCacheFactoryBean'>
 <property name='name' value='default'/>
</bean>

The factory bean ConcurrentMapCacheFactoryBean is a bean which is in turn responsible for creating a Cache bean.

My first attempt at translating this setup to a @Configuration style was the following:

@Bean
public SimpleCacheManager cacheManager(){
 SimpleCacheManager cacheManager = new SimpleCacheManager();
 List<Cache> caches = new ArrayList<Cache>();
 ConcurrentMapCacheFactoryBean cacheFactoryBean = new ConcurrentMapCacheFactoryBean();
 cacheFactoryBean.setName('default');
 caches.add(cacheFactoryBean.getObject());
 cacheManager.setCaches(caches );
 return cacheManager;
}

This did not work however, the reason is that here I have bypassed some Spring bean lifecycle mechanisms altogether. It turns out that ConcurrentMapCacheFactoryBean also implements the InitializingBean interface and does a eager initialization of the cache in the ‘afterPropertiesSet’ method of InitializingBean. Now by directly calling factoryBean.getObject() , I was completely bypassing the afterPropertiesSet method.

There are two possible solutions:
1. Define the FactoryBean the same way it is defined in the XML:

@Bean
public SimpleCacheManager cacheManager(){
 SimpleCacheManager cacheManager = new SimpleCacheManager();
 List<Cache> caches = new ArrayList<Cache>();
 caches.add(cacheBean().getObject());
 cacheManager.setCaches(caches );
 return cacheManager;
}
 
@Bean
public ConcurrentMapCacheFactoryBean cacheBean(){
 ConcurrentMapCacheFactoryBean cacheFactoryBean = new ConcurrentMapCacheFactoryBean();
 cacheFactoryBean.setName('default');
 return cacheFactoryBean;
}

In this case, there is an explicit FactoryBean being returned from a @Bean method, and Spring will take care of calling the lifecycle methods on this bean.

2. Replicate the behavior in the relevant lifecycle methods, in this specific instance I know that the FactoryBean instantiates the ConcurrentMapCache in the afterPropertiesSet method, I can replicate this behavior directly this way:

@Bean
public SimpleCacheManager cacheManager(){
 SimpleCacheManager cacheManager = new SimpleCacheManager();
 List<Cache> caches = new ArrayList<Cache>();
 caches.add(cacheBean());
 cacheManager.setCaches(caches );
 return cacheManager;
}
 
@Bean
public Cache  cacheBean(){
 Cache  cache = new ConcurrentMapCache('default');
 return cache;
}

Something to keep in mind when translating a FactoryBean from xml to @Configuration.

Note:
A working one page test as a gist is available here:

package org.bk.samples.cache;
 
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.equalTo;
 
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
 
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.Cache;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cache.concurrent.ConcurrentMapCacheFactoryBean;
import org.springframework.cache.support.SimpleCacheManager;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes={TestSpringCache.TestConfiguration.class})
public class TestSpringCache {
 
 @Autowired TestService testService;
 
 @Test
 public void testCache() {
  String response1 = testService.cachedMethod('param1', 'param2');
  String response2 = testService.cachedMethod('param1', 'param2');
  assertThat(response2, equalTo(response1));
 }
 
 
 @Configuration
 @EnableCaching
 @ComponentScan('org.bk.samples.cache')
 public static class TestConfiguration{
 
  @Bean
  public SimpleCacheManager cacheManager(){
   SimpleCacheManager cacheManager = new SimpleCacheManager();
   List<Cache> caches = new ArrayList<Cache>();
   caches.add(cacheBean().getObject());
   cacheManager.setCaches(caches );
   return cacheManager;
  }
 
  @Bean
  public ConcurrentMapCacheFactoryBean cacheBean(){
   ConcurrentMapCacheFactoryBean cacheFactoryBean = new ConcurrentMapCacheFactoryBean();
   cacheFactoryBean.setName('default');
   return cacheFactoryBean;
  }
 }
 
}
 
interface TestService{
 String cachedMethod(String param1,String param2);
}
 
@Component
class TestServiceImpl implements TestService{
 
 @Cacheable(value='default', key='#p0.concat('-').concat(#p1)')
 public String cachedMethod(String param1, String param2){
  return 'response ' + new Random().nextInt();
 }
}