#CacheEvict with key="#id" throws NullPointerException - spring-cache

Question

I'm trying to use Spring Caching annotations #Cacheable and #CacheEvict together with the GuavaCacheManager.
I've created a test case with these two tests:
cachesById - verifies that two invocations to a method annotatted with #Cacheable returns the same object
evict - verifies that two different instances are returned if a method annotated with #CacheEvict is called in-between those two invocations
Both work fine when i don't specify a key for #CacheEvict, however when I do i get the following exception:
java.lang.NullPointerException
at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:210)
at com.google.common.cache.LocalCache$LocalManualCache.invalidate(LocalCache.java:4764)
at org.springframework.cache.guava.GuavaCache.evict(GuavaCache.java:135)
at org.springframework.cache.interceptor.AbstractCacheInvoker.doEvict(AbstractCacheInvoker.java:95)
at org.springframework.cache.interceptor.CacheAspectSupport.performCacheEvict(CacheAspectSupport.java:409)
at org.springframework.cache.interceptor.CacheAspectSupport.processCacheEvicts(CacheAspectSupport.java:392)
at org.springframework.cache.interceptor.CacheAspectSupport.execute(CacheAspectSupport.java:362)
at org.springframework.cache.interceptor.CacheAspectSupport.execute(CacheAspectSupport.java:299)
at org.springframework.cache.interceptor.CacheInterceptor.invoke(CacheInterceptor.java:61)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:653)
at com.myorg.caching.CacheTest$Repo$$EnhancerBySpringCGLIB$$eed50f3e.update(<generated>)
at com.myorg.caching.CacheTest.evict(CacheTest.java:50)
This can be reproduced by executing the below test.
#RunWith(SpringJUnit4ClassRunner.class)
#ContextConfiguration(
classes = { Repo.class, CacheTest.SpringConfig.class },
loader = AnnotationConfigContextLoader.class)
public class CacheTest {
private static final String CACHE_NAME = "cacheName";
#Inject
private Repo repo;
#Test
public void cachesById() {
Entity aResult1 = repo.getEntity(1);
Entity aResult2 = repo.getEntity(1);
assertEquals(aResult1.getId(), aResult2.getId());
assertSame(aResult1, aResult2);
}
#Test
public void evict() {
Entity aResult1 = repo.getEntity(1);
repo.update(aResult1);
Entity aResult2 = repo.getEntity(1);
assertEquals(aResult1.getId(), aResult2.getId());
assertNotSame(aResult1, aResult2);
}
/** Mock repository/entity classes below. */
#Component
public static class Repo {
#Cacheable(value = CACHE_NAME, key = "#id")
public Entity getEntity(int id) {
return new Entity(id);
}
#CacheEvict(value = CACHE_NAME, key = "#id")
public void update(Entity e) {
}
}
public static class Entity {
private int id;
public Entity(int id) {
super();
this.id = id;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
}
/** Guava Cachemanager Spring configuration */
#Configuration
#EnableCaching
public static class SpringConfig {
#Bean
public CacheManager cacheManager() {
GuavaCacheManager manager = new GuavaCacheManager(CACHE_NAME);
manager.setCacheBuilder(CacheBuilder.newBuilder().expireAfterWrite(
1, TimeUnit.MINUTES).recordStats());
return manager;
}
}
}
However the test passes if I change
#CacheEvict(value = CACHE_NAME, key = "#id")
public void update(Entity e) {
into:
#CacheEvict(value = CACHE_NAME)
public void update(Entity e) {
..but then I'm missing the point where I need to specify the cache key for Entity. Does anyone know what I'm missing?
Thanks!

Answer 1

You have to fix you component class from
#Component
public static class Repo {
#Cacheable(value = CACHE_NAME, key = "#id")
public Entity getEntity(int id) {
return new Entity(id);
}
#CacheEvict(value = CACHE_NAME, key = "#id")
public void update(Entity e) {
}
}
to
#Component
public static class Repo {
#Cacheable(value = CACHE_NAME, key = "#id")
public Entity getEntity(int id) {
return new Entity(id);
}
#CacheEvict(value = CACHE_NAME, key = "#e?.id")
public void update(Entity e) {
}
}
Why? In getEntity method you're caching an Entity object using int id, you have to pass the same int id into the #CacheEvict annotated method. You don't have to change method's signature - by using SPEL you can "get into" entity and use its id field.
Hope I helped.