Add loader.system (flag to copy properties to System)

spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/PropertiesLauncher.java

@@ -96,6 +96,13 @@ public class PropertiesLauncher implements ArchiveFilter {
 	 */
 	public static final String CONFIG_LOCATION = "loader.config.location";
 
+	/**
+	 * Properties key for boolean flag (default false) which if set will cause the
+	 * external configuration properties to be copied to System properties (assuming that
+	 * is allowed by Java security).
+	 */
+	public static final String SET_SYSTEM_PROPERTIES = "loader.system";
+
 	private static final List<String> DEFAULT_PATHS = Arrays.asList("lib/");
 
 	private List<String> paths = new ArrayList<String>(DEFAULT_PATHS);
@@ -213,10 +220,19 @@ public class PropertiesLauncher implements ArchiveFilter {
 					this.properties.put(key, value);
 				}
 			}
+			if (SystemPropertyUtils.resolvePlaceholders(
+					"${" + SET_SYSTEM_PROPERTIES + ":false}").equals("true")) {
+				this.logger.info("Adding resolved properties to System properties");
+				for (Object key : Collections.list(this.properties.propertyNames())) {
+					String value = this.properties.getProperty((String) key);
+					System.setProperty((String) key, value);
+				}
+			}
 		}
 		else {
 			this.logger.info("Not found: " + config);
 		}
+
 	}
 
 	private InputStream getResource(String config) throws Exception {

spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/util/SystemPropertyUtils.java

@@ -161,7 +161,7 @@ public abstract class SystemPropertyUtils {
 			System.err.println("Could not resolve placeholder '" + placeholderName
 					+ "' in [" + text + "] as system property: " + ex);
 		}
-		return properties.getProperty(placeholderName);
+		return properties == null ? null : properties.getProperty(placeholderName);
 	}
 
 	private static int findPlaceholderEndIndex(CharSequence buf, int startIndex) {

spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/PropertiesLauncherTests.java

@@ -33,6 +33,7 @@ public class PropertiesLauncherTests {
 
 	@After
 	public void close() {
+		System.clearProperty("loader.system");
 		System.clearProperty("loader.home");
 		System.clearProperty("loader.path");
 		System.clearProperty("loader.main");
@@ -50,6 +51,7 @@ public class PropertiesLauncherTests {
 	public void testUserSpecifiedMain() throws Exception {
 		this.launcher.initialize(new File("."));
 		assertEquals("demo.Application", this.launcher.getMainClass(null));
+		assertEquals(null, System.getProperty("loader.main"));
 	}
 
 	@Test
@@ -68,4 +70,11 @@ public class PropertiesLauncherTests {
 		assertEquals("foo.Bar", this.launcher.getMainClass(null));
 	}
 
+	@Test
+	public void testSystemPropertiesSet() throws Exception {
+		System.setProperty("loader.system", "true");
+		this.launcher.initialize(new File("."));
+		assertEquals("demo.Application", System.getProperty("loader.main"));
+	}
+
 }