Add a property source that produces a random value that is cached (#719)

* Add a property source that produces a random value that is cached.

spring-cloud-context/src/main/java/org/springframework/cloud/util/random/CachedRandomPropertySource.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright 2012-2020 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.cloud.util.random;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.springframework.boot.env.RandomValuePropertySource;
+import org.springframework.core.env.PropertySource;
+import org.springframework.util.StringUtils;
+
+/**
+ * @author Ryan Baxter
+ */
+public class CachedRandomPropertySource
+		extends PropertySource<RandomValuePropertySource> {
+
+	private static final String NAME = "cachedrandom";
+
+	private static final String PREFIX = NAME + ".";
+
+	private static Map<String, Map<String, Object>> cache = new ConcurrentHashMap<>();
+
+	public CachedRandomPropertySource(
+			RandomValuePropertySource randomValuePropertySource) {
+		super(NAME, randomValuePropertySource);
+
+	}
+
+	CachedRandomPropertySource(RandomValuePropertySource randomValuePropertySource,
+			Map<String, Map<String, Object>> cache) {
+		super(NAME, randomValuePropertySource);
+		this.cache = cache;
+	}
+
+	@Override
+	public Object getProperty(String name) {
+		if (!name.startsWith(PREFIX) || name.length() == PREFIX.length()) {
+			return null;
+		}
+		else {
+			if (logger.isTraceEnabled()) {
+				logger.trace("Generating random property for '" + name + "'");
+			}
+			// TO avoid any weirdness from the type or key including a "." we look for the
+			// last "." and substring everything instead of splitting on the "."
+			String keyAndType = name.substring(PREFIX.length());
+			int lastIndexOfDot = keyAndType.lastIndexOf(".");
+			if (lastIndexOfDot < 0) {
+				return null;
+			}
+			String key = keyAndType.substring(0, lastIndexOfDot);
+			String type = keyAndType.substring(lastIndexOfDot + 1);
+			if (StringUtils.hasText(key) && StringUtils.hasText(type)) {
+				return getRandom(type, key);
+			}
+			else {
+				return null;
+			}
+		}
+	}
+
+	private Object getRandom(String type, String key) {
+		Map<String, Object> randomValueCache = getCacheForKey(key);
+		if (logger.isDebugEnabled()) {
+			logger.debug("Looking in random cache for key " + key + " with type " + type);
+		}
+		return randomValueCache.computeIfAbsent(type, (theType) -> {
+			if (logger.isDebugEnabled()) {
+				logger.debug(
+						"No random value found in cache for key and value, generating a new value");
+			}
+			return getSource().getProperty("random." + type);
+		});
+	}
+
+	private Map<String, Object> getCacheForKey(String key) {
+		if (logger.isDebugEnabled()) {
+			logger.debug("Looking in random cache for key: " + key);
+		}
+		return cache.computeIfAbsent(key, theKey -> {
+			if (logger.isDebugEnabled()) {
+				logger.debug("No cached value found for key: " + key);
+			}
+			return new ConcurrentHashMap<>();
+		});
+	}
+
+	public static void clearCache() {
+		if (cache != null) {
+			cache.clear();
+		}
+	}
+
+}

spring-cloud-context/src/main/java/org/springframework/cloud/util/random/CachedRandomPropertySourceAutoConfiguration.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2012-2020 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.cloud.util.random;
+
+import javax.annotation.PostConstruct;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.env.RandomValuePropertySource;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.env.MutablePropertySources;
+import org.springframework.core.env.PropertySource;
+
+/**
+ * @author Ryan Baxter
+ */
+@Configuration(proxyBeanMethods = false)
+public class CachedRandomPropertySourceAutoConfiguration {
+
+	@Autowired
+	ConfigurableEnvironment environment;
+
+	@PostConstruct
+	public void initialize() {
+		MutablePropertySources propertySources = environment.getPropertySources();
+		PropertySource propertySource = propertySources
+				.get(RandomValuePropertySource.RANDOM_PROPERTY_SOURCE_NAME);
+		if (propertySource != null) {
+			propertySources.addLast(new CachedRandomPropertySource(
+					RandomValuePropertySource.class.cast(propertySource)));
+		}
+	}
+
+}

spring-cloud-context/src/main/resources/META-INF/spring.factories

@@ -15,4 +15,5 @@ org.springframework.cloud.bootstrap.BootstrapConfiguration=\
 org.springframework.cloud.bootstrap.config.PropertySourceBootstrapConfiguration,\
 org.springframework.cloud.bootstrap.encrypt.EncryptionBootstrapConfiguration,\
 org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration,\
-org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration
+org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration,\
+org.springframework.cloud.util.random.CachedRandomPropertySourceAutoConfiguration