Use sorted properties to make build info output repeatable

Closes gh-14494

Author: wilkinsona

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/tasks/buildinfo/BuildInfoIntegrationTests.java

@@ -22,12 +22,15 @@
 import java.util.Properties;
 
 import org.gradle.testkit.runner.BuildResult;
+import org.gradle.testkit.runner.InvalidRunnerConfigurationException;
 import org.gradle.testkit.runner.TaskOutcome;
+import org.gradle.testkit.runner.UnexpectedBuildFailure;
 import org.junit.jupiter.api.TestTemplate;
 import org.junit.jupiter.api.extension.ExtendWith;
 
 import org.springframework.boot.gradle.junit.GradleCompatibilityExtension;
 import org.springframework.boot.gradle.testkit.GradleBuild;
+import org.springframework.boot.loader.tools.FileUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -92,6 +95,22 @@ public void notUpToDateWhenExecutedTwiceWithFixedTimeAndChangedProjectVersion()
 		assertThat(result.task(":buildInfo").getOutcome()).isEqualTo(TaskOutcome.SUCCESS);
 	}
 
+	@TestTemplate
+	public void reproducibleOutputWithFixedTime() throws InvalidRunnerConfigurationException,
+			UnexpectedBuildFailure, IOException, InterruptedException {
+		assertThat(this.gradleBuild.build("buildInfo", "-PnullTime").task(":buildInfo")
+				.getOutcome()).isEqualTo(TaskOutcome.SUCCESS);
+		File buildInfoProperties = new File(this.gradleBuild.getProjectDir(),
+				"build/build-info.properties");
+		String firstHash = FileUtils.sha1Hash(buildInfoProperties);
+		assertThat(buildInfoProperties.delete()).isTrue();
+		Thread.sleep(1500);
+		assertThat(this.gradleBuild.build("buildInfo", "-PnullTime")
+				.task(":buildInfo").getOutcome()).isEqualTo(TaskOutcome.SUCCESS);
+		String secondHash = FileUtils.sha1Hash(buildInfoProperties);
+		assertThat(firstHash).isEqualTo(secondHash);
+	}
+
 	private Properties buildInfoProperties() {
 		File file = new File(this.gradleBuild.getProjectDir(),
 				"build/build-info.properties");

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2018 the original author or authors.
+ * Copyright 2012-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,6 +24,8 @@
 import java.util.Map;
 import java.util.Properties;
 
+import org.springframework.core.CollectionFactory;
+
 /**
  * A {@code BuildPropertiesWriter} writes the {@code build-info.properties} for
  * consumption by the Actuator.
@@ -68,7 +70,7 @@ private void createFileIfNecessary(File file) throws IOException {
 	}
 
 	protected Properties createBuildInfo(ProjectDetails project) {
-		Properties properties = new Properties();
+		Properties properties = CollectionFactory.createSortedProperties(true);
 		properties.put("build.group", project.getGroup());
 		properties.put("build.artifact", project.getArtifact());
 		properties.put("build.name", project.getName());