Cache map interface and default implementation

Author: aschrijver

src/main/java/io/engagingspaces/vertx/dataloader/CacheMap.java

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+/*
+ * Copyright (c) 2016 The original author or authors
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * and Apache License v2.0 which accompanies this distribution.
+ *
+ *      The Eclipse Public License is available at
+ *      http://www.eclipse.org/legal/epl-v10.html
+ *
+ *      The Apache License v2.0 is available at
+ *      http://www.opensource.org/licenses/apache2.0.php
+ *
+ * You may elect to redistribute this code under either of these licenses.
+ */
+
+package io.engagingspaces.vertx.dataloader;
+
+import io.engagingspaces.vertx.dataloader.impl.DefaultCacheMap;
+
+/**
+ * Cache map interface for data loaders that use caching.
+ * <p>
+ * The default implementation used by the data loader is based on a {@link java.util.LinkedHashMap}. Note that the
+ * implementation could also have used a regular {@link java.util.Map} instead of this {@link CacheMap}, but
+ * this aligns better to the reference data loader implementation provided by Facebook
+ * <p>
+ * Also it doesn't require you to implement the full set of map overloads, just the required methods.
+ *
+ * @param <U> type parameter indicating the type of the cache keys
+ * @param <V> type parameter indicating the type of the data that is cached
+ *
+ * @author <a href="https://github.com/aschrijver/">Arnold Schrijver</a>
+ */
+public interface CacheMap<U, V> {
+
+    /**
+     * Creates a new cache map, using the default implementation that is based on a {@link java.util.LinkedHashMap}.
+     *
+     * @param <U> type parameter indicating the type of the cache keys
+     * @param <V> type parameter indicating the type of the data that is cached
+     * @return the cache map
+     */
+    static <U, V> CacheMap<U, V> simpleMap() {
+        return new DefaultCacheMap<>();
+    }
+
+    /**
+     * Checks whether the specified key is contained in the cach map.
+     *
+     * @param key the key to check
+     * @return {@code true} if the cache contains the key, {@code false} otherwise
+     */
+    boolean containsKey(U key);
+
+    /**
+     * Gets the specified key from the cache map.
+     * <p>
+     * May throw an exception if the key does not exists, depending on the cache map implementation that is used,
+     * so be sure to check {@link CacheMap#containsKey(Object)} first.
+     *
+     * @param key the key to retrieve
+     * @return the cached value, or {@code null} if not found (depends on cache implementation)
+     */
+    V get(U key);
+
+    /**
+     * Creates a new cache map entry with the specified key and value, or updates the value if the key already exists.
+     *
+     * @param key   the key to cache
+     * @param value the value to cache
+     * @return the cache map for fluent coding
+     */
+    CacheMap set(U key, V value);
+
+    /**
+     * Deletes the entry with the specified key from the cache map, if it exists.
+     *
+     * @param key the key to delete
+     * @return the cache map for fluent coding
+     */
+    CacheMap delete(U key);
+
+    /**
+     * Clears all entries of the cache map
+     *
+     * @return the cache map for fluent coding
+     */
+    CacheMap clear();
+}

src/main/java/io/engagingspaces/vertx/dataloader/impl/DefaultCacheMap.java

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+/*
+ * Copyright (c) 2016 The original author or authors
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * and Apache License v2.0 which accompanies this distribution.
+ *
+ *      The Eclipse Public License is available at
+ *      http://www.eclipse.org/legal/epl-v10.html
+ *
+ *      The Apache License v2.0 is available at
+ *      http://www.opensource.org/licenses/apache2.0.php
+ *
+ * You may elect to redistribute this code under either of these licenses.
+ */
+
+package io.engagingspaces.vertx.dataloader.impl;
+
+import io.engagingspaces.vertx.dataloader.CacheMap;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ *
+ * @param <K>
+ * @param <V>
+ *
+ * @author <a href="https://github.com/aschrijver/">Arnold Schrijver</a>
+ */
+public class DefaultCacheMap<K, V> implements CacheMap<K, V> {
+
+    private Map<K, V> cache;
+
+    /**
+     * Default constructor
+     */
+    public DefaultCacheMap() {
+        cache = new HashMap<>();
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public boolean containsKey(K key) {
+        return cache.containsKey(key);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public V get(K key) {
+        return cache.get(key);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public CacheMap set(K key, V value) {
+        cache.put(key, value);
+        return this;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public CacheMap delete(K key) {
+        cache.remove(key);
+        return this;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public CacheMap clear() {
+        cache.clear();
+        return this;
+    }
+}