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本文主要研究一下dubbo的CacheFilter
CacheFilter
dubbo-2.7.2/dubbo-filter/dubbo-filter-cache/src/main/java/org/apache/dubbo/cache/filter/CacheFilter.java
@Activate(group = {CONSUMER, PROVIDER}, value = CACHE_KEY)public class CacheFilter implements Filter { private CacheFactory cacheFactory; /** * Dubbo will populate and set the cache factory instance based on service/method/consumer/provider configured * cache attribute value. Dubbo will search for the class name implementing configured <b>cache</b> in file org.apache.dubbo.cache.CacheFactory * under META-INF sub folders. * * @param cacheFactory instance of CacheFactory based on <b>cache</b> type */ public void setCacheFactory(CacheFactory cacheFactory) { this.cacheFactory = cacheFactory; } /** * If cache is configured, dubbo will invoke method on each method call. If cache value is returned by cache store * then it will return otherwise call the remote method and return value. If remote method's return valeu has error * then it will not cache the value. * @param invoker service * @param invocation invocation. * @return Cache returned value if found by the underlying cache store. If cache miss it will call target method. * @throws RpcException */ @Override public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException { if (cacheFactory != null && ConfigUtils.isNotEmpty(invoker.getUrl().getMethodParameter(invocation.getMethodName(), CACHE_KEY))) { Cache cache = cacheFactory.getCache(invoker.getUrl(), invocation); if (cache != null) { String key = StringUtils.toArgumentString(invocation.getArguments()); Object value = cache.get(key); if (value != null) { if (value instanceof ValueWrapper) { return AsyncRpcResult.newDefaultAsyncResult(((ValueWrapper) value).get(), invocation); } else { return AsyncRpcResult.newDefaultAsyncResult(value, invocation); } } Result result = invoker.invoke(invocation); if (!result.hasException()) { cache.put(key, new ValueWrapper(result.getValue())); } return result; } } return invoker.invoke(invocation); } /** * Cache value wrapper. */ static class ValueWrapper implements Serializable { private static final long serialVersionUID = -1777337318019193256L; private final Object value; public ValueWrapper (Object value) { this.value = value; } public Object get() { return this.value; } }}- CacheFilter实现了Filter接口，它的invoke方法会先判断cacheFactory是否不为null且invoker的URL中包含cache参数，如果该条件成立则从cacheFactory获取cache，然后在从cache中获取value，如果value不为null则返回AsyncRpcResult.newDefaultAsyncResult，如果value为null则执行invoke成功之后将该value缓存到cache中
实例
dubbo-2.7.2/dubbo-filter/dubbo-filter-cache/src/test/java/org/apache/dubbo/cache/filter/CacheFilterTest.java
public class CacheFilterTest { private RpcInvocation invocation; private CacheFilter cacheFilter = new CacheFilter(); private Invoker<?> invoker = mock(Invoker.class); private Invoker<?> invoker1 = mock(Invoker.class); private Invoker<?> invoker2 = mock(Invoker.class); private Invoker<?> invoker3 = mock(Invoker.class); private Invoker<?> invoker4 = mock(Invoker.class); static Stream<Arguments> cacheFactories() { return Stream.of( Arguments.of("lru", new LruCacheFactory()), Arguments.of("jcache", new JCacheFactory()), Arguments.of("threadlocal", new ThreadLocalCacheFactory()), Arguments.of("expiring", new ExpiringCacheFactory()) ); } public void setUp(String cacheType, CacheFactory cacheFactory) { invocation = new RpcInvocation(); cacheFilter.setCacheFactory(cacheFactory); URL url = URL.valueOf("test://test:11/test?cache=" + cacheType); given(invoker.invoke(invocation)).willReturn(AsyncRpcResult.newDefaultAsyncResult("value", invocation)); given(invoker.getUrl()).willReturn(url); given(invoker1.invoke(invocation)).willReturn(AsyncRpcResult.newDefaultAsyncResult("value1", invocation)); given(invoker1.getUrl()).willReturn(url); given(invoker2.invoke(invocation)).willReturn(AsyncRpcResult.newDefaultAsyncResult("value2", invocation)); given(invoker2.getUrl()).willReturn(url); given(invoker3.invoke(invocation)).willReturn(AsyncRpcResult.newDefaultAsyncResult(new RuntimeException(), invocation)); given(invoker3.getUrl()).willReturn(url); given(invoker4.invoke(invocation)).willReturn(AsyncRpcResult.newDefaultAsyncResult(invocation)); given(invoker4.getUrl()).willReturn(url); } @ParameterizedTest @MethodSource("cacheFactories") public void testNonArgsMethod(String cacheType, CacheFactory cacheFactory) { setUp(cacheType, cacheFactory); invocation.setMethodName("echo"); invocation.setParameterTypes(new Class<?>[]{}); invocation.setArguments(new Object[]{}); cacheFilter.invoke(invoker, invocation); Result rpcResult1 = cacheFilter.invoke(invoker1, invocation); Result rpcResult2 = cacheFilter.invoke(invoker2, invocation); Assertions.assertEquals(rpcResult1.getValue(), rpcResult2.getValue()); Assertions.assertEquals(rpcResult1.getValue(), "value"); } @ParameterizedTest @MethodSource("cacheFactories") public void testMethodWithArgs(String cacheType, CacheFactory cacheFactory) { setUp(cacheType, cacheFactory); invocation.setMethodName("echo1"); invocation.setParameterTypes(new Class<?>[]{String.class}); invocation.setArguments(new Object[]{"arg1"}); cacheFilter.invoke(invoker, invocation); Result rpcResult1 = cacheFilter.invoke(invoker1, invocation); Result rpcResult2 = cacheFilter.invoke(invoker2, invocation); Assertions.assertEquals(rpcResult1.getValue(), rpcResult2.getValue()); Assertions.assertEquals(rpcResult1.getValue(), "value"); } @ParameterizedTest @MethodSource("cacheFactories") public void testException(String cacheType, CacheFactory cacheFactory) { setUp(cacheType, cacheFactory); invocation.setMethodName("echo1"); invocation.setParameterTypes(new Class<?>[]{String.class}); invocation.setArguments(new Object[]{"arg2"}); cacheFilter.invoke(invoker3, invocation); Result rpcResult = cacheFilter.invoke(invoker2, invocation); Assertions.assertEquals(rpcResult.getValue(), "value2"); } @ParameterizedTest @MethodSource("cacheFactories") public void testNull(String cacheType, CacheFactory cacheFactory) { setUp(cacheType, cacheFactory); invocation.setMethodName("echo1"); invocation.setParameterTypes(new Class<?>[]{String.class}); invocation.setArguments(new Object[]{"arg3"}); cacheFilter.invoke(invoker4, invocation); Result result1 = cacheFilter.invoke(invoker1, invocation); Result result2 = cacheFilter.invoke(invoker2, invocation); Assertions.assertEquals(result1.getValue(), null); Assertions.assertEquals(result2.getValue(), null); }}- 这里分别验证了无参方法、带参数方法、抛异常的方法、value为null的场景
小结
CacheFilter实现了Filter接口，它的invoke方法会先判断cacheFactory是否不为null且invoker的URL中包含cache参数，如果该条件成立则从cacheFactory获取cache，然后在从cache中获取value，如果value不为null则返回AsyncRpcResult.newDefaultAsyncResult，如果value为null则执行invoke成功之后将该value缓存到cache中
doc
- CacheFilter