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

docs/src/main/asciidoc/spring-cloud-commons.adoc

@@ -1026,6 +1026,21 @@ public class MyConfiguration {
 
 include::spring-cloud-circuitbreaker.adoc[leveloffset=+1]
 
+== CachedRandomPropertySource
+
+Spring Cloud Context provides a `PropertySource` that caches random values based on a key.  Outside of the caching
+functionality it works the same as Spring Boot's https://github.com/spring-projects/spring-boot/blob/master/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/env/RandomValuePropertySource.java[`RandomValuePropertySource`].
+This random value might be useful in the case where you want a random value that is consistent even after the Spring Application
+context restarts.  The property value takes the form of `cachedrandom.[yourkey].[type]` where `yourkey` is the key in the cache.  The `type` value can
+be any type supported by Spring Boot's `RandomValuePropertySource`.
+
+====
+[source,properties,indent=0]
+----
+myrandom=${cachedrandom.appname.value}
+----
+====
+
 == Configuration Properties
 
 To see the list of all Spring Cloud Commons related configuration properties please check link:appendix.html[the Appendix page].

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

spring-cloud-context/src/test/java/org/springframework/cloud/context/refresh/ContextRefresherIntegrationTests.java

@@ -37,7 +37,7 @@
 
 @RunWith(SpringRunner.class)
 @SpringBootTest(classes = TestConfiguration.class,
-		properties = { "spring.datasource.hikari.read-only=false" })
+		properties = { "spring.datasource.hikari.read-only=false", "debug=true" })
 public class ContextRefresherIntegrationTests {
 
 	@Autowired
@@ -81,6 +81,17 @@ public void testUpdateHikari() throws Exception {
 		then(this.properties.getMessage()).isEqualTo("Hello scope!");
 	}
 
+	@Test
+	@DirtiesContext
+	public void testCachedRandom() {
+		long cachedRandomLong = properties.getCachedRandomLong();
+		long randomLong = properties.randomLong();
+		then(cachedRandomLong).isNotNull();
+		this.refresher.refresh();
+		then(randomLong).isNotEqualTo(properties.randomLong());
+		then(cachedRandomLong).isEqualTo(properties.cachedRandomLong);
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	@EnableConfigurationProperties(TestProperties.class)
 	@EnableAutoConfiguration
@@ -96,6 +107,10 @@ protected static class TestProperties {
 
 		private int delay;
 
+		private Long cachedRandomLong;
+
+		private Long randomLong;
+
 		@ManagedAttribute
 		public String getMessage() {
 			return this.message;
@@ -114,6 +129,22 @@ public void setDelay(int delay) {
 			this.delay = delay;
 		}
 
+		public long getCachedRandomLong() {
+			return cachedRandomLong;
+		}
+
+		public void setCachedRandomLong(long cachedRandomLong) {
+			this.cachedRandomLong = cachedRandomLong;
+		}
+
+		public long randomLong() {
+			return randomLong;
+		}
+
+		public void setRandomLong(long randomLong) {
+			this.randomLong = randomLong;
+		}
+
 	}
 
 }

spring-cloud-context/src/test/java/org/springframework/cloud/util/random/CachedRandomPropertySourceTests.java

@@ -0,0 +1,79 @@
+/*
+ * 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.HashMap;
+import java.util.Map;
+import java.util.function.Function;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+
+import org.springframework.boot.env.RandomValuePropertySource;
+import org.springframework.test.annotation.DirtiesContext;
+
+import static org.assertj.core.api.BDDAssertions.then;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.ArgumentMatchers.isA;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+/**
+ * @author Ryan Baxter
+ */
+@RunWith(MockitoJUnitRunner.class)
+@DirtiesContext
+public class CachedRandomPropertySourceTests {
+
+	@Mock
+	RandomValuePropertySource randomValuePropertySource;
+
+	@Before
+	public void setup() {
+
+		when(randomValuePropertySource.getProperty(eq("random.long")))
+				.thenReturn(new Long(1234));
+	}
+
+	@Test
+	public void getProperty() {
+		Map<String, Map<String, Object>> cache = new HashMap<>();
+		Map<String, Object> typeCache = new HashMap<>();
+		typeCache.put("long", new Long(5678));
+		Map<String, Object> spyedTypeCache = spy(typeCache);
+		cache.put("foo", spyedTypeCache);
+		Map<String, Map<String, Object>> spyedCache = spy(cache);
+
+		CachedRandomPropertySource cachedRandomPropertySource = new CachedRandomPropertySource(
+				randomValuePropertySource, spyedCache);
+		then(cachedRandomPropertySource.getProperty("foo.app.long")).isNull();
+		then(cachedRandomPropertySource.getProperty("cachedrandom.app")).isNull();
+
+		then(cachedRandomPropertySource.getProperty("cachedrandom.app.long"))
+				.isEqualTo(new Long(1234));
+		then(cachedRandomPropertySource.getProperty("cachedrandom.foo.long"))
+				.isEqualTo(new Long(5678));
+		verify(spyedCache, times(1)).computeIfAbsent(eq("app"), isA(Function.class));
+		verify(spyedTypeCache, times(1)).computeIfAbsent(eq("long"), isA(Function.class));
+	}
+
+}

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

@@ -1,7 +1,8 @@
 # Bootstrap components
 org.springframework.cloud.bootstrap.BootstrapConfiguration=\
 org.springframework.cloud.bootstrap.TestBootstrapConfiguration,\
-org.springframework.cloud.bootstrap.TestHigherPriorityBootstrapConfiguration
+org.springframework.cloud.bootstrap.TestHigherPriorityBootstrapConfiguration,\
+org.springframework.cloud.util.random.CachedRandomPropertySourceAutoConfiguration
 
 
 org.springframework.boot.env.EnvironmentPostProcessor=\

spring-cloud-context/src/test/resources/application.properties

@@ -1,5 +1,7 @@
 message:Hello scope!
 delay:0
+cachedRandomLong: ${cachedrandom.app.long}
+randomLong: ${random.long}
 debug:true
 #logging.level.org.springframework.web: DEBUG
 #logging.level.org.springframework.context.annotation: DEBUG