缓存声明

Bamboo2022年6月8日

编程语言
Spring

java
缓存
Spring Framework

大约 6 分钟

对于缓存声明，Spring的缓存抽象提供了一组Java注解：

@Cacheable：缓存的增加。
@CacheEvict: 缓存的删除。
@CachePut：在不干扰方法执行的情况下更新缓存。
@Caching：重新组合多个缓存操作以应用于一个方法。
@CacheConfig：在类级别共享一些常见的缓存相关设置。
@EnableCaching：启用缓存。

@Cacheable

@Cacheable是一个注解，用于标记一个方法是否可以被缓存,将结果缓存到指定的缓存中，以便以后可以直接从缓存中获取。在调用方法前，Spring会检查缓存中是否存在相应的结果，如果存在，则直接返回缓存中的结果，否则调用方法并将结果缓存到指定的缓存中。

Cacheable包含以下属性：

cacheNames/value ：用来指定缓存组件的名字
key ：缓存数据时使用的 key，可以用它来指定。默认是使用方法参数的值。（这个 key 你可以使用 spEL 表达式来编写）
keyGenerator ：key 的生成器。 key 和 keyGenerator 二选一使用
cacheManager ：可以用来指定缓存管理器。从哪个缓存管理器里面获取缓存。
condition ：可以用来指定符合条件的情况下才缓存
unless ：否定缓存。当 unless 指定的条件为 true ，方法的返回值就不会被缓存。当然你也可以获取到结果进行判断。（通过 #result 获取方法结果）
sync ：是否使用异步模式。

cacheNames/value

用来指定缓存的缓存组件的名称，可以指定一个或多个缓存组件，支持数组方式。

提示

方法调用前，Spring会依次检查缓存组件中是否存在相应的缓存，如果存在，则不再调用方法，而是直接从缓存中获取结果返回。

不包含该值的所有其他缓存也会更新，即使缓存的方法实际上并未被调用。

public interface SpringCacheService {
    @Cacheable(value = {"books","books1"}, key = "#id")
     Integer getCake(Integer id);
}

key

缓存数据时使用的 key。默认使用的是方法参数的值。可以使用 spEL 表达式去编写。

keyGenerator

key 的生成器。key 和 keyGenerator 二选一使用。

cacheManager

可以用来指定缓存管理器。从哪个缓存管理器里面获取缓存。

condition

可以用来指定符合条件的情况下才缓存。

unless

否定缓存。当 unless 指定的条件为 true ，方法的返回值就不会被缓存。当然你也可以获取到结果进行判断。（通过 #result 获取方法结果）

sync

是否使用异步模式。

@CacheEvict

@CachePut

@Caching

@CacheConfig

@EnableCaching

Cacheable.java

/*
 * 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;

}

缓存声明

# @Cacheable

# cacheNames/value

# key

# keyGenerator

# cacheManager

# condition

# unless

# sync

# @CacheEvict

# @CachePut

# @Caching

# @CacheConfig

# @EnableCaching