Resolve placeholders in banner through Enviornment

see #1191

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

@@ -139,6 +139,7 @@ import org.springframework.web.context.support.StandardServletEnvironment;
  * @author Phillip Webb
  * @author Dave Syer
  * @author Andy Wilkinson
+ * @author Christian Dupuis
  * @see #run(Object, String[])
  * @see #run(Object[], String[])
  * @see #SpringApplication(Object...)
@@ -478,10 +479,11 @@ public class SpringApplication {
 		Resource resource = resourceLoader.getResource(location);
 		if (resource.exists()) {
 			try {
-				System.out.println(StreamUtils.copyToString(
+				String banner = StreamUtils.copyToString(
 						resource.getInputStream(),
 						environment.getProperty("banner.charset", Charset.class,
-								Charset.forName("UTF-8"))));
+								Charset.forName("UTF-8")));
+				System.out.println(environment.resolvePlaceholders(banner));
 				return;
 			}
 			catch (Exception ex) {

spring-boot/src/test/java/org/springframework/boot/SpringApplicationTests.java

@@ -83,6 +83,7 @@ import static org.mockito.Mockito.verify;
  * @author Phillip Webb
  * @author Dave Syer
  * @author Andy Wilkinson
+ * @author Christian Dupuis
  */
 public class SpringApplicationTests {
 
@@ -162,6 +163,15 @@ public class SpringApplicationTests {
 		verify(application, never()).printBanner();
 	}
 
+	@Test
+	public void customBannerWithProperties() throws Exception {
+		SpringApplication application = spy(new SpringApplication(ExampleConfig.class));
+		application.setWebEnvironment(false);
+		application.run("--banner.location=classpath:test-banner-with-placeholder.txt",
+				"--test.property=123456");
+		verify(application, never()).printBanner();
+	}
+
 	@Test
 	public void customId() throws Exception {
 		SpringApplication application = new SpringApplication(ExampleConfig.class);

spring-boot/src/test/resources/test-banner-with-placeholder.txt

@@ -0,0 +1,3 @@
+Running a Test!
+
+${test.property}