Add config file property sources after existing

Change ConfigFileApplicationContextInitializer to add config file
property sources after existing sources. This allows environment
variables and system properties to override file properties.

Issue: #55739594

spring-boot/src/main/java/org/springframework/boot/context/initializer/ConfigFileApplicationContextInitializer.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.context.initializer;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -39,7 +40,6 @@ import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.core.env.CommandLinePropertySource;
 import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.Environment;
-import org.springframework.core.env.MutablePropertySources;
 import org.springframework.core.env.PropertySource;
 import org.springframework.core.io.DefaultResourceLoader;
 import org.springframework.core.io.Resource;
@@ -127,6 +127,7 @@ public class ConfigFileApplicationContextInitializer implements
 	private void load(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {
 
 		List<String> candidates = getCandidateLocations();
+		Collections.reverse(candidates);
 
 		// Initial load allows profiles to be activated
 		for (String candidate : candidates) {
@@ -186,14 +187,7 @@ public class ConfigFileApplicationContextInitializer implements
 			}
 
 		}
-		MutablePropertySources propertySources = environment.getPropertySources();
-		if (propertySources.contains(COMMAND_LINE_PROPERTY_SOURCE_NAME)) {
-			propertySources.addAfter(COMMAND_LINE_PROPERTY_SOURCE_NAME, propertySource);
-		}
-		else {
-			propertySources.addFirst(propertySource);
-		}
-
+		environment.getPropertySources().addLast(propertySource);
 	}
 
 	private PropertySource<?> getPropertySource(Resource resource,

spring-boot/src/test/java/org/springframework/boot/context/initializer/ConfigFileApplicationContextInitializerTests.java

@@ -19,6 +19,7 @@ package org.springframework.boot.context.initializer;
 import java.util.HashMap;
 import java.util.Map;
 
+import org.junit.After;
 import org.junit.Test;
 import org.springframework.context.support.StaticApplicationContext;
 import org.springframework.core.env.MapPropertySource;
@@ -40,6 +41,11 @@ public class ConfigFileApplicationContextInitializerTests {
 
 	private ConfigFileApplicationContextInitializer initializer = new ConfigFileApplicationContextInitializer();
 
+	@After
+	public void cleanup() {
+		System.clearProperty("my.property");
+	}
+
 	@Test
 	public void loadPropertiesFile() throws Exception {
 		this.initializer.setNames("testproperties");
@@ -81,6 +87,15 @@ public class ConfigFileApplicationContextInitializerTests {
 		assertThat(property, equalTo("fromcommandline"));
 	}
 
+	@Test
+	public void systemPropertyWins() throws Exception {
+		System.setProperty("my.property", "fromsystem");
+		this.initializer.setNames("testproperties");
+		this.initializer.initialize(this.context);
+		String property = this.context.getEnvironment().getProperty("my.property");
+		assertThat(property, equalTo("fromsystem"));
+	}
+
 	@Test
 	public void loadPropertiesThenProfileProperties() throws Exception {
 		this.initializer.setNames("enableprofile");