Honour existing java.awt.headless configuration

Previously, SpringApplication would set the java.awt.headless system
property even if it had already been set. This commit updates
SpringApplication to honour any existing configuration when setting
the property.

Fixes #1189

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

@@ -77,38 +77,38 @@ import org.springframework.web.context.support.StandardServletEnvironment;
  * Classes that can be used to bootstrap and launch a Spring application from a Java main
  * method. By default class will perform the following steps to bootstrap your
  * application:
- * 
+ *
  * <ul>
  * <li>Create an appropriate {@link ApplicationContext} instance (depending on your
  * classpath)</li>
- * 
+ *
  * <li>Register a {@link CommandLinePropertySource} to expose command line arguments as
  * Spring properties</li>
- * 
+ *
  * <li>Refresh the application context, loading all singleton beans</li>
- * 
+ *
  * <li>Trigger any {@link CommandLineRunner} beans</li>
  * </ul>
- * 
+ *
  * In most circumstances the static {@link #run(Object, String[])} method can be called
  * directly from your {@literal main} method to bootstrap your application:
- * 
+ *
  * <pre class="code">
  * &#064;Configuration
  * &#064;EnableAutoConfiguration
  * public class MyApplication  {
- * 
+ *
  * // ... Bean definitions
- * 
+ *
  * public static void main(String[] args) throws Exception {
  *   SpringApplication.run(MyApplication.class, args);
  * }
  * </pre>
- * 
+ *
  * <p>
  * For more advanced configuration a {@link SpringApplication} instance can be created and
  * customized before being run:
- * 
+ *
  * <pre class="code">
  * public static void main(String[] args) throws Exception {
  *   SpringApplication app = new SpringApplication(MyApplication.class);
@@ -116,28 +116,29 @@ import org.springframework.web.context.support.StandardServletEnvironment;
  *   app.run(args)
  * }
  * </pre>
- * 
+ *
  * {@link SpringApplication}s can read beans from a variety of different sources. It is
  * generally recommended that a single {@code @Configuration} class is used to bootstrap
  * your application, however, any of the following sources can also be used:
- * 
+ *
  * <p>
  * <ul>
  * <li>{@link Class} - A Java class to be loaded by {@link AnnotatedBeanDefinitionReader}</li>
- * 
+ *
  * <li>{@link Resource} - An XML resource to be loaded by {@link XmlBeanDefinitionReader},
  * or a groovy script to be loaded by {@link GroovyBeanDefinitionReader}</li>
- * 
+ *
  * <li>{@link Package} - A Java package to be scanned by
  * {@link ClassPathBeanDefinitionScanner}</li>
- * 
+ *
  * <li>{@link CharSequence} - A class name, resource handle or package name to loaded as
  * appropriate. If the {@link CharSequence} cannot be resolved to class and does not
  * resolve to a {@link Resource} that exists it will be considered a {@link Package}.</li>
  * </ul>
- * 
+ *
  * @author Phillip Webb
  * @author Dave Syer
+ * @author Andy Wilkinson
  * @see #run(Object, String[])
  * @see #run(Object[], String[])
  * @see #SpringApplication(Object...)
@@ -151,7 +152,9 @@ public class SpringApplication {
 			+ "boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext";
 
 	private static final String[] WEB_ENVIRONMENT_CLASSES = { "javax.servlet.Servlet",
-			"org.springframework.web.context.ConfigurableWebApplicationContext" };
+	"org.springframework.web.context.ConfigurableWebApplicationContext" };
+
+	private static final String SYSTEM_PROPERTY_JAVA_AWT_HEADLESS = "java.awt.headless";
 
 	private final Log log = LogFactory.getLog(getClass());
 
@@ -262,7 +265,10 @@ public class SpringApplication {
 		stopWatch.start();
 		ConfigurableApplicationContext context = null;
 
-		System.setProperty("java.awt.headless", Boolean.toString(this.headless));
+		System.setProperty(
+				SYSTEM_PROPERTY_JAVA_AWT_HEADLESS,
+				System.getProperty(SYSTEM_PROPERTY_JAVA_AWT_HEADLESS,
+						Boolean.toString(this.headless)));
 
 		Collection<SpringApplicationRunListener> runListeners = getRunListeners(args);
 		for (SpringApplicationRunListener runListener : runListeners) {
@@ -540,7 +546,7 @@ public class SpringApplication {
 		if (this.resourceLoader != null) {
 			if (context instanceof GenericApplicationContext) {
 				((GenericApplicationContext) context)
-						.setResourceLoader(this.resourceLoader);
+				.setResourceLoader(this.resourceLoader);
 			}
 			if (context instanceof DefaultResourceLoader) {
 				((DefaultResourceLoader) context).setClassLoader(this.resourceLoader
@@ -573,7 +579,7 @@ public class SpringApplication {
 	protected void logStartupInfo(boolean isRoot) {
 		if (isRoot) {
 			new StartupInfoLogger(this.mainApplicationClass)
-					.logStarting(getApplicationLog());
+			.logStarting(getApplicationLog());
 		}
 	}
 

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

@@ -23,6 +23,7 @@ import java.util.Set;
 import java.util.concurrent.atomic.AtomicReference;
 
 import org.junit.After;
+import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
@@ -78,12 +79,15 @@ import static org.mockito.Mockito.verify;
 
 /**
  * Tests for {@link SpringApplication}.
- * 
+ *
  * @author Phillip Webb
  * @author Dave Syer
+ * @author Andy Wilkinson
  */
 public class SpringApplicationTests {
 
+	private String headlessProperty;
+
 	@Rule
 	public ExpectedException thrown = ExpectedException.none();
 
@@ -96,6 +100,23 @@ public class SpringApplicationTests {
 		throw new IllegalStateException("Could not obtain Environment");
 	}
 
+	@Before
+	public void storeAndClearHeadlessProperty() {
+		this.headlessProperty = System.getProperty("java.awt.headless");
+		System.clearProperty("java.awt.headless");
+	}
+
+	@After
+	public void reinstateHeadlessProperty() {
+		if (this.headlessProperty == null) {
+			System.clearProperty("java.awt.headless");
+		}
+		else {
+			System.setProperty("java.awt.headless", this.headlessProperty);
+		}
+
+	}
+
 	@After
 	public void close() {
 		if (this.context != null) {
@@ -504,6 +525,15 @@ public class SpringApplicationTests {
 		assertThat(System.getProperty("java.awt.headless"), equalTo("false"));
 	}
 
+	@Test
+	public void headlessSystemPropertyTakesPrecedence() throws Exception {
+		System.setProperty("java.awt.headless", "false");
+		TestSpringApplication application = new TestSpringApplication(ExampleConfig.class);
+		application.setWebEnvironment(false);
+		application.run();
+		assertThat(System.getProperty("java.awt.headless"), equalTo("false"));
+	}
+
 	private boolean hasPropertySource(ConfigurableEnvironment environment,
 			Class<?> propertySourceClass, String name) {
 		for (PropertySource<?> source : environment.getPropertySources()) {