ehcache cacheLoaderWriter 使用

ゝ一纸荒年。 2022-10-20 12:15 132阅读 0赞

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### ehcache cacheLoaderWriter 使用 ###

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**简介**

**cache-aside pattern**

**读操作：**先读取缓存，如果缓存里面没有数据，再读取后端数据，将数据返回并放入缓存中

**写操作：**数据同时写入后端数据库与缓存

#读操作
    v = cache.get(k)
    if (v == null) {
      v = sor.get(k)
      cache.put(k, v)
    }
    
    #写操作
    v = newV
    sor.put(k, v)
    cache.put(k, v)

**cache-as-sor pattern**

**read-through：**缓存里面如果有数据，直接返回；如果没有数据，调用方法从后端获取数据返回，并将其缓存，下次获取同一个数据，如果缓存里面的数据没有过期或者删除，直接从缓存里面返回数据

**write-through：**缓存调用写方法**同步写入后端数据库**

**write-behind：**缓存调用写方法**异步写入后端数据库**

**ehcache同时支持以上两种模式，cache-as-sor模式通过cacheloaderwriter实现**

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**相关类与接口**

**CacheLoaderWriter**

public interface CacheLoaderWriter<K, V> {
        V load(K var1) throws Exception;              //read-through
    
        default Map<K, V> loadAll(Iterable<? extends K> keys) throws BulkCacheLoadingException, Exception {
            Map<K, V> entries = new HashMap();
            Iterator var3 = keys.iterator();
    
            while(var3.hasNext()) {
                K k = var3.next();
                entries.put(k, this.load(k));
            }
    
            return entries;
        }
    
        void write(K var1, V var2) throws Exception;  //write-through
    
        default void writeAll(Iterable<? extends Entry<? extends K, ? extends V>> entries) throws BulkCacheWritingException, Exception {
            Iterator var2 = entries.iterator();
    
            while(var2.hasNext()) {
                Entry<? extends K, ? extends V> entry = (Entry)var2.next();
                this.write(entry.getKey(), entry.getValue());
            }
    
        }
    
        void delete(K var1) throws Exception;
    
        default void deleteAll(Iterable<? extends K> keys) throws BulkCacheWritingException, Exception {
            Iterator var2 = keys.iterator();
    
            while(var2.hasNext()) {
                K k = var2.next();
                this.delete(k);
            }
    
        }
    }

**WriteBehindConfiguration**

public interface WriteBehindConfiguration<R> extends ServiceConfiguration<WriteBehindProvider, R> {
    
        int getConcurrency();
        int getMaxQueueSize();
        String getThreadPoolAlias();
    
    
        WriteBehindConfiguration.BatchingConfiguration getBatchingConfiguration();
    
        public interface BatchingConfiguration {
    
            int getBatchSize();
    
            long getMaxDelay();
            TimeUnit getMaxDelayUnit();
    
            boolean isCoalescing();
        }
    }

**WriteBehindConfigurationBuilder**

public abstract class WriteBehindConfigurationBuilder implements Builder<WriteBehindConfiguration<?>> {
        protected int concurrency;        //并行度
        protected int queueSize;          //队列长度
        protected String threadPoolAlias; //writebehind使用的线程池
    
        private WriteBehindConfigurationBuilder() {
            this.concurrency = 1;
            this.queueSize = 2147483647;
            this.threadPoolAlias = null;
        }
    
        private WriteBehindConfigurationBuilder(WriteBehindConfigurationBuilder other) {
            this.concurrency = 1;
            this.queueSize = 2147483647;
            this.threadPoolAlias = null;
            this.concurrency = other.concurrency;
            this.queueSize = other.queueSize;
            this.threadPoolAlias = other.threadPoolAlias;
        }
    
        public static WriteBehindConfigurationBuilder.BatchedWriteBehindConfigurationBuilder newBatchedWriteBehindConfiguration(long maxDelay, TimeUnit maxDelayUnit, int batchSize) {
            return new WriteBehindConfigurationBuilder.BatchedWriteBehindConfigurationBuilder(maxDelay, maxDelayUnit, batchSize);
        }
    
        public static WriteBehindConfigurationBuilder.UnBatchedWriteBehindConfigurationBuilder newUnBatchedWriteBehindConfiguration() {
            return new WriteBehindConfigurationBuilder.UnBatchedWriteBehindConfigurationBuilder();
        }
    
        WriteBehindConfiguration<?> buildWith(BatchingConfiguration batching) {
            return new DefaultWriteBehindConfiguration(this.threadPoolAlias, this.concurrency, this.queueSize, batching);
        }
    
        public abstract WriteBehindConfigurationBuilder queueSize(int var1);
    
        public abstract WriteBehindConfigurationBuilder concurrencyLevel(int var1);
    
        public abstract WriteBehindConfigurationBuilder useThreadPool(String var1);
    
    
    ************
    内部类：UnBatchedWriteBehindConfigurationBuilder
    
        public static class UnBatchedWriteBehindConfigurationBuilder extends WriteBehindConfigurationBuilder {
                            //非批处理
    
            private UnBatchedWriteBehindConfigurationBuilder() {
            private UnBatchedWriteBehindConfigurationBuilder(WriteBehindConfigurationBuilder.UnBatchedWriteBehindConfigurationBuilder other) {
    
    
            public WriteBehindConfigurationBuilder.UnBatchedWriteBehindConfigurationBuilder queueSize(int size) {
            public WriteBehindConfigurationBuilder.UnBatchedWriteBehindConfigurationBuilder concurrencyLevel(int concurrency) {
            public WriteBehindConfigurationBuilder.UnBatchedWriteBehindConfigurationBuilder useThreadPool(String alias) {
    
            public WriteBehindConfiguration<?> build() {
    
    
    ************
    内部类：BatchedWriteBehindConfigurationBuilder
    
        public static final class BatchedWriteBehindConfigurationBuilder extends WriteBehindConfigurationBuilder {
            private TimeUnit maxDelayUnit;
            private long maxDelay;       //写入key的最大延时
            private int batchSize;       //批处理数量
            private boolean coalescing;  //设为true，每个批次中相同的key若有多个，最新设置的key到达后端，其余不设置
    
            private BatchedWriteBehindConfigurationBuilder(long maxDelay, TimeUnit maxDelayUnit, int batchSize) {
            private BatchedWriteBehindConfigurationBuilder(WriteBehindConfigurationBuilder.BatchedWriteBehindConfigurationBuilder other) {
    
    
            public WriteBehindConfigurationBuilder.BatchedWriteBehindConfigurationBuilder enableCoalescing() {
            public WriteBehindConfigurationBuilder.BatchedWriteBehindConfigurationBuilder disableCoalescing() {
    
            public WriteBehindConfigurationBuilder.BatchedWriteBehindConfigurationBuilder batchSize(int batchSize) {
            private void setBatchSize(int batchSize) throws IllegalArgumentException {
    
            public WriteBehindConfigurationBuilder.BatchedWriteBehindConfigurationBuilder maxWriteDelay(long maxDelay, TimeUnit maxDelayUnit) {
                WriteBehindConfigurationBuilder.BatchedWriteBehindConfigurationBuilder otherBuilder = new WriteBehindConfigurationBuilder.BatchedWriteBehindConfigurationBuilder(this);
            private void setMaxWriteDelay(long maxDelay, TimeUnit maxDelayUnit) throws IllegalArgumentException {
    
            public WriteBehindConfigurationBuilder.BatchedWriteBehindConfigurationBuilder queueSize(int size) {
            public WriteBehindConfigurationBuilder.BatchedWriteBehindConfigurationBuilder concurrencyLevel(int concurrency) {
            public WriteBehindConfigurationBuilder.BatchedWriteBehindConfigurationBuilder useThreadPool(String alias) {
    
            public WriteBehindConfiguration<?> build() {

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**示例**

class CustomCacheLoaderWriter implements CacheLoaderWriter<String,String>{
    
        private static Map<String,String> map=new HashMap<>();
    
        static {
            map.put("1","瓜田李下 1");
            map.put("2","瓜田李下 2");
            map.put("3","瓜田李下 3");
            map.put("4","瓜田李下 4");
            map.put("5","瓜田李下 5");
            map.put("6","瓜田李下 6");
        }
    
        @Override
        public String load(String s) throws Exception {
            return map.getOrDefault(s, "null");
        }
    
        @Override
        public void write(String s, String s2) throws Exception {
            map.put(s,s2);
        }
    
        @Override
        public void delete(String s) throws Exception {
            map.remove(s);
        }
    }
    
    public class Test4 {
    
        public static void main(String[] args){
            CacheManager cacheManager= CacheManagerBuilder.newCacheManagerBuilder()
                    .using(PooledExecutionServiceConfigurationBuilder.newPooledExecutionServiceConfigurationBuilder()
                            .defaultPool("default",5,10)
                            .pool("pool",2,6)
                            .build())
                    .withDefaultWriteBehindThreadPool("pool")
                    .withCache("custom", CacheConfigurationBuilder.newCacheConfigurationBuilder(String.class,String.class,
                            ResourcePoolsBuilder.newResourcePoolsBuilder().heap(10, MemoryUnit.MB).build())
                            .withLoaderWriter(new CustomCacheLoaderWriter())
                            .withService(WriteBehindConfigurationBuilder
                                    .newBatchedWriteBehindConfiguration(10, TimeUnit.SECONDS,3)
                                    .queueSize(4)
                                    .concurrencyLevel(2)
                                    .enableCoalescing()
                                    .build()
                            ).build()
                    ).build(true);
    
            Cache<String,String> cache=cacheManager.getCache("custom",String.class,String.class);
            System.out.println(cache.get("1"));
    
            cache.put("11","22");
            System.out.println(cache.get("11"));
    
            cacheManager.close();
        }
    }

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**控制台输出**

22:48:53.985 [main] DEBUG org.ehcache.core.spi.ServiceLocator - Starting 17 Services...
    22:48:54.000 [main] DEBUG org.ehcache.core.internal.statistics.DefaultStatisticsService - Starting service
    22:48:54.000 [main] DEBUG org.ehcache.core.spi.ServiceLocator - All Services successfully started, 17 Services in 15ms
    22:48:54.000 [main] DEBUG org.ehcache.core.EhcacheManager - Creating Cache 'custom' in EhcacheManager.
    22:48:54.016 [main] DEBUG org.ehcache.impl.internal.spi.serialization.DefaultSerializationProvider - Serializer for <java.lang.String> : org.ehcache.impl.serialization.StringSerializer@365185bd
    22:48:54.016 [main] DEBUG org.ehcache.impl.internal.spi.serialization.DefaultSerializationProvider - Serializer for <java.lang.String> : org.ehcache.impl.serialization.StringSerializer@782663d3
    22:48:54.032 [main] DEBUG org.ehcache.impl.internal.spi.copy.DefaultCopyProvider - Copier for <java.lang.String> : org.ehcache.impl.copy.IdentityCopier@71623278
    22:48:54.032 [main] DEBUG org.ehcache.impl.internal.spi.copy.DefaultCopyProvider - Copier for <java.lang.String> : org.ehcache.impl.copy.IdentityCopier@768b970c
    22:48:54.047 [main] INFO org.ehcache.sizeof.filters.AnnotationSizeOfFilter - Using regular expression provided through VM argument org.ehcache.sizeof.filters.AnnotationSizeOfFilter.pattern for IgnoreSizeOf annotation : ^.*cache\..*IgnoreSizeOf$
    22:48:54.175 [main] INFO org.ehcache.sizeof.impl.JvmInformation - Detected JVM data model settings of: 64-Bit HotSpot JVM with Compressed OOPs
    22:48:54.227 [main] INFO org.ehcache.sizeof.impl.AgentLoader - Failed to attach to VM and load the agent: class java.io.IOException: Can not attach to current VM
    22:48:54.290 [main] DEBUG org.ehcache.impl.internal.store.heap.OnHeapStore - No expiration strategy detected
    22:48:54.352 [main] DEBUG class org.ehcache.core.Ehcache-custom - Initialize successful.
    22:48:54.352 [main] INFO org.ehcache.core.EhcacheManager - Cache 'custom' created in EhcacheManager.
    22:48:54.352 [main] DEBUG org.ehcache.core.internal.statistics.DefaultStatisticsService - Moving from UNINITIALIZED to AVAILABLE
    22:48:54.352 [main] DEBUG org.ehcache.core.internal.statistics.DefaultStatisticsService - Cache added custom
    22:48:54.368 [main] DEBUG org.ehcache.core.EhcacheManager - Initialize successful.
    22:48:54.368 [main] DEBUG org.ehcache.sizeof.filters.AnnotationSizeOfFilter - org.ehcache.sizeof.annotations.IgnoreSizeOf matched IgnoreSizeOf annotation pattern ^.*cache\..*IgnoreSizeOf$
    瓜田李下 1
    22