Extract ConcurrentLruCache for reuse in NamedParameterJdbcTemplate

Closes gh-24197

spring-core/src/main/java/org/springframework/util/ConcurrentLruCache.java

@@ -0,0 +1,143 @@
+/*
+ * Copyright 2002-2020 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.util;
+
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentLinkedDeque;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.function.Function;
+
+/**
+ * Simple LRU (Least Recently Used) cache, bounded by a specified cache limit.
+ *
+ * <p>This implementation is backed by a {@code ConcurrentHashMap} for storing
+ * the cached values and a {@code ConcurrentLinkedDeque} for ordering the keys
+ * and choosing the least recently used key when the cache is at full capacity.
+ *
+ * @author Brian Clozel
+ * @author Juergen Hoeller
+ * @since 5.3
+ * @param <K> the type of the key used for cache retrieval
+ * @param <V> the type of the cached values
+ * @see #get
+ */
+public class ConcurrentLruCache<K, V> {
+
+	private final int sizeLimit;
+
+	private final Function<K, V> generator;
+
+	private final ConcurrentHashMap<K, V> cache = new ConcurrentHashMap<>();
+
+	private final ConcurrentLinkedDeque<K> queue = new ConcurrentLinkedDeque<>();
+
+	private final ReadWriteLock lock = new ReentrantReadWriteLock();
+
+	private volatile int size;
+
+
+	/**
+	 * Create a new cache instance with the given limit and generator function.
+	 * @param sizeLimit the maximum number of entries in the cache
+	 * (0 indicates no caching, always generating a new value)
+	 * @param generator a function to generate a new value for a given key
+	 */
+	public ConcurrentLruCache(int sizeLimit, Function<K, V> generator) {
+		Assert.isTrue(sizeLimit >= 0, "Cache size limit must not be negative");
+		Assert.notNull(generator, "Generator function must not be null");
+		this.sizeLimit = sizeLimit;
+		this.generator = generator;
+	}
+
+
+	/**
+	 * Retrieve an entry from the cache, potentially triggering generation
+	 * of the value.
+	 * @param key the key to retrieve the entry for
+	 * @return the cached or newly generated value
+	 */
+	public V get(K key) {
+		if (this.sizeLimit == 0) {
+			return this.generator.apply(key);
+		}
+
+		V cached = this.cache.get(key);
+		if (cached != null) {
+			if (this.size < this.sizeLimit) {
+				return cached;
+			}
+			this.lock.readLock().lock();
+			try {
+				if (this.queue.removeLastOccurrence(key)) {
+					this.queue.offer(key);
+				}
+				return cached;
+			}
+			finally {
+				this.lock.readLock().unlock();
+			}
+		}
+
+		this.lock.writeLock().lock();
+		try {
+			// Retrying in case of concurrent reads on the same key
+			cached = this.cache.get(key);
+			if (cached != null) {
+				if (this.queue.removeLastOccurrence(key)) {
+					this.queue.offer(key);
+				}
+				return cached;
+			}
+			// Generate value first, to prevent size inconsistency
+			V value = this.generator.apply(key);
+			int cacheSize = this.size;
+			if (cacheSize == this.sizeLimit) {
+				K leastUsed = this.queue.poll();
+				if (leastUsed != null) {
+					this.cache.remove(leastUsed);
+					cacheSize--;
+				}
+			}
+			this.queue.offer(key);
+			this.cache.put(key, value);
+			this.size = cacheSize + 1;
+			return value;
+		}
+		finally {
+			this.lock.writeLock().unlock();
+		}
+	}
+
+	/**
+	 * Return the current size of the cache.
+	 * @see #sizeLimit()
+	 */
+	public int size() {
+		return this.size;
+	}
+
+	/**
+	 * Return the the maximum number of entries in the cache
+	 * (0 indicates no caching, always generating a new value).
+	 * @see #size()
+	 */
+	public int sizeLimit() {
+		return this.sizeLimit;
+	}
+
+}

spring-core/src/main/java/org/springframework/util/MimeTypeUtils.java

@@ -28,11 +28,6 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Random;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentLinkedDeque;
-import java.util.concurrent.locks.ReadWriteLock;
-import java.util.concurrent.locks.ReentrantReadWriteLock;
-import java.util.function.Function;
 import java.util.stream.Collectors;
 
 import org.springframework.lang.Nullable;
@@ -406,84 +401,4 @@ public abstract class MimeTypeUtils {
 		return new String(generateMultipartBoundary(), StandardCharsets.US_ASCII);
 	}
 
-
-	/**
-	 * Simple Least Recently Used cache, bounded by the maximum size given
-	 * to the class constructor.
-	 * <p>This implementation is backed by a {@code ConcurrentHashMap} for storing
-	 * the cached values and a {@code ConcurrentLinkedQueue} for ordering the keys
-	 * and choosing the least recently used key when the cache is at full capacity.
-	 * @param <K> the type of the key used for caching
-	 * @param <V> the type of the cached values
-	 */
-	private static class ConcurrentLruCache<K, V> {
-
-		private final int maxSize;
-
-		private final ConcurrentLinkedDeque<K> queue = new ConcurrentLinkedDeque<>();
-
-		private final ConcurrentHashMap<K, V> cache = new ConcurrentHashMap<>();
-
-		private final ReadWriteLock lock;
-
-		private final Function<K, V> generator;
-
-		private volatile int size;
-
-		public ConcurrentLruCache(int maxSize, Function<K, V> generator) {
-			Assert.isTrue(maxSize > 0, "LRU max size should be positive");
-			Assert.notNull(generator, "Generator function should not be null");
-			this.maxSize = maxSize;
-			this.generator = generator;
-			this.lock = new ReentrantReadWriteLock();
-		}
-
-		public V get(K key) {
-			V cached = this.cache.get(key);
-			if (cached != null) {
-				if (this.size < this.maxSize) {
-					return cached;
-				}
-				this.lock.readLock().lock();
-				try {
-					if (this.queue.removeLastOccurrence(key)) {
-						this.queue.offer(key);
-					}
-					return cached;
-				}
-				finally {
-					this.lock.readLock().unlock();
-				}
-			}
-			this.lock.writeLock().lock();
-			try {
-				// Retrying in case of concurrent reads on the same key
-				cached = this.cache.get(key);
-				if (cached  != null) {
-					if (this.queue.removeLastOccurrence(key)) {
-						this.queue.offer(key);
-					}
-					return cached;
-				}
-				// Generate value first, to prevent size inconsistency
-				V value = this.generator.apply(key);
-				int cacheSize = this.size;
-				if (cacheSize == this.maxSize) {
-					K leastUsed = this.queue.poll();
-					if (leastUsed != null) {
-						this.cache.remove(leastUsed);
-						cacheSize--;
-					}
-				}
-				this.queue.offer(key);
-				this.cache.put(key, value);
-				this.size = cacheSize + 1;
-				return value;
-			}
-			finally {
-				this.lock.writeLock().unlock();
-			}
-		}
-	}
-
 }

spring-jdbc/src/main/java/org/springframework/jdbc/core/namedparam/NamedParameterJdbcTemplate.java

@@ -18,7 +18,6 @@ package org.springframework.jdbc.core.namedparam;
 
 import java.sql.PreparedStatement;
 import java.sql.SQLException;
-import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.function.Consumer;
@@ -45,6 +44,7 @@ import org.springframework.jdbc.support.KeyHolder;
 import org.springframework.jdbc.support.rowset.SqlRowSet;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ConcurrentLruCache;
 
 /**
  * Template class with a basic set of JDBC operations, allowing the use
@@ -76,17 +76,9 @@ public class NamedParameterJdbcTemplate implements NamedParameterJdbcOperations
 	/** The JdbcTemplate we are wrapping. */
 	private final JdbcOperations classicJdbcTemplate;
 
-	private volatile int cacheLimit = DEFAULT_CACHE_LIMIT;
-
 	/** Cache of original SQL String to ParsedSql representation. */
-	@SuppressWarnings("serial")
+	private volatile ConcurrentLruCache<String, ParsedSql> parsedSqlCache =
-	private final Map<String, ParsedSql> parsedSqlCache =
+			new ConcurrentLruCache<>(DEFAULT_CACHE_LIMIT, NamedParameterUtils::parseSqlStatement);
-			new LinkedHashMap<String, ParsedSql>(DEFAULT_CACHE_LIMIT, 0.75f, true) {
-				@Override
-				protected boolean removeEldestEntry(Map.Entry<String, ParsedSql> eldest) {
-					return size() > getCacheLimit();
-				}
-			};
 
 
 	/**
@@ -133,17 +125,17 @@ public class NamedParameterJdbcTemplate implements NamedParameterJdbcOperations
 
 	/**
 	 * Specify the maximum number of entries for this template's SQL cache.
-	 * Default is 256.
+	 * Default is 256. 0 indicates no caching, always parsing each statement.
 	 */
 	public void setCacheLimit(int cacheLimit) {
-		this.cacheLimit = cacheLimit;
+		this.parsedSqlCache = new ConcurrentLruCache<>(cacheLimit, NamedParameterUtils::parseSqlStatement);
 	}
 
 	/**
 	 * Return the maximum number of entries for this template's SQL cache.
 	 */
 	public int getCacheLimit() {
-		return this.cacheLimit;
+		return this.parsedSqlCache.sizeLimit();
 	}
 
 
@@ -441,12 +433,7 @@ public class NamedParameterJdbcTemplate implements NamedParameterJdbcOperations
 	 * @return a representation of the parsed SQL statement
 	 */
 	protected ParsedSql getParsedSql(String sql) {
-		if (getCacheLimit() <= 0) {
+		return this.parsedSqlCache.get(sql);
-			return NamedParameterUtils.parseSqlStatement(sql);
-		}
-		synchronized (this.parsedSqlCache) {
-			return this.parsedSqlCache.computeIfAbsent(sql, NamedParameterUtils::parseSqlStatement);
-		}
 	}
 
 	/**