Add GeodeLoggingApplicationListener registered with Spring Boot to handle backwards compatibility and existing logging configuration expressed with SDG.

User may configure logging using @ClientCacheApplication(logLevel = INFO), or by annotating their Spring application class with @EnableLogging(logLevel = INFO) or using 1 of SDG's logging configuration properties ['spring.data.gemfire.cache.log-level', 'spring.data.gemfire.logging.level'], therefore, SBDG makes a best attempt to honor those logging configuration settings.

Resolves gh-73.

spring-geode/src/main/java/org/springframework/geode/context/logging/GeodeLoggingApplicationListener.java

@@ -0,0 +1,129 @@
+/*
+ * Copyright 2019 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.geode.context.logging;
+
+import java.util.Arrays;
+import java.util.Properties;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent;
+import org.springframework.boot.context.logging.LoggingApplicationListener;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationEvent;
+import org.springframework.context.event.GenericApplicationListener;
+import org.springframework.core.Ordered;
+import org.springframework.core.ResolvableType;
+import org.springframework.core.env.Environment;
+import org.springframework.data.gemfire.config.annotation.EnableLogging;
+import org.springframework.lang.NonNull;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
+
+/**
+ * Spring {@link GenericApplicationListener} used to configure Apache Geode Logging from existing Spring Data
+ * for Apache Geode Logging configuration support, such as when using the {@link EnableLogging} annotation
+ * or alternatively using {@link Properties}.
+ *
+ * This listener must be ordered before the Spring Boot {@link LoggingApplicationListener}.
+ *
+ * @author John Blum
+ * @see java.util.Properties
+ * @see org.springframework.boot.SpringApplication
+ * @see org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent
+ * @see org.springframework.boot.context.logging.LoggingApplicationListener
+ * @see org.springframework.context.ApplicationContext
+ * @see org.springframework.context.ApplicationEvent
+ * @see org.springframework.context.event.GenericApplicationListener
+ * @see org.springframework.core.Ordered
+ * @see org.springframework.core.env.Environment
+ * @since 1.3.0
+ */
+public class GeodeLoggingApplicationListener implements GenericApplicationListener {
+
+	private static final Class<?>[] EVENT_TYPES = { ApplicationEnvironmentPreparedEvent.class };
+	private static final Class<?>[] SOURCE_TYPES = { ApplicationContext.class, SpringApplication.class };
+
+	public static final String SPRING_BOOT_DATA_GEMFIRE_LOG_LEVEL_PROPERTY = "spring.boot.data.gemfire.log.level";
+	public static final String SPRING_DATA_GEMFIRE_CACHE_LOG_LEVEL = "spring.data.gemfire.cache.log-level";
+	public static final String SPRING_DATA_GEMFIRE_LOGGING_LOG_LEVEL = "spring.data.gemfire.logging.level";
+
+	@Override
+	public int getOrder() {
+
+		return LoggingApplicationListener.DEFAULT_ORDER > Ordered.HIGHEST_PRECEDENCE
+			? LoggingApplicationListener.DEFAULT_ORDER - 1
+			: Ordered.HIGHEST_PRECEDENCE;
+	}
+
+	@Override
+	public void onApplicationEvent(@Nullable ApplicationEvent event) {
+
+		if (event instanceof ApplicationEnvironmentPreparedEvent) {
+
+			ApplicationEnvironmentPreparedEvent environmentPreparedEvent = (ApplicationEnvironmentPreparedEvent) event;
+
+			onApplicationEnvironmentPreparedEvent(environmentPreparedEvent);
+		}
+	}
+
+	protected void onApplicationEnvironmentPreparedEvent(
+			@NonNull ApplicationEnvironmentPreparedEvent environmentPreparedEvent) {
+
+		Assert.notNull(environmentPreparedEvent, "ApplicationEnvironmentPreparedEvent must not be null");
+
+		Environment environment = environmentPreparedEvent.getEnvironment();
+
+		if (isSystemPropertyNotSet(SPRING_BOOT_DATA_GEMFIRE_LOG_LEVEL_PROPERTY)) {
+
+			String logLevel = environment.getProperty(SPRING_BOOT_DATA_GEMFIRE_LOG_LEVEL_PROPERTY,
+				environment.getProperty(SPRING_DATA_GEMFIRE_LOGGING_LOG_LEVEL,
+				environment.getProperty(SPRING_DATA_GEMFIRE_CACHE_LOG_LEVEL)));
+
+			setSystemProperty(SPRING_BOOT_DATA_GEMFIRE_LOG_LEVEL_PROPERTY, logLevel);
+		}
+	}
+
+	protected boolean isSystemPropertySet(@Nullable String propertyName) {
+		return StringUtils.hasText(propertyName) && StringUtils.hasText(System.getProperty(propertyName));
+	}
+
+	protected boolean isSystemPropertyNotSet(@Nullable String propertyName) {
+		return !isSystemPropertySet(propertyName);
+	}
+
+	protected void setSystemProperty(@NonNull String propertyName, @Nullable String propertyValue) {
+
+		Assert.hasText(propertyName, () -> String.format("PropertyName [%s] is required", propertyName));
+
+		if (StringUtils.hasText(propertyValue)) {
+			System.setProperty(propertyName, propertyValue);
+		}
+	}
+
+	@Override
+	public boolean supportsEventType(@NonNull ResolvableType eventType) {
+
+		Class<?> rawType = eventType.getRawClass();
+
+		return rawType != null && Arrays.stream(EVENT_TYPES).anyMatch(it -> it.isAssignableFrom(rawType));
+	}
+
+	@Override
+	public boolean supportsSourceType(@Nullable Class<?> sourceType) {
+		return sourceType != null && Arrays.stream(SOURCE_TYPES).anyMatch(it -> it.isAssignableFrom(sourceType));
+	}
+}