Allow for commandLineArgs to be already present in Environment

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

@@ -51,9 +51,11 @@ import org.springframework.context.support.GenericApplicationContext;
 import org.springframework.core.GenericTypeResolver;
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
 import org.springframework.core.env.CommandLinePropertySource;
+import org.springframework.core.env.CompositePropertySource;
 import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.Environment;
 import org.springframework.core.env.MapPropertySource;
+import org.springframework.core.env.MutablePropertySources;
 import org.springframework.core.env.PropertySource;
 import org.springframework.core.env.SimpleCommandLinePropertySource;
 import org.springframework.core.env.StandardEnvironment;
@@ -375,13 +377,24 @@ public class SpringApplication {
 	 * @param args run arguments
 	 */
 	protected void addPropertySources(ConfigurableEnvironment environment, String[] args) {
+		MutablePropertySources sources = environment.getPropertySources();
 		if (this.defaultProperties != null && !this.defaultProperties.isEmpty()) {
-			environment.getPropertySources().addLast(
-					new MapPropertySource("defaultProperties", this.defaultProperties));
+			sources.addLast(new MapPropertySource("defaultProperties",
+					this.defaultProperties));
 		}
-		if (this.addCommandLineProperties) {
-			environment.getPropertySources().addFirst(
-					new SimpleCommandLinePropertySource(args));
+		if (this.addCommandLineProperties && args.length > 0) {
+			String name = CommandLinePropertySource.COMMAND_LINE_PROPERTY_SOURCE_NAME;
+			if (sources.contains(name)) {
+				PropertySource<?> source = sources.get(name);
+				CompositePropertySource composite = new CompositePropertySource(name);
+				composite.addPropertySource(new SimpleCommandLinePropertySource(name
+						+ "-" + args.hashCode(), args));
+				composite.addPropertySource(source);
+				sources.replace(name, composite);
+			}
+			else {
+				sources.addFirst(new SimpleCommandLinePropertySource(args));
+			}
 		}
 	}
 

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

@@ -17,6 +17,7 @@
 package org.springframework.boot;
 
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicReference;
 
@@ -43,6 +44,7 @@ import org.springframework.context.event.ContextRefreshedEvent;
 import org.springframework.context.support.StaticApplicationContext;
 import org.springframework.core.Ordered;
 import org.springframework.core.env.CommandLinePropertySource;
+import org.springframework.core.env.CompositePropertySource;
 import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.Environment;
 import org.springframework.core.env.MapPropertySource;
@@ -58,6 +60,7 @@ import static org.hamcrest.Matchers.instanceOf;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.sameInstance;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
@@ -244,14 +247,41 @@ public class SpringApplicationTests {
 
 	@Test
 	public void commandLinePropertySource() throws Exception {
+		SpringApplication application = new SpringApplication(ExampleConfig.class);
+		application.setWebEnvironment(false);
+		ConfigurableEnvironment environment = new StandardEnvironment();
+		application.setEnvironment(environment);
+		application.run("--foo=bar");
+		assertTrue(hasPropertySource(environment, CommandLinePropertySource.class,
+				"commandLineArgs"));
+	}
+
+	@Test
+	public void commandLinePropertySourceEnhancesEnvironment() throws Exception {
+		SpringApplication application = new SpringApplication(ExampleConfig.class);
+		application.setWebEnvironment(false);
+		ConfigurableEnvironment environment = new StandardEnvironment();
+		environment.getPropertySources().addFirst(
+				new MapPropertySource("commandLineArgs", Collections
+						.<String, Object> singletonMap("foo", "original")));
+		application.setEnvironment(environment);
+		application.run("--foo=bar", "--bar=foo");
+		assertTrue(hasPropertySource(environment, CompositePropertySource.class,
+				"commandLineArgs"));
+		assertEquals("foo", environment.getProperty("bar"));
+		// New command line properties take precedence
+		assertEquals("bar", environment.getProperty("foo"));
+	}
+
+	@Test
+	public void emptyCommandLinePropertySourceNotAdded() throws Exception {
 		SpringApplication application = new SpringApplication(ExampleConfig.class);
 		application.setWebEnvironment(false);
 		ConfigurableEnvironment environment = new StandardEnvironment();
 		application.setEnvironment(environment);
 		application.run();
-		assertThat(
-				hasPropertySource(environment, CommandLinePropertySource.class,
-						"commandLineArgs"), equalTo(true));
+		assertFalse(hasPropertySource(environment, PropertySource.class,
+				"commandLineArgs"));
 	}
 
 	@Test
@@ -261,10 +291,9 @@ public class SpringApplicationTests {
 		application.setAddCommandLineProperties(false);
 		ConfigurableEnvironment environment = new StandardEnvironment();
 		application.setEnvironment(environment);
-		application.run();
-		assertThat(
-				hasPropertySource(environment, MapPropertySource.class, "commandLineArgs"),
-				equalTo(false));
+		application.run("--foo=bar");
+		assertFalse(hasPropertySource(environment, PropertySource.class,
+				"commandLineArgs"));
 	}
 
 	@Test