Java tutorial
/* * Copyright 2002-2016 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * https://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.springframework.cache.annotation; import java.lang.annotation.Documented; import java.lang.annotation.ElementType; import java.lang.annotation.Inherited; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; import java.util.concurrent.Callable; import org.springframework.core.annotation.AliasFor; /** * Annotation indicating that the result of invoking a method (or all methods * in a class) can be cached. * * <p>Each time an advised method is invoked, caching behavior will be applied, * checking whether the method has been already invoked for the given arguments. * A sensible default simply uses the method parameters to compute the key, but * a SpEL expression can be provided via the {@link #key} attribute, or a custom * {@link org.springframework.cache.interceptor.KeyGenerator} implementation can * replace the default one (see {@link #keyGenerator}). * * <p>If no value is found in the cache for the computed key, the target method * will be invoked and the returned value stored in the associated cache. Note * that Java8's {@code Optional} return types are automatically handled and its * content is stored in the cache if present. * * <p>This annotation may be used as a <em>meta-annotation</em> to create custom * <em>composed annotations</em> with attribute overrides. * * @author Costin Leau * @author Phillip Webb * @author Stephane Nicoll * @author Sam Brannen * @since 3.1 * @see CacheConfig */ @Target({ ElementType.TYPE, ElementType.METHOD }) @Retention(RetentionPolicy.RUNTIME) @Inherited @Documented public @interface Cacheable { /** * Alias for {@link #cacheNames}. */ @AliasFor("cacheNames") String[] value() default {}; /** * Names of the caches in which method invocation results are stored. * <p>Names may be used to determine the target cache (or caches), matching * the qualifier value or bean name of a specific bean definition. * @since 4.2 * @see #value * @see CacheConfig#cacheNames */ @AliasFor("value") String[] cacheNames() default {}; /** * Spring Expression Language (SpEL) expression for computing the key dynamically. * <p>Default is {@code ""}, meaning all method parameters are considered as a key, * unless a custom {@link #keyGenerator} has been configured. * <p>The SpEL expression evaluates against a dedicated context that provides the * following meta-data: * <ul> * <li>{@code #root.method}, {@code #root.target}, and {@code #root.caches} for * references to the {@link java.lang.reflect.Method method}, target object, and * affected cache(s) respectively.</li> * <li>Shortcuts for the method name ({@code #root.methodName}) and target class * ({@code #root.targetClass}) are also available. * <li>Method arguments can be accessed by index. For instance the second argument * can be accessed via {@code #root.args[1]}, {@code #p1} or {@code #a1}. Arguments * can also be accessed by name if that information is available.</li> * </ul> */ String key() default ""; /** * The bean name of the custom {@link org.springframework.cache.interceptor.KeyGenerator} * to use. * <p>Mutually exclusive with the {@link #key} attribute. * @see CacheConfig#keyGenerator */ String keyGenerator() default ""; /** * The bean name of the custom {@link org.springframework.cache.CacheManager} to use to * create a default {@link org.springframework.cache.interceptor.CacheResolver} if none * is set already. * <p>Mutually exclusive with the {@link #cacheResolver} attribute. * @see org.springframework.cache.interceptor.SimpleCacheResolver * @see CacheConfig#cacheManager */ String cacheManager() default ""; /** * The bean name of the custom {@link org.springframework.cache.interceptor.CacheResolver} * to use. * @see CacheConfig#cacheResolver */ String cacheResolver() default ""; /** * Spring Expression Language (SpEL) expression used for making the method * caching conditional. * <p>Default is {@code ""}, meaning the method result is always cached. * <p>The SpEL expression evaluates against a dedicated context that provides the * following meta-data: * <ul> * <li>{@code #root.method}, {@code #root.target}, and {@code #root.caches} for * references to the {@link java.lang.reflect.Method method}, target object, and * affected cache(s) respectively.</li> * <li>Shortcuts for the method name ({@code #root.methodName}) and target class * ({@code #root.targetClass}) are also available. * <li>Method arguments can be accessed by index. For instance the second argument * can be accessed via {@code #root.args[1]}, {@code #p1} or {@code #a1}. Arguments * can also be accessed by name if that information is available.</li> * </ul> */ String condition() default ""; /** * Spring Expression Language (SpEL) expression used to veto method caching. * <p>Unlike {@link #condition}, this expression is evaluated after the method * has been called and can therefore refer to the {@code result}. * <p>Default is {@code ""}, meaning that caching is never vetoed. * <p>The SpEL expression evaluates against a dedicated context that provides the * following meta-data: * <ul> * <li>{@code #result} for a reference to the result of the method invocation. For * supported wrappers such as {@code Optional}, {@code #result} refers to the actual * object, not the wrapper</li> * <li>{@code #root.method}, {@code #root.target}, and {@code #root.caches} for * references to the {@link java.lang.reflect.Method method}, target object, and * affected cache(s) respectively.</li> * <li>Shortcuts for the method name ({@code #root.methodName}) and target class * ({@code #root.targetClass}) are also available. * <li>Method arguments can be accessed by index. For instance the second argument * can be accessed via {@code #root.args[1]}, {@code #p1} or {@code #a1}. Arguments * can also be accessed by name if that information is available.</li> * </ul> * @since 3.2 */ String unless() default ""; /** * Synchronize the invocation of the underlying method if several threads are * attempting to load a value for the same key. The synchronization leads to * a couple of limitations: * <ol> * <li>{@link #unless()} is not supported</li> * <li>Only one cache may be specified</li> * <li>No other cache-related operation can be combined</li> * </ol> * This is effectively a hint and the actual cache provider that you are * using may not support it in a synchronized fashion. Check your provider * documentation for more details on the actual semantics. * @since 4.3 * @see org.springframework.cache.Cache#get(Object, Callable) */ boolean sync() default false; }