26. SpringBoot 初识缓存及 SimpleCacheConfiguration源码解析

1.引入一下starter:

web、cache、Mybatis、MySQL

@MapperScan("com.everjiankang.cache.dao")
@SpringBootApplication
@EnableCaching　　　　　　　//启用缓存
public class Springboot01CacheApplication {
    public static void main(String[] args) {
        SpringApplication.run(Springboot01CacheApplication.class, args);
    }
}

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    UserMapper userMapper;

/**
     * 将方法的运行结果进行缓存；以后再要相同的数据，直接从缓存中获取，不用调用方法；
     * CacheManager管理多个Cache组件的，对缓存的真正CRUD操作在Cache组件中，每一个缓存组件有自己唯一一个名字；
     *
     *
     * 原理：
     *   1、自动配置类；CacheAutoConfiguration
     *   2、缓存的配置类
     *   org.springframework.boot.autoconfigure.cache.GenericCacheConfiguration
     *   org.springframework.boot.autoconfigure.cache.JCacheCacheConfiguration
     *   org.springframework.boot.autoconfigure.cache.EhCacheCacheConfiguration
     *   org.springframework.boot.autoconfigure.cache.HazelcastCacheConfiguration
     *   org.springframework.boot.autoconfigure.cache.InfinispanCacheConfiguration
     *   org.springframework.boot.autoconfigure.cache.CouchbaseCacheConfiguration
     *   org.springframework.boot.autoconfigure.cache.RedisCacheConfiguration
     *   org.springframework.boot.autoconfigure.cache.CaffeineCacheConfiguration
     *   org.springframework.boot.autoconfigure.cache.GuavaCacheConfiguration
     *   org.springframework.boot.autoconfigure.cache.SimpleCacheConfiguration【默认】
     *   org.springframework.boot.autoconfigure.cache.NoOpCacheConfiguration
     *   3、哪个配置类默认生效：SimpleCacheConfiguration；
     *
     *   4、给容器中注册了一个CacheManager：ConcurrentMapCacheManager
     *   5、可以获取和创建ConcurrentMapCache类型的缓存组件；他的作用将数据保存在ConcurrentMap中；
     *
     *   运行流程：
     *   @Cacheable：
     *   1、方法运行之前，先去查询Cache（缓存组件），按照cacheNames指定的名字获取；
     *      （CacheManager先获取相应的缓存），第一次获取缓存如果没有Cache组件会自动创建。
     *   2、去Cache中查找缓存的内容，使用一个key，默认就是方法的参数；
     *      key是按照某种策略生成的；默认是使用keyGenerator生成的，默认使用SimpleKeyGenerator生成key；
     *          SimpleKeyGenerator生成key的默认策略；
     *                  如果没有参数；key=new SimpleKey()；
     *                  如果有一个参数：key=参数的值
     *                  如果有多个参数：key=new SimpleKey(params)；
     *   3、没有查到缓存就调用目标方法；
     *   4、将目标方法返回的结果，放进缓存中
     *
     *   @Cacheable标注的方法执行之前先来检查缓存中有没有这个数据，默认按照参数的值作为key去查询缓存，
     *   如果没有就运行方法并将结果放入缓存；以后再来调用就可以直接使用缓存中的数据；
     *
     *   核心：
     *      1）、使用CacheManager【ConcurrentMapCacheManager】按照名字得到Cache【ConcurrentMapCache】组件
     *      2）、key使用keyGenerator生成的，默认是SimpleKeyGenerator
     *
     *
     *   几个属性：
     *      cacheNames/value：指定缓存组件的名字;将方法的返回结果放在哪个缓存中，是数组的方式，可以指定多个缓存；
     *
     *      key：缓存数据使用的key；可以用它来指定。默认是使用方法参数的值  1-方法的返回值
     *              编写SpEL； #i d;参数id的值   #a0  #p0  #root.args[0]
     *              getEmp[2]
     *
     *      keyGenerator：key的生成器；可以自己指定key的生成器的组件id
     *              key/keyGenerator：二选一使用;
     *
     *
     *      cacheManager：指定缓存管理器；或者cacheResolver指定获取解析器
     *
     *      condition：指定符合条件的情况下才缓存；
     *              ,condition = "#id>0"
     *          condition = "#a0>1"：第一个参数的值》1的时候才进行缓存
     *
     *      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；可以获取到结果进行判断
     *              unless = "#result == null"
     *              unless = "#a0==2":如果第一个参数的值是2，结果不缓存；
     *      sync：是否使用异步模式
     * @param id
     * @return
     *
     */
    @Cacheable(cacheNames = {"user"})
    @Override
    public User selectByPrimaryKey(Integer id) {
        return userMapper.selectByPrimaryKey(id);
    }

}

package org.springframework.boot.autoconfigure.cache;

@Configuration
@ConditionalOnClass({CacheManager.class})
@ConditionalOnBean({CacheAspectSupport.class})
@ConditionalOnMissingBean(
    value = {CacheManager.class},
    name = {"cacheResolver"}
)
@EnableConfigurationProperties({CacheProperties.class})
@AutoConfigureAfter({CouchbaseAutoConfiguration.class, HazelcastAutoConfiguration.class, HibernateJpaAutoConfiguration.class, RedisAutoConfiguration.class})
@Import({CacheAutoConfiguration.CacheConfigurationImportSelector.class})
public class CacheAutoConfiguration {
    public CacheAutoConfiguration() {
    }

    @Bean
    @ConditionalOnMissingBean
    public CacheManagerCustomizers cacheManagerCustomizers(ObjectProvider<CacheManagerCustomizer<?>> customizers) {
        return new CacheManagerCustomizers((List)customizers.orderedStream().collect(Collectors.toList()));
    }

    @Bean
    public CacheAutoConfiguration.CacheManagerValidator cacheAutoConfigurationValidator(CacheProperties cacheProperties, ObjectProvider<CacheManager> cacheManager) {
        return new CacheAutoConfiguration.CacheManagerValidator(cacheProperties, cacheManager);
    }

    static class CacheConfigurationImportSelector implements ImportSelector {
        CacheConfigurationImportSelector() {
        }

　　　　　/**在Spring Boot项目启动的过程中，导入缓存的配置组件*/
        public String[] selectImports(AnnotationMetadata importingClassMetadata) {
            CacheType[] types = CacheType.values();
            String[] imports = new String[types.length];

            for(int i = 0; i < types.length; ++i) {
                imports[i] = CacheConfigurations.getConfigurationClass(types[i]);
            }
　　　　　　　　/** imports的值，缓存配置类
　　　　　　　　　　org.springframework.boot.autoconfigure.cache.GenericCacheConfiguration
　　　　　　　　　　org.springframework.boot.autoconfigure.cache.JCacheCacheConfiguration
　　　　　　　　　　org.springframework.boot.autoconfigure.cache.EhCacheCacheConfiguration
　　　　　　　　　　org.springframework.boot.autoconfigure.cache.HazelcastCacheConfiguration
　　　　　　　　　　org.springframework.boot.autoconfigure.cache.InfinispanCacheConfiguration

　　　　　　　　　　org.springframework.boot.autoconfigure.cache.CouchbaseCacheConfiguration
　　　　　　　　　　org.springframework.boot.autoconfigure.cache.RedisCacheConfiguration
　　　　　　　　　　org.springframework.boot.autoconfigure.cache.CaffeineCacheConfiguration
　　　　　　　　　　org.springframework.boot.autoconfigure.cache.SimpleCacheConfiguration
　　　　　　　　　　org.springframework.boot.autoconfigure.cache.NoOpCacheConfiguration
　　　　　　　　*/
　　　　　　　　return imports;
        }
    }

    static class CacheManagerValidator implements InitializingBean {
        private final CacheProperties cacheProperties;
        private final ObjectProvider<CacheManager> cacheManager;

        CacheManagerValidator(CacheProperties cacheProperties, ObjectProvider<CacheManager> cacheManager) {
            this.cacheProperties = cacheProperties;
            this.cacheManager = cacheManager;
        }

        public void afterPropertiesSet() {
            Assert.notNull(this.cacheManager.getIfAvailable(), () -> {
                return "No cache manager could be auto-configured, check your configuration (caching type is '" + this.cacheProperties.getType() + "')";
            });
        }
    }

    @Configuration
    @ConditionalOnClass({LocalContainerEntityManagerFactoryBean.class})
    @ConditionalOnBean({AbstractEntityManagerFactoryBean.class})
    protected static class CacheManagerJpaDependencyConfiguration extends EntityManagerFactoryDependsOnPostProcessor {
        public CacheManagerJpaDependencyConfiguration() {
            super(new String[]{"cacheManager"});
        }
    }
}

 在配置文件中加入

　　debug=true

然后启动项目,控制台关于缓存的启动log如下：

   SimpleCacheConfiguration matched:
      - Cache org.springframework.boot.autoconfigure.cache.SimpleCacheConfiguration automatic cache type (CacheCondition)
      - @ConditionalOnMissingBean (types: org.springframework.cache.CacheManager; SearchStrategy: all) did not find any beans (OnBeanCondition)

 　CaffeineCacheConfiguration:
      Did not match:
         - @ConditionalOnClass did not find required class 'com.github.benmanes.caffeine.cache.Caffeine' (OnClassCondition)

   CouchbaseCacheConfiguration:
      Did not match:
         - @ConditionalOnClass did not find required classes 'com.couchbase.client.java.Bucket', 'com.couchbase.client.spring.cache.CouchbaseCacheManager' (OnClassCondition)


   EhCacheCacheConfiguration:
      Did not match:
         - @ConditionalOnClass did not find required class 'net.sf.ehcache.Cache' (OnClassCondition)

   GenericCacheConfiguration:
      Did not match:
         - @ConditionalOnBean (types: org.springframework.cache.Cache; SearchStrategy: all) did not find any beans of type org.springframework.cache.Cache (OnBeanCondition)
      Matched:
         - Cache org.springframework.boot.autoconfigure.cache.GenericCacheConfiguration automatic cache type (CacheCondition)


   HazelcastCacheConfiguration:
      Did not match:
         - @ConditionalOnClass did not find required classes 'com.hazelcast.core.HazelcastInstance', 'com.hazelcast.spring.cache.HazelcastCacheManager' (OnClassCondition)


   InfinispanCacheConfiguration:
      Did not match:
         - @ConditionalOnClass did not find required class 'org.infinispan.spring.provider.SpringEmbeddedCacheManager' (OnClassCondition)


   JCacheCacheConfiguration:
      Did not match:
         - @ConditionalOnClass did not find required class 'javax.cache.Caching' (OnClassCondition)


   NoOpCacheConfiguration:
      Did not match:
         - @ConditionalOnMissingBean (types: org.springframework.cache.CacheManager; SearchStrategy: all) 
　　　　　　　　　　found beans of type 'org.springframework.cache.CacheManager' cacheManager (OnBeanCondition)
      Matched:
         - Cache org.springframework.boot.autoconfigure.cache.NoOpCacheConfiguration automatic cache type (CacheCondition)


   RedisCacheConfiguration:
      Did not match:
         - @ConditionalOnClass did not find required class 'org.springframework.data.redis.connection.RedisConnectionFactory' (OnClassCondition)

 

@Configuration
@ConditionalOnMissingBean({CacheManager.class})
@Conditional({CacheCondition.class})
class SimpleCacheConfiguration {
    private final CacheProperties cacheProperties;
    private final CacheManagerCustomizers customizerInvoker;

    SimpleCacheConfiguration(CacheProperties cacheProperties, CacheManagerCustomizers customizerInvoker) {
        this.cacheProperties = cacheProperties;
        this.customizerInvoker = customizerInvoker;
    }

    @Bean
    public ConcurrentMapCacheManager cacheManager() {
        ConcurrentMapCacheManager cacheManager = new ConcurrentMapCacheManager();
        List<String> cacheNames = this.cacheProperties.getCacheNames();
        if (!cacheNames.isEmpty()) {
            cacheManager.setCacheNames(cacheNames);
        }

        return (ConcurrentMapCacheManager)this.customizerInvoker.customize(cacheManager);
    }
}

package org.springframework.cache;

import java.util.Collection;
import org.springframework.lang.Nullable;

public interface CacheManager {
    @Nullable
    Cache getCache(String var1);

    Collection<String> getCacheNames();
}

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package org.springframework.cache.concurrent;

public class ConcurrentMapCacheManager implements CacheManager, BeanClassLoaderAware {
    private final ConcurrentMap<String, Cache> cacheMap = new ConcurrentHashMap(16);
    private boolean dynamic = true;
    private boolean allowNullValues = true;
    private boolean storeByValue = false;
    @Nullable
    private SerializationDelegate serialization;

    public ConcurrentMapCacheManager() {
    }

    public ConcurrentMapCacheManager(String... cacheNames) {
        this.setCacheNames(Arrays.asList(cacheNames));
    }

    public void setCacheNames(@Nullable Collection<String> cacheNames) {
        if (cacheNames != null) {
            Iterator var2 = cacheNames.iterator();

            while(var2.hasNext()) {
                String name = (String)var2.next();
                this.cacheMap.put(name, this.createConcurrentMapCache(name));
            }

            this.dynamic = false;
        } else {
            this.dynamic = true;
        }

    }

    public void setAllowNullValues(boolean allowNullValues) {
        if (allowNullValues != this.allowNullValues) {
            this.allowNullValues = allowNullValues;
            this.recreateCaches();
        }

    }

    public boolean isAllowNullValues() {
        return this.allowNullValues;
    }

    public void setStoreByValue(boolean storeByValue) {
        if (storeByValue != this.storeByValue) {
            this.storeByValue = storeByValue;
            this.recreateCaches();
        }

    }

    public boolean isStoreByValue() {
        return this.storeByValue;
    }

    public void setBeanClassLoader(ClassLoader classLoader) {
        this.serialization = new SerializationDelegate(classLoader);
        if (this.isStoreByValue()) {
            this.recreateCaches();
        }

    }

    public Collection<String> getCacheNames() {
        return Collections.unmodifiableSet(this.cacheMap.keySet());
    }

    @Nullable
    public Cache getCache(String name) {
        Cache cache = (Cache)this.cacheMap.get(name);
        if (cache == null && this.dynamic) {
            ConcurrentMap var3 = this.cacheMap;
            synchronized(this.cacheMap) {
                cache = (Cache)this.cacheMap.get(name);
                if (cache == null) {
                    cache = this.createConcurrentMapCache(name);
                    this.cacheMap.put(name, cache);
                }
            }
        }

        return cache;
    }

    private void recreateCaches() {
        Iterator var1 = this.cacheMap.entrySet().iterator();

        while(var1.hasNext()) {
            Entry<String, Cache> entry = (Entry)var1.next();
            entry.setValue(this.createConcurrentMapCache((String)entry.getKey()));
        }

    }

    protected Cache createConcurrentMapCache(String name) {
        SerializationDelegate actualSerialization = this.isStoreByValue() ? this.serialization : null;
        return new ConcurrentMapCache(name, new ConcurrentHashMap(256), this.isAllowNullValues(), actualSerialization);
    }
}

package org.springframework.cache.concurrent;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.function.Function;
import org.springframework.cache.Cache.ValueRetrievalException;
import org.springframework.cache.Cache.ValueWrapper;
import org.springframework.cache.support.AbstractValueAdaptingCache;
import org.springframework.core.serializer.support.SerializationDelegate;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

public class ConcurrentMapCache extends AbstractValueAdaptingCache {
    private final String name;
    private final ConcurrentMap<Object, Object> store;  //真正存数据的地方
    @Nullable
    private final SerializationDelegate serialization;

    public ConcurrentMapCache(String name) {
        this(name, new ConcurrentHashMap(256), true);
    }

    public ConcurrentMapCache(String name, boolean allowNullValues) {
        this(name, new ConcurrentHashMap(256), allowNullValues);
    }

    public ConcurrentMapCache(String name, ConcurrentMap<Object, Object> store, boolean allowNullValues) {
        this(name, store, allowNullValues, (SerializationDelegate)null);
    }

    protected ConcurrentMapCache(String name, ConcurrentMap<Object, Object> store, boolean allowNullValues, @Nullable SerializationDelegate serialization) {
        super(allowNullValues);
        Assert.notNull(name, "Name must not be null");
        Assert.notNull(store, "Store must not be null");
        this.name = name;
        this.store = store;
        this.serialization = serialization;
    }

    public final boolean isStoreByValue() {
        return this.serialization != null;
    }

    public final String getName() {
        return this.name;
    }

    public final ConcurrentMap<Object, Object> getNativeCache() {
        return this.store;
    }

    @Nullable
    protected Object lookup(Object key) {
        return this.store.get(key);
    }

    @Nullable
    public <T> T get(Object key, Callable<T> valueLoader) {
        return this.fromStoreValue(this.store.computeIfAbsent(key, (r) -> {
            try {
                return this.toStoreValue(valueLoader.call());
            } catch (Throwable var5) {
                throw new ValueRetrievalException(key, valueLoader, var5);
            }
        }));
    }

    public void put(Object key, @Nullable Object value) {
        this.store.put(key, this.toStoreValue(value));
    }

    @Nullable
    public ValueWrapper putIfAbsent(Object key, @Nullable Object value) {
        Object existing = this.store.putIfAbsent(key, this.toStoreValue(value));
        return this.toValueWrapper(existing);
    }

    public void evict(Object key) {
        this.store.remove(key);
    }

    public void clear() {
        this.store.clear();
    }

    protected Object toStoreValue(@Nullable Object userValue) {
        Object storeValue = super.toStoreValue(userValue);
        if (this.serialization != null) {
            try {
                return this.serializeValue(this.serialization, storeValue);
            } catch (Throwable var4) {
                throw new IllegalArgumentException("Failed to serialize cache value '" + userValue + "'. Does it implement Serializable?", var4);
            }
        } else {
            return storeValue;
        }
    }

    private Object serializeValue(SerializationDelegate serialization, Object storeValue) throws IOException {
        ByteArrayOutputStream out = new ByteArrayOutputStream();

        byte[] var4;
        try {
            serialization.serialize(storeValue, out);
            var4 = out.toByteArray();
        } finally {
            out.close();
        }

        return var4;
    }

    protected Object fromStoreValue(@Nullable Object storeValue) {
        if (storeValue != null && this.serialization != null) {
            try {
                return super.fromStoreValue(this.deserializeValue(this.serialization, storeValue));
            } catch (Throwable var3) {
                throw new IllegalArgumentException("Failed to deserialize cache value '" + storeValue + "'", var3);
            }
        } else {
            return super.fromStoreValue(storeValue);
        }
    }

    private Object deserializeValue(SerializationDelegate serialization, Object storeValue) throws IOException {
        ByteArrayInputStream in = new ByteArrayInputStream((byte[])((byte[])storeValue));

        Object var4;
        try {
            var4 = serialization.deserialize(in);
        } finally {
            in.close();
        }

        return var4;
    }
}

package org.springframework.cache.interceptor;

public abstract class CacheAspectSupport extends AbstractCacheInvoker implements BeanFactoryAware, InitializingBean, SmartInitializingSingleton {
    @Nullable
    private Object execute(CacheOperationInvoker invoker, Method method, CacheAspectSupport.CacheOperationContexts contexts) {
        if (contexts.isSynchronized()) {
            CacheAspectSupport.CacheOperationContext context = (CacheAspectSupport.CacheOperationContext)contexts.get(CacheableOperation.class).iterator().next();
            if (this.isConditionPassing(context, CacheOperationExpressionEvaluator.NO_RESULT)) {
                Object key = this.generateKey(context, CacheOperationExpressionEvaluator.NO_RESULT);
                Cache cache = (Cache)context.getCaches().iterator().next();

                try {
                    return this.wrapCacheValue(method, cache.get(key, () -> {
                        return this.unwrapReturnValue(this.invokeOperation(invoker));
                    }));
                } catch (ValueRetrievalException var10) {
                    throw (ThrowableWrapper)var10.getCause();
                }
            } else {
                return this.invokeOperation(invoker);
            }
        } else {
            this.processCacheEvicts(contexts.get(CacheEvictOperation.class), true, CacheOperationExpressionEvaluator.NO_RESULT);
            ValueWrapper cacheHit = this.findCachedItem(contexts.get(CacheableOperation.class));
            List<CacheAspectSupport.CachePutRequest> cachePutRequests = new LinkedList();
            if (cacheHit == null) {
                this.collectPutRequests(contexts.get(CacheableOperation.class), CacheOperationExpressionEvaluator.NO_RESULT, cachePutRequests);
            }

            Object cacheValue;
            Object returnValue;
            if (cacheHit != null && !this.hasCachePut(contexts)) {
                cacheValue = cacheHit.get();
                returnValue = this.wrapCacheValue(method, cacheValue);
            } else {
                returnValue = this.invokeOperation(invoker);
                cacheValue = this.unwrapReturnValue(returnValue);
            }

            this.collectPutRequests(contexts.get(CachePutOperation.class), cacheValue, cachePutRequests);
            Iterator var8 = cachePutRequests.iterator();

            while(var8.hasNext()) {
                CacheAspectSupport.CachePutRequest cachePutRequest = (CacheAspectSupport.CachePutRequest)var8.next();
                cachePutRequest.apply(cacheValue);
            }

            this.processCacheEvicts(contexts.get(CacheEvictOperation.class), false, cacheValue);
            return returnValue;
        }
    }


private void performCacheEvict(CacheAspectSupport.CacheOperationContext context, CacheEvictOperation operation, @Nullable Object result) {
        Object key = null;
        Iterator var5 = context.getCaches().iterator();

        while(var5.hasNext()) {
            Cache cache = (Cache)var5.next();
            if (operation.isCacheWide()) {
                this.logInvalidating(context, operation, (Object)null);
                this.doClear(cache);
            } else {
                if (key == null) {
                    key = this.generateKey(context, result);
                }

                this.logInvalidating(context, operation, key);
                this.doEvict(cache, key);
            }
        }

    }


}

Key生成策略

package org.springframework.cache.interceptor;

import java.lang.reflect.Method;

public class SimpleKeyGenerator implements KeyGenerator {
    public SimpleKeyGenerator() {
    }

    public Object generate(Object target, Method method, Object... params) {
        return generateKey(params);
    }

    public static Object generateKey(Object... params) {
        if (params.length == 0) {
            return SimpleKey.EMPTY;
        } else {
            if (params.length == 1) {
                Object param = params[0];
                if (param != null && !param.getClass().isArray()) {
                    return param;
                }
            }

            return new SimpleKey(params);
        }
    }
}