SpringCache源碼分析，你學(xué)會(huì)了嗎？
作者：IT動(dòng)力
ProxyCachingConfiguration總的來說就是聲明了一個(gè)SpringCacheAnnotationParser和一個(gè)CacheInterceptor。在使用自定義的切點(diǎn)類，在切點(diǎn)前后切入一個(gè)CacheInterceptor來實(shí)現(xiàn)緩存的邏輯。
1、入口說明
@EnableCaching是開啟SpringCache的一個(gè)總開關(guān)，開啟時(shí)候我們的緩存相關(guān)注解才會(huì)生效，所以我們@EnableCaching開始作為入口進(jìn)行分析，
2、分析@EnableCaching注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(CachingConfigurationSelector.class) // 這里有一個(gè)Import，導(dǎo)入了一個(gè)Selector類
public @interface EnableCaching {
// 是否創(chuàng)建cglib代理，默認(rèn)為false, 也就是使用jdk動(dòng)態(tài)代理
boolean proxyTargetClass() default false;
// 增強(qiáng)模式 默認(rèn)使用JDK動(dòng)態(tài)代理，引入cglib可以使用ASPECTJ
AdviceMode mode() default AdviceMode.PROXY;
// 排序字段
int order() default Ordered.LOWEST_PRECEDENCE;
}2.1、分析導(dǎo)入的CachingConfigurationSelector類
public class CachingConfigurationSelector extends AdviceModeImportSelector<EnableCaching> {
// ...此處省略一萬行代碼
// CachingConfigurationSelector繼承了AdviceModeImportSelector， 而AdviceModeImportSelector又實(shí)現(xiàn)了ImportSelector
// 所以我們實(shí)現(xiàn)類selectImports，用于返回要導(dǎo)入的配置類列表
@Override
public String[] selectImports(AdviceMode adviceMode) {
// 如果是jdk動(dòng)態(tài)代理，走getProxyImports邏輯。如果是cglib動(dòng)態(tài)代理，走getAspectJImports邏輯
switch (adviceMode) {
case PROXY:
return getProxyImports();
case ASPECTJ:
return getAspectJImports();
default:
return null;
}
}
// 獲取要進(jìn)行自動(dòng)配置的配置類
private String[] getProxyImports() {
List<String> result = new ArrayList<>(3);
// 這里添加了兩個(gè)類，AutoProxyRegistrar（自動(dòng)代理注冊(cè)器），ProxyCachingConfiguration（代理緩存配置類）
// AutoProxyRegistrar點(diǎn)進(jìn)去可以發(fā)現(xiàn)，里面其實(shí)就是提供了registerBeanDefinitions方法用于注冊(cè)BeanDefinition
result.add(AutoProxyRegistrar.class.getName());
// ProxyCachingConfiguration點(diǎn)進(jìn)去發(fā)現(xiàn)，配置類緩存相關(guān)的一些Bean（就是SpringCache的一些核心Bean）
result.add(ProxyCachingConfiguration.class.getName());
if (jsr107Present && jcacheImplPresent) {
result.add(PROXY_JCACHE_CONFIGURATION_CLASS);
}
return StringUtils.toStringArray(result);
}
// ...此處省略一萬行代碼
}CachingConfigurationSelector繼承了AdviceModeImportSelector， 而AdviceModeImportSelector又實(shí)現(xiàn)了ImportSelector,所以我們實(shí)現(xiàn)了selectImports方法，用于返回要導(dǎo)入的配置類列表.
selectImports會(huì)去判斷，如果是jdk動(dòng)態(tài)代理，走getProxyImports邏輯。如果是cglib動(dòng)態(tài)代理，走getAspectJImports邏輯。
我們直接關(guān)注JDK動(dòng)態(tài)代理的方法getProxyImports。這里面添加了兩個(gè)類AutoProxyRegistrar和ProxyCachingConfiguration。
AutoProxyRegistrar點(diǎn)進(jìn)去可以發(fā)現(xiàn)，里面其實(shí)就是提供了registerBeanDefinitions方法用于注冊(cè)BeanDefinition。
ProxyCachingConfiguration點(diǎn)進(jìn)去發(fā)現(xiàn)，配置類緩存相關(guān)的一些Bean（就是SpringCache的一些核心Bean），所以我們會(huì)重點(diǎn)關(guān)注ProxyCachingConfiguration并著重分析。
2.1.1、分析ProxyCachingConfiguration配置類
@Configuration(proxyBeanMethods = false)
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public class ProxyCachingConfiguration extends AbstractCachingConfiguration {
// BeanFactoryCacheOperationSourceAdvisor是對(duì)CacheOperationSource進(jìn)行增強(qiáng)，其實(shí)就是添加一個(gè)攔截器，用于獲取相關(guān)緩存的注解信息
// 所以有些邏輯會(huì)在CacheInterceptor里
@Bean(name = CacheManagementConfigUtils.CACHE_ADVISOR_BEAN_NAME)
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public BeanFactoryCacheOperationSourceAdvisor cacheAdvisor(
CacheOperationSource cacheOperationSource, CacheInterceptor cacheInterceptor) {
BeanFactoryCacheOperationSourceAdvisor advisor = new BeanFactoryCacheOperationSourceAdvisor();
advisor.setCacheOperationSource(cacheOperationSource);
advisor.setAdvice(cacheInterceptor);
if (this.enableCaching != null) {
advisor.setOrder(this.enableCaching.<Integer>getNumber("order"));
}
return advisor;
}
// 定義一個(gè)CacheOperationSource，主要用于獲取類或者方法上的注解。
@Bean
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public CacheOperationSource cacheOperationSource() {
return new AnnotationCacheOperationSource();
}
// 定義了一個(gè)攔截器，該攔截器用于用于攔截緩存相關(guān)注解，做AOP操作。比如先查詢緩存，查詢到直接返回，查詢不到就執(zhí)行方法體，將結(jié)果寫入緩存。
@Bean
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public CacheInterceptor cacheInterceptor(CacheOperationSource cacheOperationSource) {
CacheInterceptor interceptor = new CacheInterceptor();
// 緩存攔截器在這里注入了cacheManager（緩存管理器）
interceptor.configure(this.errorHandler, this.keyGenerator, this.cacheResolver, this.cacheManager);
interceptor.setCacheOperationSource(cacheOperationSource);
return interceptor;
}
}來分析一下BeanFactoryCacheOperationSourceAdvisor
public class BeanFactoryCacheOperationSourceAdvisor extends AbstractBeanFactoryPointcutAdvisor {
@Nullable
private CacheOperationSource cacheOperationSource;
// 定義我們自己的切點(diǎn)，緩存操作切點(diǎn)
private final CacheOperationSourcePointcut pointcut = new CacheOperationSourcePointcut() {
// 該切點(diǎn)存在一個(gè)方法，獲取CacheOperationSource（獲取切點(diǎn)的那些注解操作）。
@Override
@Nullable
protected CacheOperationSource getCacheOperationSource() {
return cacheOperationSource;
}
};
// 使用該方法設(shè)置CacheOperationSource，在上一層有設(shè)置advisor.setCacheOperationSource(cacheOperationSource);
// 把這個(gè)數(shù)據(jù)塞入BeanFactoryCacheOperationSourceAdvisor, 以便于在自定義的切點(diǎn)類CacheOperationSourcePointcut中可以獲取
public void setCacheOperationSource(CacheOperationSource cacheOperationSource) {
this.cacheOperationSource = cacheOperationSource;
}
// 設(shè)置ClassFilter到CacheOperationSourcePointcut
public void setClassFilter(ClassFilter classFilter) {
this.pointcut.setClassFilter(classFilter);
}
// 重寫getPointcut。也就是獲取切點(diǎn)的方法，因?yàn)樾枰獙?duì)切點(diǎn)進(jìn)行增強(qiáng)
@Override
public Pointcut getPointcut() {
return this.pointcut;
}
}BeanFactoryCacheOperationSourceAdvisor繼承了AbstractBeanFactoryPointcutAdvisor，重寫了Pointcut getPointcut()方法。
使用自定義的切點(diǎn)類CacheOperationSourcePointcut來作為切面的切點(diǎn)。而里面需要用到CacheOperationSource和ClassFilter。在BeanFactoryCacheOperationSourceAdvisor實(shí)例化時(shí)就已經(jīng)設(shè)置。
而上面又執(zhí)行了advisor.setAdvice(cacheInterceptor); 其實(shí)就是對(duì)這個(gè)切點(diǎn)添加了一個(gè)緩存攔截器，所以核心邏輯就在攔截器里面。
先再來看一下AnnotationCacheOperationSource
public class AnnotationCacheOperationSource extends AbstractFallbackCacheOperationSource implements Serializable {
private final boolean publicMethodsOnly;
// 緩存注解解析集合
private final Set<CacheAnnotationParser> annotationParsers;
public AnnotationCacheOperationSource() {
this(true);
}
public AnnotationCacheOperationSource(boolean publicMethodsOnly) {
this.publicMethodsOnly = publicMethodsOnly;
// 重點(diǎn)：解析集合從SpringCacheAnnotationParser中獲取，這個(gè)解析類就是解析注解的核心
this.annotationParsers = Collections.singleton(new SpringCacheAnnotationParser());
}
// ...此處省略一萬行代碼
// 判斷是否時(shí)候選類
@Override
public boolean isCandidateClass(Class<?> targetClass) {
for (CacheAnnotationParser parser : this.annotationParsers) {
if (parser.isCandidateClass(targetClass)) {
return true;
}
}
return false;
}
// 重點(diǎn)：查找類級(jí)別的CacheOperation列表，就是看標(biāo)注在類上的@Cacheable,@CacheEvict的集合
@Override
@Nullable
protected Collection<CacheOperation> findCacheOperations(Class<?> clazz) {
return determineCacheOperations(parser -> parser.parseCacheAnnotations(clazz));
}
// 重點(diǎn)：查找方法級(jí)別的CacheOperation列表，就是看標(biāo)注在方法上的@Cacheable,@CacheEvict的集合
@Override
@Nullable
protected Collection<CacheOperation> findCacheOperations(Method method) {
return determineCacheOperations(parser -> parser.parseCacheAnnotations(method));
}
// ...此處省略一萬行代碼
}接著看一下SpringCacheAnnotationParser
public class SpringCacheAnnotationParser implements CacheAnnotationParser, Serializable {
private static final Set<Class<? extends Annotation>> CACHE_OPERATION_ANNOTATIONS = new LinkedHashSet<>(8);
// 初始化緩存操作的注解集合
static {
CACHE_OPERATION_ANNOTATIONS.add(Cacheable.class);
CACHE_OPERATION_ANNOTATIONS.add(CacheEvict.class);
CACHE_OPERATION_ANNOTATIONS.add(CachePut.class);
CACHE_OPERATION_ANNOTATIONS.add(Caching.class);
}
// 解析類級(jí)別的注解，封裝為CacheOperation集合
@Override
@Nullable
public Collection<CacheOperation> parseCacheAnnotations(Class<?> type) {
DefaultCacheConfig defaultConfig = new DefaultCacheConfig(type);
return parseCacheAnnotations(defaultConfig, type);
}
// 解析方法級(jí)別的注解，封裝為CacheOperation集合
@Override
@Nullable
public Collection<CacheOperation> parseCacheAnnotations(Method method) {
DefaultCacheConfig defaultConfig = new DefaultCacheConfig(method.getDeclaringClass());
return parseCacheAnnotations(defaultConfig, method);
}
// 解析注解
@Nullable
private Collection<CacheOperation> parseCacheAnnotations(DefaultCacheConfig cachingConfig, AnnotatedElement ae) {
Collection<CacheOperation> ops = parseCacheAnnotations(cachingConfig, ae, false);
if (ops != null && ops.size() > 1) {
// More than one operation found -> local declarations override interface-declared ones...
Collection<CacheOperation> localOps = parseCacheAnnotations(cachingConfig, ae, true);
if (localOps != null) {
return localOps;
}
}
return ops;
}
// 具體解析注解的方法，包含了Cacheable，CacheEvict，CachePut，Caching等
@Nullable
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;
}
// ...此處省略了一萬行代碼，基本這個(gè)類都是解析這些注解并封裝為CacheOperation集合
}所以，SpringCacheAnnotationParser的作用就是將這些注解解析出來，并且封裝為Collection<CacheOperation>，供其他地方使用。
ProxyCachingConfiguration總的來說就是聲明了一個(gè)SpringCacheAnnotationParser和一個(gè)CacheInterceptor。在使用自定義的切點(diǎn)類，在切點(diǎn)前后切入一個(gè)CacheInterceptor來實(shí)現(xiàn)緩存的邏輯。
所以我們就找到的緩存的核心類CacheInterceptor，并且在構(gòu)造攔截器時(shí)，傳入了cacheManager作為緩存管理。
2.1.2、分析CacheInterceptor類
public class CacheInterceptor extends CacheAspectSupport implements MethodInterceptor, Serializable {
// 攔截原始方法的執(zhí)行，在方法前后增加橫切邏輯
@Override
@Nullable
public Object invoke(final MethodInvocation invocation) throws Throwable {
Method method = invocation.getMethod();
CacheOperationInvoker aopAllianceInvoker = () -> {
try {
return invocation.proceed();
}
catch (Throwable ex) {
throw new CacheOperationInvoker.ThrowableWrapper(ex);
}
};
Object target = invocation.getThis();
Assert.state(target != null, "Target must not be null");
try {
// 調(diào)用父類的execute方法，實(shí)現(xiàn)緩存的邏輯
return execute(aopAllianceInvoker, target, method, invocation.getArguments());
}
catch (CacheOperationInvoker.ThrowableWrapper th) {
throw th.getOriginal();
}
}
}可以看到，這個(gè)類很簡單，就是拿到原方法的invoke，然后通過父類CacheAspectSupport的execute方法實(shí)現(xiàn)緩存邏輯。
關(guān)注CacheAspectSupport的execute方法
public abstract class CacheAspectSupport extends AbstractCacheInvoker
implements BeanFactoryAware, InitializingBean, SmartInitializingSingleton {
protected final Log logger = LogFactory.getLog(getClass());
private final Map<CacheOperationCacheKey, CacheOperationMetadata> metadataCache = new ConcurrentHashMap<>(1024);
private final CacheOperationExpressionEvaluator evaluator = new CacheOperationExpressionEvaluator();
@Nullable
private CacheOperationSource cacheOperationSource;
private SingletonSupplier<KeyGenerator> keyGenerator = SingletonSupplier.of(SimpleKeyGenerator::new);
@Nullable
private SingletonSupplier<CacheResolver> cacheResolver;
@Nullable
private BeanFactory beanFactory;
private boolean initialized = false;
@Nullable
protected Object execute(CacheOperationInvoker invoker, Object target, Method method, Object[] args) {
// 如果bean已經(jīng)被初始化了，則調(diào)用相應(yīng)的緩存增強(qiáng)
if (this.initialized) {
Class<?> targetClass = getTargetClass(target);
CacheOperationSource cacheOperationSource = getCacheOperationSource();
if (cacheOperationSource != null) {
// 通過CacheOperationSource，獲取所有的CacheOperation列表(就是那一堆標(biāo)有緩存注解的類和方法的集合)
Collection<CacheOperation> operations = cacheOperationSource.getCacheOperations(method, targetClass);
if (!CollectionUtils.isEmpty(operations)) {
// 調(diào)用重載的execute方法
return execute(invoker, method,
new CacheOperationContexts(operations, method, args, target, targetClass));
}
}
}
// 否則，執(zhí)行原方法返回即可
return invoker.invoke();
}
// 執(zhí)行方法（核心）
@Nullable
private Object execute(final CacheOperationInvoker invoker, Method method, CacheOperationContexts contexts) {
// Special handling of synchronized invocation
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, handleSynchronizedGet(invoker, key, cache));
} catch (Cache.ValueRetrievalException ex) {
// Directly propagate ThrowableWrapper from the invoker,
// or potentially also an IllegalArgumentException etc.
ReflectionUtils.rethrowRuntimeException(ex.getCause());
}
} else {
// No caching required, only call the underlying method
return invokeOperation(invoker);
}
}
// 如果存在@CacheEvict注解、并且標(biāo)記為在調(diào)用前執(zhí)行，調(diào)用processCacheEvicts進(jìn)行緩存清除操作
processCacheEvicts(contexts.get(CacheEvictOperation.class), true,
CacheOperationExpressionEvaluator.NO_RESULT);
// 如果存在Cacheable注解、調(diào)用findCachedItem查詢緩存
Cache.ValueWrapper cacheHit = findCachedItem(contexts.get(CacheableOperation.class));
// 如果沒有命中緩存，則調(diào)用cachePutRequests，存儲(chǔ)在List<CachePutRequest>中，后續(xù)執(zhí)行原始方法后會(huì)寫入緩存
List<CachePutRequest> cachePutRequests = new ArrayList<>();
if (cacheHit == null) {
collectPutRequests(contexts.get(CacheableOperation.class),
CacheOperationExpressionEvaluator.NO_RESULT, cachePutRequests);
}
Object cacheValue;
Object returnValue;
// 如果緩存命中且沒有@CachePut注解，使用緩存的值作為返回值
if (cacheHit != null && !hasCachePut(contexts)) {
// If there are no put requests, just use the cache hit
cacheValue = cacheHit.get();
returnValue = wrapCacheValue(method, cacheValue);
}
// 緩存沒有命中或者有@CachePut注解
else {
// 調(diào)用原始方法作為返回值
returnValue = invokeOperation(invoker);
// 將原始方法的返回值作為緩存值
cacheValue = unwrapReturnValue(returnValue);
}
// 如果有@CachePut注解，則新增到cachePutRequests
collectPutRequests(contexts.get(CachePutOperation.class), cacheValue, cachePutRequests);
// 緩存未命中或者存在@CachePut注解，調(diào)用CachePutRequest的apply方法將數(shù)據(jù)寫入緩存
for (CachePutRequest cachePutRequest : cachePutRequests) {
cachePutRequest.apply(cacheValue);
}
// 如果有@CacheEvict注解，并且標(biāo)記為在調(diào)用后執(zhí)行，則還需要執(zhí)行清除緩存操作
processCacheEvicts(contexts.get(CacheEvictOperation.class), false, cacheValue);
return returnValue;
}
// 此處省略一萬行代碼
}總結(jié)來說，
- 如果存在@CacheEvict注解，并且標(biāo)記在方法執(zhí)行前執(zhí)行，就執(zhí)行清除緩存相關(guān)操作。
- 使用findCachedItem獲取緩存，緩存沒有命中，加入collectPutRequests，后續(xù)進(jìn)行寫入緩存操作。
- 如果命中緩存并且沒有@CachePut注解，獲取命中的值作為方法的返回值
- 如果沒有命中，或者包含了@CachePut注解，加入collectPutRequests，后續(xù)進(jìn)行寫入緩存操作。
- 遍歷cachePutRequests，將需要寫入緩存的數(shù)據(jù)寫入緩存
- 如果存在@CacheEvict注解，并且標(biāo)記在方法執(zhí)行后執(zhí)行，就執(zhí)行清除緩存相關(guān)操作。
還沒完呢，因?yàn)槲覀兌x的CacheManager怎么沒有用到呢？我們繼續(xù)跟蹤下去，以get緩存方法為例子分析。
關(guān)注findCachedItem獲取緩存方法
@Nullable
private Cache.ValueWrapper findCachedItem(Collection<CacheOperationContext> contexts) {
// 遍歷上下文列表
Object result = CacheOperationExpressionEvaluator.NO_RESULT;
for (CacheOperationContext context : contexts) {
if (isConditionPassing(context, result)) {
Object key = generateKey(context, result);
// 根據(jù)生成的key獲取緩存值
Cache.ValueWrapper cached = findInCaches(context, key);
if (cached != null) {
return cached;
}
else {
if (logger.isTraceEnabled()) {
logger.trace("No cache entry for key '" + key + "' in cache(s) " + context.getCacheNames());
}
}
}
}
return null;
}關(guān)注findInCaches獲取緩存方法
@Nullable
private Cache.ValueWrapper findInCaches(CacheOperationContext context, Object key) {
// 遍歷緩存集合（getCaches），使用緩存的key去和獲取緩存
for (Cache cache : context.getCaches()) {
// 最終是使用Cache接口的get方法去獲取緩存的
Cache.ValueWrapper wrapper = doGet(cache, key);
if (wrapper != null) {
if (logger.isTraceEnabled()) {
logger.trace("Cache entry for key '" + key + "' found in cache '" + cache.getName() + "'");
}
return wrapper;
}
}
return null;
}關(guān)注doGet獲取緩存方法
@Nullable
protected Cache.ValueWrapper doGet(Cache cache, Object key) {
try {
return cache.get(key);
}
catch (RuntimeException ex) {
getErrorHandler().handleCacheGetError(ex, cache, key);
return null; // If the exception is handled, return a cache miss
}
}我們發(fā)現(xiàn)，最終是通過Cache接口的get方法去獲取緩存的，那么我們只要知道Cache集合對(duì)象是在哪里傳入進(jìn)來的就清楚了整個(gè)邏輯。
重新回到execute方法
@Nullable
protected Object execute(CacheOperationInvoker invoker, Object target, Method method, Object[] args) {
// Check whether aspect is enabled (to cope with cases where the AJ is pulled in automatically)
if (this.initialized) {
Class<?> targetClass = getTargetClass(target);
CacheOperationSource cacheOperationSource = getCacheOperationSource();
if (cacheOperationSource != null) {
Collection<CacheOperation> operations = cacheOperationSource.getCacheOperations(method, targetClass);
if (!CollectionUtils.isEmpty(operations)) {
// 這里創(chuàng)建了一個(gè)CacheOperationContexts，我們有理由猜測CacheOperationContext.getCaches方法就是在這里面
return execute(invoker, method,
new CacheOperationContexts(operations, method, args, target, targetClass));
}
}
}
return invoker.invoke();
}跟蹤C(jī)acheOperationContexts
private class CacheOperationContexts {
// 就是一個(gè)CacheOperationContext的集合，key是CacheOperation或者其子類
private final MultiValueMap<Class<? extends CacheOperation>, CacheOperationContext> contexts;
// 是否開啟了sync=true屬性
private final boolean sync;
public CacheOperationContexts(Collection<? extends CacheOperation> operations, Method method,
Object[] args, Object target, Class<?> targetClass) {
// 根據(jù)CacheOperation集合，方法，參數(shù)創(chuàng)建了一個(gè)CacheOperationContext集合
this.contexts = new LinkedMultiValueMap<>(operations.size());
for (CacheOperation op : operations) {
// 重點(diǎn)：getOperationContext是具體創(chuàng)建CacheOperationContext的方法
this.contexts.add(op.getClass(), getOperationContext(op, method, args, target, targetClass));
}
// 獲取sync屬性并賦值給this.sync
this.sync = determineSyncFlag(method);
}
public Collection<CacheOperationContext> get(Class<? extends CacheOperation> operationClass) {
Collection<CacheOperationContext> result = this.contexts.get(operationClass);
return (result != null ? result : Collections.emptyList());
}
public boolean isSynchronized() {
return this.sync;
}
// ...此處省略了一萬行代碼
}關(guān)注getOperationContext創(chuàng)建CacheOperationContext
protected CacheOperationContext getOperationContext(
CacheOperation operation, Method method, Object[] args, Object target, Class<?> targetClass) {
CacheOperationMetadata metadata = getCacheOperationMetadata(operation, method, targetClass);
// 其實(shí)就是實(shí)例化一個(gè)CacheOperationContext
return new CacheOperationContext(metadata, args, target);
}其實(shí)就是拿到CacheOperationMetadata（CacheOperation的元數(shù)據(jù)信息），然后傳給CacheOperationContext進(jìn)行實(shí)例化CacheOperationContext。
關(guān)注CacheOperationContext的構(gòu)造方法
上面實(shí)例化了CacheOperationContext，所以其構(gòu)造方法內(nèi)一定做了寫什么事情。比如初始化操作。
// 緩存的集合
private final Collection<? extends Cache> caches;
public CacheOperationContext(CacheOperationMetadata metadata, Object[] args, Object target) {
this.metadata = metadata;
this.args = extractArgs(metadata.method, args);
this.target = target;
// 初始化了緩存名稱列表和緩存集合
this.caches = CacheAspectSupport.this.getCaches(this, metadata.cacheResolver);
this.cacheNames = createCacheNames(this.caches);
}關(guān)注getCaches（獲取緩存集合）
protected Collection<? extends Cache> getCaches(
CacheOperationInvocationContext<CacheOperation> context, CacheResolver cacheResolver) {
// 這里可以知道是通過CacheResolver來獲取的緩存集合
Collection<? extends Cache> caches = cacheResolver.resolveCaches(context);
if (caches.isEmpty()) {
throw new IllegalStateException("No cache could be resolved for '" +
context.getOperation() + "' using resolver '" + cacheResolver +
"'. At least one cache should be provided per cache operation.");
}
return caches;
}關(guān)注CacheResolver以及實(shí)現(xiàn)類
@FunctionalInterface
public interface CacheResolver {
// 根據(jù)CacheOperationInvocationContext獲取緩存集合
Collection<? extends Cache> resolveCaches(CacheOperationInvocationContext<?> context);
}CacheResolver的抽象實(shí)現(xiàn)類AbstractCacheResolver
public abstract class AbstractCacheResolver implements CacheResolver, InitializingBean {
// 這里就有CacheManager（緩存管理器）
@Nullable
private CacheManager cacheManager;
protected AbstractCacheResolver() {
}
// 構(gòu)造注入
protected AbstractCacheResolver(CacheManager cacheManager) {
this.cacheManager = cacheManager;
}
// set注入
public void setCacheManager(CacheManager cacheManager) {
this.cacheManager = cacheManager;
}
// 獲取CacheManager
public CacheManager getCacheManager() {
Assert.state(this.cacheManager != null, "No CacheManager set");
return this.cacheManager;
}
@Override
public void afterPropertiesSet() {
Assert.notNull(this.cacheManager, "CacheManager is required");
}
// 獲取緩存集合
@Override
public Collection<? extends Cache> resolveCaches(CacheOperationInvocationContext<?> context) {
// 先獲取緩存名稱
Collection<String> cacheNames = getCacheNames(context);
if (cacheNames == null) {
return Collections.emptyList();
}
Collection<Cache> result = new ArrayList<>(cacheNames.size());
// 遍歷名稱，通過CacheManager獲取緩存，加入緩存集合
for (String cacheName : cacheNames) {
Cache cache = getCacheManager().getCache(cacheName);
if (cache == null) {
throw new IllegalArgumentException("Cannot find cache named '" +
cacheName + "' for " + context.getOperation());
}
result.add(cache);
}
return result;
}
// 獲取緩存名稱集合
@Nullable
protected abstract Collection<String> getCacheNames(CacheOperationInvocationContext<?> context);
}而我們的CacheManager默認(rèn)使用SimpleCacheManager，我們注入了CustomRedisCacheManager, 所以會(huì)調(diào)用CustomRedisCacheManager的getCache方法獲取緩存。
而getCache方法在父類AbstractCacheManager已經(jīng)實(shí)現(xiàn)了。
// SpringCache最底層的數(shù)據(jù)結(jié)構(gòu)就是以一個(gè)ConcurrentMap
private final ConcurrentMap<String, Cache> cacheMap = new ConcurrentHashMap<>(16);
@Override
@Nullable
public Cache getCache(String name) {
// 先從cacheMap中獲取Cache, 獲取到了直接返回
Cache cache = this.cacheMap.get(name);
if (cache != null) {
return cache;
}
// 獲取不到，使用雙重檢測所寫入數(shù)據(jù)到cacheMap
Cache missingCache = getMissingCache(name);
if (missingCache != null) {
// Fully synchronize now for missing cache registration
synchronized (this.cacheMap) {
cache = this.cacheMap.get(name);
if (cache == null) {
cache = decorateCache(missingCache);
this.cacheMap.put(name, cache);
updateCacheNames(name);
}
}
}
return cache;
}到了這里，SpringCache的流程我們就真正的清楚了。
所以，SpringCache的源碼分析就到此為止了。
責(zé)任編輯：武曉燕
來源：
今日頭條
