Add RestartScope and Restart attributes

Add a "restart" Spring `Scope` that remains between application
restarts. Allows beans such as the livereload server to remain active
during restarts and not disconnect clients.

See gh-3085

spring-boot-developer-tools/src/main/java/org/springframework/boot/developertools/restart/RestartScope.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2012-2015 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
+ *
+ *      http://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.boot.developertools.restart;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.springframework.context.annotation.Scope;
+
+/**
+ * Restart {@code @Scope} Annotation used to indicate that a bean shoul remain beteen
+ * restarts.
+ *
+ * @author Phillip Webb
+ * @since 1.3.0
+ * @see RestartScopeInitializer
+ */
+@Target({ ElementType.TYPE, ElementType.METHOD })
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+@Scope("restart")
+public @interface RestartScope {
+
+}

spring-boot-developer-tools/src/main/java/org/springframework/boot/developertools/restart/RestartScopeInitializer.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2012-2015 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
+ *
+ *      http://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.boot.developertools.restart;
+
+import org.springframework.beans.factory.ObjectFactory;
+import org.springframework.beans.factory.config.Scope;
+import org.springframework.context.ApplicationContextInitializer;
+import org.springframework.context.ConfigurableApplicationContext;
+
+/**
+ * Support for a 'restart' {@link Scope} that allows beans to remain between restarts.
+ *
+ * @author Phillip Webb
+ * @since 1.3.0
+ */
+public class RestartScopeInitializer implements
+		ApplicationContextInitializer<ConfigurableApplicationContext> {
+
+	@Override
+	public void initialize(ConfigurableApplicationContext applicationContext) {
+		applicationContext.getBeanFactory().registerScope("restart", new RestartScope());
+	}
+
+	/**
+	 * {@link Scope} that stores beans as {@link Restarter} attributes.
+	 */
+	private static class RestartScope implements Scope {
+
+		@Override
+		public Object get(String name, ObjectFactory<?> objectFactory) {
+			return Restarter.getInstance().getOrAddAttribute(name, objectFactory);
+		}
+
+		@Override
+		public Object remove(String name) {
+			return Restarter.getInstance().removeAttribute(name);
+		}
+
+		@Override
+		public void registerDestructionCallback(String name, Runnable callback) {
+		}
+
+		@Override
+		public Object resolveContextualObject(String key) {
+			return null;
+		}
+
+		@Override
+		public String getConversationId() {
+			return null;
+		}
+	}
+
+}

spring-boot-developer-tools/src/main/java/org/springframework/boot/developertools/restart/Restarter.java

@@ -22,6 +22,7 @@ import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 import java.net.URL;
 import java.util.Arrays;
+import java.util.HashMap;
 import java.util.IdentityHashMap;
 import java.util.Iterator;
 import java.util.LinkedList;
@@ -38,6 +39,7 @@ import java.util.concurrent.locks.ReentrantLock;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.springframework.beans.CachedIntrospectionResults;
+import org.springframework.beans.factory.ObjectFactory;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.developertools.restart.classloader.RestartClassLoader;
 import org.springframework.boot.logging.DeferredLog;
@@ -89,6 +91,8 @@ public class Restarter {
 
 	private final UncaughtExceptionHandler exceptionHandler;
 
+	private final Map<String, Object> attributes = new HashMap<String, Object>();
+
 	private final BlockingDeque<LeakSafeThread> leakSafeThreads = new LinkedBlockingDeque<LeakSafeThread>();
 
 	private boolean finished = false;
@@ -344,6 +348,22 @@ public class Restarter {
 		}
 	}
 
+	public Object getOrAddAttribute(final String name,
+			final ObjectFactory<?> objectFactory) {
+		synchronized (this.attributes) {
+			if (!this.attributes.containsKey(name)) {
+				this.attributes.put(name, objectFactory.getObject());
+			}
+			return this.attributes.get(name);
+		}
+	}
+
+	public Object removeAttribute(String name) {
+		synchronized (this.attributes) {
+			return this.attributes.remove(name);
+		}
+	}
+
 	/**
 	 * Return the initial set of URLs as configured by the {@link RestartInitializer}.
 	 * @return the initial URLs or {@code null}

spring-boot-developer-tools/src/main/resources/META-INF/spring.factories

@@ -1,3 +1,7 @@
+# Application Initializers
+org.springframework.context.ApplicationContextInitializer=\
+org.springframework.boot.developertools.restart.RestartScopeInitializer
+
 # Application Listeners
 org.springframework.context.ApplicationListener=\
 org.springframework.boot.developertools.restart.RestartApplicationListener