SpringAOP的完美案例
使用案例
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>
spring:
redis:
cluster:
nodes:
- 10.9.15.32:6388
- 10.9.15.33:6383
- 10.9.15.34:6382
- 10.9.15.35:6382
- 10.9.15.36:6389
- 10.9.15.38:6379
@Configuration
public class RedisConfig {
@Bean
public CacheManager cacheManager(RedisConnectionFactory factory) {
RedisSerializer<String> redisSerializer = new StringRedisSerializer();
Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
// 解决查询缓存转换异常的问题
ObjectMapper om = new ObjectMapper();
om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
jackson2JsonRedisSerializer.setObjectMapper(om);
// 配置序列化
RedisCacheConfiguration config = RedisCacheConfiguration.defaultCacheConfig();
config = config.serializeKeysWith(RedisSerializationContext.SerializationPair.fromSerializer(redisSerializer))
.serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(jackson2JsonRedisSerializer));
RedisCacheManager cacheManager = RedisCacheManager.builder(factory).cacheDefaults(config).build();
return cacheManager;
}
}
@SpringBootApplication
@EnableCaching
public class CacheApplication {
public static void main(String[] args) {
CacheApplication .run(SakuraPortalApplication.class, args);
}
}
@Cacheable(value = "mockMeta", key = "#serviceId")
public MockMeta getMockMeta(Long serviceId) {
return mapper.selectByPrimaryKey(serviceId);
}
原理解析
EnableCaching
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(CachingConfigurationSelector.class)
public @interface EnableCaching {
// 指定动态代理方式，属性值为false时，表示使用jdk代理，为true时则表示使用cglib代理。只有当mode等于PROXY时才生效
boolean proxyTargetClass() default false;
// aop的模式，有 SpringAOP 和 ASPECTJ 两种
AdviceMode mode() default AdviceMode.PROXY;
// 当一个joinpoint上有多个advice时，用于指定顺序
int order() default Ordered.LOWEST_PRECEDENCE;
}
@Import用来整合所有在@Configuration注解中定义的bean配置
CachingConfigurationSelector
public class CachingConfigurationSelector extends AdviceModeImportSelector<EnableCaching> {
@Override
public String[] selectImports(AdviceMode adviceMode) {
switch (adviceMode) {
case PROXY:
return getProxyImports();
case ASPECTJ:
return getAspectJImports();
default:
return null;
}
}
private String[] getProxyImports() {
List<String> result = new ArrayList<>(3);
result.add(AutoProxyRegistrar.class.getName());
result.add(ProxyCachingConfiguration.class.getName());
if (jsr107Present && jcacheImplPresent) {
result.add(PROXY_JCACHE_CONFIGURATION_CLASS);
}
return StringUtils.toStringArray(result);
}
}
不关注ASPECTJ的AOP模式
CachingConfigurationSelector的类继承关系如下：
在其父类AdviceModeImportSelector的selectImports方法中，最终会回调子类的selectImports方法
@Override
public final String[] selectImports(AnnotationMetadata importingClassMetadata) {
Class<?> annType = GenericTypeResolver.resolveTypeArgument(getClass(), AdviceModeImportSelector.class);
Assert.state(annType != null, "Unresolvable type argument for AdviceModeImportSelector");
AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor(importingClassMetadata, annType);
if (attributes == null) {
throw new IllegalArgumentException(String.format(
"@%s is not present on importing class '%s' as expected",
annType.getSimpleName(), importingClassMetadata.getClassName()));
}
AdviceMode adviceMode = attributes.getEnum(getAdviceModeAttributeName());
String[] imports = selectImports(adviceMode);
if (imports == null) {
throw new IllegalArgumentException("Unknown AdviceMode: " + adviceMode);
}
return imports;
}
在getProxyImports方法中，会涉及到两个关键的类的加载：AutoProxyRegistrar、ProxyCachingConfiguration
AutoProxyRegistrar
public class AutoProxyRegistrar implements ImportBeanDefinitionRegistrar {
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
boolean candidateFound = false;
Set<String> annoTypes = importingClassMetadata.getAnnotationTypes();
for (String annoType : annoTypes) {
AnnotationAttributes candidate = AnnotationConfigUtils.attributesFor(importingClassMetadata, annoType);
if (candidate == null) {
continue;
}
Object mode = candidate.get("mode");
Object proxyTargetClass = candidate.get("proxyTargetClass");
if (mode != null && proxyTargetClass != null && AdviceMode.class == mode.getClass() &&
Boolean.class == proxyTargetClass.getClass()) {
candidateFound = true;
if (mode == AdviceMode.PROXY) {
AopConfigUtils.registerAutoProxyCreatorIfNecessary(registry);
if ((Boolean) proxyTargetClass) {
AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry);
return;
}
}
}
}
}
}
所有实现了ImportBeanDefinitionRegistrar接口的类的都会被ConfigurationClassPostProcessor处理，ConfigurationClassPostProcessor实现了BeanFactoryPostProcessor接口，所以ImportBeanDefinitionRegistrar中动态注册的bean是优先于依赖其的bean初始化的，也能被AOP等机制处理。
从上面的代码中可以发现，如果使用JDK动态代理，会执行以下代码，AutoProxyCreator 代表一个能创建代理对象的对象
AopConfigUtils.registerAutoProxyCreatorIfNecessary(registry);
@Nullable
public static BeanDefinition registerAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry) {
return registerAutoProxyCreatorIfNecessary(registry, null);
}
@Nullable
public static BeanDefinition registerAutoProxyCreatorIfNecessary(
BeanDefinitionRegistry registry, @Nullable Object source) {
return registerOrEscalateApcAsRequired(InfrastructureAdvisorAutoProxyCreator.class, registry, source);
}
InfrastructureAdvisorAutoProxyCreator
public class InfrastructureAdvisorAutoProxyCreator extends AbstractAdvisorAutoProxyCreator {
@Nullable
private ConfigurableListableBeanFactory beanFactory;
@Override
protected void initBeanFactory(ConfigurableListableBeanFactory beanFactory) {
super.initBeanFactory(beanFactory);
this.beanFactory = beanFactory;
}
@Override
protected boolean isEligibleAdvisorBean(String beanName) {
return (this.beanFactory != null && this.beanFactory.containsBeanDefinition(beanName) &&
this.beanFactory.getBeanDefinition(beanName).getRole() == BeanDefinition.ROLE_INFRASTRUCTURE);
}
}
有关于的类继承关系如下：
实现了顶层的BeanPostProcessor接口，这代表在初始换bean前后可以执行相应的逻辑。SpringAOP的起点就是在AbstractAutoProxyCreator中的postProcessAfterInitialization方法中，创建代理之前有个前置校验，如下：
protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
if (StringUtils.hasLength(beanName) && this.targetSourcedBeans.contains(beanName)) {
return bean;
}
if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
return bean;
}
// 前置校验，如果不通过就不创建代理对象
if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return bean;
}
// Create proxy if we have advice.
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
if (specificInterceptors != DO_NOT_PROXY) {
this.advisedBeans.put(cacheKey, Boolean.TRUE);
Object proxy = createProxy(
bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
this.proxyTypes.put(cacheKey, proxy.getClass());
return proxy;
}
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return bean;
}
前面已经说过InfrastructureAdvisorAutoProxyCreator的作用是用于创建代理对象，至于为哪些bean创建代理，则是其isEligibleAdvisorBean方法指定，其源码如下：
@Override
protected boolean isEligibleAdvisorBean(String beanName) {
return (this.beanFactory != null && this.beanFactory.containsBeanDefinition(beanName) &&
this.beanFactory.getBeanDefinition(beanName).getRole() == BeanDefinition.ROLE_INFRASTRUCTURE);
}
即：只有bean的role属性=BeanDefinition.ROLE_INFRASTRUCTURE的时候才会为这个bean创建代理对象
ProxyCachingConfiguration
上面已经创建了一个针对于Cache的AutoProxyCreator，接下来创建的是相关的Advisor
@Configuration
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public class ProxyCachingConfiguration extends AbstractCachingConfiguration {
@Bean(name = CacheManagementConfigUtils.CACHE_ADVISOR_BEAN_NAME)
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public BeanFactoryCacheOperationSourceAdvisor cacheAdvisor() {
BeanFactoryCacheOperationSourceAdvisor advisor = new BeanFactoryCacheOperationSourceAdvisor();
advisor.setCacheOperationSource(cacheOperationSource());
advisor.setAdvice(cacheInterceptor());
if (this.enableCaching != null) {
advisor.setOrder(this.enableCaching.<Integer>getNumber("order"));
}
return advisor;
}
@Bean
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public CacheOperationSource cacheOperationSource() {
return new AnnotationCacheOperationSource();
}
@Bean
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public CacheInterceptor cacheInterceptor() {
CacheInterceptor interceptor = new CacheInterceptor();
interceptor.configure(this.errorHandler, this.keyGenerator, this.cacheResolver, this.cacheManager);
interceptor.setCacheOperationSource(cacheOperationSource());
return interceptor;
}
}
AnnotationCacheOperationSource顶层的接口是CacheOperationSource，用于获取某个方法上缓存相关的操作(Return the collection of cache operations for this method)。
缓存相关的操作被抽象成CacheOperation，其实现类有：CacheEvictOperation、CachePutOperation、CacheableOperation。
接下来感觉有点无从下手，其实这里主要就是生成一个advisor，即 BeanFactoryCacheOperationSourceAdvisor。advisor就包括了pointcut和advice，advice就是对应这里的CacheInterceptor
BeanFactoryCacheOperationSourceAdvisor
public class BeanFactoryCacheOperationSourceAdvisor extends AbstractBeanFactoryPointcutAdvisor {
@Nullable
private CacheOperationSource cacheOperationSource;
private final CacheOperationSourcePointcut pointcut = new CacheOperationSourcePointcut() {
@Override
@Nullable
protected CacheOperationSource getCacheOperationSource() {
return cacheOperationSource;
}
};
/**
* Set the cache operation attribute source which is used to find cache
* attributes. This should usually be identical to the source reference
* set on the cache interceptor itself.
*/
public void setCacheOperationSource(CacheOperationSource cacheOperationSource) {
this.cacheOperationSource = cacheOperationSource;
}
/**
* Set the {@link ClassFilter} to use for this pointcut.
* Default is {@link ClassFilter#TRUE}.
*/
public void setClassFilter(ClassFilter classFilter) {
this.pointcut.setClassFilter(classFilter);
}
@Override
public Pointcut getPointcut() {
return this.pointcut;
}
}
CacheOperationSourcePointcut对应pointcut，主要关注它的match方法
@Override
public boolean matches(Method method, Class<?> targetClass) {
if (CacheManager.class.isAssignableFrom(targetClass)) {
return false;
}
CacheOperationSource cas = getCacheOperationSource();
return (cas != null && !CollectionUtils.isEmpty(cas.getCacheOperations(method, targetClass)));
}
cas.getCacheOperations 即对应 AnnotationCacheOperationSource的getCacheOperations方法，该方法实现在AbstractFallbackCacheOperationSource中，AnnotationCacheOperationSource继承自AbstractFallbackCacheOperationSource
public Collection<CacheOperation> getCacheOperations(Method method, @Nullable Class<?> targetClass) {
if (method.getDeclaringClass() == Object.class) {
return null;
}
Object cacheKey = getCacheKey(method, targetClass);
Collection<CacheOperation> cached = this.attributeCache.get(cacheKey);
if (cached != null) {
return (cached != NULL_CACHING_ATTRIBUTE ? cached : null);
}
else {
Collection<CacheOperation> cacheOps = computeCacheOperations(method, targetClass);
if (cacheOps != null) {
if (logger.isTraceEnabled()) {
logger.trace("Adding cacheable method '" + method.getName() + "' with attribute: " + cacheOps);
}
this.attributeCache.put(cacheKey, cacheOps);
}
else {
this.attributeCache.put(cacheKey, NULL_CACHING_ATTRIBUTE);
}
return cacheOps;
}
}
主要就是查到对应的method上是否有那几个Cache注解，调用栈比较深，这里简单概括
AbstractFallbackCacheOperationSource # getCacheOperations =>
AbstractFallbackCacheOperationSource # computeCacheOperations =>
AnnotationCacheOperationSource # findCacheOperations =>
AnnotationCacheOperationSource # determineCacheOperations =>
SpringCacheAnnotationParser # parseCacheAnnotations
具体的查找过程，主要就是这几个注解：Cacheable、CacheEvict、CachePut、Caching
private Collection<CacheOperation> parseCacheAnnotations(
DefaultCacheConfig cachingConfig, AnnotatedElement ae, boolean localOnly) {
Collection<? extends Annotation> anns = (localOnly ?
AnnotatedElementUtils.getAllMergedAnnotations(ae, CACHE_OPERATION_ANNOTATIONS) :
AnnotatedElementUtils.findAllMergedAnnotations(ae, CACHE_OPERATION_ANNOTATIONS));
if (anns.isEmpty()) {
return null;
}
final Collection<CacheOperation> ops = new ArrayList<>(1);
anns.stream().filter(ann -> ann instanceof Cacheable).forEach(
ann -> ops.add(parseCacheableAnnotation(ae, cachingConfig, (Cacheable) ann)));
anns.stream().filter(ann -> ann instanceof CacheEvict).forEach(
ann -> ops.add(parseEvictAnnotation(ae, cachingConfig, (CacheEvict) ann)));
anns.stream().filter(ann -> ann instanceof CachePut).forEach(
ann -> ops.add(parsePutAnnotation(ae, cachingConfig, (CachePut) ann)));
anns.stream().filter(ann -> ann instanceof Caching).forEach(
ann -> parseCachingAnnotation(ae, cachingConfig, (Caching) ann, ops));
return ops;
}
CacheInterceptor
CacheInterceptor其实就是插入的逻辑
public class CacheInterceptor extends CacheAspectSupport implements MethodInterceptor, Serializable {
@Override
@Nullable
public Object invoke(final MethodInvocation invocation) throws Throwable {
Method method = invocation.getMethod();
CacheOperationInvoker aopAllianceInvoker = () -> {
try {
// 执行目标方法
return invocation.proceed();
}
catch (Throwable ex) {
throw new CacheOperationInvoker.ThrowableWrapper(ex);
}
};
try {
return execute(aopAllianceInvoker, invocation.getThis(), method, invocation.getArguments());
}
catch (CacheOperationInvoker.ThrowableWrapper th) {
throw th.getOriginal();
}
}
}
CacheAspectSupport中的execute方法
protected Object execute(CacheOperationInvoker invoker, Object target, Method method, Object[] args) {
if (this.initialized) {
Class<?> targetClass = getTargetClass(target);
CacheOperationSource cacheOperationSource = getCacheOperationSource();
if (cacheOperationSource != null) {
Collection<CacheOperation> operations = cacheOperationSource.getCacheOperations(method, targetClass);
if (!CollectionUtils.isEmpty(operations)) {
return execute(invoker, method,
new CacheOperationContexts(operations, method, args, target, targetClass));
}
}
}
return invoker.invoke();
}
CacheOperationContexts中有一个MultiValueMap类型的contexts属性
private class CacheOperationContexts {
private final MultiValueMap<Class<? extends CacheOperation>, CacheOperationContext> contexts;
private final boolean sync;
public CacheOperationContexts(Collection<? extends CacheOperation> operations, Method method,
Object[] args, Object target, Class<?> targetClass) {
this.contexts = new LinkedMultiValueMap<>(operations.size());
for (CacheOperation op : operations) {
this.contexts.add(op.getClass(), getOperationContext(op, method, args, target, targetClass));
}
this.sync = determineSyncFlag(method);
}
}
protected class CacheOperationContext implements CacheOperationInvocationContext<CacheOperation> {
private final CacheOperationMetadata metadata;
private final Object[] args;
private final Object target;
private final Collection<? extends Cache> caches;
private final Collection<String> cacheNames;
}
LinkedMultiValueMap中维护的是: key -> LinkList 的数据结构，所以每个CacheOperation对应一个CacheOperationContext列表。
这里value有三个值，也就相当于有三个Cache
@Cacheable(value = {"mockMeta", "mockMeta2", "mockMeta3"}, key = "#serviceId")
public MockMeta getMockMeta(Long serviceId) {
......
}
封装好CacheOperationContexts之后，接下来执行excute方法
@Nullable
private Object execute(final CacheOperationInvoker invoker, Method method, CacheOperationContexts contexts) {
// 执行@Cacheable注解对应的操作，只有@Cacheable注解有sync属性，当sync为true时，contexts.isSynchronized()返回true，执行以下方法。不关注！
if (contexts.isSynchronized()) {
CacheOperationContext context = contexts.get(CacheableOperation.class).iterator().next();
if (isConditionPassing(context, CacheOperationExpressionEvaluator.NO_RESULT)) {
Object key = generateKey(context, CacheOperationExpressionEvaluator.NO_RESULT);
Cache cache = context.getCaches().iterator().next();
try {
return wrapCacheValue(method, cache.get(key, () -> unwrapReturnValue(invokeOperation(invoker))));
}
catch (Cache.ValueRetrievalException ex) {
// The invoker wraps any Throwable in a ThrowableWrapper instance so we
// can just make sure that one bubbles up the stack.
throw (CacheOperationInvoker.ThrowableWrapper) ex.getCause();
}
}
else {
// No caching required, only call the underlying method
return invokeOperation(invoker);
}
}
// 对应@CacheEvict注解，有一个beforeInvocation属性，默认为false。如果beforeInvocation为true，则在执行目标方法前清除缓存
processCacheEvicts(contexts.get(CacheEvictOperation.class), true,
CacheOperationExpressionEvaluator.NO_RESULT);
// 对应@Cacheable注解，尝试从缓存中获得key对应的值
Cache.ValueWrapper cacheHit = findCachedItem(contexts.get(CacheableOperation.class));
// 如果没有获取到缓存，就将CacheableOperation类型的CacheOperationContext封装到CachePutRequest中，并保存到cachePutRequests集合内
List<CachePutRequest> cachePutRequests = new LinkedList<>();
if (cacheHit == null) {
collectPutRequests(contexts.get(CacheableOperation.class),
CacheOperationExpressionEvaluator.NO_RESULT, cachePutRequests);
}
Object cacheValue;
Object returnValue;
// 找到了缓存，就包装返回值
if (cacheHit != null && !hasCachePut(contexts)) {
// If there are no put requests, just use the cache hit
cacheValue = cacheHit.get();
returnValue = wrapCacheValue(method, cacheValue);
}
// 没有找到缓存，通过执行目标方法拿到返回值
else {
// 执行目标方法
returnValue = invokeOperation(invoker);
cacheValue = unwrapReturnValue(returnValue);
}
// 对应@CachePut注解，将CachePutOperation类型的CacheOperationContext封装到CachePutRequest中，并保存到cachePutRequests集合内
collectPutRequests(contexts.get(CachePutOperation.class), cacheValue, cachePutRequests);
// 处理cachePutRequests，即将值放到缓存！从上面的代码流程可以发现，只有当@Cacheable不命中或者有@CachePut注解的时候，才会生成requests，也只有这种情况下才需要将值放到缓存中
for (CachePutRequest cachePutRequest : cachePutRequests) {
// 写入缓存
cachePutRequest.apply(cacheValue);
}
// 如果@CacheEvict注解的beforeInvocation属性为false，则在执行目标方法之后清除缓存
processCacheEvicts(contexts.get(CacheEvictOperation.class), false, cacheValue);
return returnValue;
}
写入缓存
private class CachePutRequest {
private final CacheOperationContext context;
private final Object key;
public CachePutRequest(CacheOperationContext context, Object key) {
this.context = context;
this.key = key;
}
public void apply(@Nullable Object result) {
if (this.context.canPutToCache(result)) {
for (Cache cache : this.context.getCaches()) {
doPut(cache, this.key, result);
}
}
}
}
// AbstractCacheInvoker # doPut
protected void doPut(Cache cache, Object key, @Nullable Object result) {
try {
cache.put(key, result);
}
catch (RuntimeException ex) {
getErrorHandler().handleCachePutError(ex, cache, key, result);
}
}
// 例如 RedisCache # put
public void put(Object key, @Nullable Object value) {
Object cacheValue = this.preProcessCacheValue(value);
if (!this.isAllowNullValues() && cacheValue == null) {
throw new IllegalArgumentException(String.format("Cache '%s' does not allow 'null' values. Avoid storing null via '@Cacheable(unless=\"#result == null\")' or configure RedisCache to allow 'null' via RedisCacheConfiguration.", this.name));
} else {
this.cacheWriter.put(this.name, this.createAndConvertCacheKey(key), this.serializeCacheValue(cacheValue), this.cacheConfig.getTtl());
}
}
总结一下这部分流程：
1、处理@Cacheable注解sync属性为true情况；
2、如果@CacheEvict注解的beforeInvocation属性为true，则清除缓存；
3、根据@Cacheable注解，尝试从缓存中获得key对应的值：如果命中，包装返回值；如果没有命中，执行名表方法的到返回值，然后包装返回值；
4、如果@Cacheable没有命中，将CacheableOperation类型的CacheOperationContext封装到CachePutRequest中，并保存到cachePutRequests集合内；
5、如果有@CachePut注解，将CachePutOperation类型的CacheOperationContext封装到CachePutRequest中，并保存到cachePutRequests集合内；
6、遍历cachePutRequests，写入缓存；
7、返回值；
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