关于Spring Cache 缓存拦截器( CacheInterceptor)

关于Spring Cache 缓存拦截器( CacheInterceptor)

目录Spring Cache 缓存拦截器( CacheInterceptor)spring cache常用的三种缓存操作具体整个流程是这样的CacheInterceptor.java定义Cacheable注解定义Rediskey.javaCache.javaRedisCache.javaCacheManager.javaAbstractCacheManager.javaRedisCacheManager.java实现CacheInterceptor.java配置Spring.xml测试使用

Spring Cache 缓存拦截器( CacheInterceptor)

打开Spring Cache的核心缓存拦截器CacheInterceptor，可以看到具体实现：

public class CacheInterceptor extends CacheAspectSupport implements MethodInterceptor, Serializable {

@Override

public Object invoke(final MethodInvocation invocation) throws Throwable {

Method method = invocation.getMethod();

CacheOperationInvoker aopAllianceInvoker = new CacheOperationInvoker() {

@Override

public Object invoke() {

try {

return invocation.proceed();

}

catch (Throwable ex) {

throw new ThrowableWrapper(ex);

}

}

};

try {

return execute(aopAllianceInvoker, invocation.getThis(), method, invocation.getArguments());

}

catch (CacheOperationInvoker.ThrowableWrapper th) {

throw th.getOriginal();

}

}

}

CacheInterceptor默认实现了Spring aop的MethodInterceptor接口，MethodInterceptor的功能是做方法拦截。拦截的方法都会调用invoke方法，在invoke方法里面主要缓存逻辑是在execute方法里面，该方法是继承了父类CacheAspectSupport。

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);

//获取执行方法上所有的缓存操作集合。如果有缓存操作则执行到execute(...)，如果没有就执行invoker.invoke()直接调用执行方法了

Collection operations = getCacheOperationSource().getCacheOperations(method, targetClass);

if (!CollectionUtils.isEmpty(operations)) {

return execute(invoker, method, new CacheOperationContexts(operations, method, args, target, targetClass));

}

}

return invoker.invoke();

}

集合Collection operations中存放了所有的缓存操作CachePutOperation、CacheableOperation、CacheEvictOperation

spring cache常用的三种缓存操作

@CachePut：执行方法后，将方法返回结果存放到缓存中。不管有没有缓存过，执行方法都会执行，并缓存返回结果（unless可以否决进行缓存）。（当然，这里说的缓存都要满足condition条件）

@Cacheable：如果没有缓存过，获取执行方法的返回结果；如果缓存过，则直接从缓存中获取，不再执行方法。

@CacheEvict：如果设置了beforeIntercepte则在方法执行前进行缓存删除操作，如果没有，则在执行方法调用完后进行缓存删除操作。

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, cache.get(key, new Callable

@Override

public Object call() throws Exception {

return 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);

}

}

// 处理beforeIntercepte=true的缓存删除操作

processCacheEvicts(contexts.get(CacheEvictOperation.class), true,

CacheOperationExpressionEvaluator.NO_RESULT);

// 从缓存中查找，是否有匹配@Cacheable的缓存数据

Cache.ValueWrapper cacheHit = findCachedItem(contexts.get(CacheableOperation.class));

// 如果@Cacheable没有被缓存，那么就需要将数据缓存起来，这里将@Cacheable操作收集成CachePutRequest集合，以便后续做@CachePut缓存数据存放。

List cachePutRequests = new LinkedList();

if (cacheHit == null) {

collectPutRequests(contexts.get(CacheableOperation.class),

CacheOperationExpressionEvaluator.NO_RESULT, cachePutRequests);

}

Object cacheValue;

Object returnValue;

//如果没有@CachePut操作，就使用@Cacheable获取的结果http://（可能也没有@Cableable，所以result可能为空）。

if (cacheHit != null && cachePutRequests.isEmpty() && !hasCachePut(contexts)) {

//如果没有@CachePut操作，并且cacheHit不为空，说明命中缓存了，直接返回缓存结果

cacheValue = cacheHit.get();

returnValue = wrapCacheValue(method, cacheValue);

}

else {

// 否则执行具体方法内容，返回缓存的结果

returnValue = invokeOperation(invoker);

cacheValue = unwrapReturnValue(returnValue);

}

// Collect any explicit @CachePuts

collectPutRequests(contexts.get(CachePutOperation.class), cacheValue, cachePutRequests);

// Process any collected put requests, either from @CachePut or a @Cacheable miss

for (CachePutRequest cachePutRequest : cachePutRequests) {

cachePutRequest.apply(cacheValue);

}

// Process any late evictions

processCacheEvicts(contexts.get(CacheEvictOperation.class), false, cacheValue);

return returnValue;

}

//根据key从缓存中查找，返回的结果是ValueWrapper，它是返回结果的包装器

private Cache.ValueWrapper findCachedItem(Collection contexts) {

Object result = CacheOperationExpressionEvaluator.NO_RESULT;

for (CacheOperationContext context : contexts) {

if (isConditionPassing(context, result)) {

Object key = generateKey(context, result);

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;

}

private Cache.ValueWrapper findInCaches(CacheOperationContext context, Object key) {

for (Cache cache : context.getCaches()) {

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;

}

具体整个流程是这样的

CacheInterceptor.java

项目中基本上都需要使用到Cache的功能, 但是Spring提供的Cacheable并不能很好的满足我们的需求, 所以这里自己借助Spring思想完成自己的业务逻辑.

定义Cacheable注解

@Target({ElementType.METHOD, ElementType.TYPE})

@Retention(RetentionPolicy.RUNTIME)

@Inherited

@Documented

public @interface Cacheable {

RedisKey value();

String key();

}

定义Rediskey.java

public enum RedisKeyEnum {

TEST_CACHE("test:", 24, TimeUnit.HOURS, "Test");

/**

* 缓存Key的前缀

*/

private String keyPrefix;

/**

* 过期时间

*/

private long timeout;

/**

* 过期时间单位

*/

private TimeUnit timeUnit;

/**

* 描述

*/

private String desc;

private static final String REDIS_KEY_DEFUALT_SEPARATOR = ":";

RedisKey(String keyPrefix, long timeout, TimeUnit timeUnit, String desc){

this.keyPrefix = keyPrefix;

this.timeout = timeout;

this.timeUnit = timeUnit;

this.desc = desc;

}

public long getTimeout() {

return timeout;

}

public TimeUnit getTimeUnit() {

return timeUnit;

}

public String getDesc() {

return desc;

}

/**

* 获取完整的缓存Key

* @param keys

* @return

*/

public String getKey(String... keys) {

if(keys == null || keys.length <= 0){

return this.keyPrefix;

}

String redisKey = keyPrefix;

for (int i = 0, length = keys.length; i < length; i++) {

String key = keys[i];

redisKey += key;

if (i < length - 1) {

redisKey += REDIS_KEY_DEFUALT_SEPARATOR;

}

}

return redisKey;

}

}

Cache.java

public interface Cache {

/**

* 返回缓存名称

* @return

*/

String getName();

/**

* 添加一个缓存实例

*

* @param key

* @param value

*/

V put(K key, V value);

/**

* 添加一个可过期的缓存实例

* @param key

* @param value

* @param expire

* @param timeUnit

* @return

*/

V put(K key, V value, long expire, TimeUnit timeUnit);

/**

* 返回缓存数据

*

* @param key

* @return

*/

V get(K key);

/**

* 删除一个缓存实例, 并返回缓存数据

*

* @param key

* @return

*/

void remove(K key);

/**

* 获取所有的缓存key

* @return

*/

Set keys();

/**

* 获取所有的缓存key

* @return

*/

Set keys(K pattern);

/**

* 获取所有的缓存数据

* @return

*/

Collection values();

/**

* 清空所有缓存

*/

void clear();

}

RedisCache.java

public class RedisCache implements Cache {

public static final String DEFAULT_CACHE_NAME = RedisCache.class.getName() + "_CACHE_NAME";

private RedisTemplate redisTemplate;

private ValueOperations valueOperations;

public RedisCache(RedisTemplate redisTemplate) {

this.redisTemplate = redisTemplate;

this.valueOperations = redisTemplate.opsForValue();

DataType dataType = redisTemplate.type("a");

}

@Override

public String getName() {

return DEFAULT_CACHE_NAME;

}

@Override

public V put(K key, V value) {

valueOperations.set(key, value);

return value;

}

@Override

public V put(K key, V value, long expire, TimeUnit timeUnit) {

valueOperations.set(key, value, expire, timeUnit);

return value;

}

@Override

public V get(K key) {

return valueOperations.get(key);

}

@Override

public void remove(K key) {

// V value = valueOperations.get(key);

redisTemplate.delete(key);

}

@Override

public Set keys() {

return null;

}

@Override

public Set keys(K pattern) {

return redisTemplate.keys(pattern);

}

@Override

public Collection values() {

return null;

}

@Override

public void clear() {

}

}

CacheManager.java

public interface CacheManager {

/**

* 获取缓存

* @return

*/

Cache getCache(String name);

/**

* 获取所有的缓存名称

*/

Collection getCacheNames();

}

AbstractCacheManager.java

public abstract class AbstractCacheManager implements CacheManager, InitializingBean, DisposableBean {

private static final Logger logger = LoggerFactory.getLogger(AbstractCacheManager.class);

private final Map cacheMap = new ConcurrentHashMap<>(16);

private volatile Set cacheNames = Collections.emptySet();

private static final String DEFAULT_CACHE_NAME_SUFFIX = "_CACHE_NAME";

@Override

public void afterPropertiesSet() throws Exception {

initlalizingCache();

}

private void initlalizingCache(){

Collection extends Cache> caches = loadCaches();

synchronized (this.cacheMap) {

this.cacheNames = Collections.emptySet();

this.cacheMap.clear();

Set cacheNames = new LinkedHashSet(caches.size());

for (Cache cache : caches) {

String name = cache.getName();

if(StringUtils.isEmpty(name)){

name = cache.getClass().getName() + DEFAULT_CACHE_NAME_SUFFIX;

}

this.cacheMap.put(name, cache);

cacheNames.add(name);

}

this.cacheNames = Collections.unmodifiableSet(cacheNames);

}

}

@Override

public Cache getCache(String name) {

Cache cache = cacheMap.get(name);

if(cache != null){

return cache;

}

return null;

}

protected abstract Collection extends Cache> loadCaches();

@Override

public Collection getCacheNames() {

return this.cacheNames;

}

@Override

public void destroy() throws Exception {

cacheMap.clear();

}

}

RedisCacheManager.java

public class RedisCacheManager extends AbstractCacheManager {

private RedisTemplate redisTemplate;

public RedisCacheManager(RedisTemplate redisTemplate) {

this.redisTemplate = redisTemplate;

}

@Override

protected Collection extends Cache> loadCaches() {

Collection> caches = new ArrayList<>();

RedisCache redisCache = new RedisCache<>(redisTemplate);

caches.add(redisCache);

return caches;

}

}

实现CacheInterceptor.java

/**

* 缓存数据过滤器, 缓存到redis数据中的数据是ServiceResult.getDateMap()数据

* 使用: 在service方法上添加com.chinaredstar.urms.annotations.Cacheable注解, 并指定RedisKeyEunm和cache key, cache key支持Spel表达式

* 以下情况不缓存数据:

* 1: 返回状态为fasle时, 不缓存数据

* 2: 返回dataMap为空时, 不缓存数据

* 3: 返回数据结构不是ServiceReslut实例时, 不缓存数据

*

* 当缓存问题时, 不影响正常业务, 但所有的请求都会打到DB上, 对DB有很大的冲击

*/

public class CacheInterceptor implements MethodInterceptor {

private static final Logger logger = LoggerFactory.getLogger(CacheInterceptor.class);

private static final ParameterNameDiscoverer parameterNameDiscoverer = new DefaultParameterNameDiscoverer();

private CacheManager cacheManager;

public void setCacheManager(CacheManager cacheManager) {

this.cacheManager = cacheManager;

}

@Override

public Object invoke(MethodInvocation methodInvocation) throws Throwable {

Method method = methodInvocation.getMethod();

Object[] args = methodInvocation.getArguments();

Cacheable cacheable = method.getAnnotation(Cacheable.class);

if (cacheable == null) {

return methodInvocation.proceed();

}

String key = parseCacheKey(method, args, cacheable.key());

logger.info(">>>>>>>> -- 获取缓存key : {}", key);

if(StringUtils.isEmpty(key)){

return methodInvocation.proceed();

}

RedisKey redisKey = cacheable.value();

Cache cache = cacheManager.getCache(RedisCache.DEFAULT_CACHE_NAME);

Object value = null;

try{

value = cache.get(redisKey.getKey(key));

} catch (Exception e){

logger.info(">>>>>>>> -- 从缓存中获取数据异常 : {}", ExceptionUtil.exceptionStackTrace(e));

}

if (value != null) {

logger.info(">>>>>>>> -- 从缓存中获取数据 : {}", jsonUtil.toJson(value));

return ServiceResult.newInstance(true, value);

}

value = methodInvocation.proceed();

logger.info(">>>>>>>> -- 从接口中获取数据 : {}", JsonUtil.toJson(value));

if ( value != null && value instanceof ServiceResult ) {

ServiceResult result = (ServiceResult) value;

if(!result.isSuccess() || result.getDataMap() == null){

return value;

}

try{

cache.put(redisKey.getKey(key), result.getDataMap(), redisKey.getTimeout(), redisKey.getTimeUnit());

} catch (Exception e){

logger.info(">>>>>>>> -- 将数据放入缓存异常 : {}", ExceptionUtil.exceptionStackTrace(e));

}

}

return value;

}

/**

* 使用SpeL解析缓存key

* @param method

* @param args

* @param expressionString

* @return

*/

private String parseCacheKey(Method method, Object[] args, String expressionString) {

String[] parameterNames = parameterNameDiscoverer.getParameterNames(method);

EvaluationContext context = new StandardEvaluationContext();

if (parameterNames != null && parameterNames.length > 0

&& args != null && args.length > 0

&& args.length == parameterNames.length ) {

for (int i = 0, length = parameterNames.length; i < length; i++) {

context.setVariable(parameterNames[i], args[i]);

}

}

ExpressionParser parser = new SpelExpressionParser();

Expression expression = parser.parseExpression(expressionString);

return (String) expression.getValue(context);

}

}

配置Spring.xml

测试使用

@Cacheable(value = RedisKey.TEST_CACHE, key = "#code + ':' + #user.id")

public ServiceResult test(String code, User user){

return new ServiceResult("success");

}

说明

Cacheable其中的参数key拼接的规则支持Spring SpeL表达式。其规则和Spring Cacheable使用方法一致。

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