Add SpringApplicationInitializer strategy

Add SpringApplicationInitializer that can be used to initialize a
SpringApplication before it runs. An ApplicationContextInitializer
can optionally implement this interface.

spring-bootstrap/src/main/java/org/springframework/bootstrap/SpringApplication.java

@@ -235,6 +235,7 @@ public class SpringApplication {
 	 * @return a running {@link ApplicationContext}
 	 */
 	public ApplicationContext run(String... args) {
+		applySpringApplicationInitializers();
 		if (this.showBanner) {
 			printBanner();
 		}
@@ -253,6 +254,14 @@ public class SpringApplication {
 		return context;
 	}
 
+	private void applySpringApplicationInitializers() {
+		for (ApplicationContextInitializer<?> initializer : this.initializers) {
+			if (initializer instanceof SpringApplicationInitializer) {
+				((SpringApplicationInitializer) initializer).initialize(this);
+			}
+		}
+	}
+
 	/**
 	 * Print a simple banner message to the console. Subclasses can override this method
 	 * to provide additional or alternative banners.

spring-bootstrap/src/main/java/org/springframework/bootstrap/SpringApplicationInitializer.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2012-2013 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.bootstrap;
+
+/**
+ * Strategy interface that can be used to initialize a {@link SpringApplication} before it
+ * is run.
+ * 
+ * @author Phillip Webb
+ */
+public interface SpringApplicationInitializer {
+
+	/**
+	 * Initialize the applcation
+	 * @param springApplication the spring application.
+	 */
+	void initialize(SpringApplication springApplication);
+
+}